DarthJudie/biosetpart1 · Datasets at Hugging Face

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Ecosystems	And that has to do with the currents in the ocean.
Ecosystems	So we need nutrients and we also need availability of light.
Ecosystems	Obviously in the Sahara we're not going to have a lot of primary productivity but we're going to have more as we move up into this area, the coniferous forest or for sure in the rain forest.
Ecosystems	And so what do we measure primary productivity in?
Ecosystems	Well it's grams of carbon per meter squared per year.
Ecosystems	In other words if we were to go out in this prairie and mark one meter, so we'll say one meter area like that, in one year it's the amount of carbon that would be added.
Ecosystems	Now how is that carbon being added?
Ecosystems	We're taking in carbon dioxide from the atmosphere.
Ecosystems	We're using light from the sun.
Ecosystems	And then we're making it into livable material.
Ecosystems	And so it's easy to measure in an area like this.
Ecosystems	Just put a quadrant down and measure that.
Ecosystems	Sometimes it's harder if you're in a, this would be a terrestrial area or an ecosystem.
Ecosystems	This would be an aquatic area.
Ecosystems	So when you're in water lots of times it's harder to measure the matter that's being created.
Ecosystems	So sometimes we'll measure the gases that are being produced.
Ecosystems	So we can look at the oxygen that's being produced in an aquatic environment.
Ecosystems	So right here we're going to have higher levels of oxygen being created because the producers are taking that carbon dioxide and making it into matter.
Ecosystems	So primary productivity is going to be just a measure of how much life can be created in an area.
Ecosystems	Food chains measure where this life goes.
Ecosystems	And so if we start here, on the right side I've got what are called trophic levels.
Ecosystems	And so we should define what a trophic level is first.
Ecosystems	Trophic just means an eating level.
Ecosystems	And so the lowest level, trophic level one we call that, are going to be producers.
Ecosystems	And so if we're looking at a food chain here in Lake Ontario, what are the producers going to be out in this lake?
Ecosystems	It's mostly going to be algae.
Ecosystems	So what they're doing is converting energy from the sun into livable material.
Ecosystems	And so we would call this trophic level one.
Ecosystems	Or sometimes we call these producers.
Ecosystems	Okay.
Ecosystems	So if we go to the next level, next level, trophic level two, these are going to be consumers.
Ecosystems	And so consumers remember can't make their own food.
Ecosystems	They have to get their food from somewhere else.
Ecosystems	And so if we were to do a food chain, the food chain is going to go like that.
Ecosystems	Now the arrow you should get used to.
Ecosystems	The arrow is always going to go from what's eaten to what eats it.
Ecosystems	And the way I remember this is if you look at the head of the arrow it's like the mouth.
Ecosystems	So it's like the mouth of Pac-Man.
Ecosystems	And so whatever is eating is going to be on this side of the arrow.
Ecosystems	And whatever is eaten is going to be on that side of the arrow.
Ecosystems	So now we go to the third level.
Ecosystems	Third level is going to be, we call these second level consumers.
Ecosystems	But those are going to feed on these organisms.
Ecosystems	So algae is eaten by amphipods which are a little crustacean.
Ecosystems	Those are fed on by rainbow smelt.
Ecosystems	And then if we were to go one more level, then we get to the level of Chinook salmon.
Ecosystems	So this would be the fourth trophic level or we call this a first, second, third level consumer.
Ecosystems	Now this is a food chain.
Ecosystems	Food chains are linear.
Ecosystems	They go from what's eaten to what eats it to what eats that to what eats that.
Ecosystems	So it just goes in one direction.
Ecosystems	But you can imagine that there's a lot more food chains in Lake Ontario than the one that I've just drawn here.
Ecosystems	And so if we were to add the other food chains, now we get what's called a food web.
Ecosystems	A food web is going to show all the connections.
Ecosystems	Not only this one to amphipods to rainbow smelt to Chinook salmon, which I think were actually introduced into Lake Ontario, but it's also going to show the flow of perch to walleye.
Ecosystems	It's going to show all these interactions.
Ecosystems	And in any ecosystem, this is a fairly simple food web.
Ecosystems	It's just showing the major ones.
Ecosystems	Obviously if we were to include all the different types of algae this would be a massive food web.
Ecosystems	And so in an ecosystem there's all these connections between the organisms.
Ecosystems	And it's pretty detailed.
Ecosystems	Now each of those have adaptations that allow them to live where they are.
Ecosystems	In other words the green algae are adapted to this kind of an environment.
Ecosystems	Same with the diatoms.
Ecosystems	Okay.
Ecosystems	Next thing I need to talk about is growth.
Ecosystems	And we've mentioned this when we talked about communities and how populations grow.
Ecosystems	In general all growth is going to be exponential.
Ecosystems	So if we were to go with amphipods, they're going to create more amphipods and eventually we get exponential growth.
Ecosystems	I could use a color that you could actually see.
Ecosystems	So we get exponential growth like that.
Ecosystems	But the problem is as you start to grow there's going to be limiting factors.
Ecosystems	Pretty soon you're too crowded.
Ecosystems	There's not enough food.
Ecosystems	There's competition.
Ecosystems	There's also going to just be drought.
Ecosystems	There's going to be meteorological geological changes that can limit that growth.
Ecosystems	And so all growth will eventually become logistic.
Ecosystems	In other words it's eventually going to reach what we call a limit.
Ecosystems	In science we call that K or K stands for carrying capacity.
Ecosystems	So carrying capacity is going to be the maximum level that an ecosystem can support of a specific population.
Ecosystems	Now it's not going to be linear like this.
Ecosystems	This is just using a mathematical representation.
Ecosystems	Obviously populations are going to bounce up and down and they're going to bounce up and down on this carrying capacity.
Ecosystems	But in general all populations will undergo that.
Ecosystems	Let's look at some real populations.
Ecosystems	So wolves were reintroduced into Yellowstone Park in 1995.
Ecosystems	So they put some packs there.
Ecosystems	This is actually a picture of one of the first wolves coming out of the enclosure.
Ecosystems	They brought them from Canada and they left them in an enclosure for months if I remember.
Ecosystems	Because they didn't want them just to run back to Canada.
Ecosystems	So they eventually released them.
Ecosystems	And let's look at what their population has grown.
Ecosystems	So blue is all the wolves in Yellowstone Park and then the other two bars are just in different areas.
Ecosystems	But if we look at the population growth, population growth has varied a little bit.
Ecosystems	But it's gone up and down and up and down and up.
Ecosystems	And so what's it doing?
Ecosystems	Well you can see that this part was more exponential growth.
Ecosystems	And now it's approaching what's called logistic growth.
Ecosystems	In other words there's just a certain number of wolves that you can actually support in Yellowstone Park.

Ecosystems

And that has to do with the currents in the ocean.

Ecosystems

So we need nutrients and we also need availability of light.

Ecosystems

Obviously in the Sahara we're not going to have a lot of primary productivity but we're going to have more as we move up into this area, the coniferous forest or for sure in the rain forest.

Ecosystems

And so what do we measure primary productivity in?

Ecosystems

Well it's grams of carbon per meter squared per year.

Ecosystems

In other words if we were to go out in this prairie and mark one meter, so we'll say one meter area like that, in one year it's the amount of carbon that would be added.

Ecosystems

Now how is that carbon being added?

Ecosystems

We're taking in carbon dioxide from the atmosphere.

Ecosystems

We're using light from the sun.

Ecosystems

And then we're making it into livable material.

Ecosystems

And so it's easy to measure in an area like this.

Ecosystems

Just put a quadrant down and measure that.

Ecosystems

Sometimes it's harder if you're in a, this would be a terrestrial area or an ecosystem.

Ecosystems

This would be an aquatic area.

Ecosystems

So when you're in water lots of times it's harder to measure the matter that's being created.

Ecosystems

So sometimes we'll measure the gases that are being produced.

Ecosystems

So we can look at the oxygen that's being produced in an aquatic environment.

Ecosystems

So right here we're going to have higher levels of oxygen being created because the producers are taking that carbon dioxide and making it into matter.

Ecosystems

So primary productivity is going to be just a measure of how much life can be created in an area.

Ecosystems

Food chains measure where this life goes.

Ecosystems

And so if we start here, on the right side I've got what are called trophic levels.

Ecosystems

And so we should define what a trophic level is first.

Ecosystems

Trophic just means an eating level.

Ecosystems

And so the lowest level, trophic level one we call that, are going to be producers.

Ecosystems

And so if we're looking at a food chain here in Lake Ontario, what are the producers going to be out in this lake?

Ecosystems

It's mostly going to be algae.

Ecosystems

So what they're doing is converting energy from the sun into livable material.

Ecosystems

And so we would call this trophic level one.

Ecosystems

Or sometimes we call these producers.

Ecosystems

Okay.

Ecosystems

So if we go to the next level, next level, trophic level two, these are going to be consumers.

Ecosystems

And so consumers remember can't make their own food.

Ecosystems

They have to get their food from somewhere else.

Ecosystems

And so if we were to do a food chain, the food chain is going to go like that.

Ecosystems

Now the arrow you should get used to.

Ecosystems

The arrow is always going to go from what's eaten to what eats it.

Ecosystems

And the way I remember this is if you look at the head of the arrow it's like the mouth.

Ecosystems

So it's like the mouth of Pac-Man.

Ecosystems

And so whatever is eating is going to be on this side of the arrow.

Ecosystems

And whatever is eaten is going to be on that side of the arrow.

Ecosystems

So now we go to the third level.

Ecosystems

Third level is going to be, we call these second level consumers.

Ecosystems

But those are going to feed on these organisms.

Ecosystems

So algae is eaten by amphipods which are a little crustacean.

Ecosystems

Those are fed on by rainbow smelt.

Ecosystems

And then if we were to go one more level, then we get to the level of Chinook salmon.

Ecosystems

So this would be the fourth trophic level or we call this a first, second, third level consumer.

Ecosystems

Now this is a food chain.

Ecosystems

Food chains are linear.

Ecosystems

They go from what's eaten to what eats it to what eats that to what eats that.

Ecosystems

So it just goes in one direction.

Ecosystems

But you can imagine that there's a lot more food chains in Lake Ontario than the one that I've just drawn here.

Ecosystems

And so if we were to add the other food chains, now we get what's called a food web.

Ecosystems

A food web is going to show all the connections.

Ecosystems

Not only this one to amphipods to rainbow smelt to Chinook salmon, which I think were actually introduced into Lake Ontario, but it's also going to show the flow of perch to walleye.

Ecosystems

It's going to show all these interactions.

Ecosystems

And in any ecosystem, this is a fairly simple food web.

Ecosystems

It's just showing the major ones.

Ecosystems

Obviously if we were to include all the different types of algae this would be a massive food web.

Ecosystems

And so in an ecosystem there's all these connections between the organisms.

Ecosystems

And it's pretty detailed.

Ecosystems

Now each of those have adaptations that allow them to live where they are.

Ecosystems

In other words the green algae are adapted to this kind of an environment.

Ecosystems

Same with the diatoms.

Ecosystems

Okay.

Ecosystems

Next thing I need to talk about is growth.

Ecosystems

And we've mentioned this when we talked about communities and how populations grow.

Ecosystems

In general all growth is going to be exponential.

Ecosystems

So if we were to go with amphipods, they're going to create more amphipods and eventually we get exponential growth.

Ecosystems

I could use a color that you could actually see.

Ecosystems

So we get exponential growth like that.

Ecosystems

But the problem is as you start to grow there's going to be limiting factors.

Ecosystems

Pretty soon you're too crowded.

Ecosystems

There's not enough food.

Ecosystems

There's competition.

Ecosystems

There's also going to just be drought.

Ecosystems

There's going to be meteorological geological changes that can limit that growth.

Ecosystems

And so all growth will eventually become logistic.

Ecosystems

In other words it's eventually going to reach what we call a limit.

Ecosystems

In science we call that K or K stands for carrying capacity.

Ecosystems

So carrying capacity is going to be the maximum level that an ecosystem can support of a specific population.

Ecosystems

Now it's not going to be linear like this.

Ecosystems

This is just using a mathematical representation.

Ecosystems

Obviously populations are going to bounce up and down and they're going to bounce up and down on this carrying capacity.

Ecosystems

But in general all populations will undergo that.

Ecosystems

Let's look at some real populations.

Ecosystems

So wolves were reintroduced into Yellowstone Park in 1995.

Ecosystems

So they put some packs there.

Ecosystems

This is actually a picture of one of the first wolves coming out of the enclosure.

Ecosystems

They brought them from Canada and they left them in an enclosure for months if I remember.

Ecosystems

Because they didn't want them just to run back to Canada.

Ecosystems

So they eventually released them.

Ecosystems

And let's look at what their population has grown.

Ecosystems

So blue is all the wolves in Yellowstone Park and then the other two bars are just in different areas.

Ecosystems

But if we look at the population growth, population growth has varied a little bit.

Ecosystems

But it's gone up and down and up and down and up.

Ecosystems

And so what's it doing?

Ecosystems

Well you can see that this part was more exponential growth.

Ecosystems

And now it's approaching what's called logistic growth.

Ecosystems

In other words there's just a certain number of wolves that you can actually support in Yellowstone Park.