question
stringlengths 14
399
| choices
listlengths 4
4
| answer
stringclasses 4
values | context
stringlengths 732
6.9k
|
|---|---|---|---|
What is the term for a random change in allele frequencies that occurs in a small population?
|
[
"evolution",
"speciation",
"genetic drift",
"mutation"
] |
C
|
Genetic drift is a random change in allele frequencies that occurs in a small population. When a small number of parents produce just a few offspring, allele frequencies in the offspring may differ, by chance, from allele frequencies in the parents.
Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance.Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. It can also cause initially rare alleles to become much more frequent and even fixed. When few copies of an allele exist, the effect of genetic drift is more notable, and when many copies exist, the effect is less notable.
Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. Specifically, it is the fraction of all chromosomes in the population that carry that allele over the total population or sample size. Microevolution is the change in allele frequencies that occurs over time within a population.
The expected allele frequency spectrum may be calculated using either a coalescent or diffusion approach. The demographic history of a population and natural selection affect allele frequency dynamics, and these effects are reflected in the shape of the allele frequency spectrum. For the simple case of selective neutral alleles segregating in a population that has reached demographic equilibrium (that is, without recent population size changes or gene flow), the expected allele frequency spectrum x = ( x 1 , … , x n − 1 ) {\displaystyle \mathbf {x} =(x_{1},\ldots ,x_{n-1})} for a sample of size n {\displaystyle n} is given by x i = θ 1 i , {\displaystyle x_{i}=\theta {\frac {1}{i}},} where θ = 2 N μ {\displaystyle \theta =2N\mu } is the population scaled mutation rate. Deviations from demographic equilibrium or neutrality will change the shape of the expected frequency spectrum.
Large populations are more likely to maintain genetic material and thus generally have higher genetic diversity. Small populations are more likely to experience the loss of diversity over time by random chance, which is called genetic drift. When an allele (variant of a gene) drifts to fixation, the other allele at the same locus is lost, resulting in a loss in genetic diversity. In small population sizes, inbreeding, or mating between individuals with similar genetic makeup, is more likely to occur, thus perpetuating more common alleles to the point of fixation, thus decreasing genetic diversity.
While directional selection eventually leads to the loss of all alleles except the favored one (unless one allele is dominant, in which case recessive alleles can survive at low frequencies), some forms of selection, such as balancing selection, lead to equilibrium without loss of alleles. Mutation will have a very subtle effect on allele frequencies through the introduction of new allele into a population. Mutation rates are of the order 10−4 to 10−8, and the change in allele frequency will be, at most, the same order.
|
Aerobic exercise helps improve the cardiovascular system, while what exercise causes muscles to get bigger and stronger?
|
[
"anaerobic",
"endurance",
"skeletal",
"enzymatic"
] |
A
|
Aerobic exercise helps improve the cardiovascular system, while anaerobic exercise causes muscles to get bigger and stronger.
Muscle fibers grow when exercised and shrink when not in use. This is due to the fact that exercise stimulates the increase in myofibrils which increase the overall size of muscle cells. Well exercised muscles can not only add more size but can also develop more mitochondria, myoglobin, glycogen and a higher density of capillaries. However muscle cells cannot divide to produce new cells, and as a result there are fewer muscle cells in an adult than in a newborn.
However, as muscles become adapted to the exercises, soreness tends to decrease.Weight training aims to build muscle by prompting two different types of hypertrophy: sarcoplasmic and myofibrillar. Sarcoplasmic hypertrophy leads to larger muscles and so is favored by bodybuilders more than myofibrillar hypertrophy, which builds athletic strength. Sarcoplasmic hypertrophy is triggered by increasing repetitions, whereas myofibrillar hypertrophy is triggered by lifting heavier weight. In either case, there is an increase in both size and strength of the muscles (compared to what happens if that same individual does not lift weights at all), although the emphasis is different.
There is an emerging understanding of skeletal muscle as a secretory organ, and of myokines as mediators of physical fitness through the practice of regular physical exercise (aerobic exercise and strength training), as well as new awareness of the anti-inflammatory and thus disease prevention aspects of exercise. Different muscle fiber types – slow twitch muscle fibers, oxidative muscle fibers, intermediate twitch muscle fibers, and fast twitch muscle fibers – release different clusters of myokines during contraction. This implies that variation of exercise types, particularly aerobic training/endurance training and muscle contraction against resistance (strength training) may offer differing myokine-induced benefits.
Physical fitness has been shown to have benefits in preventing ill health and assisting recovery from injury or illness. Along with the physical health benefits of fitness, it has also been shown to have a positive impact on mental health as well by assisting in treating anxiety and depression. Physical fitness can also prevent or treat many other chronic health conditions brought on by unhealthy lifestyle or aging as well and has been listed frequently as one of the most popular and advantageous self-care therapies. Working out can also help some people sleep better by building up sleeping pressure and possibly alleviate some mood disorders in certain individuals.Developing research has demonstrated that many of the benefits of exercise are mediated through the role of skeletal muscle as an endocrine organ. That is, contracting muscles release multiple substances known as myokines, which promote the growth of new tissue, tissue repair, and various anti-inflammatory functions, which in turn reduce the risk of developing various inflammatory diseases.
Physical fitness has been shown to have benefits in preventing ill health and assisting recovery from injury or illness. Along with the physical health benefits of fitness, it has also been shown to have a positive impact on mental health as well by assisting in treating anxiety and depression. Physical fitness can also prevent or treat many other chronic health conditions brought on by unhealthy lifestyle or aging as well and has been listed frequently as one of the most popular and advantageous self-care therapies. Working out can also help some people sleep better by building up sleeping pressure and possibly alleviate some mood disorders in certain individuals.Developing research has demonstrated that many of the benefits of exercise are mediated through the role of skeletal muscle as an endocrine organ. That is, contracting muscles release multiple substances known as myokines, which promote the growth of new tissue, tissue repair, and various anti-inflammatory functions, which in turn reduce the risk of developing various inflammatory diseases.
|
An excessive posterior curvature of the thoracic region is also known as what?
|
[
"lordosis",
"kyphosis",
"babesiosis",
"osmosis"
] |
B
|
Vertebral Column Developmental anomalies, pathological changes, or obesity can enhance the normal vertebral column curves, resulting in the development of abnormal or excessive curvatures (Figure 7.21). Kyphosis, also referred to as humpback or hunchback, is an excessive posterior curvature of the thoracic region. This can develop when osteoporosis causes weakening and erosion of the anterior portions of the upper thoracic vertebrae, resulting in their gradual collapse (Figure 7.22). Lordosis, or swayback, is an excessive anterior curvature of the lumbar region and is most commonly associated with obesity or late pregnancy. The accumulation of body weight in the abdominal region results an anterior shift in the line of gravity that carries the weight of the body. This causes in an anterior tilt of the pelvis and a pronounced enhancement of the lumbar curve. Scoliosis is an abnormal, lateral curvature, accompanied by twisting of the vertebral column. Compensatory curves may also develop in other areas of the vertebral column to help maintain the head positioned over the feet. Scoliosis is the most common vertebral abnormality among girls. The cause is usually unknown, but it may result from weakness of the back muscles, defects such as differential growth rates in the right and left sides of the vertebral column, or differences in the length of the lower limbs. When present, scoliosis tends to get worse during adolescent growth spurts. Although most individuals do not require treatment, a back brace may be recommended for growing children. In extreme cases, surgery may be required. Excessive vertebral curves can be identified while an individual stands in the anatomical position. Observe the vertebral profile from the side and then from behind to check for kyphosis or lordosis. Then have the person bend forward. If scoliosis is present, an individual will have difficulty in bending directly forward, and the right and left sides of the back will not be level with each other in the bent position.
Kyphosis is an abnormally excessive convex curvature of the spine as it occurs in the thoracic and sacral regions. Abnormal inward concave lordotic curving of the cervical and lumbar regions of the spine is called lordosis. It can result from degenerative disc disease; developmental abnormalities, most commonly Scheuermann's disease; Copenhagen disease, osteoporosis with compression fractures of the vertebra; multiple myeloma; or trauma. A normal thoracic spine extends from the 1st thoracic to the 12th thoracic vertebra and should have a slight kyphotic angle, ranging from 20° to 45°.
In very rare instances, this vessel arises from the thoracic aorta, as low down as the fourth thoracic vertebra. Occasionally, it perforates the Scalenus anterior; more rarely it passes in front of that muscle.
These are the general characteristics of the second through eighth thoracic vertebrae. The first and ninth through twelfth vertebrae contain certain peculiarities, and are detailed below. The bodies in the middle of the thoracic region are heart-shaped and as broad in the anteroposterior as in the transverse direction. At the ends of the thoracic region they resemble respectively those of the cervical and lumbar vertebrae.
Each thoracic vertebrae has a pair of huge wing-like transverse processes, many of which overlap. The dorsal end of the ribs are remarkably thin and almost fail to make contact with the transverse processes.
The first thoracic vertebra has, on either side of the body, an entire articular facet for the head of the first rib, and a demi-facet for the upper half of the head of the second rib. The body is like that of a cervical vertebra, being broad, concave, and lipped on either side. The superior articular surfaces are directed upward and backward; the spinous process is thick, long, and almost horizontal. The transverse processes are long, and the upper vertebral notches are deeper than those of the other thoracic vertebrae. The thoracic spinal nerve 1 (T1) passes out underneath it.
|
What are the two main divisions of the human nervous system?
|
[
"somatic and autonomic",
"central and identical",
"central and peripheral",
"left and right"
] |
C
|
The two main divisions of the human nervous system are the central nervous system and the peripheral nervous system. The peripheral nervous system has additional divisions.
The autonomic nervous system itself consists of two parts: the sympathetic nervous system and the parasympathetic nervous system. Some authors also include sensory neurons whose cell bodies lie in the periphery (for senses such as hearing) as part of the PNS; others, however, omit them.The vertebrate nervous system can also be divided into areas called gray matter and white matter.
In vertebrates, the nervous system is segregated into the internal structure of the brain and spinal cord (together called the central nervous system, or CNS) and the routes of the nerves that connect to the rest of the body (known as the peripheral nervous system, or PNS). The delineation of distinct structures and regions of the nervous system has been critical in investigating how it works. For example, much of what neuroscientists have learned comes from observing how damage or "lesions" to specific brain areas affects behavior or other neural functions.
This region is known as the paleomammalian brain, the major parts of which are the hippocampi and amygdalas, often referred to as the limbic system. The limbic system deals with more complex functions including emotional, sexual and fighting behaviors. Of course, animals that are not vertebrates also have brains, and their brains have undergone separate evolutionary histories.The brainstem and limbic system are largely based on nuclei, which are essentially balled-up clusters of tightly packed neurons and the axon fibers that connect them to each other, as well as to neurons in other locations.
The scientific study of the nervous system increased significantly during the second half of the twentieth century, principally due to advances in molecular biology, electrophysiology, and computational neuroscience. This has allowed neuroscientists to study the nervous system in all its aspects: how it is structured, how it works, how it develops, how it malfunctions, and how it can be changed. For example, it has become possible to understand, in much detail, the complex processes occurring within a single neuron. Neurons are cells specialized for communication.
The efferent leg of the peripheral nervous system is responsible for conveying commands to the muscles and glands, and is ultimately responsible for voluntary movement. Nerves move muscles in response to voluntary and autonomic (involuntary) signals from the brain. Deep muscles, superficial muscles, muscles of the face and internal muscles all correspond with dedicated regions in the primary motor cortex of the brain, directly anterior to the central sulcus that divides the frontal and parietal lobes. In addition, muscles react to reflexive nerve stimuli that do not always send signals all the way to the brain.
|
What is composed of two strands of nucleotides in a double-helical structure?
|
[
"molecule",
"dna",
"RNA",
"bacteria"
] |
B
|
DNA Double-Helical Structure DNA has a double-helical structure (Figure 2.23). It is composed of two strands, or polymers, of nucleotides. The strands are formed with bonds between phosphate and sugar groups of adjacent nucleotides. The strands are bonded to each other at their bases with hydrogen bonds, and the strands coil about each other along their length, hence the “double helix” description, which means a double spiral.
The helicase is a monomeric translocase and utilizes ATP to unwind DNA. The preferred substrates are single-stranded DNA containing 3' overhangs. The processivity of PcrA is increased in the presence of plasmid replication initiation protein.
Nucleotides are the fundamental molecules that combine in series to form RNA. They consist of a nitrogenous base attached to a sugar-phosphate backbone. RNA is made of long stretches of specific nucleotides arranged so that their sequence of bases carries information. The RNA world hypothesis holds that in the primordial soup (or sandwich), there existed free-floating nucleotides.
DNA is a long polymer made from repeating units called nucleotides. The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. In all species it is composed of two helical chains, bound to each other by hydrogen bonds. Both chains are coiled around the same axis, and have the same pitch of 34 ångströms (3.4 nm).
Where the helix is unwound, the coding strand consists of unpaired bases, while the template strand consists of an RNA:DNA composite, followed by a number of unpaired bases at the rear. This hybrid consists of the most recently added nucleotides of the RNA transcript, complementary base-paired to the template strand. The number of base-pairs in the hybrid is under investigation, but it has been suggested that the hybrid is formed from the last 10 nucleotides added.
DNA sequences are known to appear in the form of double helices in living cells, in which one DNA strand is hybridized to its complementary strand through a series of hydrogen bonds. For the purpose of this entry, we shall focus on only oligonucleotides. DNA computing involves allowing synthetic oligonucleotide strands to hybridize in such a way as to perform computation. DNA computing requires that the self-assembly of the oligonucleotide strands happen in such a way that hybridization should occur in a manner compatible with the goals of computation.
|
The body is made up of how many types of tissue?
|
[
"four",
"five",
"seven",
"six"
] |
A
|
As for all animals, your body is made of four types of tissue: epidermal, muscle, nerve, and connective tissues. Plants, too, are built of tissues, but not surprisingly, their very different lifestyles derive from different kinds of tissues. All three types of plant cells are found in most plant tissues. Three major types of plant tissues are dermal, ground, and vascular tissues.
Fibromuscular tissue is made up of fibrous tissue and muscular tissue. New vascularised connective tissue that forms in the process of wound healing is termed granulation tissue. All of the special connective tissue types have been included as a subset of fascia in the fascial system, with blood and lymph classed as liquid fascia.Bone and cartilage can be further classified as supportive connective tissue. Blood and lymph can also be categorized as fluid connective tissue, and liquid fascia.
The main cell types are fibroblasts, macrophages and adipocytes (the subcutaneous tissue contains 50% of body fat). Fat serves as padding and insulation for the body. Microorganisms like Staphylococcus epidermis colonize the skin surface. The density of skin flora depends on region of the skin. The disinfected skin surface gets recolonized from bacteria residing in the deeper areas of the hair follicle, gut and urogenital openings.
The hollow tubular structure of bones provide considerable resistance against compression while staying lightweight. Most cells in bones are either osteoblasts, osteoclasts, or osteocytes.Bone tissue is a type of dense connective tissue. One of the types of tissue that makes up bone tissue is mineralized tissue and this gives it rigidity and a honeycomb-like three-dimensional internal structure.
The source of the contents will be mentioned as follows on Wikipedia articles included under the scope of this project: This article incorporates text from a free content work. Licensed under CC BY 4.0. Text taken from Anatomy and Physiology, J. Gordon Betts et al, Openstax. https://openstax.org/books/anatomy-and-physiology/pages/4-1-types-of-tissues. == References ==
There are three distinct types of muscle: skeletal muscle, cardiac or heart muscle, and smooth (non-striated) muscle. Muscles provide strength, balance, posture, movement, and heat for the body to keep warm.There are approximately 640 muscles in an adult male human body. A kind of elastic tissue makes up each muscle, which consists of thousands, or tens of thousands, of small muscle fibers. Each fiber comprises many tiny strands called fibrils, impulses from nerve cells control the contraction of each muscle fiber.
|
The great astronomer edwin hubble discovered that all distant galaxies are receding from our milky way galaxy with velocities proportional to their what?
|
[
"masses",
"distances",
"paths",
"dimensions"
] |
B
|
(a) A jet airplane flying from Darwin, Australia, has an air speed of 260 m/s in a direction 5.0º south of west. It is in the jet stream, which is blowing at 35.0 m/s in a direction 15º south of east. What is the velocity of the airplane relative to the Earth? (b) Discuss whether your answers are consistent with your expectations for the effect of the wind on the plane’s path. (a) In what direction would the ship in Exercise 3.57 have to travel in order to have a velocity straight north relative to the Earth, assuming its speed relative to the water remains 7.00 m/s ? (b) What would its speed be relative to the Earth? 60. (a) Another airplane is flying in a jet stream that is blowing at 45.0 m/s in a direction 20º south of east (as in Exercise 3.58). Its direction of motion relative to the Earth is 45.0º south of west, while its direction of travel relative to the air is 5.00º south of west. What is the airplane’s speed relative to the air mass? (b) What is the airplane’s speed relative to the Earth? 61. A sandal is dropped from the top of a 15.0-m-high mast on a ship moving at 1.75 m/s due south. Calculate the velocity of the sandal when it hits the deck of the ship: (a) relative to the ship and (b) relative to a stationary observer on shore. (c) Discuss how the answers give a consistent result for the position at which the sandal hits the deck. The velocity of the wind relative to the water is crucial to sailboats. Suppose a sailboat is in an ocean current that has a velocity of 2.20 m/s in a direction 30.0º east of north relative to the Earth. It encounters a wind that has a velocity of 4.50 m/s in a direction of 50.0º south of west relative to the Earth. What is the velocity of the wind relative to the water? 63. The great astronomer Edwin Hubble discovered that all distant galaxies are receding from our Milky Way Galaxy with velocities proportional to their distances. It appears to an observer on the Earth that we are at the center of an expanding universe. Figure 3.64 illustrates this for five galaxies lying along a straight line, with the Milky Way Galaxy at the center. Using the data from the figure, calculate the velocities: (a) relative to galaxy 2 and (b) relative to galaxy 5. The results mean that observers on all galaxies will see themselves at the center of the expanding universe, and they would likely be aware of relative velocities, concluding that it is not possible to locate the center of expansion with the given information.
However, when the universe was much younger, the expansion rate, and thus the Hubble "constant", was larger than it is today. For more distant galaxies, then, whose light has been travelling to us for much longer times, the approximation of constant expansion rate fails, and the Hubble law becomes a non-linear integral relationship and dependent on the history of the expansion rate since the emission of the light from the galaxy in question. Observations of the redshift-distance relationship can be used, then, to determine the expansion history of the universe and thus the matter and energy content.While it was long believed that the expansion rate has been continuously decreasing since the Big Bang, observations beginning in 1988 of the redshift-distance relationship using Type Ia supernovae have suggested that in comparatively recent times the expansion rate of the universe has begun to accelerate.
The Sun was found to be part of a galaxy made up of more than 1010 stars (10 billion stars). The existence of other galaxies, one of the matters of the great debate, was settled by Edwin Hubble, who identified the Andromeda nebula as a different galaxy, and many others at large distances and receding, moving away from our galaxy. Physical cosmology, a discipline that has a large intersection with astronomy, made huge advances during the 20th century, with the model of the hot Big Bang heavily supported by the evidence provided by astronomy and physics, such as the redshifts of very distant galaxies and radio sources, the cosmic microwave background radiation, Hubble's law and cosmological abundances of elements.
The most distant objects exhibit larger redshifts corresponding to the Hubble flow of the universe. The largest-observed redshift, corresponding to the greatest distance and furthest back in time, is that of the cosmic microwave background radiation; the numerical value of its redshift is about z = 1089 (z = 0 corresponds to present time), and it shows the state of the universe about 13.8 billion years ago, and 379,000 years after the initial moments of the Big Bang.The luminous point-like cores of quasars were the first "high-redshift" (z > 0.1) objects discovered before the improvement of telescopes allowed for the discovery of other high-redshift galaxies.For galaxies more distant than the Local Group and the nearby Virgo Cluster, but within a thousand megaparsecs or so, the redshift is approximately proportional to the galaxy's distance. This correlation was first observed by Edwin Hubble and has come to be known as Hubble's law. Vesto Slipher was the first to discover galactic redshifts, in about the year 1912, while Hubble correlated Slipher's measurements with distances he measured by other means to formulate his Law.
The Hubble–Reynolds law models the surface brightness of elliptical galaxies as I ( R ) = I 0 ( 1 + R / R H ) 2 {\displaystyle I(R)={\frac {I_{0}}{(1+R/R_{H})^{2}}}} Where I ( R ) {\displaystyle I(R)} is the surface brightness at radius R {\displaystyle R} , I 0 {\displaystyle I_{0}} is the central brightness, and R H {\displaystyle R_{H}} is the radius at which the surface brightness is diminished by a factor of 1/4. It is asymptotically similar to the De Vaucouleurs' law which is a special case of the Sersic profile for elliptical galaxies.The law is named for the astronomers Edwin Hubble and John Henry Reynolds. It was first formulated by Reynolds in 1913 from his observations of galaxies (then still known as nebulae). It was later re-derived by Hubble in 1930 specifically in observations of elliptical galaxies. == References ==
And, in order to ensure this situation, the cosmologist postulates spatial isotropy and spatial homogeneity, which is his way of stating that the Universe must be pretty much alike everywhere and in all directions." The redshift observations of Hubble, in which galaxies appear to be moving away from us at a rate proportional to their distance from us, are now understood to be associated with the expansion of the universe. All observers anywhere in the Universe will observe the same effect.
|
What is friction that acts on objects while it is rolling over a surface called?
|
[
"blowing friction",
"rolling friction",
"opposing friction",
"surface friction"
] |
B
|
Rolling friction is friction that acts on objects when they are rolling over a surface. Rolling friction is much weaker than sliding friction or static friction. This explains why most forms of ground transportation use wheels, including bicycles, cars, 4-wheelers, roller skates, scooters, and skateboards. Ball bearings are another use of rolling friction. You can see what they look like in the Figure below . They let parts of a wheel or other machine roll rather than slide over on another.
Similar to rolling friction there are energy terms in charge transfer, which contribute to friction. In static friction there is coupling between elastic strains, polarization and surface charge which contributes to the frictional force. In sliding friction, when asperities contact and there is charge transfer, some of the charge returns as the contacts are released, some does not and will contribute to the macroscopically observed friction.
Various characteristics of ball core structure and coverstock composition affect a ball's motion throughout its skid, hook and roll phases. Such motion is largely (about 75%) governed by the lane's frictional interaction with the ball, which exhibits both chemical friction characteristics and physical friction characteristics. Also, the ball's internal structure—especially the density, shape (symmetric vs. asymmetric), and orientation of its core (also called "weight block") relative to the ball's axis of rotation—substantially affect ball motion.A "dull" (rough) ball surface, having spikes and pores, provides greater friction in the oil-covered front end of the lane but reduced frictional contact in the dry back end of the lane, and thus enables an earlier hook. In contrast, a "gloss" (smooth) ball surface tends to glide atop oil on the front end but establishes greater frictional contact in the dry back end, thus promoting a sharper hook downlane.
In mechanical engineering, a rolling-element bearing, also known as a rolling bearing, is a bearing which carries a load by placing rolling elements (such as balls or rollers) between two concentric, grooved rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding. One of the earliest and best-known rolling-element bearings are sets of logs laid on the ground with a large stone block on top. As the stone is pulled, the logs roll along the ground with little sliding friction.
In this case, the frictional force may depend strongly on the area of contact. Some drag racing tires are adhesive for this reason. However, despite the complexity of the fundamental physics behind friction, the relationships are accurate enough to be useful in many applications.
“Dynamics with friction and persistent contact” (with M.D.P. Monteiro Marques, A. Petrov), Z. Angew. Math.
|
Traditionally, mammals were divided into groups based on what?
|
[
"their sizes",
"their colors",
"their behaviors",
"their characteristics"
] |
D
|
Traditionally, mammals were divided into groups based on their characteristics. Scientists took into consideration their anatomy (body structure), their habitats, and their feeding habits. Mammals are divided into three subclasses and about 26 orders. Some of the groups of mammals include:.
Historically, Aristotle divided animals into those with blood and those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous with Animalia) and the Protozoa, single-celled organisms no longer considered animals.
In the Triassic period some groups of archosaurs (a group that includes crocodiles and dinosaurs) developed bipedalism; among the dinosaurs, all the early forms and many later groups were habitual or exclusive bipeds; the birds are members of a clade of exclusively bipedal dinosaurs, the theropods. Within mammals, habitual bipedalism has evolved multiple times, with the macropods, kangaroo rats and mice, springhare, hopping mice, pangolins and hominin apes (australopithecines, including humans) as well as various other extinct groups evolving the trait independently.
The relationships among the three extant divisions of mammals (monotremes, marsupials, and placentals) were long a matter of debate among taxonomists. Most morphological evidence comparing traits such as number and arrangement of teeth and structure of the reproductive and waste elimination systems as well as most genetic and molecular evidence favors a closer evolutionary relationship between the marsupials and placental mammals than either has with the monotremes. The ancestors of marsupials, part of a larger group called metatherians, probably split from those of placental mammals (eutherians) during the mid-Jurassic period, though no fossil evidence of metatherians themselves are known from this time. From DNA and protein analyses, the time of divergence of the two lineages has been estimated to be around 100 to 120 mya.
The use of multiple outgroups is preferable because it provides a more robust phylogeny, buffering against poor outgroup candidates and testing the ingroup's hypothesized monophyly.To qualify as an outgroup, a taxon must satisfy the following two characteristics: It must not be a member of the ingroup. It must be related to the ingroup, closely enough for meaningful comparisons to the ingroup.Therefore, an appropriate outgroup must be unambiguously outside the clade of interest in the phylogenetic study. An outgroup that is nested within the ingroup will, when used to root the phylogeny, result in incorrect conclusions about phylogenetic relationships and trait evolution.
Mammals having a penile bone (in males) and a clitoral bone (in females) include various eutherians: Order Primates, although not in lorises, humans, spider monkeys, or woolly monkeys Order Rodentia (rodents), though not in the related order Lagomorpha (rabbits, hares, etc.) Order Eulipotyphla (insectivores, including shrews and hedgehogs) Order Carnivora (including members of many well-known families, such as ursids (bears), canids (dogs), pinnipeds (walruses, seals, sea lions), procyonids (raccoons etc.), mustelids (otters, weasels, skunks and others)). The baculum is usually longer in the Canoidea than in the Feloidea, although fossas have long bacula and giant pandas have short bacula. Order Chiroptera (bats).It is absent in humans, ungulates (hoofed mammals), elephants, monotremes (platypus, echidna), marsupials, lagomorphs, hyenas, binturongs, sirenians, and cetaceans (whales, dolphins, and porpoises), among others. Evidence suggests that the baculum was independently evolved 9 times and lost in 10 separate lineages.
|
What type of bonds do alkanes only contain?
|
[
"hydrogen bonds",
"carbon-carbon single bonds",
"carbon-hydrogen bonds",
"hydrogen-carbon bonds"
] |
B
|
Alkanes contain only carbon-carbon single bonds.
alkane Also paraffin. Any fully saturated acyclic hydrocarbon, i.e. one in which all carbon–carbon bonds are single bonds. alkene Also olefin.
By virtue of their strong C–H bonds (~100 kcal/mol) and C–C bonds (~90 kcal/mol, but usually less sterically accessible), they are also relatively unreactive toward free radicals, although many electron-deficient radicals will react with alkanes in the absence of other electron-rich bonds (see below). This inertness is the source of the term paraffins (with the meaning here of "lacking affinity"). In crude oil the alkane molecules have remained chemically unchanged for millions of years.Free radicals, molecules with unpaired electrons, play a large role in most reactions of alkanes, such as cracking and reformation where long-chain alkanes are converted into shorter-chain alkanes and straight-chain alkanes into branched-chain isomers.
Cyclic alkanes are simply prefixed with "cyclo-": for example, C4H8 is cyclobutane (not to be confused with butene) and C6H12 is cyclohexane (not to be confused with hexene). Branched alkanes are named as a straight-chain alkane with attached alkyl groups. They are prefixed with a number indicating the carbon the group is attached to, counting from the end of the alkane chain.
The ionization of alkanes weakens the C-C bond, ultimately resulting in the decomposition. As the bond breaks, a charged, even electron species (R+) and a neutral radical species (R•) are generated. Highly substituted carbocations are more stable than the nonsubstituted ones. An example is depicted below.
Octacosanol is insoluble in water but freely soluble in low molecular-weight alkanes and in chloroform.
|
Which part of the wave helps make the wave bend and cause refraction?
|
[
"dense part",
"heavy part",
"bright part",
"shallow part"
] |
D
|
Lymph that collects in tissues slowly passes into tiny lymph vessels. Lymph then travels from smaller to larger lymph vessels. Muscles around the lymph vessels contract and squeeze the lymph through the vessels. The lymph vessels also contract to help move the lymph along. Eventually, lymph reaches the main lymph vessels, which are located in the chest. From these vessels, lymph drains into two large veins of the cardiovascular system. This is how lymph returns to the blood.
In the atmosphere, vertical gradients of wind speed and temperature lead to refraction. The wind speed is usually increasing with height, which leads to a downward bending of the sound rays towards the ground. The same holds if the temperature is increasing with height (inversion). If the temperature is decreasing with height and the wind speed is low, sound rays are bent upwards.
Light is emitted from a source such as a vapor lamp. A slit selects a thin strip of light which passes through the collimator where it gets parallelized. The aligned light then passes through the prism in which it is refracted twice (once when entering and once when leaving). Due to the nature of a dispersive element the angle with which light is refracted depends on its wavelength.
Rays—lines normal to wave crests between which a fixed amount of energy flux is contained—converge on local shallows and shoals. Therefore, the wave energy between rays is concentrated as they converge, with a resulting increase in wave height. Because these effects are related to a spatial variation in the phase speed, and because the phase speed also changes with the ambient current – due to the Doppler shift – the same effects of refraction and altering wave height also occur due to current variations. In the case of meeting an adverse current the wave steepens, i.e. its wave height increases while the wavelength decreases, similar to the shoaling when the water depth decreases.
The bottom exerts a frictional drag on the bottom of the wave, which decreases the celerity (or the speed of the waveform), and causes refraction. Slowing the wave forces it to shorten which increases the height and steepness, and the top (crest) falls because the velocity of the top of the wave becomes greater than the velocity of the bottom of the wave where the drag occurs.The surf zone is the place of convergence of multiple waves types creating complex wave patterns. A wave suitable for surfing results from maximum speeds of 5 metres per second (16 ft/s).
But Young was alone in such efforts until Fresnel entered the field.Huygens, in his investigation of double refraction, noticed something that he could not explain: when light passes through two similarly oriented calcite crystals at normal incidence, the ordinary ray emerging from the first crystal suffers only the ordinary refraction in the second, while the extraordinary ray emerging from the first suffers only the extraordinary refraction in the second; but when the second crystal is rotated 90° about the incident rays, the roles are interchanged, so that the ordinary ray emerging from the first crystal suffers only the extraordinary refraction in the second, and vice versa. This discovery gave Newton another reason to reject the wave theory: rays of light evidently had "sides". Corpuscles could have sides (or poles, as they would later be called); but waves of light could not, because (so it seemed) any such waves would need to be longitudinal (with vibrations in the direction of propagation).
|
What are passed from one generation to the next so species can survive?
|
[
"selections",
"mutations",
"fluctuations",
"adaptatioins"
] |
D
|
Death plays a role in extinction, the cessation of existence of a species or group of taxa, reducing biodiversity, due to extinction being generally considered to be the death of the last individual of that species (although the capacity to breed and recover may have been lost before this point). Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively.
Hence, the sixth mass extinction theme is applied to flora and fauna existing in diverse habitats, such as the Panamanian rainforest, the Great Barrier Reef, the Andes, Bikini Atoll, city zoos, and the author's own backyard. The book also applies this theme to a number of other habitats and organisms throughout the world. After researching the current mainstream view of the relevant peer-reviewed science, Kolbert estimates flora and fauna loss by the end of the 21st century to be between 20 and 50 percent "of all living species on earth".
In the context of space exploration, Haynes describes ecopoiesis as the "fabrication of a sustainable ecosystem on a currently lifeless, sterile planet". Fogg defines ecopoiesis as a type of planetary engineering and is one of the first stages of terraformation. This primary stage of ecosystem creation is usually restricted to the initial seeding of microbial life. A 2019 opinion piece by Lopez, Peixoto and Rosado has reintroduced microbiology as a necessary component of any possible colonization strategy based on the principles of microbial symbiosis and their beneficial ecosystem services. As conditions approach that of Earth, plant life could be brought in, and this will accelerate the production of oxygen, theoretically making the planet eventually able to support animal life.
The difference between the realized and the fundamental niche is important in understanding how interactions with a variety of different species in one environment affects the fitness of another species. This is not only important in understanding how a species functions in an ecosystem, but it is also important in determining the potential and realized success of invasive species. Invasive species could thrive or be killed off in an environment where they would theoretically be able to exist based on the presence or lack of there of different species. To survive, an invasive species first has to successfully survive the journey to the new area, they then have to be able to survive in that habitat.
The chief tactic was to produce a genetically diverse collection of trees for reproduction and reintroduction into the wild. Other priorities were to protect the habitat of remaining populations, and to study the disease and methods of propagation.Only two updates of the federal recovery plan have been published since the 1986 original recovery plan. There was an update in 2010 and another in 2020.
|
What kind of lines does a diffraction grating produce?
|
[
"nearly spaced lines",
"evenly spaced lines",
"properly spaced lines",
"randomly spaced lines"
] |
B
|
27.5 Single Slit Diffraction Light passing through a single slit forms a diffraction pattern somewhat different from those formed by double slits or diffraction gratings. Figure 27.21 shows a single slit diffraction pattern. Note that the central maximum is larger than those on either side, and that the intensity decreases rapidly on either side. In contrast, a diffraction grating produces evenly spaced lines that dim slowly on either side of center.
In optics, a diffraction grating is an optical grating with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structural coloration. The directions or diffraction angles of these beams depend on the wave (light) incident angle to the diffraction grating, the spacing or distance between adjacent diffracting elements (e.g., parallel slits for a transmission grating) on the grating, and the wavelength of the incident light. The grating acts as a dispersive element.
The slope of the triangular groove in a ruled grating is typically adjusted to enhance the brightness of a particular diffraction order. This is called blazing a grating.
The detailed diffracted light property distribution (e.g., intensity) depends on the detailed structure of the grating elements as well as on the number of elements in the grating, but it always gives maxima in the directions given by the grating equation. Depending on how a grating modulates incident light on it to cause the diffracted light, there are the following grating types. Transmission amplitude diffraction grating, that spatially and periodically modulates the intensity of an incident wave that transmits though the grating (and the diffracted wave is the consequence from this modulation).
Another method for manufacturing diffraction gratings uses a photosensitive gel sandwiched between two substrates. A holographic interference pattern exposes the gel, which is later developed. These gratings, called volume phase holography diffraction gratings (or VPH diffraction gratings) have no physical grooves, but instead a periodic modulation of the refractive index within the gel. This removes much of the surface scattering effects typically seen in other types of gratings.
The free spectral range of a diffraction grating is the largest wavelength range for a given order that does not overlap the same range in an adjacent order. If the (m + 1)-th order of λ {\displaystyle \lambda } and m-th order of ( λ + Δ λ ) {\displaystyle (\lambda +\Delta \lambda )} lie at the same angle, then Δ λ = λ m . {\displaystyle \Delta \lambda ={\frac {\lambda }{m}}.}
|
Which type of ferns have yellow sporangia and no leaves?
|
[
"Ostrich fern",
"Hothouse fern",
"whisk ferns",
"Boston fern"
] |
C
|
Forest and Kim Starr/Starr Environmental. Whisk ferns have yellow sporangia and no leaves . CC BY 3.0.
The ferns are also referred to as Polypodiophyta or, when treated as a subdivision of Tracheophyta (vascular plants), Polypodiopsida, although this name sometimes only refers to leptosporangiate ferns. Traditionally, all of the spore producing vascular plants were informally denominated the pteridophytes, rendering the term synonymous with ferns and fern allies. This can be confusing because members of the division Pteridophyta were also denominated pteridophytes (sensu stricto).
The Hymenophyllaceae, the filmy ferns and bristle ferns, are a family of two to nine genera (depending on classification system) and about 650 known species of ferns, with a subcosmopolitan distribution, but generally restricted to very damp places or to locations where they are wetted by spray from waterfalls or springs. A recent fossil find shows that ferns of Hymenophyllaceae have existed since at least the Upper Triassic.
Polysporangiophytes, also called polysporangiates or formally Polysporangiophyta, are plants in which the spore-bearing generation (sporophyte) has branching stems (axes) that bear sporangia. The name literally means 'many sporangia plant'. The clade includes all land plants (embryophytes) except for the bryophytes (liverworts, mosses and hornworts) whose sporophytes are normally unbranched, even if a few exceptional cases occur. While the definition is independent of the presence of vascular tissue, all living polysporangiophytes also have vascular tissue, i.e., are vascular plants or tracheophytes. Extinct polysporangiophytes are known that have no vascular tissue and so are not tracheophytes.
Fern species live in a wide variety of habitats, from remote mountain elevations, to dry desert rock faces, bodies of water or open fields. Ferns in general may be thought of as largely being specialists in marginal habitats, often succeeding in places where various environmental factors limit the success of flowering plants. Some ferns are among the world's most serious weed species, including the bracken fern growing in the Scottish highlands, or the mosquito fern (Azolla) growing in tropical lakes, both species forming large aggressively spreading colonies. There are four particular types of habitats that ferns are found in: moist, shady forests; crevices in rock faces, especially when sheltered from the full sun; acid wetlands including bogs and swamps; and tropical trees, where many species are epiphytes (something like a quarter to a third of all fern species).Especially the epiphytic ferns have turned out to be hosts of a huge diversity of invertebrates.
Semiaquatic plants include: Semiaquatic angiosperms (e.g., mangroves, water spinach, water cabbage, and the entire order Nymphaeales) Semiaquatic conifers, such as pond cypress Semiaquatic ferns, such as Pilularia americana A semiaquatic horsetail, Equisetum fluviatile Semiaquatic quillworts, such as Isoetes melanospora Semiaquatic club mosses, such as Lycopodiella inundata Semiaquatic mosses, such as Sphagnum macrophyllum Semiaquatic liverworts, such as Riccia fluitans
|
Ice masses, acquifers, and the deep ocean are examples of water what?
|
[
"lakes",
"reservoirs",
"seas",
"fields"
] |
B
|
The atmosphere is an exchange pool for water. Ice masses, aquifers, and the deep ocean are water reservoirs.
Water in the Beaufort Gyre is far less saline than that of the Chukchi Sea due to inflow from large Canadian and Siberian rivers.The final defined water mass in the Arctic Ocean is called Arctic Surface Water and is found in the depth range of 150–200 m (490–660 ft). The most important feature of this water mass is a section referred to as the sub-surface layer. It is a product of Atlantic water that enters through canyons and is subjected to intense mixing on the Siberian Shelf.
The "ice giant" (sometimes known as "water giant") planets Uranus and Neptune are thought to have a supercritical water ocean beneath their clouds, which accounts for about two-thirds of their total mass, most likely surrounding small rocky cores, although a 2006 study by Wiktorowicz and Ingersall ruled out the possibility of such a water "ocean" existing on Neptune. This kind of planet is thought to be common in extrasolar planetary systems.
The freshwater injected into the ocean by melting icebergs can change the density of the seawater in the vicinity of the iceberg. Fresh melt water released at depth is lighter, and therefore more buoyant, than the surrounding seawater causing it to rise towards the surface. Icebergs can also act as floating breakwaters, impacting ocean waves.Icebergs contain variable concentrations of nutrients and minerals that are released into the ocean during melting. Iceberg-derived nutrients, particularly the iron contained in sediments, can fuel blooms of phytoplankton. Samples collected from icebergs in Antarctica, Patagonia, Greenland, Svalbard, and Iceland, however, show that iron concentrations vary significantly, complicating efforts to generalize the impacts of icebergs on marine ecosystems.
Sea ice is the outcome of freezing seawater. It is porous and mechanically weaker than glacial ice. Sea ice dynamics are highly complex. Driven by winds and currents, sea ice may ultimately develop into pressure ridges, a pile-up of ice fragments, or rubble, making up long, linear features.
This condition is most commonly observed in the oceans around Antarctica where melting of the undersides of ice shelves at high-pressure results in liquid melt-water that can be below the freezing temperature. It is supposed that the water does not immediately refreeze due to a lack of nucleation sites. This provides a challenge to oceanographic instrumentation as ice crystals will readily form on the equipment, potentially affecting the data quality. Ultimately the presence of extremely cold seawater will affect the growth of sea ice.
|
This heat is used to convert water into steam, which is then used to turn a turbine, thus generating what?
|
[
"solar power",
"electrical power",
"radiation power",
"heating power"
] |
B
|
The generation of electricity is critical for the operation of nearly all aspects of modern society. The following diagram illustrates the types of fuels used to generate electrical power in the Unites States. In 2009, almost 45% of the power generated in the U. S. was derived from coal, with natural gas making up another 23% of the total. The third primary source of electrical energy is nuclear power, which accounts for approximately 20% of the total amount generated. All of these fuels give off energy in the form of heat. This heat is used to convert water into steam, which is then used to turn a turbine, thus generating electrical power.
Inside the tubes the cooling water runs in a parallel way, while steam moves in a vertical downward position from the wide opening at the top and travel through the tube. Furthermore, boilers are categorized as initial application of heat exchangers. The word steam generator was regularly used to describe a boiler unit where a hot liquid stream is the source of heat rather than the combustion products. Depending on the dimensions and configurations the boilers are manufactured. Several boilers are only able to produce hot fluid while on the other hand the others are manufactured for steam production.
A boiling water reactor uses demineralized water as a coolant and neutron moderator. Heat is produced by nuclear fission in the reactor core, and this causes the cooling water to boil, producing steam. The steam is directly used to drive a turbine, after which it is cooled in a condenser and converted back to liquid water. This water is then returned to the reactor core, completing the loop.
Steam turbines could be built to operate on higher pressure and temperature steam. A fundamental principle of thermodynamics is that the higher the temperature of the steam entering an engine, the higher the efficiency. The introduction of steam turbines motivated a series of improvements in temperatures and pressures. The resulting increased conversion efficiency lowered electricity prices.The power density of boilers was increased by using forced combustion air and by using compressed air to feed pulverized coal. Also, coal handling was mechanized and automated.
The extracted or exhaust steam is used for process heating. Steam at ordinary process heating conditions still has a considerable amount of enthalpy that could be used for power generation, so cogeneration has an opportunity cost. A typical power generation turbine in a paper mill may have extraction pressures of 160 psig (1.103 MPa) and 60 psig (0.41 MPa).
A turbine ( or ) (from the Greek τύρβη, tyrbē, or Latin turbo, meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical power when combined with a generator. A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor.
|
What atmospheric layer lies above the highest altitude an airplane can go and below the lowest altitude a spacecraft can orbit?
|
[
"mesosphere",
"stratosphere",
"troposphere",
"thermosphere"
] |
A
|
Not so fast. The mesosphere is the least known layer of the atmosphere. The mesosphere lies above the highest altitude an airplane can go. It lies below the lowest altitude a spacecraft can orbit. Maybe that's just as well. If you were in the mesosphere without a space suit, your blood would boil! This is because the pressure is so low that liquids would boil at normal body temperature.
The stratosphere () is the second layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air high in the sky and the cool layers of air in the low sky, close to the planetary surface of the Earth. The increase of temperature with altitude is a result of the absorption of the Sun's ultraviolet (UV) radiation by the ozone layer. The temperature inversion is in contrast to the troposphere, near the Earth's surface, where temperature decreases with altitude.
Since the tropopause responds to the average temperature of the entire layer that lies underneath it, it is at its maximum levels over the Equator, and reaches minimum heights over the poles. On account of this, the coolest layer in the atmosphere lies at about 17 km over the equator. Due to the variation in starting height, the tropopause extremes are referred to as the equatorial tropopause and the polar tropopause.
The middle layer of the Uranian atmosphere is the stratosphere, where temperature generally increases with altitude from 53 K (−220 °C; −364 °F) in the tropopause to between 800 and 850 K (527 and 577 °C; 980 and 1,070 °F) at the base of the thermosphere. The heating of the stratosphere is caused by absorption of solar UV and IR radiation by methane and other hydrocarbons, which form in this part of the atmosphere as a result of methane photolysis. Heat is also conducted from the hot thermosphere. The hydrocarbons occupy a relatively narrow layer at altitudes of between 100 and 300 km corresponding to a pressure range of 1000 to 10 Pa and temperatures of between 75 and 170 K (−198 and −103 °C; −325 and −154 °F).The most abundant hydrocarbons are methane, acetylene and ethane with mixing ratios of around 10−7 relative to hydrogen.
Within the five principal layers above, which are largely determined by temperature, several secondary layers may be distinguished by other properties: The ozone layer is contained within the stratosphere. In this layer ozone concentrations are about 2 to 8 parts per million, which is much higher than in the lower atmosphere but still very small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from about 15–35 km (9.3–21.7 mi; 49,000–115,000 ft), though the thickness varies seasonally and geographically. About 90% of the ozone in Earth's atmosphere is contained in the stratosphere.
Under specific circumstances, upper level cold lows can break off from the base of the tropical upper tropospheric trough (TUTT), which is located mid-ocean in the Northern Hemisphere during the summer months. These upper tropospheric cyclonic vortices, also known as TUTT cells or TUTT lows, usually move slowly from east-northeast to west-southwest, and their bases generally do not extend below 20,000 feet (6,100 m) in altitude. A weak inverted surface trough within the trade wind is generally found underneath them, and they may also be associated with broad areas of high-level clouds.
|
Where are sensors for thermoregulation concentrated in the brain?
|
[
"thyroid",
"pituitary gland",
"the hypothalamus",
"medulla"
] |
C
|
The morphology for heat exchange occurs via cerebral arteries and the ophthalmic rete, a network of arteries originating from the ophthalmic artery. The ophthalmic rete is analogous to the carotid rete found in mammals, as it also facilitates transfer of heat from arterial blood coming from the core to venous blood returning from the evaporative surfaces at the head.Researchers suggest that common ostriches also employ a 'selective brain warming' mechanism in response to cooler surrounding temperatures in the evenings. The brain was found to maintain a warmer temperature when compared to carotid arterial blood supply.
It also contains mechanoreceptors that provide the sense of touch and thermoreceptors that provide the sense of heat. In addition, hair follicles, sweat glands, sebaceous glands (oil glands), apocrine glands, lymphatic vessels, nerves and blood vessels are present in the dermis. Those blood vessels provide nourishment and waste removal for both dermal and epidermal cells.
Subsequently, the blood travelling through the dilated skin vessels is heated during circulation. Delivery of the heat to subcutaneous regions of the body is facilitated by the body's impaired vasodilation.Skin temperature may also be an indicator of the presence of cancer. Widespread methods for detection of cancer involve identification of non-neuronal thermoregulation of blood perfusion as well as periodic alterations to, or aberrant oscillations in, the spatial homogeneity of skin temperature.
A medical thermometer or clinical thermometer is a device used for measuring human or animal body temperature. The tip of the thermometer is inserted into the mouth under the tongue (oral or sub-lingual temperature), under the armpit (axillary temperature), into the rectum via the anus (rectal temperature), into the ear (tympanic temperature), or on the forehead (temporal temperature).
Other receptors, neurokinin 3 receptors, which are expressed in the median preoptic nucleus, are also involved in thermoregulation. Activation of these receptors in rats causes decrease in core temperature. These receptors are highly expressed in the median preoptic area in response to decreased estrogen levels in menopausal women, and are thought to play a role in the generation of hot flashes during menopause.
|
What is the first step in the breakdown of glucose to extract energy for cellular metabolism?
|
[
"mutation",
"mitosis",
"glycolysis",
"photosynthesis"
] |
C
|
7.2 | Glycolysis By the end of this section, you will be able to: • Describe the overall result in terms of molecules produced in the breakdown of glucose by glycolysis • Compare the output of glycolysis in terms of ATP molecules and NADH molecules produced You have read that nearly all of the energy used by living cells comes to them in the bonds of the sugar, glucose. Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. Nearly all living organisms carry out glycolysis as part of their metabolism. The process does not use oxygen and is therefore anaerobic. Glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells. Glucose enters heterotrophic cells in two ways. One method is through secondary active transport in which the transport takes place against the glucose concentration gradient. The other mechanism uses a group of integral proteins called GLUT proteins, also known as glucose transporter proteins. These transporters assist in the facilitated diffusion of glucose. Glycolysis begins with the six carbon ring-shaped structure of a single glucose molecule and ends with two molecules of a three-carbon sugar called pyruvate. Glycolysis consists of two distinct phases. The first part of the glycolysis pathway traps the glucose molecule in the cell and uses energy to modify it so that the six-carbon sugar molecule can be split evenly into the two three-carbon molecules. The second part of glycolysis extracts energy from the molecules and stores it in the form of ATP and NADH, the reduced form of NAD.
An alternative route for glucose breakdown is the pentose phosphate pathway, which reduces the coenzyme NADPH and produces pentose sugars such as ribose, the sugar component of nucleic acids.Fats are catabolized by hydrolysis to free fatty acids and glycerol. The glycerol enters glycolysis and the fatty acids are broken down by beta oxidation to release acetyl-CoA, which then is fed into the citric acid cycle. Fatty acids release more energy upon oxidation than carbohydrates.
The first step in ED is phosphorylation of glucose by a family of enzymes called hexokinases to form glucose 6-phosphate (G6P). This reaction consumes ATP, but it acts to keep the glucose concentration low, promoting continuous transport of glucose into the cell through the plasma membrane transporters. In addition, it blocks the glucose from leaking out – the cell lacks transporters for G6P, and free diffusion out of the cell is prevented due to the charged nature of G6P. Glucose may alternatively be formed from the phosphorolysis or hydrolysis of intracellular starch or glycogen.
Phosphorylation of sugars is often the first stage in their catabolism. Phosphorylation allows cells to accumulate sugars because the phosphate group prevents the molecules from diffusing back across their transporter. Phosphorylation of glucose is a key reaction in sugar metabolism. The chemical equation for the conversion of D-glucose to D-glucose-6-phosphate in the first step of glycolysis is given by: D-glucose + ATP → D-glucose 6-phosphate + ADPΔG° = −16.7 kJ/mol (° indicates measurement at standard condition)
Glucose metabolism begins with glycolysis, in which the molecule is broken down into pyruvate in ten enzymatic steps. A significant proportion of pyruvate is converted into lactate (usually 10:1). The human metabolism produces about 20 mmol/kg of lactic acid every 24 hours. This happens predominantly in tissues (especially muscle) that have high levels of the "A" isoform of the enzyme lactate dehydrogenase (LDHA), which predominantly converts pyruvate into lactate.
High blood glucose releases insulin, stimulating the translocation of specific glucose transporters to the cell membrane; glucose is phosphorylated to glucose 6-phosphate during transport across the membrane by ATP-D-glucose 6-phosphotransferase and non-specific hexokinase (ATP-D-hexose 6-phosphotransferase). Liver cells are freely permeable to glucose, and the initial rate of phosphorylation of glucose is the rate-limiting step in glucose metabolism by the liver.The liver's crucial role in controlling blood sugar concentrations by breaking down glucose into carbon dioxide and glycogen is characterized by the negative Gibbs free energy (ΔG) value, which indicates that this is a point of regulation with. The hexokinase enzyme has a low Michaelis constant (Km), indicating a high affinity for glucose, so this initial phosphorylation can proceed even when glucose levels at nanoscopic scale within the blood.
|
What charge do atoms carry?
|
[
"negative",
"static",
"neutral",
"positive"
] |
C
|
Atoms, which are always neutral in electric charge, contain electrons as well as protons and neutrons. An electron has an electrical charge of -1. If an atom has three electrons, infer how many protons it has.
Atoms are the smallest neutral particles into which matter can be divided by chemical reactions. An atom consists of a small, heavy nucleus surrounded by a relatively large, light cloud of electrons. An atomic nucleus typically consists of 1 or more protons and 0 or more neutrons. Protons and neutrons are, in turn, made of quarks.
Substances composed of discrete molecules or single atoms are held together by weaker attractive forces between the molecules, such as the London dispersion force: as electrons move within the molecules, they create momentary imbalances of electrical charge, which induce similar imbalances on nearby molecules and create synchronised movements of electrons across many neighbouring molecules.The more electropositive atoms, however, tend to instead lose electrons, creating a "sea" of electrons engulfing cations. The outer orbitals of one atom overlap to share electrons with all its neighbours, creating a giant structure of molecular orbitals extending over all the atoms. This negatively charged "sea" pulls on all the ions and keeps them together in a metallic bond.
Fluorine atoms have nine electrons, one fewer than neon, and electron configuration 1s22s22p5: two electrons in a filled inner shell and seven in an outer shell requiring one more to be filled. The outer electrons are ineffective at nuclear shielding, and experience a high effective nuclear charge of 9 − 2 = 7; this affects the atom's physical properties.Fluorine's first ionization energy is third-highest among all elements, behind helium and neon, which complicates the removal of electrons from neutral fluorine atoms. It also has a high electron affinity, second only to chlorine, and tends to capture an electron to become isoelectronic with the noble gas neon; it has the highest electronegativity of any reactive element. Fluorine atoms have a small covalent radius of around 60 picometers, similar to those of its period neighbors oxygen and neon.
Partial atomic charges can be used to quantify the degree of ionic versus covalent bonding of any compound across the periodic table. The necessity for such quantities arises, for example, in molecular simulations to compute bulk and surface properties in agreement with experiment. Evidence for chemically different compounds shows that available experimental data and chemical understanding lead to justified atomic charges. Atomic charges for a given compound can be derived in multiple ways, such as: extracted from electron densities measured using high resolution x-ray, gamma ray, or electron beam diffraction experiments measured dipole moments the Extended Born thermodynamic cycle, including an analysis of covalent and ionic bonding contributions spectroscopically measured properties, such as core-electron binding energy shifts the relationship of atomic charges to melting points, solubility, and cleavage energies for a set of similar compounds with similar degree of covalent bonding the relationship of atomic charges to chemical reactivity and reaction mechanisms for similar compounds reported in the literature.The discussion of individual compounds in prior work has shown convergence in atomic charges, i.e., a high level of consistency between the assigned degree of polarity and the physical-chemical properties mentioned above.
The charge of an antiparticle equals that of the corresponding particle, but with opposite sign. The electric charge of a macroscopic object is the sum of the electric charges of the particles that it's made up of. This charge is often small, because matter is made of atoms, and atoms typically have equal numbers of protons and electrons, in which case their charges cancel out, yielding a net charge of zero, thus making the atom neutral.
|
The pleura that surrounds the lungs consists of how many layers?
|
[
"one",
"two",
"four",
"three"
] |
B
|
The pleura that surrounds the lungs consists of two layers, the ________. visceral and parietal pleurae. mediastinum and parietal pleurae. visceral and mediastinum pleurae. none of the above 14. Which of the following processes does atmospheric pressure play a role in? a. pulmonary ventilation b. production of pulmonary surfactant c. resistance d. surface tension 15. A decrease in volume leads to a(n) ________ pressure.
Both lungs have a central recession called the hilum, where the blood vessels and airways pass into the lungs making up the root of the lung. There are also bronchopulmonary lymph nodes on the hilum.The lungs are surrounded by the pulmonary pleurae. The pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs. Between the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid.
It innervates the bronchial tree and the visceral pleura. According to the relation of nerves to the root of the lung, the pulmonary plexus is divided into the anterior pulmonary plexus, which lies in front of the lung and the posterior pulmonary plexus, which lies behind the lung. The anterior pulmonary plexus is close in proximity to the pulmonary artery. The posterior pulmonary plexus is bounded by the superior edge of the pulmonary artery and the lower edge of the pulmonary vein. Both lungs are innervated primarily by the posterior pulmonary plexus; it accounts for 74–77% of the total innervation.
Since the effusion has greater density than the rest of the lung, it gravitates towards the lower portions of the pleural cavity. The pleural effusion behaves according to basic fluid dynamics, conforming to the shape of pleural space, which is determined by the lung and chest wall. If the pleural space contains both air and fluid, then an air-fluid level that is horizontal will be present, instead of conforming to the lung space.
The epithelial lining of the upper respiratory tract is interspersed with goblet cells that secrete a protective mucus. This helps to filter waste, which is eventually either swallowed into the highly acidic stomach environment or expelled via spitting. The epithelium lining the respiratory tract is covered in small hairs called cilia. These beat rhythmically out from the lungs, moving secreted mucus foreign particles toward the laryngopharynx upwards and outwards, in a process called mucociliary clearance, they prevent mucus accumulation in the lungs.
Respiratory epithelium, or airway epithelium, is a type of ciliated columnar epithelium found lining most of the respiratory tract as respiratory mucosa, where it serves to moisten and protect the airways. It is not present in the vocal cords of the larynx, or the oropharynx and laryngopharynx, where instead the epithelium is stratified squamous. It also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by the secretion of mucus and the action of mucociliary clearance.
|
Organisms that obtain food from outside themselves (i.e. they don't make their own food) are known as what?
|
[
"autotrophs",
"zygotes",
"fungi",
"heterotrophs"
] |
D
|
Fungi are heterotrophs, meaning they obtain food from outside themselves.
Fish that consume detritus and gain energy by processing its organic material are called detritivores. Omnivores ingest a wide variety of prey, encompassing floral, faunal, and detrital material. Finally, members of the parasitic guild acquire nutrition from a host species, usually another fish or large vertebrate.
Overall, however, approximately 16% of food is imported from abroad.The structures of organopónicos vary from garden to garden. Some are run by state employees, others are run cooperatively by the gardeners themselves. The government provides community farmers with the land and the water, and sells key materials such as organic compost, seeds, irrigation parts, and organic pesticides called "biocontrols" in the form of beneficial insects and plant-based oils.
In the deep sea, food chains centered on hydrothermal vents and cold seeps exist in the absence of sunlight. Chemosynthetic bacteria and archaea use hydrogen sulfide and methane from hydrothermal vents and cold seeps as an energy source (just as plants use sunlight) to produce carbohydrates; they form the base of the food chain. Consumers are organisms that eat other organisms.
Some species feed on bracket and other fungi and mycelium or on living plants (sometimes as leaf miners). Some are predators or parasites of earthworms, snails, spiders, centipedes, millipedes, and insect eggs, larvae, and pupae. The adults feed on nectar, honeydew, and the juices exuding from fresh carrion and dung.
Food webs provide a framework within which a complex network of predator–prey interactions can be organised. A food web model is a network of food chains. Each food chain starts with a primary producer or autotroph, an organism, such as a plant, which is able to manufacture its own food. Next in the chain is an organism that feeds on the primary producer, and the chain continues in this way as a string of successive predators.
|
In scientific investigations, descriptive statistics are useful for summarizing the characteristics of large what?
|
[
"organisms",
"questions",
"samples",
"tissues"
] |
C
|
The girls in the picture above make up a small sample—there are only four of them. In scientific investigations, samples may include hundreds or even thousands of people or other objects of study. Especially when samples are very large, it’s important to be able to summarize their overall characteristics with a few numbers. That’s where descriptive statistics come in. Descriptive statistics are measures that show the central tendency, or center, of a sample or the variation in a sample.
Thus, descriptive research cannot be used as the basis of a causal relationship, where one variable affects another. In other words, descriptive research can be said to have a low requirement for internal validity. The description is used for frequencies, averages, and other statistical calculations. Often the best approach, prior to writing descriptive research, is to conduct a survey investigation. Qualitative research often has the aim of description and researchers may follow up with examinations of why the observations exist and what the implications of the findings are.
In general, simple statistics allow for observations concerning specimen values across space and over time, while more complex statistics facilitate the recognition of patterning within an assemblage, as well as the presentation of large datasets. The application of different statistical techniques depends on the quantity of material available. Complex statistics require the recovery of a large number of specimens (usually around 150 from each sample involved in this type of quantitative analysis), whereas simple statistics can be applied regardless of the amount of recovered specimens – though obviously, the more specimens, the more effective the results. The quantification of microbotanical remains differs slightly from that of macrobotanical remains, mostly due to the high numbers of microbotanical specimens that are usually present in samples. As a result, relative/percentage occurrence sums are usually employed in the quantification of microbotanical remains instead of absolute taxa counts.
Statistics in Biosciences is a triannual peer-reviewed academic journal published by Springer Science+Business Media. It is the official journal of the International Chinese Statistical Association. It covers the development and application of statistical methods and their interface with other quantitative methods, such as computational and mathematical methods, in biological and life science, health science, and biopharmaceutical and biotechnological science. The journal publishes scientific papers in four formats: original articles, case studies and practice articles, review articles, and commentaries.
In descriptive statistics, the seven-number summary is a collection of seven summary statistics, and is an extension of the five-number summary. There are three similar, common forms. As with the five-number summary, it can be represented by a modified box plot, adding hatch-marks on the "whiskers" for two of the additional numbers.
Statistical analysis is essential to the field of environmental sciences, allowing researchers to gain an understanding of environmental issues through researching and developing potential solutions to the issues they study. The applications of statistical methods to environmental sciences are numerous and varied. Environmental statistics are used in many fields including; health and safety organizations, standard bodies, research institutes, water and river authorities, meteorological organizations, fisheries, protection agencies, and in risk, pollution, regulation and control concerns.Environmental statistics is especially pertinent and widely used in the academic, governmental, regulatory, technological, and consulting industries.Specific applications of statistical analysis within the field of environmental science include earthquake risk analysis, environmental policymaking, ecological sampling planning, environmental forensics.Within the scope of environmental statistics, there are two main categories of their uses. Descriptive statistics is not used to make inferences about data, but simply to describe its characteristics. Inferential statistics is used to make inferences about data, test hypotheses or make predictions.Types of studies covered in environmental statistics include: Baseline studies to document the present state of an environment to provide background in case of unknown changes in the future; Targeted studies to describe the likely impact of changes being planned or of accidental occurrences; Regular monitoring to attempt to detect changes in the environment.
|
The process of the cytoplasm splitting apart and the cell pinching in two is known as what?
|
[
"mitosis",
"electrolysis",
"cytokinesis",
"budding"
] |
C
|
The cell wall grows toward the center of the cell. The cytoplasm splits apart, and the cell pinches in two. This is called cytokinesis .
Cytokinesis, the pinching of the cell membrane in animal cells or the formation of the cell wall in plant cells, occurs, completing the creation of two daughter cells. However, cytokinesis does not fully complete resulting in "cytoplasmic bridges" which enable the cytoplasm to be shared between daughter cells until the end of meiosis II. Sister chromatids remain attached during telophase I. Cells may enter a period of rest known as interkinesis or interphase II. No DNA replication occurs during this stage.
First, it reproduces both by cell division (splitting one cell into two) and by conjugation, in which two organisms temporarily join in order to swap DNA. Second, it has two cell nuclei. The larger, called the "macronucleus", carries out the normal work of the cell by transcribing DNA into RNA, which is used to control the cell's functions.
Embryo splitting can be used for twinning to increase the number of available embryos. Cytoplasmic transfer is where the cytoplasm from a donor egg is injected into an egg with compromised mitochondria. The resulting egg is then fertilised with sperm and introduced into a womb, usually that of the woman who provided the recipient egg and nuclear DNA. Cytoplasmic transfer was created to aid women who experience infertility due to deficient or damaged mitochondria, contained within an egg's cytoplasm.
The phragmoplast is a complex assembly of microtubules (MTs), microfilaments (MFs), and endoplasmic reticulum (ER) elements, that assemble in two opposing sets perpendicular to the plane of the future cell plate during anaphase and telophase. It is initially barrel-shaped and forms from the mitotic spindle between the two daughter nuclei while nuclear envelopes reassemble around them. The cell plate initially forms as a disc between the two halves of the phragmoplast structure. While new cell plate material is added to the edges of the growing plate, the phragmoplast microtubules disappear in the center and regenerate at the edges of the growing cell plate.
After fusion of the cells, the further fusion of their nuclei is delayed. Instead, a nucleus from the fertilizing cell and a nucleus from the ascogonium become associated and begin to divide synchronously. The products of these nuclear divisions (still in pairs of unlike mating type, i.e. A/a) migrate into numerous ascogenous hyphae, which then begin to grow out of the ascogonium.
|
What kind of mountainous formation can often be found near trenches?
|
[
"earthquakes",
"caves",
"craters",
"volcanoes"
] |
D
|
deep sea trenches : Trenches are found in the sea. Some are near the edges of continents. Trenches are found near chains of active volcanoes. An example is the line of the very deepest blue, off of western South America.
)The formation process usually begins when the sea attacks lines of weakness, such as steep joints or small fault zones in a cliff face. These cracks then gradually get larger and turn into caves. If a cave wears through a headland, an arch forms.
There are three main types of mountains: volcanic, fold, and block. All three types are formed from plate tectonics: when portions of the Earth's crust move, crumple, and dive. Compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. The height of the feature makes it either a hill or, if higher and steeper, a mountain. Major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity.
These soils are formed in mountainous regions out of fine grains produced by weathering. However, due to various reasons, this fine grained material constantly slides down the slope. As a result, the time necessary for the formation of soils does not become available.
The formation is described by W.G. Pierce as thick-bedded, buff-colored sandstone, and drab to green shale. It is Upper Cretaceous in age.The formation varies in thickness from about 90 m (300 ft.) in North Dakota, to almost 600 m (2,000 ft.) in parts of Wyoming.
Trench morphology is strongly modified by the amount of sedimentation in the trench. This varies from practically no sedimentation, as in the Tonga-Kermadec trench, to almost completely filled with sediments, as with the southern Lesser Antilles trench or the eastern Alaskan trench. Sedimentation is largely controlled by whether the trench is near a continental sediment source.
|
Because it can be controlled intentionally, skeletal muscle is also called what type of muscle?
|
[
"automatic",
"necessary",
"involuntary",
"voluntary"
] |
D
|
Skeletal muscle tissue forms skeletal muscles, which attach to bones and sometimes the skin and control locomotion and any other movement that can be consciously controlled. Because it can be controlled intentionally, skeletal muscle is also called voluntary muscle. When viewed under a microscope, skeletal muscle tissue has a striped or striated appearance. This appearance results from the arrangement of the proteins inside the cell that are responsible for contraction. The cells of skeletal muscle are long and tapered and have multiple nuclei on the periphery of each cell. Smooth muscle tissue occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as in the respiratory tract and blood vessels. Smooth muscle has no striations, is not under voluntary control, and is called involuntary muscle. Smooth muscle cells have a single nucleus. Cardiac muscle tissue is only found in the heart. The contractions of cardiac muscle tissue pump blood throughout the body and maintain blood pressure. Like skeletal muscle, cardiac muscle is striated, but unlike skeletal muscle, cardiac muscle cannot be consciously controlled and is called involuntary muscle. The cells of cardiac muscle tissue are connected to each other through intercalated disks and usually have just one nucleus per cell.
Muscle action that moves the axial skeleton work over a joint with an origin and insertion of the muscle on respective side. The insertion is on the bone deemed to move towards the origin during muscle contraction. Muscles are often present that engage in several actions of the joint; able to perform for example both flexion and extension of the forearm as in the biceps and triceps respectively. This is not only to be able to revert actions of muscles, but also brings on stability of the actions though muscle coactivation.
There are three distinct types of muscle: skeletal muscle, cardiac or heart muscle, and smooth (non-striated) muscle. Muscles provide strength, balance, posture, movement, and heat for the body to keep warm.There are approximately 640 muscles in an adult male human body. A kind of elastic tissue makes up each muscle, which consists of thousands, or tens of thousands, of small muscle fibers. Each fiber comprises many tiny strands called fibrils, impulses from nerve cells control the contraction of each muscle fiber.
This stabilization mechanism is also important for unexpected loads impeded on the joint, allowing the muscles to quickly coactivate and provide stability to the joint. This mechanism is controlled neuromuscularly, which allows the muscle(s) to contract. This occurs through a motor neuron sending a signal (through creating action potentials) to the muscle fiber to contract by releasing acetylcholine.
The skeletal muscle pump or musculovenous pump is a collection of skeletal muscles that aid the heart in the circulation of blood. It is especially important in increasing venous return to the heart, but may also play a role in arterial blood flow.
The muscle spindle is a proprioceptive organ that lies embedded in the muscle. It consists of bag- and chain-type fibers, which correspond to dynamic and static responses, respectively. Spindles relay information through primary (Group Ia) and secondary (Group II) sensory afferents, with the primary afferent attached at the nucleus of the spindle and the secondary afferent attached at the end of the spindle. Spindles are conventionally thought of as encoding muscle length, velocity, and acceleration, however there is evidence to suggest that they respond to the force and yank (the first time-derivative of force) exerted on intrafusal muscle.
|
What effect in the atmosphere ensures that the earth maintains the correct temperature to support life?
|
[
"coriolis effect",
"greenhouse effect",
"ozone effect",
"smog effect"
] |
B
|
When sunlight heats Earth’s surface, some of the heat radiates back into the atmosphere. Some of this heat is absorbed by gases in the atmosphere. This is the greenhouse effect , and it helps to keep Earth warm. The greenhouse effect allows Earth to have temperatures that can support life.
The atmosphere of Earth also plays an important role. The ozone layer protects the planet from the harmful radiations from the sun, and free oxygen is abundant enough for the breathing needs of terrestrial life. Earth's magnetosphere, generated by its active core, is also important for the long-term habitability of Earth, as it prevents the solar winds from stripping the atmosphere out of the planet.
The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth are vital to the existence of life on Earth as we know it. The Earth is located in the habitable zone of the Solar System; if it were slightly closer to or farther from the Sun (about 5%, or about 8 million kilometers), the conditions which allow the three forms to be present simultaneously would be far less likely to exist.Earth's gravity allows it to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provide a temperature buffer (greenhouse effect) which helps maintain a relatively steady surface temperature.
Over the past 150 years human activities have released increasing quantities of greenhouse gases into the atmosphere. This has led to increases in mean global temperature, or global warming. Other human effects are relevant—for example, sulphate aerosols are believed to have a cooling effect. Natural factors also contribute.
However, because the Stefan–Boltzmann response mandates that this hotter planet emits more energy, eventually a new radiation balance can be reached and the temperature will be maintained at its new, higher value. Positive climate change feedbacks amplify changes in the climate system, and can lead to destabilizing effects for the climate. An increase in temperature from greenhouse gases leading to increased water vapor (which is itself a greenhouse gas) causing further warming is a positive feedback, but not a runaway effect, on Earth.
However, detrimental impacts of global warming, such as increased instances of heat and drought stress, mean that the overall effect is likely to be a reduction in plant productivity. Reduced plant productivity would be expected to accelerate the rate of global warming. Overall, these observations point to the importance of avoiding further increases in atmospheric CO2 rather than risking runaway climate change.
|
Felsic, intermediate, mafic, and ultramafic are types of composition of what rock group?
|
[
"igneous",
"Sedimentary",
"asteroids",
"metamorphic"
] |
A
|
Igneous rocks are classified by composition and texture. The composition can be felsic, intermediate, mafic, or ultramafic. The composition depends on the minerals the rock includes. A felsic rock will contain felsic minerals.
It is often separated from the others as the "alkali" or "soda" rocks, and there is a corresponding series of mafic rocks. Lastly, a small sub-group rich in olivine and without feldspar has been called the "ultramafic" rocks.
Ultramafic rock and carbonatites have their own specialized classification, but these rarely occur as volcanic rocks. Some fields of the TAS diagram are further subdivided by the ratio of potassium oxide to sodium oxide.
Feldspar (sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium-sodium) feldspars. Feldspars make up about 60% of the Earth's crust, and 41% of the Earth's continental crust by weight.Feldspars crystallize from magma as both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are also found in many types of sedimentary rocks.
Carbon dioxide has less severe impacts on mafic, felsic and rocks of other composition, such as carbonate rocks, chemical sediments, etcetera. The exception to this rule is the calc-silicate family of metamorphic rocks, which are also subjected to wide variations in mineral speciation due to the mobility of carbonate during metamorphism. Felsic and mafic rocks tend to be less affected by carbon dioxide due to their higher aluminium content. Ultramafic rocks lack aluminium, which allows carbonate to react with magnesium silicates to form talc.
Epigenetic change (secondary processes occurring at low temperatures and low pressures) may be arranged under a number of headings, each of which is typical of a group of rocks or rock-forming minerals, though usually more than one of these alterations is in progress in the same rock. Silicification, the replacement of the minerals by crystalline or crypto-crystalline silica, is most common in felsic rocks, such as rhyolite, but is also found in serpentine, etc. Kaolinization is the decomposition of the feldspars, which are the most common minerals in igneous rocks, into kaolin (along with quartz and other clay minerals); it is best shown by granites and syenites. Serpentinization is the alteration of olivine to serpentine (with magnetite); it is typical of peridotites, but occurs in most of the mafic rocks. In uralitization, secondary hornblende replaces augite; chloritization is the alteration of augite (biotite or hornblende) to chlorite, and is seen in many diabases, diorites and greenstones. Epidotization occurs also in rocks of this group, and consists in the development of epidote from biotite, hornblende, augite or plagioclase feldspar.
|
What is the base of nearly all food chains on earth?
|
[
"photosynthesis",
"glycolysis",
"atherosclerosis",
"synthesis"
] |
A
|
Photosynthesis is the base of nearly all food chains on Earth. This is true of marine food chains, too.
Food webs provide a framework within which a complex network of predator–prey interactions can be organised. A food web model is a network of food chains. Each food chain starts with a primary producer or autotroph, an organism, such as a plant, which is able to manufacture its own food. Next in the chain is an organism that feeds on the primary producer, and the chain continues in this way as a string of successive predators.
In the deep sea, food chains centered on hydrothermal vents and cold seeps exist in the absence of sunlight. Chemosynthetic bacteria and archaea use hydrogen sulfide and methane from hydrothermal vents and cold seeps as an energy source (just as plants use sunlight) to produce carbohydrates; they form the base of the food chain. Consumers are organisms that eat other organisms.
A food web, or food chain, is an example of directed network which describes the prey-predator relationship in a given ecosystem. Vertices in this type of network represent species, and the edges the prey-predator relationship. A collection of species may be represented by a single vertex if all members in that collection prey upon and are preyed on by the same organisms.
Together, these factors demonstrate that a food web's structure affects its sensitivity to reductions in biodiversity, highlighting the importance of food web studies. Amino acid isotopes are an important tool used in this field.The abundance of 15N in some amino acids reflects an organism's position in a food web. This is due to the ways organisms metabolize different amino acids when they are consumed.
A food web is often acyclic, with few exceptions such as adults preys on juveniles and parasitism. Note: In the food web main article, a food web was depicted as cyclic. That is based on the flow of the carbon and energy sources in a given ecosystem. The food web described here based solely on prey-predator roles; Organisms active in the carbon and nitrogen cycles (such as decomposers and fixers) are not considered in this description.
|
The skull is a part of a vertebrate endoskeleton that encloses and protects what organ?
|
[
"nervous system",
"lung",
"brain",
"heart"
] |
C
|
part of a vertebrate endoskeleton that encloses and protects the brain; also called the skull.
A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan "skeleton" consists of microscopic calcareous or siliceous spicules or a spongin network.
Later in development, the bone structure breaks loose from the jaw and migrates to the inner ear area. The structure is known as the middle ear, and is made up of the stapes, incus, malleus, and tympanic membrane. These correspond to the columella, quadrate, articular, and angular structures in the amphibian, bird or reptile jaw.
The ethmoidal labyrinth or lateral mass of the ethmoid bone consists of a number of thin-walled cellular cavities, the ethmoid air cells, arranged in three groups, anterior, middle, and posterior, and interposed between two vertical plates of bone; the lateral plate forms part of the orbit, the medial plate forms part of the nasal cavity. In the disarticulated bone many of these cells are opened into, but when the bones are articulated, they are closed in at every part, except where they open into the nasal cavity.
The ethmoid bone is an anterior cranial bone located between the eyes. It contributes to the medial wall of the orbit, the nasal cavity, and the nasal septum. The ethmoid has three parts: cribriform plate, ethmoidal labyrinth, and perpendicular plate. The cribriform plate forms the roof of the nasal cavity and also contributes to formation of the anterior cranial fossa, the ethmoidal labyrinth consists of a large mass on either side of the perpendicular plate, and the perpendicular plate forms the superior two-thirds of the nasal septum. Between the orbital plate and the nasal conchae are the ethmoidal sinuses or ethmoidal air cells, which are a variable number of small cavities in the lateral mass of the ethmoid.
Though invertebrate chordates – such as the tunicate larvae or the lancelets – have heads, there has been a question of how the vertebrate head, characterized by a bony skull clearly separated from the main body, might have evolved from the head structures of these animals.According to Hyman (1979), the evolution of the head in the vertebrates has occurred by the fusion of a fixed number of anterior segments, in the same manner as in other "heteronomously segmented animals". In some cases, segments or a portion of the segments disappear. The head segments also lose most of their systems, except for the nervous system. With the progressive development of cephalization, "the head incorporates more and more of the adjacent segments into its structure, so that in general it may be said that the higher the degree of cephalization the greater is the number of segments composing the head".In the 1980s, the "new head hypothesis" was proposed, suggesting that the vertebrate head is an evolutionary novelty resulting from the emergence of neural crest and cranial placodes. In 2014, a transient larva tissue of the lancelet was found to be virtually indistinguishable from the neural crest-derived cartilage which forms the vertebrate skull, suggesting that persistence of this tissue and expansion into the entire headspace could be a viable evolutionary route to formation of the vertebrate head.
|
The global pattern of precipitation is influenced by movements of what?
|
[
"pollution masses",
"air masses",
"air valleys",
"clouds"
] |
B
|
The global pattern of precipitation is influenced by movements of air masses. For example, there is a global belt of dry air masses and low precipitation at about 30° N and 30° S latitude.
Mechanisms of producing precipitation include convective, stratiform, and orographic rainfall. Convective processes involve strong vertical motions that can cause the overturning of the atmosphere in that location within an hour and cause heavy precipitation, while stratiform processes involve weaker upward motions and less intense precipitation over a longer duration. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Droughts occur mainly in areas where normal levels of rainfall are, in themselves, low.
A strong system moving through the mid latitudes, such as a cold front, can lead to high amounts from tropical systems, occurring well in advance of its center. Movement of a tropical cyclone over cool water will also limit its rainfall potential. A combination of factors can lead to exceptionally high rainfall amounts, as was seen during Hurricane Mitch in Central America.Use of forecast models can help determine the magnitude and pattern of the rainfall expected.
The central theme of hydrology is that water circulates throughout the Earth through different pathways and at different rates. The most vivid image of this is in the evaporation of water from the ocean, which forms clouds. These clouds drift over the land and produce rain. The rainwater flows into lakes, rivers, or aquifers.
Essential processes of the water cycle are precipitation and evaporation. The local amount of precipitation minus evaporation (often noted as P-E) shows the local influence of the water cycle. Changes in the magnitude of P-E are often used to show changes in the water cycle. But robust conclusions about changes in the amount of precipitation and evaporation are complex.
This process is typically active when freezing rain occurs. A stationary front is often present near the area of freezing rain and serves as the focus for forcing and rising air. Provided there is necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely nimbostratus and cumulonimbus if significant precipitation is involved.
|
What is the name of the region of a magnet that has the most pull?
|
[
"center",
"grid",
"pole",
"tail"
] |
C
|
Imagine a huge bar magnet passing through Earth’s axis, as in the Figure below . This is a good representation of Earth as a magnet. Like a bar magnet, Earth has north and south magnetic poles. A magnetic pole is the north or south end of a magnet, where the magnet exerts the most force.
Under the condition χ ρ N ≪ ρ F ± {\displaystyle \chi \rho _{N}\ll \rho _{F\pm }} this relationship can be simplified using the coefficient of the spin asymmetry δ H = β 2 1 − β 2 . {\displaystyle \delta _{H}={\frac {\beta ^{2}}{1-\beta ^{2}}}.} Such a device, with resistance depending on the orientation of electron spin, is called a spin valve. It is "open", if the magnetizations of its layers are parallel, and "closed" otherwise.
Magnetocrystalline anisotropy has a great influence on industrial uses of ferromagnetic materials. Materials with high magnetic anisotropy usually have high coercivity, that is, they are hard to demagnetize. These are called "hard" ferromagnetic materials and are used to make permanent magnets. For example, the high anisotropy of rare-earth metals is mainly responsible for the strength of rare-earth magnets.
The south magnetic pole, also known as the magnetic south pole, is the point on Earth's Southern Hemisphere where the geomagnetic field lines are directed perpendicular to the nominal surface. The Geomagnetic South Pole, a related point, is the south pole of an ideal dipole model of the Earth's magnetic field that most closely fits the Earth's actual magnetic field. For historical reasons, the "end" of a freely hanging magnet that points (roughly) north is itself called the "north pole" of the magnet, and the other end, pointing south, is called the magnet's "south pole". Because opposite poles attract, Earth's south magnetic pole is physically actually a magnetic north pole (see also North magnetic pole § Polarity).
It is antipodal to the South Geomagnetic Pole. Because of the fluid nature of the Earth's molten core, the true axis of the Earth's magnetic field is not a perfect dipole, and so the Geomagnetic Poles and the actual Magnetic Poles lie some distance apart. North Magnetic Pole Also called the Magnetic North Pole or Magnetic North.
The Earth's magnetic field is produced by convection of a liquid iron alloy in the outer core. In a dynamo process, the movements drive a feedback process in which electric currents create electric and magnetic fields that in turn act on the currents.The field at the surface of the Earth is approximately the same as if a giant bar magnet were positioned at the center of the Earth and tilted at an angle of about 11° off the rotational axis of the Earth (see the figure). The north pole of a magnetic compass needle points roughly north, toward the North Magnetic Pole. However, because a magnetic pole is attracted to its opposite, the North Magnetic Pole is actually the south pole of the geomagnetic field.
|
How many major forces of elevation cause allele frequencies to change?
|
[
"one",
"five",
"three",
"four"
] |
D
|
There are four major forces of evolution that cause allele frequencies to change. They are mutation, gene flow, genetic drift, and natural selection.
The expected allele frequency spectrum may be calculated using either a coalescent or diffusion approach. The demographic history of a population and natural selection affect allele frequency dynamics, and these effects are reflected in the shape of the allele frequency spectrum. For the simple case of selective neutral alleles segregating in a population that has reached demographic equilibrium (that is, without recent population size changes or gene flow), the expected allele frequency spectrum x = ( x 1 , … , x n − 1 ) {\displaystyle \mathbf {x} =(x_{1},\ldots ,x_{n-1})} for a sample of size n {\displaystyle n} is given by x i = θ 1 i , {\displaystyle x_{i}=\theta {\frac {1}{i}},} where θ = 2 N μ {\displaystyle \theta =2N\mu } is the population scaled mutation rate. Deviations from demographic equilibrium or neutrality will change the shape of the expected frequency spectrum.
While directional selection eventually leads to the loss of all alleles except the favored one (unless one allele is dominant, in which case recessive alleles can survive at low frequencies), some forms of selection, such as balancing selection, lead to equilibrium without loss of alleles. Mutation will have a very subtle effect on allele frequencies through the introduction of new allele into a population. Mutation rates are of the order 10−4 to 10−8, and the change in allele frequency will be, at most, the same order.
Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. Specifically, it is the fraction of all chromosomes in the population that carry that allele over the total population or sample size. Microevolution is the change in allele frequencies that occurs over time within a population.
Genetic homogenization can be analyzed in terms of allelic frequencies, which is accomplished through a comparison of how common specific genotypes are. If an allele occurs at a similar frequency between two populations, then there is greater homogenization present. Other evolutionary forces such as founder effects and bottleneck effects can also lead to genetic homogenization.
"Within a population, SNPs can be assigned a minor allele frequency—the lowest allele frequency at a locus that is observed in a particular population. This is simply the lesser of the two allele frequencies for single-nucleotide polymorphisms. With this knowledge scientists have developed new methods in analyzing population structures in less studied species.
|
Where in the atom is a neutron found?
|
[
"electron",
"proton",
"the nucleus",
"orbit"
] |
C
|
A neutron is one of three main particles that make up the atom. It is found in the nucleus and is neutral in electric charge. It has about the same mass and diameter as a proton. Neutrons are found in all atoms except for most atoms of hydrogen.
Neutrons serve as a unique probe for revealing the structure and function of matter from the microscopic down to the atomic scale. Using neutrons for research enables us to investigate the world around us as well as to develop new materials and processes to meet the needs of society. Neutrons are frequently used to address the grand challenges, to improve and develop new solutions for health, the environment, clean energy, IT and more.
Because neutrons are electrically neutral, they penetrate more deeply into matter than electrically charged particles of comparable kinetic energy, and thus are valuable as probes of bulk properties. Neutrons interact with atomic nuclei and with magnetic fields from unpaired electrons, causing pronounced interference and energy transfer effects in neutron scattering experiments. Unlike an x-ray photon with a similar wavelength, which interacts with the electron cloud surrounding the nucleus, neutrons interact primarily with the nucleus itself, as described by Fermi's pseudopotential. Neutron scattering and absorption cross sections vary widely from isotope to isotope.
A 14C atom is created when a thermal neutron displaces a proton in 14N. Minuscule amounts of 14C are produced by other radioactive processes, and a significant amount was released into the atmosphere during nuclear testing before the Limited Test Ban Treaty.
The neutron plays an important role in many nuclear reactions. For example, neutron capture often results in neutron activation, inducing radioactivity. In particular, knowledge of neutrons and their behavior has been important in the development of nuclear reactors and nuclear weapons. The fissioning of elements like uranium-235 and plutonium-239 is caused by their absorption of neutrons.
Understanding the structure of the atomic nucleus is one of the central challenges in nuclear physics.
|
In physics, what is defined as the average kinetic energy of the particles of matter?
|
[
"density",
"friction",
"temperature",
"magnetism"
] |
C
|
No doubt you already have a good idea of what temperature is. You might say that it’s how warm or cool something feels. In physics, temperature is defined as the average kinetic energy of the particles of matter. When particles of matter move more quickly, they have more kinetic energy, so their temperature is higher. With a higher temperature, matter feels warmer. When particles move more slowly, they have less kinetic energy on average, so their temperature is lower. With a lower temperature, matter feels cooler.
The magnitude of the kelvin is now defined in terms of kinetic theory, derived from the value of the Boltzmann constant. Kinetic theory provides a microscopic account of temperature for some bodies of material, especially gases, based on macroscopic systems' being composed of many microscopic particles, such as molecules and ions of various species, the particles of a species being all alike. It explains macroscopic phenomena through the classical mechanics of the microscopic particles. The equipartition theorem of kinetic theory asserts that each classical degree of freedom of a freely moving particle has an average kinetic energy of kBT/2 where kB denotes the Boltzmann constant.
As a simple example, burning one kilogram of coal releases more energy than detonating a kilogram of TNT, but because the TNT reaction releases energy more quickly, it delivers more power than the coal. If ΔW is the amount of work performed during a period of time of duration Δt, the average power Pavg over that period is given by the formula It is the average amount of work done or energy converted per unit of time. Average power is often called "power" when the context makes it clear. Instantaneous power is the limiting value of the average power as the time interval Δt approaches zero. When power P is constant, the amount of work performed in time period t can be calculated as In the context of energy conversion, it is more customary to use the symbol E rather than W.
The kinetic energy of a moving object is dependent on its velocity and is given by the equation ignoring special relativity, where Ek is the kinetic energy and m is the mass. Kinetic energy is a scalar quantity as it depends on the square of the velocity, however a related quantity, momentum, is a vector and defined by In special relativity, the dimensionless Lorentz factor appears frequently, and is given by where γ is the Lorentz factor and c is the speed of light. Escape velocity is the minimum speed a ballistic object needs to escape from a massive body such as Earth. It represents the kinetic energy that, when added to the object's gravitational potential energy (which is always negative), is equal to zero.
In radiation physics, kerma is an acronym for "kinetic energy released per unit mass" (alternately, "kinetic energy released in matter", "kinetic energy released in material",, or "kinetic energy released in materials"), defined as the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing radiation (i.e., indirectly ionizing radiation such as photons and neutrons) in a sample of matter, divided by the mass of the sample. It is defined by the quotient K = d E tr / d m {\displaystyle K=\operatorname {d} \!E_{\text{tr}}/\operatorname {d} \!m} .
The kinetic energy is a function only of the velocities vk, not the positions rk nor time t, so T = T(v1, v2, ...). The potential energy of the system reflects the energy of interaction between the particles, i.e. how much energy any one particle will have due to all the others and other external influences. For conservative forces (e.g. Newtonian gravity), it is a function of the position vectors of the particles only, so V = V(r1, r2, ...).
|
What organelles are known as the "power plants" of the cell?
|
[
"plastid",
"mitochondria",
"flagella",
"golgi body"
] |
B
|
They have lots of mitochondria. Mitochondria are called the power plants of the cell, as these organelles are where most of the cell's energy is produced. Cells that need lots of energy have lots of mitochondria.
In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name organelle comes from the idea that these structures are parts of cells, as organs are to the body, hence organelle, the suffix -elle being a diminutive. Organelles are either separately enclosed within their own lipid bilayers (also called membrane-bound organelles) or are spatially distinct functional units without a surrounding lipid bilayer (non-membrane bound organelles). Although most organelles are functional units within cells, some function units that extend outside of cells are often termed organelles, such as cilia, the flagellum and archaellum, and the trichocyst.
Division of meristematic cells provides new cells for expansion and differentiation of tissues and the initiation of new organs, providing the basic structure of the plant body. The cells are small, with small vacuoles or none, and protoplasm filling the cell completely. The plastids (chloroplasts or chromoplasts), are undifferentiated, but are present in rudimentary form (proplastids).
Each cell contains a dense cytoplasm and a prominent cell nucleus. The dense protoplasm of meristematic cells contains very few vacuoles. Normally the meristematic cells are oval, polygonal, or rectangular in shape. Meristematic tissue cells have a large nucleus with small or no vacuoles because they have no need to store anything, as opposed to their function of multiplying and increasing the girth and length of the plant, with no intercellular spaces.
A mitosome is an organelle found in some unicellular eukaryotic organisms, like in members of the supergroup Excavata. The mitosome was found and named in 1999, and its function has not yet been well characterized. It was termed a crypton by one group, but that name is no longer in use. The mitosome has been detected only in anaerobic or microaerophilic organisms that do not have mitochondria.
Some eukaryotic cells (plant cells and fungal cells) also have a cell wall. Inside the cell is the cytoplasmic region that contains the genome (DNA), ribosomes and various sorts of inclusions. The genetic material is freely found in the cytoplasm.
|
Dalton's law and henry's law both describe aspects of what type of exchange?
|
[
"energy",
"electron",
"liquid",
"gas"
] |
D
|
22.4 Gas Exchange The behavior of gases can be explained by the principles of Dalton’s law and Henry’s law, both of which describe aspects of gas exchange. Dalton’s law states that each specific gas in a mixture of gases exerts force (its partial pressure) independently of the other gases in the mixture. Henry’s law states that the amount of a specific gas that dissolves in a liquid is a function of its partial pressure. The greater the partial pressure of a gas, the more of that gas will dissolve in a liquid, as the gas moves toward equilibrium. Gas molecules move down a pressure gradient; in other words, gas moves from a region of high pressure to a region of low pressure. The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli. The amount of oxygen and carbon dioxide that diffuses across the respiratory membrane is similar. Ventilation is the process that moves air into and out of the alveoli, and perfusion affects the flow of blood in the capillaries. Both are important in gas exchange, as ventilation must be sufficient to create a high partial pressure of oxygen in the alveoli. If ventilation is insufficient and the partial pressure of oxygen drops in the alveolar air, the capillary is constricted and blood flow is redirected to alveoli with sufficient ventilation. External respiration refers to gas exchange that occurs in the alveoli, whereas internal respiration refers to gas exchange that occurs in the tissue. Both are driven by partial pressure differences.
In physical chemistry, Henry's law is a gas law that states that the amount of dissolved gas in a liquid is directly proportional to its partial pressure above the liquid. The proportionality factor is called Henry's law constant. It was formulated by the English chemist William Henry, who studied the topic in the early 19th century.
In 1801, John Dalton published the law of partial pressures from his work with ideal gas law relationship: The pressure of a mixture of non reactive gases is equal to the sum of the pressures of all of the constituent gases alone. Mathematically, this can be represented for n species as: Pressuretotal = Pressure1 + Pressure2 + ... + PressurenThe image of Dalton's journal depicts symbology he used as shorthand to record the path he followed. Among his key journal observations upon mixing unreactive "elastic fluids" (gases) were the following: Unlike liquids, heavier gases did not drift to the bottom upon mixing. Gas particle identity played no role in determining final pressure (they behaved as if their size was negligible).
This law applies to ideal solutions, or solutions that have different components but whose molecular interactions are the same as or very similar to pure solutions. Dalton's law states that the total pressure is the sum of the partial pressures of each individual component in the mixture. When a multi-component liquid is heated, the vapor pressure of each component will rise, thus causing the total vapor pressure to rise.
Dalton's law of multiple proportions says that these chemicals will present themselves in proportions that are small whole numbers; although in many systems (notably biomacromolecules and minerals) the ratios tend to require large numbers, and are frequently represented as a fraction. The law of definite composition and the law of multiple proportions are the first two of the three laws of stoichiometry, the proportions by which the chemical elements combine to form chemical compounds. The third law of stoichiometry is the law of reciprocal proportions, which provides the basis for establishing equivalent weights for each chemical element.
In the early 1800s, the English chemist John Dalton compiled experimental data gathered by himself and other scientists and discovered a pattern now known as the "law of multiple proportions". He noticed that in chemical compounds which contain a particular chemical element, the content of that element in these compounds will differ in weight by ratios of small whole numbers. This pattern suggested that each chemical element combines with other elements by a basic unit of weight, and Dalton decided to call these units "atoms".
|
What vesicles store neurotransmitters?
|
[
"hydrophobic",
"dendritic",
"Golgi apparatus",
"synaptic"
] |
D
|
Secretory Vesicles contain materials that are to be excreted from the cell, such as wastes or hormones . Secretory vesicles include synaptic vesicles and vesicles in endocrine tissues. Synaptic vesicles store neurotransmitters. They are located at presynaptic terminals in neurons. When a signal reaches the end of an axon, the synaptic vesicles fuse with the cell membrane and release the neurotransmitter. The neurotransmitter crosses the synaptic junction, and binds to a receptor on the next cell. Some cells also produce molecules, such as hormones produced by endocrine tissues, needed by other cells. These molecules are stored in secretory vesicles and released when needed. Secretory vesicles also hold enzymes needed to make extracellular structures, such as the extracellular matrix of animal cells.
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they are able to interact with neurotransmitter receptors on the target cell. The neurotransmitter's effect on the target cell is determined by the receptor it binds to. Many neurotransmitters are synthesized from simple and plentiful precursors such as amino acids, which are readily available and often require a small number of biosynthetic steps for conversion.
Neurotransmitter transport systems are responsible for the release, re-uptake and recycling of neurotransmitters at synapses. High affinity transport proteins found in the plasma membrane of presynaptic nerve terminals and glial cells are responsible for the removal, from the extracellular space, of released-transmitters, thereby terminating their actions.The majority of the transporters constitute an extensive family of homologous proteins that derive energy from the co-transport of Na+ and Cl−, in order to transport neurotransmitter molecules into the cell against their concentration gradient. Neurotransmitter sodium symporters (NSS) are targets for anti-depressants, psychostimulants and other drugs.
Neurotransmitters are chemicals that are released at synapses when the local membrane is depolarised and Ca2+ enters into the cell, typically when an action potential arrives at the synapse – neurotransmitters attach themselves to receptor molecules on the membrane of the synapse's target cell (or cells), and thereby alter the electrical or chemical properties of the receptor molecules. With few exceptions, each neuron in the brain releases the same chemical neurotransmitter, or combination of neurotransmitters, at all the synaptic connections it makes with other neurons; this rule is known as Dale's principle. Thus, a neuron can be characterized by the neurotransmitters that it releases. The great majority of psychoactive drugs exert their effects by altering specific neurotransmitter systems.
In the brain, VMAT2 proteins are located on synaptic vesicles. VMAT2 transports monoamine neurotransmitters from the cytosol of monoamine neurons into vesicles. Developmental biologist and science blogger PZ Myers argues: "It's a pump. A teeny-tiny pump responsible for packaging a neurotransmitter for export during brain activity.
Glutamate transporters are a family of neurotransmitter transporter proteins that move glutamate – the principal excitatory neurotransmitter – across a membrane. The family of glutamate transporters is composed of two primary subclasses: the excitatory amino acid transporter (EAAT) family and vesicular glutamate transporter (VGLUT) family. In the brain, EAATs remove glutamate from the synaptic cleft and extrasynaptic sites via glutamate reuptake into glial cells and neurons, while VGLUTs move glutamate from the cell cytoplasm into synaptic vesicles. Glutamate transporters also transport aspartate and are present in virtually all peripheral tissues, including the heart, liver, testes, and bone.
|
What temperature scale is obtained by adding 273 degrees from the corresponding celsius temperature?
|
[
"kelvin scale",
"whittle scale",
"seismic scale",
"ph scale"
] |
A
|
The Celsius scale is the standard SI temperature scale. It is equal to the Kelvin scale if you minus 273 from the Celsius reading. Water has a boiling point of and a freezing point of .
Since the standardization of the kelvin in the International System of Units, it has subsequently been redefined in terms of the equivalent fixing points on the Kelvin scale, so that a temperature increment of one degree Celsius is the same as an increment of one kelvin, though numerically the scales differ by an exact offset of 273.15. The Fahrenheit scale is in common use in the United States. Water freezes at 32 °F and boils at 212 °F at sea-level atmospheric pressure.
The Kelvin scale is of use in the sciences, with 0 K (−273.15 °C) representing absolute zero. Since 1743, the Celsius scale has been based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure. Prior to 1743 the values were reversed (i.e. the boiling point was 0 degrees and the freezing point was 100 degrees).
In the United States, the Fahrenheit scale is the most widely used. On this scale the freezing point of water corresponds to 32 °F and the boiling point to 212 °F. The Rankine scale, still used in fields of chemical engineering in the US, is an absolute scale based on the Fahrenheit increment.
Anders Celsius had created the temperature scale named after him in 1742. Celsius's scale was inverted compared to today, the boiling point at 0 °C and freezing point at 100 °C. In 1745, Linnaeus inverted the scale to its present standard.
It soon replaced worldwide other reference temperatures for length measurements that manufacturers of precision equipment had used before, including 0 °C, 62 °F, and 25 °C. Among the reasons for choosing 20 °C was that this was a comfortable and practical workshop temperature and that it resulted in an integer value on both the Celsius and Fahrenheit scales. It was the first ISO standard, issued originally as ISO/R 1, a ISO Recommendation.
|
Hemoglobin is a large molecule made up of proteins and iron. it consists of four folded chains of a protein called this?
|
[
"peptide",
"globin",
"histone",
"insulin"
] |
B
|
Hemoglobin Hemoglobin is a large molecule made up of proteins and iron. It consists of four folded chains of a protein called globin, designated alpha 1 and 2, and beta 1 and 2 (Figure 18.7a). Each of these globin molecules is bound to a red pigment molecule called heme, which contains an ion of iron (Fe2+) (Figure 18.7b).
Once a polypeptide chain is fully folded, it is called a protein. Often many subunits will combine to make a fully functional protein although physiological proteins do exist that contain only one polypeptide chain. Proteins may also incorporate other molecules such as the heme group in hemoglobin, a protein responsible for carrying oxygen in the blood.
(Additionally, this hydrogen bonding results in the tilting of the oxygen molecule, resulting in a Fe–O–O bond angle of around 120° that avoids the formation of Fe–O–Fe or Fe–O2–Fe bridges that would lead to electron transfer, the oxidation of Fe2+ to Fe3+, and the destruction of hemoglobin.) This results in a movement of all the protein chains that leads to the other subunits of hemoglobin changing shape to a form with larger oxygen affinity. Thus, when deoxyhemoglobin takes up oxygen, its affinity for more oxygen increases, and vice versa.
The hemoglobin protein is made of two subunits (alpha and beta). In 15 of the 16 icefish species, the beta subunit gene has been completely deleted and the alpha subunit gene has been partially deleted. One icefish species, Neopagetopsis ionah, has a more complete, but still nonfunctional, hemoglobin gene.Red blood cells (RBCs) are usually absent, and if present, are rare and defunct.
As explained before, hemoglobin is a protein which means that it's production requires adequate and enough intake of protein from the diet, but in case of protein-energy malnutrition, hemoglobin will not be produced sufficiently leading to anemia. As a result there is a reduction in cell mass and thus fewer RBCs are required to oxygenate the tissue ( reduced number of RBCs with a low hemoglobin).
Fetal hemoglobin, or foetal haemoglobin (also hemoglobin F, HbF, or α2γ2) is the main oxygen carrier protein in the human fetus. Hemoglobin F is found in fetal red blood cells, and is involved in transporting oxygen from the mother's bloodstream to organs and tissues in the fetus. It is produced at around 6 weeks of pregnancy and the levels remain high after birth until the baby is roughly 2–4 months old.
|
A new species is said to have evolved if separated members of a species evolve genetic differences that prevent what from occurring with the original members??
|
[
"extinction",
"interbreeding",
"evolution",
"re-population"
] |
B
|
Assume that some members of a species become geographically separated from the rest of the species. If they remain separated long enough, they may evolve genetic differences. If the differences prevent them from interbreeding with members of the original species, they have evolved into a new species. Speciation that occurs in this way is called allopatric speciation . An example is described in the Figure below .
This gives rise to the potential for genetic incompatibilities to evolve. These incompatibilities cause reproductive isolation, giving rise to—sometimes rapid—speciation events. : 105 Furthermore, two important predictions are invoked, namely that geological or climatic changes cause populations to become locally fragmented (or regionally when considering allopatric speciation), and that an isolated population's reproductive traits evolve enough as to prevent interbreeding upon potential secondary contact.The peripatric model results in, what have been called, progenitor-derivative species pairs, whereby the derivative species (the peripherally isolated population)—geographically and genetically isolated from the progenitor species—diverges.
In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are. Species are reproductively isolated by strong barriers to hybridization, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo.
Some multigene families are extremely homogenous, with individual genes members sharing identical or almost identical sequences. The process by which gene families maintain high homogeneity is Concerted evolution. Concerted evolution occurs through repeated cycles of unequal crossing over events and repeated cycles of gene transfer and conversion. Unequal crossing over leads to the expansion and contraction of gene families.
Reinforcement (the strengthening of isolation by selection favoring the mating of members of their own populations due to reduced fitness of hybrids) is considered to be a form of, or involved in, ecological speciation. Though, debate exists as to how to determine ultimate causes since reinforcement can complete the speciation process regardless of how it originated. Further, character displacement can have the same effect.
Each gene maps to the same chromosome in every cell. Linkage is determined by the presence of two or more loci on the same chromosome. The entire chromosomal set of a species is known as a karyotype. A seemingly logical consequence of descent from common ancestors is that more closely related species should have more chromosomes in common. However, it is now widely thought that species may have phenetically similar karyotypes due to genomic conservation. Therefore, in comparative cytogenetics, phylogenetic relationships should be determined on the basis of the polarity of chromosomal differences (derived traits).
|
What term describes the orientation of a body lying face-down?
|
[
"Under",
"Diagnal",
"Supine",
"prone"
] |
D
|
A body that is lying down is described as either prone or supine. Prone describes a face-down orientation, and supine describes a face up orientation. These terms are sometimes used in describing the position of the body during specific physical examinations or surgical procedures.
The supine position ( or ) means lying horizontally with the face and torso facing up, as opposed to the prone position, which is face down. When used in surgical procedures, it grants access to the peritoneal, thoracic and pericardial regions; as well as the head, neck and extremities.Using anatomical terms of location, the dorsal side is down, and the ventral side is up, when supine.
Posture is a nonverbal cue that is associated with positioning and that these two are used as sources of information about individual's characteristics, attitudes, and feelings about themselves and other people. There are many different types of body positioning to portray certain postures, including slouching, towering, legs spread, jaw thrust, shoulders forward, and arm crossing. The posture or bodily stance exhibited by individuals communicates a variety of messages whether good or bad. A study, for instance, identified around 200 postures that are related to maladjustment and withholding of information.Posture can be used to determine a participant's degree of attention or involvement, the difference in status between communicators, and the level of fondness a person has for the other communicator, depending on body "openness".
Typically, the orientation is given relative to a frame of reference, usually specified by a Cartesian coordinate system. Two objects sharing the same direction are said to be codirectional (as in parallel lines). Two directions are said to be opposite if they are the additive inverse of one another, as in an arbitrary unit vector and its multiplication by -1. Two directions are obtuse if they form an obtuse angle (greater than a right angle) or, equivalently, if their scalar product or scalar projection is negative.
Rotation about a transverse axis is termed trim or pitch. Rotation about a fore and aft axis is termed heel or roll. Rotation about a vertical axis is termed yaw.Longitudinal stability for longitudinal inclinations, the stability depends upon the distance between the center of gravity and the longitudinal meta-center.
When lying down, a person's weight is distributed over a much larger area. This difference in weight distribution would allow a person to cross an area of ice while crawling that might otherwise collapse under their body weight while standing up.
|
What happens to energy when an atom gains an electron?
|
[
"it is folded",
"it is used",
"it is released",
"it increases"
] |
C
|
A: Energy is released when an atom gains an electron. Halogens release the most energy when they form ions. As a result, they are very reactive elements.
Electrons and their interactions with electromagnetic fields are important in our understanding of chemistry and physics. In the classical view, the energy of an electron orbiting an atomic nucleus is larger for orbits further from the nucleus of an atom. However, quantum mechanical effects force electrons to take on discrete positions in orbitals.
Atomic energy or energy of atoms is energy carried by atoms. The term originated in 1903 when Ernest Rutherford began to speak of the possibility of atomic energy. H. G. Wells popularized the phrase "splitting the atom", before discovery of the atomic nucleus. Atomic energy includes: Nuclear binding energy, the energy required to split a nucleus of an atom.
After a statistically sufficient quantity of time, an electron in an excited state will undergo a transition to a lower state via spontaneous emission. The change in energy between the two energy levels must be accounted for (conservation of energy). In a neutral atom, the system will emit a photon of the difference in energy.
In the formulas for energy of electrons at various levels given below in an atom, the zero point for energy is set when the electron in question has completely left the atom, i.e. when the electron's principal quantum number n = ∞. When the electron is bound to the atom in any closer value of n, the electron's energy is lower and is considered negative.
In physical chemistry, a hot atom is an atom that has a high kinetic or internal energy.When molecule AB adsorbs on a surface dissociatively, both A and B adsorb on the surface, or only A adsorbs on the surface, and B desorbs from the surface.In case 2, B gains a high translational energy from the adsorption energy of A, and hot atom B is generated. For example, the hydrogen molecule, because of its light mass, gets a high translational energy. Such a hot atom does not fly into vacuum but is trapped on the surface, where it diffuses with high energy.
|
What is the name of the second most electronegative element?
|
[
"oxygen",
"nitrogen",
"Hydrogen",
"carbon"
] |
A
|
Oxygen has an oxidation state of -2 in most of its compounds. Oxygen is the second most electronegative element, so it also tends to be assigned all shared electrons. Exceptions include O 2 (oxidation state = 0), peroxides, in which two oxygen atoms are connected by a single bond (oxidation state usually = -1), and any compound in which oxygen is bonded to fluorine (pretty rare and reactive).
That would make them the heavier congeners of scandium and yttrium, rather than lanthanum and actinium. Although some alkali metal-like behaviour has been predicted, adsorption experiments suggest that lawrencium is trivalent like scandium and yttrium, not monovalent like the alkali metals. A lower limit on lawrencium's second ionization energy (>13.3 eV) was experimentally found in 2021.Even though s2p is now known to be the ground-state configuration of the lawrencium atom, ds2 should be a low-lying excited-state configuration, with an excitation energy variously calculated as 0.156 eV, 0.165 eV, or 0.626 eV. As such lawrencium may still be considered to be a d-block element, albeit with an anomalous electron configuration (like chromium or copper), as its chemical behaviour matches expectations for a heavier analogue of lutetium.
Chromium is the fourth transition metal found on the periodic table, and has an electron configuration of 3d5 4s1. It is also the first element in the periodic table whose ground-state electron configuration violates the Aufbau principle. This occurs again later in the periodic table with other elements and their electron configurations, such as copper, niobium, and molybdenum. This occurs because electrons in the same orbital repel each other due to their like charges.
The small atomic radii of carbon, nitrogen, and oxygen facilitate the formation of double or triple bonds.While it would normally be expected that hydrogen and helium, on electron configuration consistency grounds, would be located atop the s-block elements, the first row anomaly in these two elements is strong enough to warrant alternative placements. Hydrogen is occasionally positioned over fluorine, in group 17, rather than over lithium in group 1. Helium is regularly positioned over neon, in group 18, rather than over beryllium in group 2.
Fluorine atoms have nine electrons, one fewer than neon, and electron configuration 1s22s22p5: two electrons in a filled inner shell and seven in an outer shell requiring one more to be filled. The outer electrons are ineffective at nuclear shielding, and experience a high effective nuclear charge of 9 − 2 = 7; this affects the atom's physical properties.Fluorine's first ionization energy is third-highest among all elements, behind helium and neon, which complicates the removal of electrons from neutral fluorine atoms. It also has a high electron affinity, second only to chlorine, and tends to capture an electron to become isoelectronic with the noble gas neon; it has the highest electronegativity of any reactive element. Fluorine atoms have a small covalent radius of around 60 picometers, similar to those of its period neighbors oxygen and neon.
Boron is the lightest element having an electron in a p-orbital in its ground state. Unlike most other p-elements, it rarely obeys the octet rule and usually places only six electrons (in three molecular orbitals) onto its valence shell. Boron is the prototype for the boron group (the IUPAC group 13), although the other members of this group are metals and more typical p-elements (only aluminium to some extent shares boron's aversion to the octet rule).
|
What is the term for species evolving together?
|
[
"conjuration",
"coevolution",
"interconnection",
"specmutation"
] |
B
|
Coevolution occurs when species evolve together. This often happens in species that have symbiotic relationships. Examples include flowering plants and their pollinators.
evolution The change in the heritable characteristics of populations of biological organisms over successive generations, which may occur by mutation, gene flow, natural selection, or random chance. evolutionary biology The subfield of biology that studies evolution and the evolutionary processes that produced the diversity of life on Earth from a hypothesized single common ancestor. These processes include the descent of species and the origin of new species.
The evolutionary changes occurring to an organism within its population or within the wider community. exotic species An introduced species not native or endemic to a habitat. extinction The termination of an organism or of a taxon, usually a species, which occurs when the last individual organism of the taxon dies.
Distinguishing between anagenesis and cladogenesis is particularly relevant in the fossil record, where limited fossil preservation in time and space makes it difficult to distinguish between anagenesis, cladogenesis where one species replaces the other, or simple migration patterns.Recent evolutionary studies are looking at anagenesis and cladogenesis for possible answers in developing the hominin phylogenetic tree to understand morphological diversity and the origins of Australopithecus anamensis, and this case could possibly show anagenesis in the fossil record.When enough mutations have occurred and become stable in a population so that it is significantly differentiated from an ancestral population, a new species name may be assigned. A series of such species is collectively known as an evolutionary lineage. The various species along an evolutionary lineage are chronospecies. If the ancestral population of a chronospecies does not go extinct, then this is cladogenesis, and the ancestral population represents a paraphyletic species or paraspecies, being an evolutionary grade. This situation is quite common in species with widespread populations.
Analogous structures - structures similar in different organisms because, in convergent evolution, they evolved in a similar environment, rather than were inherited from a recent common ancestor. They usually serve the same or similar purposes. An example is the streamlined torpedo body shape of porpoises and sharks. So even though they evolved from different ancestors, porpoises and sharks developed analogous structures as a result of their evolution in the same aquatic environment. This is known as a homoplasy.
Reinforcement (the strengthening of isolation by selection favoring the mating of members of their own populations due to reduced fitness of hybrids) is considered to be a form of, or involved in, ecological speciation. Though, debate exists as to how to determine ultimate causes since reinforcement can complete the speciation process regardless of how it originated. Further, character displacement can have the same effect.
|
Where do the eggs develop?
|
[
"the uterus",
"the glands",
"the follicles",
"the ovaries"
] |
D
|
The majority of insects hatch from eggs. The fertilization and development takes place inside the egg, enclosed by a shell (chorion) that consists of maternal tissue. In contrast to eggs of other arthropods, most insect eggs are drought resistant. This is because inside the chorion two additional membranes develop from embryonic tissue, the amnion and the serosa.
The eggs are normally laid on surface water and go through three distinct larval stages. The larvae are usually found in still or stagnant water, like water reservoirs or liquid dung. Just before the pupation stage, the larvae leave their aquatic environment.
It is presumed to be oviparous (egg laying).
At some point, the growing egg or offspring must be expelled. There are several possible modes of reproduction. These are traditionally classified as follows: Oviparity, as in most invertebrates and reptiles, monotremes, dinosaurs and all birds which lay eggs that continue to develop after being laid, and hatch later. Viviparity, as in almost all mammals (such as whales, kangaroos and humans) which bear their young live.
Eggs are laid separately, hatching after about three weeks. They grow from larval to juvenile form in between five and six months. Juveniles eat soil-dwelling prey, and adults eat a wide variety of insects, tadpoles, and the eggs of their own species.
|
What's the other term for your wind pipe?
|
[
"trachea",
"cornea",
"cochlea",
"esophagus"
] |
A
|
The trachea , or wind pipe, is a long tube that leads down to the chest.
Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal wind shear. Vertical wind shear is a change in wind speed or direction with a change in altitude. Horizontal wind shear is a change in wind speed with a change in lateral position for a given altitude.Wind shear is a microscale meteorological phenomenon occurring over a very small distance, but it can be associated with mesoscale or synoptic scale weather features such as squall lines and cold fronts.
A short burst of high speed wind is termed a wind gust, one technical definition of a wind gust is: the maxima that exceed the lowest wind speed measured during a ten-minute time interval by 10 knots (5 m/s) for periods of seconds. A squall is an increase of the wind speed above a certain threshold, which lasts for a minute or more.
wind gap Also air gap. A pass, notch, or opening in a ridge or mountain range, originally carved by a watercourse flowing through it but which is now dry as a result of stream capture. Contrast water gap.
A mountain-gap wind, gap wind or gap flow is a local wind blowing through a gap between mountains. Gap winds are low-level winds and can be associated with strong winds of 20-40 knots and on occasion exceeding 50 knots. Gap winds are generally strongest close to gap exit. Example flows include the surface winds blowing through the Strait of Gibraltar – one of the strongest winds in this region is called Levanter.
The settlers initially used the word to refer to the hollow decorated pipe shaft alone while the pipe bowl was a separate ritual object, a "sort of reeds used to make pipes", with a suffix substitution for calumel. It corresponds to the French word chalumeau, meaning 'reed' (Modern French also means 'straw', 'blowlamp').
|
When food is scarce, starving cells secrete a molecule that stimulates neighboring cells to do what?
|
[
"compete",
"hoard energy",
"die off",
"aggregate"
] |
D
|
They maintain a symbiotic relationship with phoretic mites, which they transport, and which probably feed on mushrooms or nest parasites.
Migration then takes place from the hindgut along the gut and across the dorsal mesentery to reach the gonads (4.5 weeks in human beings). Fibronectin maps here also a polarized network together with other molecules. The somatic cells on the path of germ cells provide them attractive, repulsive, and survival signals.
Less controversially, the second phase is likely caused by direct stimulation of L-cells by digested nutrients. The rate of gastric emptying is therefore an important aspect to consider, as it regulates the entry of nutrients into the small intestines where the direct stimulation occurs.
Exocytosis is the process by which a large amount of molecules are released; thus it is a form of bulk transport. Exocytosis occurs via secretory portals at the cell plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structures at the cell plasma membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell.
While cells expend energy to transport ions and establish a transmembrane potential, they use this potential in turn to transport other ions and metabolites such as sugar. The transmembrane potential of the mitochondria drives the production of ATP, which is the common currency of biological energy. Cells may draw on the energy they store in the resting potential to drive action potentials or other forms of excitation. These changes in the membrane potential enable communication with other cells (as with action potentials) or initiate changes inside the cell, which happens in an egg when it is fertilized by a sperm.
|
What do cells secrete that binds to receptors?
|
[
"stress",
"endorphans",
"proteins",
"factor"
] |
D
|
Historically, cellular receptors have been thought to be activated when bound to their ligand, and are relatively inactive when no ligand is present. A number of receptors have been found that do not fit into this conceptual mould, and DCC is one of them. These receptors are active both with ligand bound and unbound, but the signals transmitted are different when the receptors are ligand bound.
Two models have been proposed to explain transmembrane receptors' mechanism of action. Dimerization: The dimerization model suggests that prior to ligand binding, receptors exist in a monomeric form. When agonist binding occurs, the monomers combine to form an active dimer. Rotation: Ligand binding to the extracellular part of the receptor induces a rotation (conformational change) of part of the receptor's transmembrane helices. The rotation alters which parts of the receptor are exposed on the intracellular side of the membrane, altering how the receptor can interact with other proteins within the cell.
There are two types of inhibitory receptors:
In the case of steroid hormone receptors, their stimulation leads to binding to the promoter region of steroid-responsive genes.Not all classifications of signaling molecules take into account the molecular nature of each class member. For example, odorants belong to a wide range of molecular classes, as do neurotransmitters, which range in size from small molecules such as dopamine to neuropeptides such as endorphins. Moreover, some molecules may fit into more than one class, e.g. epinephrine is a neurotransmitter when secreted by the central nervous system and a hormone when secreted by the adrenal medulla.
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they are able to interact with neurotransmitter receptors on the target cell. The neurotransmitter's effect on the target cell is determined by the receptor it binds to. Many neurotransmitters are synthesized from simple and plentiful precursors such as amino acids, which are readily available and often require a small number of biosynthetic steps for conversion.
|
What is the term for the tube that carries sound waves into the ear?
|
[
"sound canal",
"flap canal",
"tone canal",
"ear canal"
] |
D
|
The ear canal is a tube that carries sound waves into the ear. The sound waves travel through the air inside the ear canal to the eardrum.
The ear canal acts as a resonant tube (like an organ pipe) to amplify frequencies between 2–5.5 kHz with a maximum amplification of about 11 dB occurring around 4 kHz. As the organ of hearing, the cochlea consists of two membranes, Reissner’s and the basilar membrane. The basilar membrane moves to audio stimuli through the specific stimulus frequency matches the resonant frequency of a particular region of the basilar membrane.
The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear is also known as the tympanic cavity and is surrounded by the tympanic part of the temporal bone. The auditory tube (also known as the Eustachian tube or the pharyngotympanic tube) joins the tympanic cavity with the nasal cavity (nasopharynx), allowing pressure to equalize between the middle ear and throat. The primary function of the middle ear is to efficiently transfer acoustic energy from compression waves in air to fluid–membrane waves within the cochlea.
The stapes transmits these vibrations to the inner ear by pushing on the membrane covering the oval window, which separates the middle and inner ear. The inner ear contains the cochlea, the liquid-filled structure containing the hair cells. These cells serve to transform the incoming vibration to electrical signals, which can then be transmitted to the brain. The auditory nerve carries the signal generated by the hair cells away from the inner ear and towards the auditory receiving area in the cortex. The signal then travels through fibers to several subcortical structures and on to the primary auditory receiving area in the temporal lobe.
In an ideal tube, the wavelength of the sound produced is directly proportional to the length of the tube. A tube which is open at one end and closed at the other produces sound with a wavelength equal to four times the length of the tube. A tube which is open at both ends produces sound whose wavelength is just twice the length of the tube.
A duct for sound propagation also behaves like a transmission line (e.g. air conditioning duct, car muffler, ...). Its length may be similar to the wavelength of the sound passing through it, but the dimensions of its cross-section are normally smaller than one quarter the wavelength. Sound is introduced at one end of the tube by forcing the pressure across the whole cross-section to vary with time. An almost planar wavefront travels down the line at the speed of sound.
|
In the cardiovascular system, what blood vessels carry blood away from the heart?
|
[
"veins",
"capillaries",
"arteries",
"cilia"
] |
C
|
The blood vessels are an important part of the cardiovascular system. They connect the heart to every cell in the body. Arteries carry blood away from the heart, while veins return blood to the heart ( Figure below ).
Blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away from the tissues.
Blood is brought to the myocardium by the coronary arteries. These originate from the aortic root and lie on the outer or epicardial surface of the heart. Blood is then drained away by the coronary veins into the right atrium.
Seven arteries conduct blood from the heart to various regions of the body. Each artery branches extensively, and smaller arteries ultimately end in the hemocoel. Venous blood drains into the sternal sinus, where it is conveyed by channels to the gills for aeration and returned again to the pericardial sinus.
Systemic arteries can be subdivided into two types—muscular and elastic—according to the relative compositions of elastic and muscle tissue in their tunica media as well as their size and the makeup of the internal and external elastic lamina. The larger arteries (>10 mm diameter) are generally elastic and the smaller ones (0.1–10 mm) tend to be muscular. Systemic arteries deliver blood to the arterioles, and then to the capillaries, where nutrients and gases are exchanged. After traveling from the aorta, blood travels through peripheral arteries into smaller arteries called arterioles, and eventually to capillaries. Arterioles help in regulating blood pressure by the variable contraction of the smooth muscle of their walls, and deliver blood to the capillaries.
Vascular endothelial cells line the entire circulatory system, from the heart to the smallest capillaries. These cells have unique functions that include fluid filtration, such as in the glomerulus of the kidney, blood vessel tone, hemostasis, neutrophil recruitment, and hormone trafficking. Endothelium of the interior surfaces of the heart chambers is called endocardium. An impaired function can lead to serious health issues throughout the body.
|
Molecules in the gas phase can collide with the liquid surface and reenter the liquid via what?
|
[
"condensation",
"fermentation",
"combustion",
"liquidation"
] |
A
|
pressure above the liquid. Molecules in the gas phase can collide with the liquid surface and reenter the liquid via condensation. Eventually, a steady state is reached in which the number of molecules evaporating and condensing per unit time is the same, and the system is in a state of dynamic equilibrium. Under these conditions, a liquid exhibits a characteristic equilibrium vapor pressure that depends only on the temperature. We can express the nonlinear relationship between vapor pressure and temperature as a linear relationship using the Clausius–Clapeyron equation. This equation can be used to calculate the enthalpy of vaporization of a liquid from its measured vapor pressure at two or more temperatures. Volatile liquids are liquids with high vapor pressures, which tend to evaporate readily from an open container; nonvolatile liquids have low vapor pressures. When the vapor pressure equals the external pressure, bubbles of vapor form within the liquid, and it boils. The temperature at which a substance boils at a pressure of 1 atm is its normal boiling point.
Further compression of the surfactant molecules on the surface shows behavior similar to phase transitions. The ‘gas’ gets compressed into ‘liquid’ and ultimately into a perfectly closed packed array of the surfactant molecules on the surface corresponding to a ‘solid’ state. The liquid state is usually separated in the liquid-expanded and liquid-condensed states.
By nature, it is liquid. It ripples.
Even at equilibrium molecules are constantly in motion and, once in a while, a molecule in the liquid phase gains enough kinetic energy to break away from the liquid phase and enter the gas phase. Likewise, every once in a while a vapor molecule collides with the liquid surface and condenses into the liquid. At equilibrium, evaporation and condensation processes exactly balance and there is no net change in the volume of either phase.
Gas chromatography is based on a partition equilibrium of analyte between a solid or viscous liquid stationary phase (often a liquid silicone-based material) and a mobile gas (most often helium). The stationary phase is adhered to the inside of a small-diameter (commonly 0.53 – 0.18mm inside diameter) glass or fused-silica tube (a capillary column) or a solid matrix inside a larger metal tube (a packed column). It is widely used in analytical chemistry; though the high temperatures used in GC make it unsuitable for high molecular weight biopolymers or proteins (heat denatures them), frequently encountered in biochemistry, it is well suited for use in the petrochemical, environmental monitoring and remediation, and industrial chemical fields. It is also used extensively in chemistry research.
Left to equilibration, many compositions will form a uniform single phase, but depending on the temperature and pressure even a single substance may separate into two or more distinct phases. Within each phase, the properties are uniform but between the two phases properties differ. Water in a closed jar with an air space over it forms a two-phase system. Most of the water is in the liquid phase, where it is held by the mutual attraction of water molecules.
|
What guards the opening between the right atrium and the right ventricle?
|
[
"superior vena cava",
"tricuspid valve",
"brachiocephalic trunk",
"aorta"
] |
B
|
Right Atrium The right atrium serves as the receiving chamber for blood returning to the heart from the systemic circulation. The two major systemic veins, the superior and inferior venae cavae, and the large coronary vein called the coronary sinus that drains the heart myocardium empty into the right atrium. The superior vena cava drains blood from regions superior to the diaphragm: the head, neck, upper limbs, and the thoracic region. It empties into the superior and posterior portions of the right atrium. The inferior vena cava drains blood from areas inferior to the diaphragm: the lower limbs and abdominopelvic region of the body. It, too, empties into the posterior portion of the atria, but inferior to the opening of the superior vena cava. Immediately superior and slightly medial to the opening of the inferior vena cava on the posterior surface of the atrium is the opening of the coronary sinus. This thin-walled vessel drains most of the coronary veins that return systemic blood from the heart. The majority of the internal heart structures discussed in this and subsequent sections are illustrated in Figure 19.9. While the bulk of the internal surface of the right atrium is smooth, the depression of the fossa ovalis is medial, and the anterior surface demonstrates prominent ridges of muscle called the pectinate muscles. The right auricle also has pectinate muscles. The left atrium does not have pectinate muscles except in the auricle. The atria receive venous blood on a nearly continuous basis, preventing venous flow from stopping while the ventricles are contracting. While most ventricular filling occurs while the atria are relaxed, they do demonstrate a contractile phase and actively pump blood into the ventricles just prior to ventricular contraction. The opening between the atrium and ventricle is guarded by the tricuspid valve.
It arises from the lower part of the interventricular septum and crosses the interior space of the right ventricle to connect with the inferior papillary muscle. The right ventricle tapers into the pulmonary trunk, into which it ejects blood when contracting. The pulmonary trunk branches into the left and right pulmonary arteries that carry the blood to each lung. The pulmonary valve lies between the right heart and the pulmonary trunk.
At the end of the fourth week, two atrioventricular endocardial cushions appear. Initially the atrioventricular canal gives access to the primitive left ventricle, and is separated from arterial bulb by the edge of the ventricular bulb. In the fifth week, the posterior end terminates in the center part of the upper endocardial cushion. Because of this, blood can access both the left primitive ventricle and the right primitive ventricle. As the anterior and posterior pads project inwardly, they merge to form a right and left atrioventricular orifice.
Here, wires are placed in two chambers of the heart. One lead paces the atrium and one paces the ventricle. This type more closely resembles the natural pacing of the heart by assisting the heart in coordinating the function between the atria and ventricles.
The blood from the right ventricle should go to the pulmonary artery via the pulmonary valve. The blood from the pulmonary vein enters the left atrium, then flows through the mitral valve to the left ventricle. After the left ventricle is filled with blood the aortic valve opens allowing blood to go through, which the blood then enters the aorta and goes to the rest of the body.
The mitral valve (), also known as the bicuspid valve or left atrioventricular valve, is one of the four heart valves. It has two cusps or flaps and lies between the left atrium and the left ventricle of the heart. The heart valves are all one-way valves allowing blood flow in just one direction. The mitral valve and the tricuspid valve are known as the atrioventricular valves because they lie between the atria and the ventricles.In normal conditions, blood flows through an open mitral valve during diastole with contraction of the left atrium, and the mitral valve closes during systole with contraction of the left ventricle.
|
The water cycle involves movement of water between air and what?
|
[
"tree",
"animals",
"air",
"land"
] |
D
|
Atmospheric rivers that move large volumes of water vapor over long distances are an example of advection. Condensation: The transformation of water vapor to liquid water droplets in the air, creating clouds and fog. Evaporation: The transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere.
Water typically varies in temperature from the surface warmed by direct sunlight to greater depths where sunlight cannot penetrate. This differential is greatest in tropical waters, making this technology most applicable in water locations. A fluid is often vaporized to drive a turbine that may generate electricity or produce desalinized water. Systems may be either open-cycle, closed-cycle, or hybrid.
Vortices can otherwise be known as a circular motion of a liquid. In the cases of the absence of forces, the liquid settles. This makes the water stay still instead of moving.
Essential processes of the water cycle are precipitation and evaporation. The local amount of precipitation minus evaporation (often noted as P-E) shows the local influence of the water cycle. Changes in the magnitude of P-E are often used to show changes in the water cycle. But robust conclusions about changes in the amount of precipitation and evaporation are complex.
The central theme of hydrology is that water circulates throughout the Earth through different pathways and at different rates. The most vivid image of this is in the evaporation of water from the ocean, which forms clouds. These clouds drift over the land and produce rain. The rainwater flows into lakes, rivers, or aquifers.
|
When we consider a chemical reaction, we need to take into account both the system and what?
|
[
"date",
"fluctuations",
"time",
"sorroundings"
] |
D
|
When we consider a chemical reaction, we need to take into account both the system and the surroundings. The system includes the components involved in the chemical reaction itself. These will often take place in a flask, a beaker, a test tube, or some other container. The surroundings include everything that is not part of the system. When potassium reacts with water, part of the heat energy generated in the reaction is released into the surroundings. The boundary between system and surroundings is arbitrary, and it is generally chosen in a way that makes observations and calculations easier.
In chemistry, reactivity is the impulse for which a chemical substance undergoes a chemical reaction, either by itself or with other materials, with an overall release of energy. Reactivity refers to: the chemical reactions of a single substance, the chemical reactions of two or more substances that interact with each other, the systematic study of sets of reactions of these two kinds, methodology that applies to the study of reactivity of chemicals of all kinds, experimental methods that are used to observe these processes theories to predict and to account for these processes.The chemical reactivity of a single substance (reactant) covers its behavior in which it: Decomposes Forms new substances by addition of atoms from another reactant or reactants Interacts with two or more other reactants to form two or more productsThe chemical reactivity of a substance can refer to the variety of circumstances (conditions that include temperature, pressure, presence of catalysts) in which it reacts, in combination with the: Variety of substances with which it reacts Equilibrium point of the reaction (i.e., the extent to which all of it reacts) Rate of the reactionThe term reactivity is related to the concepts of chemical stability and chemical compatibility.
A chemical element bonded to an identical chemical element is not a chemical compound since only one element, not two different elements, is involved. Chemical equilibriumIn a chemical reaction, chemical equilibrium is the state in which both reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the system. Usually, this state results when the forward reaction proceeds at the same rate as the reverse reaction.
In biochemistry, a consecutive series of chemical reactions (where the product of one reaction is the reactant of the next reaction) form metabolic pathways. These reactions are often catalyzed by protein enzymes. Enzymes increase the rates of biochemical reactions, so that metabolic syntheses and decompositions impossible under ordinary conditions can occur at the temperature and concentrations present within a cell. The general concept of a chemical reaction has been extended to reactions between entities smaller than atoms, including nuclear reactions, radioactive decays and reactions between elementary particles, as described by quantum field theory.
Chemical reactions, as macroscopic unit operations, consist of simply a very large number of elementary reactions, where a single molecule reacts with another molecule. As the reacting molecules (or moieties) consist of a definite set of atoms in an integer ratio, the ratio between reactants in a complete reaction is also in integer ratio.
Where this assumption holds, a set of reactions can be coarse-grained into one reaction rule. This coarse-graining preserves the important properties of the underlying reactions. For instance, if the reactions are based on chemical kinetics, so are the rules derived from them.
|
What is a layer of tissue that lies between the shell and the body?
|
[
"mantle",
"stem",
"silt",
"node"
] |
A
|
Two unique features of mollusks are the mantle and radula (see Figure above ). The mantle is a layer of tissue that lies between the shell and the body. It secretes calcium carbonate to form the shell. It forms a cavity, called the mantle cavity, between the mantle and the body. The mantle cavity pumps water for filter feeding. The radula is a feeding organ with teeth made of chitin. It is located in front of the mouth in the head region. Herbivorous mollusks use the radula to scrape food such as algae off rocks. Predatory mollusks use the radula to drill holes in the shells of their prey.
The body of the polyp may be roughly compared in a structure to a sac, the wall of which is composed of two layers of cells. The outer layer is known technically as the ectoderm, the inner layer as the endoderm (or gastroderm). Between ectoderm and endoderm is a supporting layer of structureless gelatinous substance termed mesoglea, secreted by the cell layers of the body wall. The mesoglea can be thinner than the endoderm or ectoderm or comprise the bulk of the body as in larger jellyfish.
The dermis is the underlying connective tissue layer that supports the epidermis. It is composed of dense irregular connective tissue and areolar connective tissue such as a collagen with elastin arranged in a diffusely bundled and woven pattern. The dermis has two layers: the papillary dermis and the reticular layer. The papillary layer is the superficial layer that forms finger-like projections into the epidermis (dermal papillae), and consists of highly vascularized, loose connective tissue.
It has a fusiform (spindle-shaped) body, with a maximum length of 90 mm. At the posterior or backside of the animal is a caudal fin, which was supported by two sets of orthogonal fin rays. The exterior lacks any other organs. The internal anatomy consists of a foregut and a midgut. The gut lacks a midsection and an anus. Beneath the midgut is a disc shaped organ, tentatively called a ferrodiscus; the purpose of this organ is unknown, however it has a high concentration of iron.
The cardiac skeleton is made of dense connective tissue which gives structure to the heart by forming the atrioventricular septum—which separates the atria from the ventricles—and the fibrous rings which serve as bases for the four heart valves. Collagen extensions from the valve rings seal and limit electrical activity of the atria from influencing electrical pathways that cross the ventricles.
Like those of cnidarians, (jellyfish, sea anemones, etc.), ctenophores' bodies consist of a relatively thick, jelly-like mesoglea sandwiched between two epithelia, layers of cells bound by inter-cell connections and by a fibrous basement membrane that they secrete. The epithelia of ctenophores have two layers of cells rather than one, and some of the cells in the upper layer have several cilia per cell.The outer layer of the epidermis (outer skin) consists of: sensory cells; cells that secrete mucus, which protects the body; and interstitial cells, which can transform into other types of cell. In specialized parts of the body, the outer layer also contains colloblasts, found along the surface of tentacles and used in capturing prey, or cells bearing multiple large cilia, for locomotion. The inner layer of the epidermis contains a nerve net, and myoepithelial cells that act as muscles.The internal cavity forms: a mouth that can usually be closed by muscles; a pharynx ("throat"); a wider area in the center that acts as a stomach; and a system of internal canals.
|
In what country can some of the largest natural crystals be found?
|
[
"mexico",
"spain",
"germany",
"canada"
] |
A
|
Some of the largest, and most beautiful, natural crystals can be found in the Naica mine, in Mexico. These gypsum crystals were formed over thousands of years. Groundwater that is rich in calcium and sulfur flowed through an underground cave. Check it out:.
Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Large crystals of mica used for various applications are typically mined from granitic pegmatites.The largest documented single crystal of mica (phlogopite) was found in Lacey Mine, Ontario, Canada; it measured 10 m × 4.3 m × 4.3 m (33 ft × 14 ft × 14 ft) and weighed about 330 tonnes (320 long tons; 360 short tons). Similar-sized crystals were also found in Karelia, Russia.Scrap and flake mica is produced all over the world. In 2010, the major producers were Russia (100,000 tonnes), Finland (68,000 t), United States (53,000 t), South Korea (50,000 t), France (20,000 t) and Canada (15,000 t).
Iron and magnetic ores were mined from 1882, gold, copper and mica from the late 1890s, and marble from 1911. More than 1,600 identifiable minerals and non-metallic collectibles can be found in the area,: 184 including 175 species of gemstones. : 410 Aside from uranium, mines in the Bancroft area produced sought-after gemstones of 175 species, most notably calcite, clinohumite, corundum, diopside, dravite, edenite, euxenite-(Y), ferri-fluoro-katophorite, fluorapatite, fluorite, fluoro-richterite, ilmenite, kainosite-(Y), molybdenite, nepheline, phlogopite, crystals of the pyrochlore supergroup, thorite, titanite, tremolite, uraninite, uranophane, and zircon. Madawaska Mine produced samples of the very rare kainosite-(Y), globally renowned samples of the common calcite and fluorite, "superb" samples of ilmenite, and "fine" samples of molybdenite. : 410–417 Marble mined in Bancroft was used to make the floor of the Whitney Block and the Royal Ontario Museum.
The top producers of sphalerite include the United States, Russia, Mexico, Germany, Australia, Canada, China, Ireland, Peru, Kazakhstan and England.Sources of high quality crystals include:
Well formed crystals are rare. It has a Mohs hardness of 6.5 and a specific gravity of 2.9. It has a brittle fracture and no cleavage.
The first emerald mine had been opened in 1831. However, recent research suggests that the stone was discovered by Yakov Kokovin.Alexandrite 5 carats (1,000 mg) and larger were traditionally thought to be found only in the Ural Mountains, but have since been found in larger sizes in Brazil.
|
What are the primary producers in terrestrial biomes?
|
[
"plants",
"soil",
"gases",
"animals"
] |
A
|
Plants are the primary producers in terrestrial biomes. They make food for themselves and other organisms by photosynthesis. The major plants in a given biome, in turn, help determine the types of animals and other organisms that can live there.
Net primary production is estimated at 21.9 gigatonnes of biomass per year for tropical forests, 8.1 for temperate forests, and 2.6 for boreal forests.Forests form distinctly different biomes at different latitudes and elevations, and with different precipitation and evapotranspiration rates. These biomes include boreal forests in subarctic climates, tropical moist forests and tropical dry forests around the Equator, and temperate forests at the middle latitudes. Forests form in areas of the Earth with high rainfall, while drier conditions produce a transition to savanna.
This margin is also known as the littoral zone and contains much of the photosynthetic algae and plants of this ecosystem called macrophytes. Other photosynthetic organisms such as phytoplankton (suspended algae) and periphytons (organisms including cyanobacteria, detritus, and other microbes) thrive here and stand as the primary producers of pond food webs. Some grazing animals like geese and muskrats consume the wetland plants directly as a source of food.
The strength of bottom-up controls on energy flow are determined by the nutritional quality, size, and growth rates of primary producers in an ecosystem. Photosynthetic material is typically rich in nitrogen (N) and phosphorus (P) and supplements the high herbivore demand for N and P across all ecosystems. Aquatic primary production is dominated by small, single-celled phytoplankton that are mostly composed of photosynthetic material, providing an efficient source of these nutrients for herbivores. In contrast, multi-cellular terrestrial plants contain many large supporting cellulose structures of high carbon but low nutrient value.
This is a contrast to on land, where most primary production is performed by vascular plants. Algae ranges from single floating cells to attached seaweeds, while vascular plants are represented in the ocean by groups such as the seagrasses and the mangroves. Larger producers, such as seagrasses and seaweeds, are mostly confined to the littoral zone and shallow waters, where they attach to the underlying substrate and are still within the photic zone.
This selection occurs most strongly in the endosphere, followed by the rhizoplane, and finally the rhizosphere. For example, root exudates can select for and promote the growth of certain beneficial microbes by serving as carbon and/or energy sources for microbial metabolism.
|
Where are aerofoils found?
|
[
"airplanes and plants",
"birds and airplanes",
"birds and busses",
"birds and cars"
] |
B
|
Birds also have wings that function as an aerofoil . The surface of the aerofoil is curved to help the bird control and use the air currents to fly. Aerofoils are also found on the wings of airplanes.
Windfoiling otherwise known as Windsurf Foiling are windsurf boards equipped with 2 'T'-shaped hydrofoil wings of opposite orientation connected by a fuselauge and a mast inserting into the board. The front wing is larger and provides upwards lift while the rear wing provides stability with downward lift. Many of the hydrofoils used in windfoiling can vary in size in order to obtain a greater combination of lift and top speed. The most recent development in windfoiling was the creation of the IQFoil one design Olympic Windsurfing class by Starboard Windsurfing used to replace the RS:X in the 2024 Olympics. The IQFoil contains a fully battened, cambered sail alongside a board made of a carbon reflex sandwich design and a carbon and aluminum foil. The class was created in 2020 and is similar to the open windfoiling class used in the PWA(Professional Windsurfing Association) competitions.
A trefoil (from Latin trifolium 'three-leaved plant') is a graphic form composed of the outline of three overlapping rings, used in architecture, Pagan and Christian symbolism, among other areas. The term is also applied to other symbols with a threefold shape. A similar shape with four rings is called a quatrefoil.
Supercritical airfoils designed to independently maximize laminar flow above and below the wing. The numbering is identical to the 7-series airfoils except that the sequence begins with an "8" to identify the series.
The tinfoil barb is often seen in large aquaria as companions to large cichlids e.g. the oscar cichlid, Astronotus ocellatus. The tinfoil barb is an active, peaceful species that spends most of its time in the mid-level and bottom of the water. A greedy eater, it will attempt to fill its mouth with as much food as possible during feedings. In captivity, it will eat almost anything provided to it.
In parallel, postwar Germany and the Netherlands also conducted their own research efforts into optimal transonic airfoil designs, intending for these efforts to support civil aviation programmes. Up until the 1970s, there was considerable focus upon developing an airfoil that performed isentropic recompression, a shock-free return of the airflow to subsonic speeds.In the United States, the supercritical airfoil was an area of research during the 1960s; one of the leading American figures in the field was Richard Whitcomb. A specially modified North American T-2C Buckeye functioned as an early aerial testbed for the supercritical wing, performing numerous evaluation flights during this period in support of the research effort.
|
What is the si unit for pressure?
|
[
"watt",
"laurent",
"le",
"pascal"
] |
D
|
Summary Four quantities must be known for a complete physical description of a sample of a gas: temperature, volume, amount, and pressure. Pressure is force per unit area of surface; the SI unit for pressure is the pascal (Pa), defined as 1 newton per square meter (N/m2). The pressure exerted by an object is proportional to the force it exerts and inversely proportional to the area on which the force is exerted. The pressure exerted by Earth’s atmosphere, called atmospheric pressure, is about 101 kPa or 14.7 lb/in.2 at sea level. Atmospheric pressure can be measured with abarometer, a closed, inverted tube filled with mercury. The height of the mercury column is proportional to atmospheric pressure, which is often reported in units ofmillimeters of mercury (mmHg), also called torr. Standard atmospheric pressure, the pressure required to support a column of mercury 760 mm tall, is yet.
(mol/s)/(m2·mol/m3) = m/sNote, the units will vary based upon which units the driving force is expressed in. The driving force shown here as ' Δ c A {\displaystyle {\Delta c_{A}}} ' is expressed in units of moles per unit of volume, but in some cases the driving force is represented by other measures of concentration with different units. For example, the driving force may be partial pressures when dealing with mass transfer in a gas phase and thus use units of pressure.
The International System of Units, internationally known by the abbreviation SI (for Système International),: 125: iii is the modern form: 117 of the metric system and the world's most widely used system of measurement. : 123 Established and maintained by the General Conference on Weights and Measures (CGPM), it is the only system of measurement with an official status in nearly every country in the world, employed in science, technology, industry, and everyday commerce. The SI comprises a coherent system of units of measurement starting with seven base units, which are the second (symbol s, the unit of time), metre (m, length), kilogram (kg, mass), ampere (A, electric current), kelvin (K, thermodynamic temperature), mole (mol, amount of substance), and candela (cd, luminous intensity). The system can accommodate coherent units for an unlimited number of additional quantities.
The quantities and equations that provide the context in which the SI units are defined are now referred to as the International System of Quantities (ISQ). The ISQ is based on the quantities underlying each of the seven base units of the SI. Other quantities, such as area, pressure, and electrical resistance, are derived from these base quantities by clear, non-contradictory equations. The ISQ defines the quantities that are measured with the SI units. The ISQ is formalised, in part, in the international standard ISO/IEC 80000, which was completed in 2009 with the publication of ISO 80000-1, and has largely been revised in 2019–2020 with the remainder being under review.
The SI-unit for mass concentration is kg/m3 (kilogram/cubic metre). This is the same as mg/mL and g/L. Another commonly used unit is g/(100 mL), which is identical to g/dL (gram/decilitre).
This is a tabulated listing of the orders of magnitude in relation to pressure expressed in pascals. == References ==
|
Marine fishes take in divalent ions by incessantly drinking what?
|
[
"sand",
"oxygen",
"algae",
"seawater"
] |
D
|
In teleost (advanced ray-finned) fishes, the gills, kidney and digestive tract are involved in maintenance of body fluid balance, as the main osmoregulatory organs. Gills in particular are considered the primary organ by which ionic concentration is controlled in marine teleosts. Unusually, the catfishes in the eeltail family Plotosidae have an extra-branchial salt-secreting dendritic organ.
In places where this plankton-feeding species has been introduced, they are thought to compete with native planktivorous fishes, which in North America include paddlefish (Polyodon spathula), bigmouth buffalo (Ictiobus cyprinellus), gizzard shad (Dorosoma cepedianum), and young fish of almost all species.Because they feed on plankton, they are sometimes successfully used for controlling water quality, especially in the control of noxious blue-green algae (cyanobacteria). Certain species of blue-green algae, notably the often toxic Microcystis, can pass through the gut of silver carp unharmed, picking up nutrients in the process. Thus, in some cases, blue-green algae blooms have been exacerbated by silver carp, and Microcystis has also been shown to produce more toxins in the presence of silver carp. These carp, which have natural defenses to their toxins, sometimes can contain enough algal toxins in their systems to become hazardous to eat.
The southern bluefin tuna have a large gill surface area which is important for oxygen consumption and handling high osmoregulatory costs, associated with the high resting metabolic rate. They can adapt to increasing water salinity, where the ionocyte increase in size, gill filaments become thicker, the surface area of the basolateral membrane increases, and the intracellular tubular system proliferates. Teleost fish do not have the loop of Henle in the kidneys and are, therefore, not able to produce hyperosmotic urine.
The electron transport chain is not affected and continues using oxygen, without producing ATP. While the general opinion is that TFM typically does not harm other fish (due to the relationship between true fish and lampreys), lampricide can be problematic for many amphibians, such as mudpuppies (genus Necturus) which often share the same habitats. Also, some more "primitive" species of fish, such as the sturgeon in the Great Lakes are sensitive to chemicals such as TFM.
In high concentrations it discolors the water which often appears reddish-brown in color. It produces a toxin which paralyses the central nervous system of fish so they cannot breathe. Dead fish wash up on beaches around Texas and Florida.
|
The simplest and smallest particle of matter that still has chemical properties of the element is called?
|
[
"a molecule",
"an atom",
"a nucleus",
"an isotope"
] |
B
|
Inside of elements, you will find identical atoms. An atom is the simplest and smallest particle of matter that still has chemical properties of the element. Atoms are the building block of all of the elements that make up the matter in your body or any other living or non-living thing. Atoms are so small that only the most powerful microscopes can see them.
Atoms are the smallest neutral particles into which matter can be divided by chemical reactions. An atom consists of a small, heavy nucleus surrounded by a relatively large, light cloud of electrons. An atomic nucleus typically consists of 1 or more protons and 0 or more neutrons. Protons and neutrons are, in turn, made of quarks.
This postulate, however, does not apply to the universe's most abundant and simplest element: hydrogen, with an atomic number of 1. This may be because, in its ionized form, a hydrogen atom becomes a single proton, of which it is theorized to have been one of the first major conglomerates of quarks during the initial second of the Universe's inflation period, following the Big Bang. In this period, when inflation of the universe had brought it from an infinitesimal point to about the size of a modern galaxy, temperatures in the particle soup fell from over a trillion degrees to several million degrees. This period allowed for the fusion of single protons and deuterium nuclei to form helium and lithium nuclei but was too short for every H+ ion to be reconstituted into heavier elements.
As heat is added to this substance it melts into a liquid at its melting point, boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms. Forms of matter that are not composed of molecules and are organized by different forces can also be considered different states of matter.
: 29 According to Plato, the four elements are derived from a common source or prima materia (first matter), associated with chaos. Prima materia is also the name alchemists assign to the starting ingredient for the creation of the philosopher's stone. The importance of this philosophical first matter persisted throughout the history of alchemy. In the seventeenth century, Thomas Vaughan writes, "the first matter of the stone is the very same with the first matter of all things. ": 211
The force-carrying particles are not themselves building blocks. As one consequence, mass and energy (which to our present knowledge cannot be created or destroyed) cannot always be related to matter (which can be created out of non-matter particles such as photons, or even out of pure energy, such as kinetic energy). Force mediators are usually not considered matter: the mediators of the electric force (photons) possess energy (see Planck relation) and the mediators of the weak force (W and Z bosons) have mass, but neither are considered matter either. However, while these quanta are not considered matter, they do contribute to the total mass of atoms, subatomic particles, and all systems that contain them.
|
Frequency and intensity are two measurable properties of what?
|
[
"wave",
"heat",
"lines",
"troughs"
] |
A
|
All waves can be defined in terms of their frequency and intensity.
Measurement of frequency can be done in the following ways:
Range–frequency theory postulates that the actual judgments reflect a compromise between these two principles. Mathematically, the subjective judgment J of stimulus i in context k is conceived as a compromise between the range, R, and the frequency, F, principles, in which the weighting parameter, w, is a value between zero and one: Jik = (w)*Rik + (1-w)*Fik The relative weighting of range and frequency values has been found to be roughly equal, that is to say that w is roughly .5. A number of experiments have shown that w can either be increased or reduced.
Slowly adapting or tonic receptors respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can not become "stronger" for a specific frequency.
In radiometry, spectral radiance or specific intensity is the radiance of a surface per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of spectral radiance in frequency is the watt per steradian per square metre per hertz (W·sr−1·m−2·Hz−1) and that of spectral radiance in wavelength is the watt per steradian per square metre per metre (W·sr−1·m−3)—commonly the watt per steradian per square metre per nanometre (W·sr−1·m−2·nm−1). The microflick is also used to measure spectral radiance in some fields.Spectral radiance gives a full radiometric description of the field of classical electromagnetic radiation of any kind, including thermal radiation and light.
Rather than shining a monochromatic beam of light (a beam composed of only a single wavelength) at the sample, this technique shines a beam containing many frequencies of light at once and measures how much of that beam is absorbed by the sample. Next, the beam is modified to contain a different combination of frequencies, giving a second data point. This process is rapidly repeated many times over a short time span.
|
While most mammals give birth to live young, monotremes can do what?
|
[
"reproduce asexually",
"lay eggs",
"adopt offspring",
"steal eggs"
] |
B
|
Monotremes can lay eggs, but most mammals give birth to live young.
It is not only mammals that give birth. Some reptiles, amphibians, fish and invertebrates carry their developing young inside them. Some of these are ovoviviparous, with the eggs being hatched inside the mother's body, and others are viviparous, with the embryo developing inside their body, as in the case of mammals.
They are omnipresent in non-placental mammaliformes, though Megazostrodon and Erythrotherium appear to have lacked them.It has been suggested that the original function of lactation (milk production) was to keep eggs moist. Much of the argument is based on monotremes, the egg-laying mammals. In human females, mammary glands become fully developed during puberty, regardless of pregnancy.
The requiem sharks maintain a placental link to the developing young, this practice is known as viviparity. This is more analogous to mammalian gestation than to that of other fishes.
At some point, the growing egg or offspring must be expelled. There are several possible modes of reproduction. These are traditionally classified as follows: Oviparity, as in most invertebrates and reptiles, monotremes, dinosaurs and all birds which lay eggs that continue to develop after being laid, and hatch later. Viviparity, as in almost all mammals (such as whales, kangaroos and humans) which bear their young live.
The gray short-tailed opossum possesses several features that make it an ideal research model, particularly in studies of marsupials, as well as the immunological and developmental research on mammalian systems. It breeds relatively easily in laboratory settings, and neonates are exposed and can be readily accessed because, unlike other marsupial species, female opossums lack a pouch: neonates simply cling to the teats. Opossums are born at a stage that is approximately equivalent to 13- to 15-day-old fetal rats or 40-day-old human embryos.
|
What happens to old oceanic crust at convergent boundaries?
|
[
"destroyed",
"created",
"dissolves",
"emerges"
] |
A
|
It’s much easier to precisely make mirrors than to precisely make glass lenses. For that reason, reflectors can be made larger than refractors. Larger telescopes can collect more light. This means that they can study dimmer or more distant objects. The largest optical telescopes in the world today are reflectors. Telescopes can also be made to use both lenses and mirrors.
The new crust that is formed at divergent boundaries within oceanic crust is almost entirely magmatic in origin.
Transitional crust, separating true oceanic and continental crusts, is the foundation of any passive margin. This forms during the rifting stage and consists of two endmembers: volcanic and non-volcanic. This classification scheme only applies to rifted and transtensional margin; transitional crust of sheared margins is very poorly known.
The movement of the island arcs towards the continent could be possible if, at some point, the ancient Benioff zones dipped toward the present ocean rather than toward the continent, as in most arcs today. This will have resulted in the loss of ocean floor between the arc and the continent, and consequently, in the migration of the arc during spreading episodes.The fracture zones in which some active island arcs terminate may be interpreted in terms of plate tectonics as resulting from movement along transform faults, which are plate margins where the crust is neither being consumed nor generated. Thus the present location of these inactive island chains is due to the present pattern of lithospheric plates. However, their volcanic history, which indicates that they are fragments of older island arcs, is not necessarily related to the present plate pattern and may be due to differences in position of plate margins in the past.
Dykes are perpetually formed as long as magma continues to flow through the plate boundary, creating a distinct, stratigraphic-like sequences of rocky columns within the seafloor. Ophiolites are formed when these sections of oceanic crust are revealed above sea level and embedded within coastal crust. Older dykes formed near divergence zones are pushed away as new seafloor is created, a phenomenon known as seafloor spreading, and over time, the oldest dykes are pushed far enough from convergence zones to be exposed above sea level.
However, the formation process through detachment faults hypothesis has its limitations, such as the scarce seismic evidence that low-angle normal faulting exists, where the presumably significant offset along such faults - which transect the lithosphere at a low angle - should be involved with some friction. The rarity of eclogite in oceanic core complexes also casts doubt on the likelihood of a deep source in such domains. The abundance of peridotites in oceanic core complexes could be accounted for by a unique variation of ocean-ocean subduction at the junction of slow-spreading oceanic ridges and fracture zones.
|
When electrons are shared between two atoms, they make a bond called a what?
|
[
"metallic bond",
"covalent bond",
"ionic bond",
"hydrogen bond"
] |
B
|
Ionic bonding typically occurs when it is easy for one atom to lose one or more electrons and another atom to gain one or more electrons. However, some atoms won’t give up or gain electrons easily. Yet they still participate in compound formation. How? There is another mechanism for obtaining a complete valence shell: sharing electrons. When electrons are shared between two atoms, they make a bond called a covalent bond. Let us illustrate a covalent bond by using H atoms, with the understanding that H atoms need only two electrons to fill the 1s subshell. Each H atom starts with a single electron in its valence shell:.
Ionic bonding is a kind of chemical bonding that arises from the mutual attraction of oppositely charged ions. Ions of like charge repel each other, and ions of opposite charge attract each other. Therefore, ions do not usually exist on their own, but will bind with ions of opposite charge to form a crystal lattice. The resulting compound is called an ionic compound, and is said to be held together by ionic bonding.
This transfer causes one atom to assume a net positive charge, and the other to assume a net negative charge. The bond then results from electrostatic attraction between the positive and negatively charged ions. Ionic bonds may be seen as extreme examples of polarization in covalent bonds.
Two electrons fill the lower-energy bonding orbital, σg(1s), while the remaining two fill the higher-energy antibonding orbital, σu*(1s). Thus, the resulting electron density around the molecule does not support the formation of a bond between the two atoms; without a stable bond holding the atoms together, the molecule would not be expected to exist. Another way of looking at it is that there are two bonding electrons and two antibonding electrons; therefore, the bond order is 0 and no bond exists (the molecule has one bound state supported by the Van der Waals potential).
The combination of two phenomena gives rise to metallic bonding: delocalization of electrons and the availability of a far larger number of delocalized energy states than of delocalized electrons. The latter could be called electron deficiency.
Substances composed of discrete molecules or single atoms are held together by weaker attractive forces between the molecules, such as the London dispersion force: as electrons move within the molecules, they create momentary imbalances of electrical charge, which induce similar imbalances on nearby molecules and create synchronised movements of electrons across many neighbouring molecules.The more electropositive atoms, however, tend to instead lose electrons, creating a "sea" of electrons engulfing cations. The outer orbitals of one atom overlap to share electrons with all its neighbours, creating a giant structure of molecular orbitals extending over all the atoms. This negatively charged "sea" pulls on all the ions and keeps them together in a metallic bond.
|
What happens to the temperature of matter as light is absorbed?
|
[
"it stays the same",
"it increases",
"it triples",
"it drops"
] |
B
|
http://www. chem. ufl. edu/~itl/2045/lectures/lec_d. html.
Thermoluminescence is light from the re-emission of absorbed energy when a substance is heated.
The maximum absorption of light is near 670 nm. The specifics of absorption depend on a number of factors, including protonation, adsorption to other materials, and metachromasy - the formation of dimers and higher-order aggregates depending on concentration and other interactions:
The heat transfer by radiation is proportional to the power of four of the absolute surface temperature. The emissivity of a material (usually written ε or e) is the relative ability of its surface to emit energy by radiation. A black body has an emissivity of 1 and a perfect reflector has an emissivity of 0.In radiative heat transfer, a view factor quantifies the relative importance of the radiation that leaves an object (person or surface) and strikes another one, considering the other surrounding objects.
This caveat also applies to UV, even though almost all of it is not ionizing, because UV can damage molecules due to electronic excitation, which is far greater per unit energy than heating effects.Infrared radiation in the spectral distribution of a black body is usually considered a form of heat, since it has an equivalent temperature and is associated with an entropy change per unit of thermal energy. However, "heat" is a technical term in physics and thermodynamics and is often confused with thermal energy. Any type of electromagnetic energy can be transformed into thermal energy in interaction with matter.
The integration of Planck's law over all frequencies provides the total energy per unit of time per unit of surface area radiated by a black body maintained at a temperature T, and is known as the Stefan–Boltzmann law: P / A = σ T 4 , {\displaystyle P/A=\sigma T^{4}\ ,} where σ is the Stefan–Boltzmann constant, σ ≈ 5.67×10−8 W⋅m−2⋅K−4 To remain in thermal equilibrium at constant temperature T, the black body must absorb or internally generate this amount of power P over the given area A. The cooling of a body due to thermal radiation is often approximated using the Stefan–Boltzmann law supplemented with a "gray body" emissivity ε ≤ 1 (P/A = εσT4). The rate of decrease of the temperature of the emitting body can be estimated from the power radiated and the body's heat capacity. This approach is a simplification that ignores details of the mechanisms behind heat redistribution (which may include changing composition, phase transitions or restructuring of the body) that occur within the body while it cools, and assumes that at each moment in time the body is characterized by a single temperature.
|
By shocking ocean water, earthquakes can cause what deadly ocean waves?
|
[
"tsunamis",
"deep currents",
"ebb tides",
"typhoons"
] |
A
|
Earthquakes can cause tsunamis . These deadly ocean waves may result from any shock to ocean water. A shock could be a meteorite impact, landslide, or a nuclear explosion. But most come from large underwater earthquakes.
Shock waves can form due to steepening of ordinary waves. The best-known example of this phenomenon is ocean waves that form breakers on the shore. In shallow water, the speed of surface waves is dependent on the depth of the water. An incoming ocean wave has a slightly higher wave speed near the crest of each wave than near the troughs between waves, because the wave height is not infinitesimal compared to the depth of the water.
Submarine earthquakes arising from tectonic plate movements under the oceans can lead to destructive tsunamis, as can volcanoes, huge landslides, or the impact of large meteorites. A wide variety of organisms, including bacteria, protists, algae, plants, fungi, and animals, lives in the seas, which offers a wide range of marine habitats and ecosystems, ranging vertically from the sunlit surface and shoreline to the great depths and pressures of the cold, dark abyssal zone, and in latitude from the cold waters under polar ice caps to the warm waters of coral reefs in tropical regions. Many of the major groups of organisms evolved in the sea and life may have started there.
These waves are greatly affected by coastal amplification (which amplifies the local effect) and radial damping (which reduces the distal effect).Recent findings show that the nature of a tsunami is dependent upon volume, velocity, initial acceleration, length and thickness of the contributing landslide. Volume and initial acceleration are the key factors which determine whether a landslide will form a tsunami. A sudden deceleration of the landslide may also result in larger waves.
The seismic pressure waves created from an explosion may release stress within nearby plates or otherwise cause an earthquake event, an underground explosion concentrates this pressure wave and a localized earthquake event is more probable, these waves, the first and fastest wave, equivalent to a normal earthquakes P wave can inform the location of the test, the S wave and the Rayleigh wave follow, these can all be measured in most circumstances by seismic station across the globe and comparisons with actual earthquakes can be used to help determine estimated yield via differential analysis, by the modelling of the high-frequency (>4 Hz) teleseismic P wave amplitudes. However, theory does not suggest that a nuclear explosion of current yields could trigger fault rupture and cause a major quake at distances beyond a few tens of kilometers from the shot point.
Both the landslide itself (on Ischia) and tsunamis (Ischia and the coast of Campania) would be affected. There is little known about the potential for such landslide-induced tsunamis in the Pacific Ocean, except for Hawaii. A slump off Pico Stromboli Tenerife, which in case of a collapse during renewed mafic activity could affect the North Atlantic. While non-volcanic, tsunami threats from submarine landslides off the western Great Bahama Bank have been identified. They may impact The Bahamas, Cuba and Florida.
|
Where are the desmosome found in a cell?
|
[
"epithelial",
"epithelium",
"neuron",
"coating"
] |
B
|
A desmosome is a cell junction specialized for cell-to-cell adhesion. They are found in simple and stratified squamous epithelium, and in muscle tissue where they bind muscle cells to one another. These junctions are composed of complexes of cell surface adhesion proteins and linking proteins. These proteins have both an intracellular and extracellular region. Inside the cell, they attach to intracellular filaments of the cytoskeleton. Outside the cell, they attach to other adhesion proteins.
It contains numerous granulosa cells.
Diatom cells are contained within a unique silica cell wall known as a frustule made up of two valves called thecae, that typically overlap one another. The biogenic silica composing the cell wall is synthesised intracellularly by the polymerisation of silicic acid monomers. This material is then extruded to the cell exterior and added to the wall. In most species, when a diatom divides to produce two daughter cells, each cell keeps one of the two-halves and grows a smaller half within it.
Some eukaryotic cells (plant cells and fungal cells) also have a cell wall. Inside the cell is the cytoplasmic region that contains the genome (DNA), ribosomes and various sorts of inclusions. The genetic material is freely found in the cytoplasm.
Exocytosis is the process by which a large amount of molecules are released; thus it is a form of bulk transport. Exocytosis occurs via secretory portals at the cell plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structures at the cell plasma membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell.
In plants, suspensors are found in zygotes in angiosperms, connecting the endosperm to an embryo. Usually in dicots the suspensor cells divide transversally a few times to form a filamentous suspensor of 6-10 cells. The suspensor helps in pushing the embryo into the endosperm. The first cell of the suspensor towards the micropylar end becomes swollen and functions as a haustorium.
|
An action potential that starts at the axon hillock moves along the axon only toward what?
|
[
"nerve endings",
"ionic pathways",
"polar synapses",
"the synaptic terminals"
] |
D
|
The axon hillock is a specialized part of the cell body (or soma) of a neuron that connects to the axon. It can be identified using light microscopy from its appearance and location in a neuron and from its sparse distribution of Nissl substance.The axon hillock is the last site in the soma where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon. For many years, it was believed that the axon hillock was the usual site of initiation of action potentials—the trigger zone. It is now thought that the earliest site of action potential initiation is at the axonal initial segment: just between the peak of the axon hillock and the initial (unmyelinated) segment of the axon.
The Mauthner cell axon hillock is surrounded by a dense formation of neuropil, called the axon cap. The high resistance of this axon cap contributes to the typical shape of the Mauthner cell field potential (see below). In its most advanced form the axon cap consists of a core, immediately adjacent to the Mauthner cell axon, and containing a network of very thin unmyelinated fibers, and a peripheral part.
The axonal initial segment (AIS) is a structurally and functionally separate microdomain of the axon. One function of the initial segment is to separate the main part of an axon from the rest of the neuron; another function is to help initiate action potentials. Both of these functions support neuron cell polarity, in which dendrites (and, in some cases the soma) of a neuron receive input signals at the basal region, and at the apical region the neuron's axon provides output signals.The axon initial segment is unmyelinated and contains a specialized complex of proteins. It is between approximately 20 and 60 µm in length and functions as the site of action potential initiation.
Myelinated axons only allow action potentials to occur at the unmyelinated nodes of Ranvier that occur between the myelinated internodes. It is by this restriction that saltatory conduction propagates an action potential along the axon of a neuron at rates significantly higher than would be possible in unmyelinated axons (150 m/s compared to 0.5 to 10 m/s). As sodium rushes into the node it creates an electrical force which pushes on the ions already inside the axon. This rapid conduction of electrical signal reaches the next node and creates another action potential, thus refreshing the signal.
When the cumulative postsynaptic potential exceeds the resting potential, an action potential is generated by the cell body or soma and propagated along the axon. The axon may have one or more terminals and these terminals transmit neurotransmitters to the synapses with which the neuron is connected. Depending on the stimulus received by the dendrites, soma may generate one or more well-separated action potentials or spike train.
|
Fission is a type of radioactivity in which large nuclei spontaneously break apart into what?
|
[
"faster nuclei",
"smaller nuclei",
"light nuclei",
"active nuclei"
] |
B
|
Fission is a type of radioactivity in which large nuclei spontaneously break apart into smaller nuclei.
Nuclear Fission. Academic Press, New York. == References ==
Frisch named the process "fission" by analogy with biological fission of living cells. In their second publication on nuclear fission in February of 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of a nuclear chain reaction. For heavy nuclides, it is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place).
An example of this kind of a nuclear reaction occurs in the production of cobalt-60 within a nuclear reactor: The cobalt-60 then decays by the emission of a beta particle plus gamma rays into nickel-60. This reaction has a half-life of about 5.27 years, and due to the availability of cobalt-59 (100% of its natural abundance), this neutron bombarded isotope of cobalt is a valuable source of nuclear radiation (namely gamma radiation) for radiotherapy. 5927Co + 10n → 6027CoIn other cases, and depending on the kinetic energy of the neutron, the capture of a neutron can cause nuclear fission—the splitting of the atomic nucleus into two smaller nuclei. If the fission requires an input of energy, that comes from the kinetic energy of the neutron.
This is a different process than the more random nuclear disintegration that precedes light fragment emission in ternary fission, which may be a result of a nuclear reaction, but can also be a type of spontaneous radioactive decay in certain nuclides, demonstrating that input energy is not necessarily needed for fission, which remains a fundamentally different process mechanistically. Theoretically, any nucleus with Z > 40 for which the released energy (Q value) is a positive quantity, can be a cluster-emitter. In practice, observations are severely restricted to limitations imposed by currently available experimental techniques which require a sufficiently short half-life, Tc < 1032 s, and a sufficiently large branching ratio B > 10−17.
They theorised that uranium atoms bombarded with neutrons can break into two roughly equal fragments, a process they called fission. They calculated that this would result in the release of about 200 MeV, implying an energy release orders of magnitude greater than chemical reactions, and Frisch confirmed their theory experimentally. It was soon noted by Hahn that if neutrons were released during fission, then a chain reaction was possible.
|
Bones are the main organs of what system, which also includes cartilage and ligaments?
|
[
"lymphatic system",
"digestive system",
"endocrine system",
"skeletal system"
] |
D
|
Bones are the main organs of the skeletal system. The skeletal system also includes cartilage and ligaments.
The skeletal portion of the system serves as the main storage system for calcium and phosphorus and contains critical components of the hematopoietic system.This system describes how bones are connected to other bones and muscle fibers via connective tissue such as tendons and ligaments. The bones provide stability to the body. Muscles keep bones in place and also play a role in the movement of bones.
Bone is formed by one of two processes: endochondral ossification or intramembranous ossification. Endochondral ossification is the process of forming bone from cartilage and this is the usual method. This form of bone development is the more complex form: it follows the formation of a first skeleton of cartilage made by chondrocytes, which is then removed and replaced by bone, made by osteoblasts.
The hollow tubular structure of bones provide considerable resistance against compression while staying lightweight. Most cells in bones are either osteoblasts, osteoclasts, or osteocytes.Bone tissue is a type of dense connective tissue. One of the types of tissue that makes up bone tissue is mineralized tissue and this gives it rigidity and a honeycomb-like three-dimensional internal structure.
Bone is a form of connective tissue found in the body, composed largely of hardened hydroxyapatite-containing collagen. In larger mammals, it is arranged in osteon regions. Bone matrix allows mineral salts such as calcium to be stored and provides protection for internal organs and support for locomotion.
This is followed by definition of specific cellular subtypes (meniscal progenitors, articular progenitors, synovial progenitors, and ligament progenitors) that will eventually form the joint capsule. Finally, the joint capsule matures and forms a cavity, with a central meniscus, and an encasement of synovium. This final structure will form several distinct layers of the articular cartilage found in all synovial joints including the Deep Zone (closest to the bone), Middle Zone, and Superficial Zone (closest to the synovial fluid).
|
Most waves strike the shore at an angle. this causes what?
|
[
"longshore drift",
"erosion",
"tide",
"fontaine drift"
] |
A
|
Below the topsoil is the “B“ horizon. This is also called the subsoil . Soluble minerals and clays accumulate in the subsoil. Because it has less organic material, this layer is lighter brown in color than topsoil. It also holds more water due to the presence of iron and clay. There is less organic material in this layer.
Shock waves can form due to steepening of ordinary waves. The best-known example of this phenomenon is ocean waves that form breakers on the shore. In shallow water, the speed of surface waves is dependent on the depth of the water. An incoming ocean wave has a slightly higher wave speed near the crest of each wave than near the troughs between waves, because the wave height is not infinitesimal compared to the depth of the water.
Backwash breaking parallel to or obliquely to the angle of the shore is sometimes also called sidewash, which can form from the reflection of a wave breaking against adjacent obstructions such as jetties, groynes, or rockwalls, or simply from the action of backwashing waves which strike a shoreline at an angle. Sidewash and backwash is relatively common, and may amplify another incoming breaking wave's size due to constructive interference. When this process happens with an open ocean swell the resulting wave can also be significantly larger due to constructive interference from either deep water refraction or diffraction, or both. This type of effect is suggested to occur at two of the largest surf breaks in the world, at Nazaré in Portugal, and Jaws in Hawaii. Backwash and sidewash also sometimes form in conjunction with rips on beaches.
These occur where waves are formed from the returning backwash of a wave which has previously gone up a steep shoreline or beach, or sometimes reflected from an ocean rockface or wall. They can sometimes form a surfable wave in a direction oblique to, or opposite from the original wave direction. An example was shown in the film Endless Summer, in Tahiti, called 'Ins and Outs'.
The middle shoreface is strongly influenced by wave action because of its depth. Closer to shore the sand is medium-grained, with shell pieces common. Since wave action is heavier, bioturbation is not likely.
The bottom exerts a frictional drag on the bottom of the wave, which decreases the celerity (or the speed of the waveform), and causes refraction. Slowing the wave forces it to shorten which increases the height and steepness, and the top (crest) falls because the velocity of the top of the wave becomes greater than the velocity of the bottom of the wave where the drag occurs.The surf zone is the place of convergence of multiple waves types creating complex wave patterns. A wave suitable for surfing results from maximum speeds of 5 metres per second (16 ft/s).
|
What is the difference between the daily high and the daily low?
|
[
"weather forecast",
"margin of error",
"tidal change",
"sunrise and sunset"
] |
C
|
The difference between the daily high and the daily low is the tidal range.
A day, in the sense of daytime that is distinguished from night time, is commonly defined as the period during which sunlight directly reaches the ground, assuming that there are no local obstacles. The length of daytime averages slightly more than half of the 24-hour day. Two effects make daytime on average longer than nights. The Sun is not a point, but has an apparent size of about 32 minutes of arc.
It depends on the demography, the economy, the weather, the climate, the season, the day of the week and other factors. For example, in industrialised regions of China or Germany, the peak demands mostly occur in day time, while solar photovoltaic system can help reduce it. However, in more service based economy such as Australia, the daily peak demands often occur in the late afternoon to early evening time (e.g. 4pm to 8pm). Residential and commercial electricity demand contributes a lot to this type of network peak demand.
Measuring a morning, fasting ACTH level helps assess for the etiology of adrenal insufficiency. Interpretation for primary adrenal insufficiency and Addison's diseaseACTH will be high - usually well above upper limits of reference range. Interpretation for secondary adrenal insufficiencyACTH will be low - usually below 35, but most people with secondary fall within the range limit.
For U.S. food and dietary supplement labeling purposes, the amount of the substance in a serving is expressed as a percent of the Daily Value (%DV). For chromium labeling purposes, 100% of the Daily Value was 120 μg. As of May 27, 2016, the percentage of daily value was revised to 35 μg to bring the chromium intake into a consensus with the official Recommended Dietary Allowance. A table of the old and new adult daily values is provided at Reference Daily Intake.
Centers of action are extensive and almost stationary low or high pressure areas which control the movement of atmospheric disturbances over a large area. This does not mean that the position of the center is constant over a specific area but that the monthly atmospheric pressure corresponds to a high or a low pressure.The French meteorologist Léon Teisserenc de Bort was the first in 1881 to apply this term to maxima and minima of pressure on daily charts. The main centers of action in the Northern Hemisphere are the Icelandic Low, the Aleutian Low, the Azores/Bermuda High, the Pacific High, the Siberian High (in winter), and the Asiatic Low (in summer). Sir Gilbert Walker used the same term to relate meteorological elements in a region to weather in the following season in other regions for the Southern Oscillation.
|
Spermatogonia are the stem cells of what male sex organs?
|
[
"testes",
"Epididymis",
"Prostate",
"ovaries"
] |
A
|
Germ Cells The least mature cells, the spermatogonia (singular = spermatogonium), line the basement membrane inside the tubule. Spermatogonia are the stem cells of the testis, which means that they are still able to differentiate into a variety of different cell types throughout adulthood. Spermatogonia divide to produce primary and secondary spermatocytes, then spermatids, which finally produce formed sperm. The process that begins with spermatogonia and concludes with the production of sperm is called spermatogenesis.
In both males and females, the sex organs consist of three structures: the gonads, the internal genitalia, and the external genitalia. In males, the gonads are the testes and in females they are the ovaries. These are the organs that produce gametes (egg and sperm), the reproductive cells that will eventually meet to form the fertilized egg (zygote).
The final category are those used for copulation, and deposition of the spermatozoa (sperm) within the male, these include the penis, urethra, vas deferens, and Cowper's gland. Major secondary sex characteristics include larger, more muscular stature, deepened voice, facial and body hair, broad shoulders, and development of an Adam's apple. An important sexual hormone of males is androgen, and particularly testosterone. The testes release a hormone that controls the development of sperm. This hormone is also responsible for the development of physical characteristics in men such as facial hair and a deep voice.
During copulation, the male inseminates the female. The spermatozoon fertilizes an ovum or various ova in the uterus or fallopian tubes, and this results in one or multiple zygotes. Sometimes, a zygote can be created by humans outside of the animal's body in the artificial process of in-vitro fertilization. After fertilization, the newly formed zygote then begins to divide through mitosis, forming an embryo, which implants in the female's endometrium. At this time, the embryo usually consists of 50 cells.
Sex organs are typically differentiated into male and female types. In humans, the male sex organs include the testes, penis, and prostate gland; the female sex organs include the ovaries, fallopian tubes, uterus, cervix, vagina, and vulva. In animals (including humans), the testis in the male and the ovary in the female are called the primary sex organs.
One cell is responsible for drilling down through the integuments, and creating a conduit for the two sperm cells to flow down. The megagametophyte has just seven cells; of these, one fuses with a sperm cell, forming the nucleus of the egg itself, and another joins with the other sperm, and dedicates itself to forming a nutrient-rich endosperm. The other cells take auxiliary roles.
|
Sensory neurons transmit nerve impulses from sense organs and internal organs to the brain via the?
|
[
"nervous system",
"nerve endings",
"spinal column",
"spinal cord"
] |
D
|
Sensory neurons transmit nerve impulses from sense organs and internal organs to the brain via the spinal cord. In other words, they carry information about the inside and outside environment to the brain.
Efferent nerve-fibers carry impulses out from the center to their endings. Most of these go to muscles and are therefore called motor impulses; some are secretory and enter glands; a portion are inhibitory, their function being to restrain secretion. Thus, nerves carry impulses outward and sensations inward.
The brain and the spinal cord are the essential components of the central nervous system and it is responsible for the integration of the signals received from the afferent nerves and initiates action. The nerve cells, known as neurons, carry impulses throughout the body and the nerve impulses are carried along the axon. These microscopic nerve fibers, where the action potential occurs, are protected by a white, fatty tissue that surrounds and insulates it, known as the myelin sheath. This insulation helps the axon of a nerve cell with the conduction and speed of the signal along the axon.
During sensation, sense organs collect various stimuli (such as a sound or smell) for transduction, meaning transformation into a form that can be understood by the brain. Sensation and perception are fundamental to nearly every aspect of an organism's cognition, behavior and thought. In organisms, a sensory organ consists of a group of interrelated sensory cells that respond to a specific type of physical stimulus.
It is via this pathway that upper motor neurons descend from the cortex and synapse on α-MNs of the brainstem. Similarly, UMNs of the cerebral cortex are in direct control of α-MNs of the spinal cord via the lateral and ventral corticospinal tracts. The sensory input to α-MNs is extensive and has its origin in Golgi tendon organs, muscle spindles, mechanoreceptors, thermoreceptors, and other sensory neurons in the periphery.
Each neuron is connected by synapses to several thousand other neurons. These neurons typically communicate with one another by means of long fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.
|
Sexually reproducing organisms alternate between which stages?
|
[
"binary and diploid",
"binary and haploid",
"diploid and traploid",
"haploid and diploid"
] |
D
|
CHAPTER SUMMARY 7.1 Sexual Reproduction Nearly all eukaryotes undergo sexual reproduction. The variation introduced into the reproductive cells by meiosis appears to be one of the advantages of sexual reproduction that has made it so successful. Meiosis and fertilization alternate in sexual life cycles. The process of meiosis produces genetically unique reproductive cells called gametes, which have half the number of chromosomes as the parent cell. Fertilization, the fusion of haploid gametes from two individuals, restores the diploid condition. Thus, sexually reproducing organisms alternate between haploid and diploid stages. However, the ways in which reproductive cells are produced and the timing between meiosis and fertilization vary greatly. There are three main categories of life cycles: diploid-dominant, demonstrated by most animals; haploid-dominant, demonstrated by all fungi and some algae; and alternation of generations, demonstrated by plants and some algae.
Species that can undergo these changes do so as a normal event within their reproductive cycle, usually cued by either social structure or the achievement of a certain age or size. In some species of fish, sequential hermaphroditism is much more common than simultaneous hermaphroditism.In animals, the different types of change are male to female (protandry or protandrous hermaphroditism), female to male (protogyny or protogynous hermaphroditism), and bidirectional (serial or bidirectional hermaphroditism). Both protogynous and protandrous hermaphroditism allow the organism to switch between functional male and functional female.
Sequential hermaphrodites (dichogamy) occur in species in which the individual first develops as one sex, but can later change into the opposite sex. This contrasts with simultaneous hermaphrodites, in which an individual possesses fully functional male and female genitalia. Sequential hermaphroditism is common in fish (particularly teleost fish) and many gastropods (such as the common slipper shell). Sequential hermaphrodites can only change sex once.
Sexual reproduction is an adaptive feature which is common to almost all multicellular organisms and various unicellular organisms. Currently the adaptive advantage of sexual reproduction is widely regarded as a major unsolved problem in biology. As discussed below, one prominent theory is that sex evolved as an efficient mechanism for producing variation, and this had the advantage of enabling organisms to adapt to changing environments. Another prominent theory, also discussed below, is that a primary advantage of outcrossing sex is the masking of the expression of deleterious mutations.
This has been noted as a rare phenomenon in many plants (e.g. Nicotiana and Crepis), and occurs as the regular reproductive method in the Saharan Cypress, Cupressus dupreziana. Recently, the first example of natural androgenesis in a vertebrate, a fish, Squalius alburnoides was discovered. It is also known in invertebrates, particularly clams in the genus Corbicula, and these asexually reproducing males are noted to have a wider range than their noninvasive non-hermaphroditic cousins, more similar to hermaphroditic invasive species in the genus, indicating that this does sometimes have evolutionary benefits.
Powdery mildew fungi reproduce both sexually and asexually. Sexual reproduction occurs via chasmothecia (formerly cleistothecium), a type of ascocarp in which genetic recombination takes place. Within each ascocarp are several asci.
|
Acids turn blue litmus paper which color?
|
[
"red",
"grey",
"white",
"purple"
] |
A
|
Certain indicator compounds, such as litmus, can be used to detect acids. Acids turn blue litmus paper red.
Chemical reactions other than acid–base can also cause a color change to litmus paper. For instance, chlorine gas turns blue litmus paper white; the litmus dye is bleached because hypochlorite ions are present. This reaction is irreversible, so the litmus is not acting as an indicator in this situation.
The main use of litmus is to test whether a solution is acidic or basic, as blue litmus paper turns red under acidic conditions, and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple. Wet litmus paper can also be used to test for water-soluble gases that affect acidity or basicity; the gas dissolves in the water and the resulting solution colors the litmus paper. For instance, ammonia gas, which is alkaline, turns red litmus paper blue.
The color changes between red in acid solutions and blue in alkalis. The term 'litmus test' has become a widely used metaphor for any test that purports to distinguish authoritatively between alternatives. Hydrangea macrophylla flowers can change color depending on soil acidity.
Use of litmus paper. A small sample of soil is mixed with distilled water, into which a strip of litmus paper is inserted. If the soil is acidic the paper turns red, if basic, blue.
Hydrochloric acid immediately bleaches it with liberation of hydrogen sulfide. Even a small addition of zinc oxide to the reddish varieties especially causes a considerable diminution in the intensity of the color. Modern, synthetic ultramarine blue is a non-toxic, soft pigment that does not need much mulling to disperse into a paint formulation.
|
The development of a head region is called what?
|
[
"cephalization",
"trichina",
"spore",
"cocklebur"
] |
A
|
Most flatworms have a distinct head region that includes nerve cells and sensory organs, such as eyespots. The development of a head region, called cephalization , evolved at the same time as bilateral symmetry in animals. This process does not occur in cnidarians, which evolved prior to flatworms and have radial symmetry.
Though invertebrate chordates – such as the tunicate larvae or the lancelets – have heads, there has been a question of how the vertebrate head, characterized by a bony skull clearly separated from the main body, might have evolved from the head structures of these animals.According to Hyman (1979), the evolution of the head in the vertebrates has occurred by the fusion of a fixed number of anterior segments, in the same manner as in other "heteronomously segmented animals". In some cases, segments or a portion of the segments disappear. The head segments also lose most of their systems, except for the nervous system. With the progressive development of cephalization, "the head incorporates more and more of the adjacent segments into its structure, so that in general it may be said that the higher the degree of cephalization the greater is the number of segments composing the head".In the 1980s, the "new head hypothesis" was proposed, suggesting that the vertebrate head is an evolutionary novelty resulting from the emergence of neural crest and cranial placodes. In 2014, a transient larva tissue of the lancelet was found to be virtually indistinguishable from the neural crest-derived cartilage which forms the vertebrate skull, suggesting that persistence of this tissue and expansion into the entire headspace could be a viable evolutionary route to formation of the vertebrate head.
The third stage is the necking region. Beyond tensile strength, a necking forms where the local cross-sectional area becomes significantly smaller than the average. The necking deformation is heterogeneous and will reinforce itself as the stress concentrates more at small section.
A Headland, in agriculture, is the area at each end of a planted field. In some areas of the United States, this area is known as the Turnrow. It is used for turning around with farm implements during field operations and is the first area to be harvested to minimize crop damage. The rows run perpendicular to the lay of the field and are usually two, three or four times the width of the implement used for planting the field.
The head's function and appearance play an analogous role in the etymology of many technical terms. Cylinder head, pothead, and weatherhead are three such examples.
In these zones, the skin is similar to normal-haired skin and has the normal high density of nerves and hair follicles. These areas include the sides and back of the neck, the inner arms, the axillae (armpits) and sides of the thorax (chest).
|
Which hormone helps cells absorb sugar from the blood?
|
[
"insulin",
"estrogen",
"cortisol",
"adrenaline"
] |
A
|
Endocrine system: A high concentration of sugar in the blood triggers secretion of insulin by an endocrine gland called the pancreas. Insulin is a hormone that helps cells absorb sugar from the blood.
The neurohypophysis stores and releases two hypothalamic hormones: Oxytocin stimulates powerful uterine contractions, which trigger labour and delivery of an infant, and milk ejection in nursing women. Its release is mediated reflexively by the hypothalamus and represents a positive feedback mechanism. Antidiuretic hormone stimulates the kidney tubules to reabsorb and conserve water, resulting in small volumes of highly concentrated urine and decreased plasma osmolality. Antidiuretic hormone is released in response to high solute concentrations in the blood and inhibited by low solute concentrations in the blood. Hyposecretion results in diabetes insipidus.
Flux through the glucose cycle is regulated by several hormones including insulin and glucagon as well as allosteric regulation of both hexokinase and glucose 6-phosphatase.
Starch is converted into glucose during digestion, and glucose is the form of sugar that is transported around the bodies of animals in the bloodstream. Although in principle there are two enantiomers of glucose (mirror images one of the other), naturally occurring glucose is D-glucose. This is also called dextrose, or grape sugar because drying grape juice produces crystals of dextrose that can be sieved from the other components.
The reaction is highly regulated by allosteric effectors such as glucose 6-phosphate (activator) and by phosphorylation reactions (deactivating). Glucose-6-phosphate allosteric activating action allows glycogen synthase to operate as a glucose-6-phosphate sensor. The inactivating phosphorylation is triggered by the hormone glucagon, which is secreted by the pancreas in response to decreased blood glucose levels.
As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones insulin, glucagon, somatostatin and pancreatic polypeptide. As a part of the digestive system, it functions as an exocrine gland secreting pancreatic juice into the duodenum through the pancreatic duct. This juice contains bicarbonate, which neutralizes acid entering the duodenum from the stomach; and digestive enzymes, which break down carbohydrates, proteins and fats in food entering the duodenum from the stomach.
|
What is the number of electrons equal to in every electrically neutral atom?
|
[
"Electrons",
"molecules",
"protons",
"nucleus"
] |
C
|
Electron Shells and the Bohr Model It should be stressed that there is a connection between the number of protons in an element, the atomic number that distinguishes one element from another, and the number of electrons it has. In all electrically neutral atoms, the number of electrons is the same as the number of protons. Thus, each element, at least when electrically neutral, has a characteristic number of electrons equal to its atomic number. An early model of the atom was developed in 1913 by Danish scientist Niels Bohr (1885–1962). The Bohr model shows the atom as a central nucleus containing protons and neutrons, with the electrons in circular orbitals at specific distances from the nucleus, as illustrated in Figure 2.6. These orbits form electron shells or energy levels, which are a way of visualizing the number of electrons in the outermost shells. These energy levels are designated by a number and the symbol “n. ” For example, 1n represents the first energy level located closest to the nucleus.
This page shows the electron configurations of the neutral gaseous atoms in their ground states. For each atom the subshells are given first in concise form, then with all subshells written out, followed by the number of electrons per shell. Electron configurations of elements beyond hassium (element 108) have never been measured; predictions are used below. As an approximate rule, electron configurations are given by the Aufbau principle and the Madelung rule.
Electrons were found to be even smaller. Later, scientists found the expected number of electrons (the same as the atomic number) in an atom by using X-rays. When an X-ray passes through an atom, some of it is scattered, while the rest passes through the atom. Since the X-ray loses its intensity primarily due to scattering at electrons, by noting the rate of decrease in X-ray intensity, the number of electrons contained in an atom can be accurately estimated.
Fluorine atoms have nine electrons, one fewer than neon, and electron configuration 1s22s22p5: two electrons in a filled inner shell and seven in an outer shell requiring one more to be filled. The outer electrons are ineffective at nuclear shielding, and experience a high effective nuclear charge of 9 − 2 = 7; this affects the atom's physical properties.Fluorine's first ionization energy is third-highest among all elements, behind helium and neon, which complicates the removal of electrons from neutral fluorine atoms. It also has a high electron affinity, second only to chlorine, and tends to capture an electron to become isoelectronic with the noble gas neon; it has the highest electronegativity of any reactive element. Fluorine atoms have a small covalent radius of around 60 picometers, similar to those of its period neighbors oxygen and neon.
Atoms are the smallest neutral particles into which matter can be divided by chemical reactions. An atom consists of a small, heavy nucleus surrounded by a relatively large, light cloud of electrons. An atomic nucleus typically consists of 1 or more protons and 0 or more neutrons. Protons and neutrons are, in turn, made of quarks.
In the case where the total number of electrons is 4n, similar arguments (omitted here) lead to the conclusion that the number of antarafacial components b + d must be odd in the allowed case and even in the forbidden case. Finally, to complete the argument, and show that this new criterion is truly equivalent to the original criterion, one needs to argue the converse statements as well, namely, that the number of antarafacial components b + d and the electron count (4n + 2 or 4n) implies the parity of a + d that is given by the Woodward–Hoffmann rules (odd for allowed, even for forbidden). Another round of (somewhat tedious) case analyses will easily show this to be the case.
|
Does climate change have a positive or negative effect on reproductive success?
|
[
"neither",
"negative",
"positive",
"both"
] |
B
|
Many researchers believe it is the synergistic effects of these factors which are ultimately detrimental to pollinator populations.In the agriculture industry, climate change is causing a "pollinator crisis". This crisis is affecting the production of crops, and the relating costs, due to a decrease in pollination processes. This disturbance can be phenological or spatial.
... we know from various sources that raising the standard of life among the poorest classes almost invariably results in a lowering of their fertility. In so far, therefore, as differential class-fertility exists, raising the environmental level will reduce any dysgenic effects which it may now have.
The effects of climate change are impacting humans everywhere in the world. Impacts can be observed on all continents and ocean regions, with low-latitude, less developed areas facing the greatest risk. Continued warming has potentially "severe, pervasive and irreversible impacts" for people and ecosystems. The risks are unevenly distributed, but are generally greater for disadvantaged people in developing and developed countries.
Climate change will also impact where infectious diseases are likely to be able to spread in the future. Many infectious diseases will spread to new geographic areas where people do not yet have suitable immune systems. The health effects of climate change are increasingly a matter of concern for the international public health policy community.
For instance, nuclear war in growing seasons can bring about sudden episodes of low temperature (-10 degree Celsius or more) for days to weeks, and drawing reference from the "year without a summer" in 1816, episodes of freezing events are capable of destroying a large quantity of crops. In addition, growing season would potentially be shortened, as reported by Robock et al., who calculated that a regional nuclear war between India and Pakistan will substantially reduce freeze-free growing season in the Northern and Southern Hemispheres for several years and devastate agricultural produce as crops do not have sufficient time to reach maturity.In contrast, the natural marine ecosystems, a major supplier of food to human societies, are less vulnerable to sudden temperature fall. However, they are highly sensitive to reduced incident sunlight and increased level of UV-B radiation.
|
What is the most common form of dwarfism in humans?
|
[
"achondroplasia",
"anemia",
"alopecia",
"malnutrition"
] |
A
|
It can be. Achondroplasia is the most common form of dwarfism in humans, and it is caused by a dominant mutation. The mutation can be passed from one generation to the next. Over 95% of unrelated individuals with Achondroplasia have the same mutation, making it one of the most common mutations in the human genome. Why?.
Primordial dwarfism (PD) is a form of dwarfism that results in a smaller body size in all stages of life beginning from before birth. More specifically, primordial dwarfism is a diagnostic category including specific types of profoundly proportionate dwarfism, in which individuals are extremely small for their age, even as a fetus. Most individuals with primordial dwarfism are not diagnosed until they are about 3–5 years of age. Medical professionals typically diagnose the fetus as being small for gestational age, or as showing intrauterine growth restriction when an ultrasound is conducted.
In contrast, insular dwarfism among predators more commonly results from the imposition of constraints associated with the limited prey resources available on islands. As opposed to island dwarfism, island gigantism is found in most major vertebrate groups and in invertebrates.
Rather than existing a "true" single nature of a dwarf, they vary in their characteristics, not only across regions and time but also between one another in the same cultural context. Some are capable of changing their form entirely. The scholar Ármann Jakobsson notes that accounts of dwarfs in the Eddas and the section of Ynglinga saga regarding Sveigðir lack prominence in their narratives and cohesive identity. Based on this, he puts forward the idea that dwarfs in these sources are set apart from other beings by their difficulty to be defined and generalised, ultimately stemming from their intrinsic nature to be hidden and as the "Other" that stands in contrast with humans.
The category dwarf planet arose from a conflict between dynamical and geophysical ideas of what a useful conception of a planet would be. In terms of the dynamics of the Solar System, the major distinction is between bodies that gravitationally dominate their neighbourhood (Mercury through Neptune) and those that do not (such as the asteroids and Kuiper belt objects). A celestial body may have a dynamic (planetary) geology at approximately the mass required for its mantle to become plastic under its own weight, which results in the body acquiring a round shape. Because this requires a much lower mass than gravitationally dominating the region of space near their orbit, there are a population of objects that are massive enough to have a world-like appearance and planetary geology, but not massive enough to clear their neighborhood.
The mass of a planet has consequences for its structure by having a large mass, especially while it is in the hand of process of formation. A body with enough mass can overcome its compressive strength and achieve a rounded shape (roughly hydrostatic equilibrium). Since 2006, these objects have been classified as dwarf planet if it orbits around the Sun (that is, if it is not the satellite of another planet). The threshold depends on a number of factors, such as composition, temperature, and the presence of tidal heating.
|
What is the term for groups of three successive nucleotide bases in dna?
|
[
"triads",
"triplets",
"tertiary bases",
"triple play"
] |
B
|
Overview of Transcription. Transcription uses the sequence of bases in a strand of DNA to make a complementary strand of mRNA. Triplets are groups of three successive nucleotide bases in DNA. Codons are complementary groups of bases in mRNA.
The convention for a nucleic acid sequence is to list the nucleotides as they occur from the 5' end to the 3' end of the polymer chain, where 5' and 3' refer to the numbering of carbons around the ribose ring which participate in forming the phosphate diester linkages of the chain. Such a sequence is called the primary structure of the biopolymer.
The nucleotide sequence of a gene's DNA specifies the amino acid sequence of a protein through the genetic code. Sets of three nucleotides, known as codons, each correspond to a specific amino acid. : 6 The principle that three sequential bases of DNA code for each amino acid was demonstrated in 1961 using frameshift mutations in the rIIB gene of bacteriophage T4 (see Crick, Brenner et al. experiment).
The sugar in DNA is 2-deoxyribose, which is a pentose (five-carbon) sugar. The sugars are joined by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. These are known as the 3′-end (three prime end), and 5′-end (five prime end) carbons, the prime symbol being used to distinguish these carbon atoms from those of the base to which the deoxyribose forms a glycosidic bond.Therefore, any DNA strand normally has one end at which there is a phosphate group attached to the 5′ carbon of a ribose (the 5′ phosphoryl) and another end at which there is a free hydroxyl group attached to the 3′ carbon of a ribose (the 3′ hydroxyl).
Nuclear DNA is a nucleic acid, a polymeric biomolecule or biopolymer, found in the nucleus of eukaryotic cells. Its structure is a double helix, with two strands wound around each other, a structure first described by Francis Crick and James D. Watson (1953) using data collected by Rosalind Franklin. Each strand is a long polymer chain of repeating nucleotides. Each nucleotide is composed of a five-carbon sugar, a phosphate group, and an organic base.
Nucleotides are the fundamental molecules that combine in series to form RNA. They consist of a nitrogenous base attached to a sugar-phosphate backbone. RNA is made of long stretches of specific nucleotides arranged so that their sequence of bases carries information. The RNA world hypothesis holds that in the primordial soup (or sandwich), there existed free-floating nucleotides.
|
The coccyx, or tailbone, results from the fusion of four small what?
|
[
"rib vertebrae",
"coccygeal vertebrae",
"arsine vertebrae",
"alangulam vertebrae"
] |
B
|
Regions of the Vertebral Column The vertebral column originally develops as a series of 33 vertebrae, but this number is eventually reduced to 24 vertebrae, plus the sacrum and coccyx. The vertebral column is subdivided into five regions, with the vertebrae in each area named for that region and numbered in descending order. In the neck, there are seven cervical vertebrae, each designated with the letter “C” followed by its number. Superiorly, the C1 vertebra articulates (forms a joint) with the occipital condyles of the skull. Inferiorly, C1 articulates with the C2 vertebra, and so on. Below these are the 12 thoracic vertebrae, designated T1–T12. The lower back contains the L1–L5 lumbar vertebrae. The single sacrum, which is also part of the pelvis, is formed by the fusion of five sacral vertebrae. Similarly, the coccyx, or tailbone, results from the fusion of four small coccygeal vertebrae. However, the sacral and coccygeal fusions do not start until age 20 and are not completed until middle age. An interesting anatomical fact is that almost all mammals have seven cervical vertebrae, regardless of body size. This means that there are large variations in the size of cervical vertebrae, ranging from the very small cervical vertebrae of a shrew to the greatly elongated vertebrae in the neck of a giraffe. In a full-grown giraffe, each cervical vertebra is 11 inches tall.
The timing of this insult may correlate to the severity of associated defects. There is also postulation that fusion may occur due to adhesion after an inflammatory response or a lack of apoptosis between the structures. Siblings documented to have splenogonadal fusion and an accessory spleen provides additional evidence of a possible genetic component.
Syncephalus: One head with a single face but four ears and two bodies. Cephalothoracopagus: Bodies fused at the head and thorax, with two faces facing in opposite directions, or sometimes with a single face and an enlarged skull. Xiphopagus: Two bodies fused in the xiphoid cartilage, which extends approximately from the navel to the lower breastbone.
The visceral and parietal pleurae, like all mesothelia, both derive from the lateral plate mesoderms. During the third week of embryogenesis, each lateral mesoderm splits into two layers. The dorsal layer joins overlying somites and ectoderm to form the somatopleure; and the ventral layer joins the underlying endoderm to form the splanchnopleure. The dehiscence of these two layers creates a fluid-filled cavity on each side, and with the ventral infolding and the subsequent midline fusion of the trilaminar disc, forms a pair of intraembryonic coeloms anterolaterally around the gut tube during the fourth week, with the splanchnopleure on the inner cavity wall and the somatopleure on the outer cavity wall.
The dorsal ligaments are strong, flat bands. The first metatarsal is joined to the first cuneiform by a broad, thin band; the second has three, one from each cuneiform bone; the third has one from the third cuneiform; the fourth has one from the third cuneiform and one from the cuboid; and the fifth, one from the cuboid.
In the latter condition the joint between the hamate and the fourth and fifth metacarpal bones has a separate synovial membrane. The synovial cavities of these joints are prolonged for a short distance between the bases of the metacarpal bones. There is a separate synovial membrane between the pisiform and triangular.
|
What is a pure substance that cannot be separated into any other substances called?
|
[
"light",
"element",
"Cells",
"Spears"
] |
B
|
An element is a pure substance that cannot be separated into any other substances. There are 92 naturally occurring elements.
A potential problem involving alkahest is that, if it dissolves everything, then it cannot be placed into a container because it would dissolve the container. This problem was first posed by German alchemist Johann Kunckel. However, the alchemist Philalethes specified that alkahest dissolved only composed materials into their constituent, elemental parts; hence, a hypothetical container made of a pure element (say, lead) would not be dissolved by alkahest.
Isomers usually have substantially different chemical properties, and often may be isolated without spontaneously interconverting. A common example is glucose vs. fructose.
The apparatus used to distill a substance is called a still, and the re-condensed substance yielded by the process is called the distillate. double bond A bond involving the covalent sharing of two pairs of electrons.
Phases may also be differentiated based on solubility as in polar (hydrophilic) or non-polar (hydrophobic). A mixture of water (a polar liquid) and oil (a non-polar liquid) will spontaneously separate into two phases. Water has a very low solubility (is insoluble) in oil, and oil has a low solubility in water.
By nature, it is liquid. It ripples.
|
How many different types of stresses are there?
|
[
"five",
"seven",
"three",
"four"
] |
D
|
Stress is the force applied to a rock. There are four types of stresses:.
Stress–strain analysis (or stress analysis) is an engineering discipline that uses many methods to determine the stresses and strains in materials and structures subjected to forces. In continuum mechanics, stress is a physical quantity that expresses the internal forces that neighboring particles of a continuous material exert on each other, while strain is the measure of the deformation of the material. In simple terms we can define stress as the force of resistance per unit area, offered by a body against deformation. Stress is the ratio of force over area (S = R/A, where S is the stress, R is the internal resisting force and A is the cross-sectional area).
Stress can be conceptualized as a life event that disrupts the equilibrium of a person's life. For instance, a person may be vulnerable to becoming depressed but will not develop depression unless he or she is exposed to a specific stress, which may trigger a depressive disorder. Stressors can take the form of a discrete event, such as the divorce of parents or a death in the family, or can be more chronic factors such as having a long-term illness or ongoing marital problems. Stresses can also be related to more daily hassles, such as school assignment deadlines.
There is no evidence within the script of stress rules in the ancient period, but stress patterns exist within the liturgical tradition(s). Accounts of these patterns are, however, contradictory. One early 20th-century account may be broadly summarized as follows: primary stress only falls on the ultima (the last syllable) or the penult (the second-to-last syllable) in finite verbs (including the imperative), stress falls on the penult: ቀተለት qatálat ("she killed"), ንግር nə́gər ("speak!
Stress resultants are simplified representations of the stress state in structural elements such as beams, plates, or shells. The geometry of typical structural elements allows the internal stress state to be simplified because of the existence of a "thickness'" direction in which the size of the element is much smaller than in other directions. As a consequence the three traction components that vary from point to point in a cross-section can be replaced with a set of resultant forces and resultant moments. These are the stress resultants (also called membrane forces, shear forces, and bending moment) that may be used to determine the detailed stress state in the structural element.
In parallel connections, the stress is additive while the strain is equal in each element. Many of these one-dimensional models can be generalized to three dimensions for the small strain regime. In the subsequent discussion, time rates strain and stress are written as ε ˙ {\displaystyle {\dot {\boldsymbol {\varepsilon }}}} and σ ˙ {\displaystyle {\dot {\boldsymbol {\sigma }}}} , respectively.
|
A molecule has two structures that can be generated. what is this called?
|
[
"resonance hybrids",
"congruence",
"ethnocentrism",
"isomerism"
] |
D
|
The cis isomer has the two single hydrogen atoms on the same side of the molecule, while the trans isomer has them on opposite sides of the molecule. In both molecules, the bonding order of the atoms is the same. In order for geometric isomers to exist, there must be a rigid structure in the molecule to prevent free rotation around a bond. If the double bond in an alkene was capable of rotating, the two geometric isomers above would not exist. In addition, the two carbon atoms must each have two different groups attached in order for there to be geometric isomers. Propene has no geometric isomers because one of the carbon atoms has two single hydrogens bonded to it.
The behavior of biologically derived computational systems such as these relies on the particular molecules that make up the system, which are primarily proteins but may also include DNA molecules. Nanobiotechnology provides the means to synthesize the multiple chemical components necessary to create such a system. The chemical nature of a protein is dictated by its sequence of amino acids—the chemical building blocks of proteins. This sequence is in turn dictated by a specific sequence of DNA nucleotides—the building blocks of DNA molecules.
They can be broken into two categories: homonuclear and heteronuclear. A homonuclear diatomic molecule is one composed of two atoms of the same element. Examples are H2, O2, and N2. A heteronuclear diatomic molecule is composed of two atoms of two different elements. Examples include CO, HCl, and NO.
Typically, the strongest intermolecular interactions form the molecular layers or columns and the weakest intermolecular interactions form the slip plane. For example, long chains or layers of acetaminophen molecules form due to the hydrogen bond donors and acceptors that flank the benzene ring. The weaker interactions between the chains or layers of acetaminophen required less energy to break than the hydrogen bonds. As a result, a slip plane is formed. A supramolecular synthon is a pair of molecules that form relatively strong intermolecular interactions in the early phases of crystallization; these molecule pairs are the basic structural motif found in a crystal lattice.
The next generation of compounds is generated by further reactions with each compound in generation 1. This methodology quickly diverges to large numbers of new compounds A generates A1, A2, A3, A4, A5 in generation 1 A1 generates A11, A12, A13 in generation 2 and so on.An entire library of new chemical compounds, for instance saccharides, can be screened for desirable properties. In another strategy divergent synthesis starts from a molecule as a central core from which successive generations of building blocks are added. A good example is the divergent synthesis of dendrimers, for example, where in each generation a new monomer reacts to the growing surface of the sphere.
A graph is connected if there is at least one path between each pair of vertices. Although chemical mixtures are one of the main interests of many chemists, due to the computational explosion, many structure generators output only connected chemical graphs. Thus, the connectivity check is one of the mandatory intermediate steps in structure generation because the aim is to generate fully saturated molecules. A molecule is saturated if all its atoms are saturated.
|
An antigen is a molecule that reacts with some component of the what response?
|
[
"digestion",
"fight or flight",
"hormones",
"immune"
] |
D
|
Chapter 42 1 Figure 42.11 C 3 Figure 42.16 If the blood of the mother and fetus mixes, memory cells that recognize the Rh antigen can form late in the first pregnancy. During subsequent pregnancies, these memory cells launch an immune attack on the fetal blood cells. Injection of anti-Rh antibody during the first pregnancy prevents the immune response from occurring. 4 D 6 A 8 D 10 B 12 D 14 C 16 C 18 D 20 C 22 If the MHC I molecules expressed on donor cells differ from the MHC I molecules expressed on recipient cells, NK cells may identify the donor cells as “non-self” and produce perforin and granzymes to induce the donor cells to undergo apoptosis, which would destroy the transplanted organ. 24 An antigen is a molecule that reacts with some component of the immune response (antibody, B cell receptor, T cell receptor). An epitope is the region on the antigen through which binding with the immune component actually occurs. 26 The TH1 response involves the secretion of cytokines to stimulate macrophages and CTLs and improve their destruction of intracellular pathogens and tumor cells. It is associated with inflammation. The TH2 response is involved in the stimulation of B cells into plasma cells that synthesize and secrete antibodies. 28 T cells bind antigens that have been digested and embedded in MHC molecules by APCs. In contrast, B cells function themselves as APCs to bind intact, unprocessed antigens. 30 Cross reactivity of antibodies can be beneficial when it allows an individual's immune system to respond to an array of similar pathogens after being exposed to just one of them. A potential cost of cross reactivity is an antibody response to parts of the body (self) in addition to the appropriate antigen.
Antigen presentation is the first step in educating the immune system to recognize new pathogens. To this end, antigen presenting cells expose protein fragments via MHC molecules to the immune system. Not all protein fragments bind, however, to the MHC molecules of a certain individual. Using mass spectrometry, the true spectrum of molecules presented to the immune system can be determined.
Antigens are bound to antibodies through weak and noncovalent interactions such as electrostatic interactions, hydrogen bonds, Van der Waals forces, and hydrophobic interactions.The principles of specificity and cross-reactivity of the antigen-antibody interaction are useful in clinical laboratory for diagnostic purposes. One basic application is determination of ABO blood group. It is also used as a molecular technique for infection with different pathogens, such as HIV, microbes, and helminth parasites.
Antibodies can come from a variety of sources, including human cells, mice, and a combination of the two (chimeric antibodies). Different sources of antibodies can provoke different kinds of immune responses. For example, the human immune system can recognize mouse antibodies (also known as murine antibodies) and trigger an immune response against them. This could reduce the effectiveness of the antibodies as a treatment and cause an immune reaction.
The immune system recognizes foreign pathogens and eliminates them. This occurs in several phases. In the early inflammation phase, the pathogens are recognized by antibodies that are already present (innate or acquired through prior infection; see also cross-reactivity). Immune-system components (e.g. complement) are bound to the antibodies and kept near, in reserve to disable them via phagocytosis by scavenger cells (e.g. macrophages).
Endogenous antigens are produced by intracellular bacteria and viruses replicating within a host cell. The host cell uses enzymes to digest virally associated proteins and displays these pieces on its surface to T-cells by coupling them to MHC. Endogenous antigens are typically displayed on MHC class I molecules, and activate CD8+ cytotoxic T-cells. With the exception of non-nucleated cells (including erythrocytes), MHC class I is expressed by all host cells.
|
What bodily system is primarily responsible for fighting pathogens in the body?
|
[
"digestion",
"Cardiovascular",
"Muscular",
"immune"
] |
D
|
21.5 | The Immune Response against Pathogens By the end of this section, you will be able to: • Explain the development of immunological competence • Describe the mucosal immune response • Discuss immune responses against bacterial, viral, fungal, and animal pathogens • Describe different ways pathogens evade immune responses Now that you understand the development of mature, naïve B cells and T cells, and some of their major functions, how do all of these various cells, proteins, and cytokines come together to actually resolve an infection? Ideally, the immune response will rid the body of a pathogen entirely. The adaptive immune response, with its rapid clonal expansion, is well suited to this purpose. Think of a primary infection as a race between the pathogen and the immune system. The pathogen bypasses barrier defenses and starts multiplying in the host’s body. During the first 4 to 5 days, the innate immune response will partially control, but not stop, pathogen growth. As the adaptive immune response gears up, however, it will begin to clear the pathogen from the body, while at the same time becoming stronger and stronger. When following antibody responses in patients with a particular disease such as a virus, this clearance is referred to as seroconversion (sero- = “serum”). Seroconversion is the reciprocal relationship between virus levels in the blood and antibody levels. As the antibody levels rise, the virus levels decline, and this is a sign that the immune response is being at least partially effective (partially, because in many diseases, seroconversion does not necessarily mean a patient is getting well). An excellent example of this is seroconversion during HIV disease (Figure 21.26). Notice that antibodies are made early in this disease, and the increase in anti-HIV antibodies correlates with a decrease in detectable virus in the blood. Although these antibodies are an important marker for diagnosing the disease, they are not sufficient to completely clear the virus. Several years later, the vast majority of these individuals, if untreated, will lose their entire adaptive immune response, including the ability to make antibodies, during the final stages of AIDS.
The immune system recognizes foreign pathogens and eliminates them. This occurs in several phases. In the early inflammation phase, the pathogens are recognized by antibodies that are already present (innate or acquired through prior infection; see also cross-reactivity). Immune-system components (e.g. complement) are bound to the antibodies and kept near, in reserve to disable them via phagocytosis by scavenger cells (e.g. macrophages).
The organism enters directly through the breakdown of mechanical defense barriers such as mucosa or skin. Conditions which lead to the development of an immunocompromised state make the patient more susceptible to ecthyma gangrenosum and sepsis. In case of sepsis, the bacteria reaches the skin via the bloodstream.
The innate immune system is made of non-specific defensive mechanisms against foreign cells inside the host including skin as a physical barrier to entry, activation of the complement cascade to identify foreign bacteria and activate necessary cell responses, and white blood cells that remove foreign substances. The adaptive immune system, or acquired immune system, is a pathogen-specific immune response that is carried out by lymphocytes through antigen presentation on MHC molecules to distinguish between self and non-self antigens.
The complement system, when activated, creates a cascade of chemical reactions that promotes opsonization, chemotaxis, and agglutination, and produces the MAC. The kinin system generates proteins capable of sustaining vasodilation and other physical inflammatory effects. The coagulation system or clotting cascade, which forms a protective protein mesh over sites of injury. The fibrinolysis system, which acts in opposition to the coagulation system, to counterbalance clotting and generate several other inflammatory mediators.
There are mechanical, chemical, and biological factors affecting the effectiveness and results of the non-specific immune response. These factors include the epithelial surfaces forming a physical barrier, fatty acids that inhibit the growth of bacteria, and the microflora of the gastrointestinal tract serving to prevent the colonization of pathogenic bacteria. The non-specific immune system involves cells to which antigens are not specific in regards to fighting infection. The non-specific immune cells mentioned above (macrophages, neutrophils, and dendritic cells) will be discussed regarding their immediate response to infection.
|
Displacement, velocity, acceleration, and force are examples of what type of quantity that has magnitude and direction?
|
[
"cycles",
"wave",
"vector",
"frequency"
] |
C
|
Vectors in Two Dimensions A vector is a quantity that has magnitude and direction. Displacement, velocity, acceleration, and force, for example, are all vectors. In one-dimensional, or straight-line, motion, the direction of a vector can be given simply by a plus or minus sign. In two dimensions (2-d), however, we specify the direction of a vector relative to some reference frame (i. , coordinate system), using an arrow having length proportional to the vector’s magnitude and pointing in the direction of the vector. Figure 3.9 shows such a graphical representation of a vector, using as an example the total displacement for the person walking in a city considered in Kinematics in Two Dimensions: An Introduction. We shall use the notation that a boldface symbol, such as D , stands for a vector. Its magnitude is represented by the symbol in italics, D , and its direction by θ . Vectors in this Text In this text, we will represent a vector with a boldface variable. For example, we will represent the quantity force with the vector F , which has both magnitude and direction. The magnitude of the vector will be represented by a variable in italics, such as.
Vectors are fundamental in the physical sciences. They can be used to represent any quantity that has magnitude, has direction, and which adheres to the rules of vector addition. An example is velocity, the magnitude of which is speed.
Types of forces often encountered in classical mechanics include elastic, frictional, contact or "normal" forces, and gravitational. The rotational version of force is torque, which produces changes in the rotational speed of an object.
Examples in physics include the linear relationship of voltage and current in an electrical conductor (Ohm's law), and the relationship of mass and weight. By contrast, more complicated relationships, such as between velocity and kinetic energy, are nonlinear. Generalized for functions in more than one dimension, linearity means the property of a function of being compatible with addition and scaling, also known as the superposition principle.
For classical (Galileo-Newtonian) mechanics, the transformation law from one inertial or accelerating (including rotation) frame (reference frame traveling at constant velocity - including zero) to another is the Galilean transform. Unprimed quantities refer to position, velocity and acceleration in one frame F; primed quantities refer to position, velocity and acceleration in another frame F' moving at translational velocity V or angular velocity Ω relative to F. Conversely F moves at velocity (—V or —Ω) relative to F'. The situation is similar for relative accelerations.
A quantity equation is an equation that remains valid independently of the unit of measurement used when expressing the physical quantities.In contrast, in a numerical-value equation, just the numerical values of the quantities occur, without units. Therefore, it is only valid when each numerical values is referenced to a specific unit. For example, a quantity equation for displacement d as speed s multiplied by time difference t would be: d = s tfor s = 5 m/s, where t and d may be expressed in any units, converted if necessary. In contrast, a corresponding numerical-value equation would be: D = 5 Twhere T is the numeric value of t when expressed in seconds and D is the numeric value of d when expressed in metres. Generally, the use of numerical-value equations is discouraged.
|
Gases such as co2 and methane can trap what energy in earth's atmosphere, before radiating it into space?
|
[
"mechanical energy",
"sunlight energy",
"potential energy",
"thermal energy"
] |
D
|
Thermal energy can be trapped in Earth’s atmosphere by gases such as CO2, water vapor, methane, and chlorofluorocarbons before it can be radiated into space—like the effect of a greenhouse. It is not yet clear how large an increase in the temperature of Earth’s surface can be attributed to this phenomenon. Venus is an example of a planet that has a runaway greenhouse effect. The atmosphere of Venus is about 95 times denser than that of Earth and contains about 95% CO2. Because Venus is closer to the sun, it also receives more solar radiation than Earth does. The result of increased solar radiation and high CO2 levels is an average surface temperature of about 450°C, which is hot enough to melt lead. Data such as those in Figure 5.22 "Changes in Atmospheric CO" indicate that atmospheric levels of greenhouse gases have increased dramatically over the past 100 years, and it seems clear that the heavy use of fossil fuels by industry is largely responsible. It is not clear, however, how large an increase in temperature (global warming) may result from a continued increase in the levels of these gases. Estimates of the effects of doubling the preindustrial levels of CO2 range from a 0°C to a 4.5°C increase in the average temperature of Earth’s surface, which is currently about.
The combined transmission spectrum of TRAPPIST-1 b and c rules out a cloud-free hydrogen-dominated atmosphere for each planet, so they are unlikely to harbor an extended gas envelope. Prior to JWST observations, other atmospheres, from a cloud-free water-vapor atmosphere to a Venus-like atmosphere, remained consistent with the featureless spectrum.In 2018, the composition of TRAPPIST-1c was determined, and has been found to be rock-based. The presence of an atmosphere could not be confirmed. An observation of the secondary eclipse of TRAPPIST-1c by the James Webb Space Telescope, announced in 2023 rules out a thick carbon dioxide atmosphere like that of Venus. This is similar to JWST results on the inner planet TRAPPIST-1b announced earlier the same year, which suggest that it does not have a thick CO2 dominated atmosphere.
At high pressures, such as are found on the bottom of the ocean, methane forms a solid clathrate with water, known as methane hydrate. An unknown, but possibly very large quantity of methane is trapped in this form in ocean sediments. Theories suggest that should global warming cause them to heat up sufficiently, all of this methane gas could again be released into the atmosphere.
The air pollution produced by biogas is similar to that of natural gas as when methane (a major constituent of biogas) is ignited for its usage as an energy source, Carbon dioxide is made as a product which is a greenhouse gas ( as described by this equation: CH4 + 2O2 → CO2 + 2H2O ). The content of toxic hydrogen sulfide presents additional risks and has been responsible for serious accidents. Leaks of unburned methane are an additional risk, because methane is a potent greenhouse gas.
To keep the carbon captured from entering the atmosphere, a method of storing it or using it would have to be found. Another way to use the top gas would be in a top recovery turbine which then generates electricity, which could be used to reduce the energy intensity of the process, if electric arc smelting is used. Carbon could also be captured from gasses in the coke oven. Currently, separating the CO2 from other gasses and components in the system, and the high cost of the equipment and infrastructure changes needed, have kept this strategy minimal, but the potential for emission reduction has been estimated to be up to 65% to 80%.
All degassed helium is lost to space eventually, due to the average speed of helium exceeding the escape velocity for the Earth. Thus, it is assumed the helium content and ratios of Earth's atmosphere have remained essentially stable. It has been observed that 3He is present in volcano emissions and oceanic ridge samples.
|
What happens when heated water is released into a body of water?
|
[
"thermal pollution",
"crystalline pollution",
"gaseous pollution",
"geysers"
] |
A
|
If heated water is released into a body of water, it may cause thermal pollution. Thermal pollution is a reduction in the quality of water because of an increase in water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and factories. This water is heated and then returned to the natural environment at a higher temperature.
That contact causes a small amount of the water to be lost as windage or drift (W) and some of the water (E) to evaporate. The heat required to evaporate the water is derived from the water itself, which cools the water back to the original basin water temperature and the water is then ready to recirculate. The evaporated water leaves its dissolved salts behind in the bulk of the water which has not been evaporated, thus raising the salt concentration in the circulating cooling water.
Fluid, usually water, in the absorber tubes collect the trapped heat and transfer it to a heat storage vault. Heat is transferred either by conduction or convection. When water is heated, kinetic energy is transferred by conduction to water molecules throughout the medium.
This superheated water contains many dissolved substances, and when it encounters the cold seawater after leaving the vent, these particles precipitate out, mostly as metal sulfides. These particles make up the "smoke" that flows from a vent, and may eventually settle on the bottom as hydrogenous sediment. Hydrothermal vents are distributed along the Earth's plate boundaries, although they may also be found at intra-plate locations such as hotspot volcanoes.
This warm water can dissolve less oxygen, and is produced in smaller quantities, producing a sluggish circulation with little deep water oxygen. The effect of this warm water propagates through the ocean, and reduces the amount of CO2 that the oceans can hold in solution, which makes the oceans release large quantities of CO2 into the atmosphere in a geologically short time (tens or thousands of years).
Plumbed directly into the water supply and heated in an under-sink or over-counter tank (fixed to the wall); hot water is dispensed through a faucet at the sink. They may have a built-in water filter and a thermostat to adjust the water temperature. There is no need to fill them, they can produce large amounts of hot water, the water temperature is adjustable, they are expensive and require plumbing work, are not portable, and waste some electricity keeping water hot at all times.
|
What term is used to describe a chemical released by an animal that affects the behavior or physiology of animals of the same species?
|
[
"pheromone",
"enzyme",
"isolate",
"amino"
] |
A
|
The amount of material left over after a certain number of half-lives can be easily calculated.
Some species (e.g., dogs and some moths) use pheromones to attract mates.In examining living organisms, biologists are confronted with diverse levels of complexity (e.g. chemical, physiological, psychological, social). They therefore investigate causal and functional relations within and between these levels. A biochemist might examine, for instance, the influence of social and ecological conditions on the release of certain neurotransmitters and hormones, and the effects of such releases on behaviour, e.g. stress during birth has a tocolytic (contraction-suppressing) effect.
Behavioural responses to stress are evoked from underlying complex physiological changes that arise consequently from stress.Real or perceived threat in the environment elicits stress response in animals, which disrupts internal homeostasis. Physiological changes cause behavioural responses in animals, including: impairment of response inhibition and lack of motivation, as well as changes in social, sexual, aggression and nurture behaviour in animals. The extent of the impact is dependent upon the type and duration of the stress, as well as the animal's past experiences. Behavioural responses to prolonged stress can also be transferred across generations.
Studies into the mechanisms underlying behavioural adjustments fall into a category of animal behaviour research described by Tinbergen. Studies of animal behaviour typically pertain to one of Tinbergen’s four questions, and these can be applied to studies regarding chemical pollution. Questions of causation focus on how pollutant-exposure disrupts the mechanisms behind normal behaviour. For example, when differences in sexual behaviours were noted in wildlife after the introduction of DDT, biochemical experiments on rats were able to show that the pollutant was inhibiting androgen binding to androgen receptors.Secondly, questions of ontogeny consider how exposure disrupts the development of behaviours.
Many animals also exhibit more complex behavioural and physiological changes indicative of the ability to experience pain: they eat less food, their normal behaviour is disrupted, their social behaviour is suppressed, they may adopt unusual behaviour patterns, they may emit characteristic distress calls, experience respiratory and cardiovascular changes, as well as inflammation and release of stress hormones.Some criteria that may indicate the potential of another species to feel pain include: Has a suitable nervous system and sensory receptors Physiological changes to noxious stimuli Displays protective motor reactions that might include reduced use of an affected area such as limping, rubbing, holding or autotomy Has opioid receptors and shows reduced responses to noxious stimuli when given analgesics and local anaesthetics Shows trade-offs between stimulus avoidance and other motivational requirements Shows avoidance learning High cognitive ability and sentience
animal behaviour See ethology. animal communication animal migration applied ecology A branch of ecology which uses ecological principles and insights to solve environment-related problems. It includes agroecology and conservation biology.
|
Producers at the base of ecological food webs are also known as?
|
[
"autotrophic",
"endoscopic",
"symbiotic",
"mutualistic"
] |
A
|
A food web is often acyclic, with few exceptions such as adults preys on juveniles and parasitism. Note: In the food web main article, a food web was depicted as cyclic. That is based on the flow of the carbon and energy sources in a given ecosystem. The food web described here based solely on prey-predator roles; Organisms active in the carbon and nitrogen cycles (such as decomposers and fixers) are not considered in this description.
Food webs provide a framework within which a complex network of predator–prey interactions can be organised. A food web model is a network of food chains. Each food chain starts with a primary producer or autotroph, an organism, such as a plant, which is able to manufacture its own food. Next in the chain is an organism that feeds on the primary producer, and the chain continues in this way as a string of successive predators.
A food web, or food chain, is an example of directed network which describes the prey-predator relationship in a given ecosystem. Vertices in this type of network represent species, and the edges the prey-predator relationship. A collection of species may be represented by a single vertex if all members in that collection prey upon and are preyed on by the same organisms.
Food webs largely define ecosystems, and the trophic levels define the position of organisms within the webs. But these trophic levels are not always simple integers, because organisms often feed at more than one trophic level. For example, some carnivores also eat plants, and some plants are carnivores. A large carnivore may eat both smaller carnivores and herbivores; the bobcat eats rabbits, but the mountain lion eats both bobcats and rabbits.
Together, these factors demonstrate that a food web's structure affects its sensitivity to reductions in biodiversity, highlighting the importance of food web studies. Amino acid isotopes are an important tool used in this field.The abundance of 15N in some amino acids reflects an organism's position in a food web. This is due to the ways organisms metabolize different amino acids when they are consumed.
|
What is the term for the gas in smog that can damage plants?
|
[
"ozone",
"dioxide",
"carbon",
"sulphur"
] |
A
|
The ozone in smog may damage plants. The effects of ozone add up over time. Plants such as trees, which normally live a long time, are most affected. Entire forests may die out if ozone levels are very high. Other plants, including crop plants, may also be damaged by ozone. You can see evidence of ozone damage in Figure below .
Photochemical smog, often referred to as "summer smog", is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone. Photochemical smog depends on primary pollutants as well as the formation of secondary pollutants. These primary pollutants include nitrogen oxides, particularly nitric oxide (NO) and nitrogen dioxide (NO2), and volatile organic compounds. The relevant secondary pollutants include peroxylacyl nitrates (PAN), tropospheric ozone, and aldehydes.
An important secondary pollutant for photochemical smog is ozone, which is formed when hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight; nitrogen dioxide (NO2), which is formed as nitric oxide (NO) combines with oxygen (O2) in the air. In addition, when SO2 and NOx are emitted they eventually are oxidized in the troposphere to nitric acid and sulfuric acid, which, when mixed with water, form the main components of acid rain. All of these harsh chemicals are usually highly reactive and oxidizing.
The three main greenhouse gases are carbon dioxide, methane, and nitrous oxide. Gardeners produce carbon dioxide directly by overcultivating soil and destroying soil carbon, by burning garden waste on bonfires, by using power tools which burn fossil fuel or use electricity generated by fossil fuels, and by using peat. Gardeners produce methane by compacting the soil and making it anaerobic, and by allowing their compost heaps to become compacted and anaerobic. Gardeners produce nitrous oxide by applying excess nitrogen fertiliser when plants are not actively growing so that the nitrogen in the fertiliser is converted by soil bacteria to nitrous oxide.
At the lower end of the plant, atmospheric air is introduced into the water using an ejector. This causes a combination of water and oxygen to be propelled upward in the upstream pipe. Upon reaching the end of the upstream pipe, the mixture enters the degassing chamber, where residual gases are separated from the oxygenated water.
The inhalation of PM by people introduces it into the lungs where it can cause respiratory illnesses, permanent lung damage, and in some individuals premature death. PM with diameters of ≤10 micrometers (PM10) can harm human health, with particles of ≤2.5 micrometers (PM2.5) being the worst.As wind-borne dust can easily migrate, respiratory irritation can occur in construction and agricultural workers close to a source as well as others including wildlife. In addition to adverse health affects, the abrasive nature of particulate matter can cause property damage and obscure visibility leading to vehicular collisions causing injury and death.Fugitive dust can also harm plant life.
|
What must happen for two ions to form an ionic bond?
|
[
"two ions need to have the same charge",
"Two ions need to be the same size",
"two ions need to have neutral charges",
"two ions need to have opposite charges"
] |
D
|
Ionic bonding is a kind of chemical bonding that arises from the mutual attraction of oppositely charged ions. Ions of like charge repel each other, and ions of opposite charge attract each other. Therefore, ions do not usually exist on their own, but will bind with ions of opposite charge to form a crystal lattice. The resulting compound is called an ionic compound, and is said to be held together by ionic bonding.
This transfer causes one atom to assume a net positive charge, and the other to assume a net negative charge. The bond then results from electrostatic attraction between the positive and negatively charged ions. Ionic bonds may be seen as extreme examples of polarization in covalent bonds.
This process is called solvation. The presence of these free ions makes aqueous ionic compound solutions good conductors of electricity. The same occurs when the compounds are heated above their melting point, i.e., they are melted. This process is known as ionization.
In the case of a non-ionic compound the chemical bonds are non-ionic such meaning the compound will probably not dissolve in water or another polar solvent. Many non-ionic compounds have chemical bonds that share the electron density that binds them together. This type of chemical bond is either a non-polar covalent bond or a polar covalent bond.
Some ionic compounds (salts) dissolve in water, which arises because of the attraction between positive and negative charges (see: solvation). For example, the salt's positive ions (e.g. Ag+) attract the partially negative oxygen atom in H2O. Likewise, the salt's negative ions (e.g. Cl−) attract the partially positive hydrogens in H2O. Note: the oxygen atom is partially negative because it is more electronegative than hydrogen, and vice versa (see: chemical polarity).
|
What is the study of the similarities and differences in the embryos of different species?
|
[
"example embryology",
"prenatal biology",
"diversified embryology",
"comparative embryology"
] |
D
|
Comparative embryology is the study of the similarities and differences in the embryos of different species. Similarities in embryos are evidence of common ancestry. All vertebrate embryos, for example, have gill slits and tails. Most vertebrates, except for fish, lose their gill slits by adulthood. Some of them also lose their tail. In humans, the tail is reduced to the tail bone. Thus, similarities organisms share as embryos may be gone by adulthood. This is why it is valuable to compare organisms in the embryonic stage. See http://www. pbs. org/wgbh/evolution/library/04/2/pdf/l_042_03. pdf for additional information and a comparative diagram of human, monkey, pig, chicken and salamander embryos.
colony comparative biology The use of comparative methods to study the similarities and differences between two or more biological organisms (e.g. two organisms from the same time period but different taxa, or two organisms from the same taxon but different times in evolutionary history). The side-by-side comparison of morphological or molecular characteristics of different organisms is the basis from which biologists infer the organisms' genetic relatedness and their natural histories. It is a fundamental tool in many biological disciplines, including anatomy, physiology, paleontology, and phylogenetics.
In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are. Species are reproductively isolated by strong barriers to hybridization, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo.
These applications include: Studying the diversity of organisms and the differentiation between extinct and living creatures. Biologists study the well-understood relationships by making many different diagrams and "trees" (cladograms, phylogenetic trees, phylogenies, etc.). Including the scientific names of organisms, species descriptions and overviews, taxonomic orders, and classifications of evolutionary and organism histories.
In anatomy, two anatomical structures are considered to be analogous when they serve similar functions but are not evolutionarily related, such as the legs of vertebrates and the legs of insects. Analogous structures are the result of independent evolution and should be contrasted with structures which shared an evolutionary line.
Analogous structures - structures similar in different organisms because, in convergent evolution, they evolved in a similar environment, rather than were inherited from a recent common ancestor. They usually serve the same or similar purposes. An example is the streamlined torpedo body shape of porpoises and sharks. So even though they evolved from different ancestors, porpoises and sharks developed analogous structures as a result of their evolution in the same aquatic environment. This is known as a homoplasy.
|
What are the main organs of the respiratory system?
|
[
"lungs",
"ovaries",
"intestines",
"kidneys"
] |
A
|
The lungs are the main organs of the respiratory system. This is where gases are exchanged between the air and the blood. Gases are also transported by the blood and exchanged between the blood and all the cells of the body.
The lower respiratory tract is part of the respiratory system, and consists of the trachea and the structures below this including the lungs. The trachea receives air from the pharynx and travels down to a place where it splits (the carina) into a right and left primary bronchus. These supply air to the right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles. These in turn supply air through alveolar ducts into the alveoli, where the exchange of gases take place.
The nervous system consists of two nerve cords which run the length of the body, with two ganglia and two transverse commissures in most of the body segments.Gas exchange is thought to take place through the entire body surface, but especially that of the phyllopodia and their associated gills, which may also be responsible for osmotic regulation. Two coiled glands at the bases of the maxillae are used to excrete nitrogenous waste, typically in the form of urea. Most of the animal's nitrogenous waste is, however, in the form of ammonia, which probably diffuses into the environment through the phyllopodia and gills.
The primary anatomical barrier is the development of lungs for proper gas exchange (although rudimentary lungs are ancestral to bony fish), however other anatomical barriers also exist. The stressors of the musculoskeletal system are different in air than they are in water, and the muscles and bones must be strong enough to withstand the increased effects of gravity on land. The tongue and the three chambered heart evolved similarly for efficient digestion and blood circulation on land respectively. The vomeronasal organ is found in many extant tetrapods but not any fish, suggesting it originated in tetrapods only.
In order for the lungs to allow gas exchange, the lungs first need to have gas in them. In modern tetrapods, three important breathing mechanisms are conserved from early ancestors, the first being a CO2/H+ detection system. In modern tetrapod breathing, the impulse to take a breath is triggered by a buildup of CO2 in the bloodstream and not a lack of O2. A similar CO2/H+ detection system is found in all Osteichthyes, which implies that the last common ancestor of all Osteichthyes had a need of this sort of detection system.
This starts at the mouth and ends at the anus, covering a distance of about nine metres.A major digestive organ is the stomach. Within its mucosa are millions of embedded gastric glands. Their secretions are vital to the functioning of the organ.
|
What do you call the traits that allow a plant, animal, or other organism to survive and reproduce in its environment?
|
[
"adaptations",
"additions",
"advantages",
"settings"
] |
A
|
Every plant and animal depends on its traits to survive. Survival may include getting food, building homes, and attracting mates. Traits that allow a plant, animal, or other organism to survive and reproduce in its environment are called adaptations .
An alternate definition often used by biologists is any species, not just plants, that can quickly adapt to any environment. Some traits of weedy species are the ability to reproduce quickly, disperse widely, live in a variety of habitats, establish a population in strange places, succeed in disturbed ecosystems and resist eradication once established. Such species often do well in human-dominated environments as other species are not able to adapt. Common examples include the common pigeon, brown rat and the raccoon.
Since animals are far less plastic than plants, ecophenotypic variation is noteworthy. When encountered, it can cause confusion in identification if it is not anticipated. The most obvious examples are again common observations, as the dwarfing of aquarium fish living in a restricted environment. In asexual reproduction, the parent passes on the entire genome to the next generation.
Ecology (from Greek: οἶκος, "house", or "environment"; -λογία, "study of") is a branch of biology concerning interactions among organisms and their biophysical environment, which includes both biotic and abiotic components. Topics of interest include the biodiversity, distribution, biomass, and populations of organisms, as well as cooperation and competition within and between species. Ecosystems are dynamically interacting systems of organisms, the communities they make up, and the non-living components of their environment. Ecosystem processes, such as primary production, pedogenesis, nutrient cycling, and niche construction, regulate the flux of energy and matter through an environment. These processes are sustained by organisms with specific life history traits.
There are a few ways that reproduction occurs within plant life, and one way is through parthenogenesis. Parthenogenesis is defined as "a form of asexual reproduction in which genetically identical offspring (clones) are produced". Another form of reproduction is through cross-fertilization, which is defined as "fertilization in which the egg and sperm are produced by different individuals", and in plants this occurs in the ovule.
The set of environmental features essential to that species' survival, is its "niche." (Ecology. Begon, Harper, Townsend)
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.