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AP Biology 7.4 Population Genetics | They only brought the gene pool of those individuals. |
AP Biology 7.4 Population Genetics | In addition, the Amish marry within their own community. |
AP Biology 7.4 Population Genetics | So Founder Effect traits such as polydactyly can be seen in descendants. |
AP Biology 7.4 Population Genetics | Well, I'll share a story with you. |
AP Biology 7.4 Population Genetics | When I have polydactyly and when I was five years old,
my mother had my extra digit cut off of my hand and I also have both hands. |
AP Biology 7.4 Population Genetics | And it was a type that's called an ulnar type and it's a type B. |
AP Biology 7.4 Population Genetics | So it wasn't a full form bone finger. |
AP Biology 7.4 Population Genetics | It was only like a tag of a finger like part of a skin that resembled a small finger. |
AP Biology 7.4 Population Genetics | And anyway, so I have been sequenced and I have two variants and two genes that have
to do with it, Ellis Van Kruvald syndrome. |
AP Biology 7.4 Population Genetics | So I didn't know all this until I started working with this for you. |
AP Biology 7.4 Population Genetics | And so that is a good day at work for me when I can put something together and learn. |
AP Biology 7.4 Population Genetics | Okay, the next way we're next. |
AP Biology 7.4 Population Genetics | Let's see. |
AP Biology 7.4 Population Genetics | We're going to talk about gene flow. |
AP Biology 7.4 Population Genetics | Okay, so this is my favorite way to talk about gene flow. |
AP Biology 7.4 Population Genetics | There is this is a immigrants on an Atlantic liner and they're coming to America. |
AP Biology 7.4 Population Genetics | And so when people move into a new city, they bring their genes with them. |
AP Biology 7.4 Population Genetics | And that's called gene flow. |
AP Biology 7.4 Population Genetics | All right, these random processes, mutations, genetic drift and gene flow can reduce
the genetic variation of a given population and can increase the differences
between populations of the same species. |
AP Biology 7.4 Population Genetics | So our science skill today is going to be about questions and methods. |
AP Biology 7.4 Population Genetics | And the task for today that we're going to focus on is state. |
AP Biology 7.4 Population Genetics | And this is what we'll be stating. |
AP Biology 7.4 Population Genetics | We'll be the null hypothesis is what we're going to be working on today. |
AP Biology 7.4 Population Genetics | Okay. |
AP Biology 7.4 Population Genetics | And we're going to be predicting the results of an experiment. |
AP Biology 7.4 Population Genetics | This is an effort from the very first year that I taught AP biology and what you see
in the diagram, you see a choice chamber and at one side it has a glucose soaked
cotton ball and on the other side it has a dry cotton ball. |
AP Biology 7.4 Population Genetics | And so let's read what the story tell us. |
AP Biology 7.4 Population Genetics | All right. |
AP Biology 7.4 Population Genetics | In an investigation of fruit fly behavior,
a covered choice chamber is used to test whether the spatial distribution of flies
is affected by the presence of a substance placed at one end of the chamber. |
AP Biology 7.4 Population Genetics | To test the flies preference for glucose,
60 flies are introduced into the middle of the choice chamber at the insertion
point indicated by the arrow in the figure above. |
AP Biology 7.4 Population Genetics | A cotton ball soaked with a 10 percent glucose solution is placed at one end
of the chamber and a dry cotton ball with no solution is placed at the other end. |
AP Biology 7.4 Population Genetics | The positions of the flies are observed and recorded every minute for 10 minutes. |
AP Biology 7.4 Population Genetics | Predict the distribution of flies in the chamber after 10 minutes and justify
your prediction. |
AP Biology 7.4 Population Genetics | So take just 20 seconds and you make
a prediction of where those 60 flies are going to be. |
AP Biology 7.4 Population Genetics | All right, how about 10 more seconds? |
AP Biology 7.4 Population Genetics | OK, I'm going to show you my prediction. |
AP Biology 7.4 Population Genetics | OK, I know those are bees and they're not flies, but it's the only shape that was
even resembled being close enough to put in here. |
AP Biology 7.4 Population Genetics | OK, so you see my we have our choice
chamber down the bottom, the glucose soaked, the dry and my prediction. |
AP Biology 7.4 Population Genetics | I predicted 58 glucose will be on the glucose soaked in one in the middle and one
on the dry cotton. |
AP Biology 7.4 Population Genetics | So let's take this another step. |
AP Biology 7.4 Population Genetics | Because I did that because they would want sugar is what I was thinking. |
AP Biology 7.4 Population Genetics | OK, before we move on, I want to ask you a question. |
AP Biology 7.4 Population Genetics | And my question to you and I hope you know the answer is what would you do
differently here? |
AP Biology 7.4 Population Genetics | What do you see as an initial problem
in this diagram and the initial start of this experiment? |
AP Biology 7.4 Population Genetics | I see that there is a dry cotton ball and there's a glucose soaked cotton ball. |
AP Biology 7.4 Population Genetics | So if I think that it would have been better
to start with not a dry, but maybe a soaked cotton ball with sterile water. |
AP Biology 7.4 Population Genetics | So it wouldn't be the wet or dry that could be interfering. |
AP Biology 7.4 Population Genetics | It would be about the glucose. |
AP Biology 7.4 Population Genetics | I just wanted to see if you maybe caught that on the first round. |
AP Biology 7.4 Population Genetics | OK, so here's B and I'll give you a couple of minutes to do B. |
AP Biology 7.4 Population Genetics | The experiment described above is repeated
with ripe bananas at one end and unripe bananas at the other end. |
AP Biology 7.4 Population Genetics | Once again, the positions of the flies are observed and recorded every minute for 10
minutes, the positions of the flies after one minute and after 10 minutes are shown
in the table below. |
AP Biology 7.4 Population Genetics | All right, I'm going to go to the next and. |
AP Biology 7.4 Population Genetics | Show you the table. |
AP Biology 7.4 Population Genetics | OK, so here's the distribution of flies in the choice chamber at one minute
and at 10 minutes, and there's at the end with the right banana. |
AP Biology 7.4 Population Genetics | At 10 minutes, we were 45 in the middle. |
AP Biology 7.4 Population Genetics | We had three and on the end we had 12. |
AP Biology 7.4 Population Genetics | Now, there is the chi square formula
because you're going to be doing chi square calculations today. |
AP Biology 7.4 Population Genetics | You're going to write a null hypothesis and you're going to be doing chi square. |
AP Biology 7.4 Population Genetics | So let's go through this formula for a minute. |
AP Biology 7.4 Population Genetics | All right. |
AP Biology 7.4 Population Genetics | So this symbol right here means summation. |
AP Biology 7.4 Population Genetics | OK, and this O is talking about observed. |
AP Biology 7.4 Population Genetics | So I would have observed 45 and the next one,
it would be observed three and then I observed 12. |
AP Biology 7.4 Population Genetics | So expected, I'm going to leave that to you because you're going to be writing a null
hypothesis. |
AP Biology 7.4 Population Genetics | And so I hope that you understand what that means. |
AP Biology 7.4 Population Genetics | And if you don't, I'll make it really clear when we get done. |
AP Biology 7.4 Population Genetics | But one more other thing about this formula, see that that chi right there,
chi square, that is not an X squared. |
AP Biology 7.4 Population Genetics | So don't find this and then think that's X square and then get the square root of this. |
AP Biology 7.4 Population Genetics | Just don't do that. |
AP Biology 7.4 Population Genetics | OK, I'm going to give you two minutes to work through this. |
AP Biology 7.4 Population Genetics | And in the beginning, I should have told you to get some paper
and a pen and in the future, some graph paper and calculator, too. |
AP Biology 7.4 Population Genetics | OK, how about another 30 seconds? |
AP Biology 7.4 Population Genetics | And 10. |
AP Biology 7.4 Population Genetics | And, OK, let's take a look at the answer. |
AP Biology 7.4 Population Genetics | OK, so to write a proper null, OK, this is what I do. |
AP Biology 7.4 Population Genetics | And I think there's three things I really need to say to cover all my bases when I
write this, and I always think, well, no has three letters, right? |
AP Biology 7.4 Population Genetics | OK, so I need to say that the number of flies will be equal in all three sections,
or I could have said it like the flies will have the same amount of preference for each area. |
AP Biology 7.4 Population Genetics | OK, then there is no statistical difference and then any difference is due to chance. |
AP Biology 7.4 Population Genetics | So I use this as a framework because I can substitute anything I'm talking about
into that first sentence and then I will add the numbers. |
AP Biology 7.4 Population Genetics | And then I will be able to know what else I need to say and have some frame of reference
to check myself back with, OK, what with what was no statistical difference with no
chance or chance, but if you do it this first time when you write your null,
you will be able to control which way you're writing and that you don't make
an error and change things up as you're writing. |
AP Biology 7.4 Population Genetics | So let's take a look at this math. |
AP Biology 7.4 Population Genetics | We had 45 observed 3, 12 and the totaling of 60. |
AP Biology 7.4 Population Genetics | And then if we didn't expect any difference in their choices, OK,
of their preferences, then there would be 20, 20 and 20. |
AP Biology 7.4 Population Genetics | And then you would have done the calculations and come up with a chi square value of forty eight point nine. |
AP Biology 7.4 Population Genetics | All right, so. |
AP Biology 7.4 Population Genetics | Here's our chi square formula,
and I'm going to run through how to do the math and then it's going to go really, really fast. |
AP Biology 7.4 Population Genetics | OK, I hope you were looking at the math and not trying to look at my fingers. |
AP Biology 7.4 Population Genetics | All right, so here is our next step. |
AP Biology 7.4 Population Genetics | We got to take this a little bit further. |
AP Biology 7.4 Population Genetics | This is a degree of freedom table and this is only a small section compared to various tables. |
AP Biology 7.4 Population Genetics | I mean, they are there. |
AP Biology 7.4 Population Genetics | A lot of information could be on a table. |
AP Biology 7.4 Population Genetics | It can be in a different orientation. |
AP Biology 7.4 Population Genetics | The p value can be at the top. |
AP Biology 7.4 Population Genetics | The degrees of freedom can be on the left, the right. |
AP Biology 7.4 Population Genetics | It can have all kind of differences,
but this is the one that the College Board has on the exam. |
AP Biology 7.4 Population Genetics | So we're in biology, we're going to use our p value of point of five. |
AP Biology 7.4 Population Genetics | And now we're going to look at our degree of freedom. |
AP Biology 7.4 Population Genetics | We had three categories, right? |
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