Hi. It's Mr. Andersen and welcome to Biology Essentials video 47. This is on ecosystems. And we happen to live next to one of the most famous ecosystems on the planet. That's the Greater Yellowstone Ecosystem.
So we live right here in Bozeman which is about 60 miles north as a crow flies from Yellowstone National Park. And so when we're talking about ecosystems we should figure out where in ecology, what level we're at. that. So remember Bebekpo is biosphere, biome, ecosystem, community, population, organism.
And so basically what is an ecosystem? An ecosystem is going to be all of the biotic and abiotic characteristics in an area. And so Yellowstone Park was founded in 1872. And it was mostly founded to protect these geothermal features. And so what is most famous would probably be Old Faithful, which is about right here.
But Yellowstone is situated on this giant Yellowstone caldera which is kind of like that. And so when they established Yellowstone Park they established it just to protect the geothermal features. So the hot springs, the boiling mud and all of that.
But what they ended up doing luckily is preserving one of the most pristine ecosystems on our planet. And so Yellowstone Park, if I look over on this map, if I were to trace it, it's about right here. So this is right on the corner of Wyoming and it goes into Montana and Idaho over here. But if you look around here there's all these national forests. And so we eventually have this giant ecosystem which is kind of in this brownish area.
They didn't really start talking about it as an ecosystem until the 1970's when they were studying grizzly bears. And they found that grizzly bears were in trouble. But this was kind of where they ranged.
So this was their range. But you can see over here that we're not sure what an actual ecosystem is. How big it is and how big we should make that. What's interesting is that this is all a national park.
And these are national forests around it. But once we move out into here we're moving into private land. And so there's an interesting kind of conflict that comes up when we move from national land to land that's actually owned by people.
The wildlife isn't but the land surely is. And so it's a hard thing to maintain. But even with all of that, greater Yellowstone ecosystem is the most pristine ecosystem in the northern latitudes, especially in North America that we have. So it's pretty cool.
It's nice to live right next door. So basically in this podcast I'm going to talk about ecosystems and how they're affected by their environment. Remember they get energy from the sun. But the matter has to be recycled. And so the combination of energy coming in and then the matter, especially carbon being recycled, we come to a new term here.
That's called primary productivity. So depending on where you are on the planet, you have either a high level or a low level of primary productivity. Basically what that is is the producers in an area.
It's how much biomass they're laying down. As a result of that we have these very complex reactions. And so those are called food chains.
It's basically a feeding chain. And if we get more complex that's called a food web. But remember every organism that's living in an ecosystem is adapted to that environment and those specific constraints. Now sometimes there will be impacts on an ecosystem.
And so those impacts can be biotic or abiotic. Remember they could be living or nonliving. But basically what that does is create competition.
And so all populations are limited by the amount of availability of these resources that they have. And so eventually all populations will undergo logistic growth. Now if we let things run naturally they tend to fit a regular balance or find an equilibrium.
But lots of times humans will make changes and those changes can have very quick impacts on an ecosystem and sometimes can lead to extinctions. And so let's get started. Let's first start by defining what primary productivity is. Primary productivity as I mentioned just a second ago is how much livable mass is being laid down by the producers in an area.
So Remember the producers are going to be those things that do photosynthesis. And so they're using energy and then they're weaving matter together to make life. And so if we look on our planet we find here in the ocean we're going to have, this is measuring the amount of chlorophyll A, we're going to have a higher primary productivity here and here than we are right at the equator.
And that has to do with the currents in the ocean. So we need nutrients and we also need availability of light. 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 forests or for sure in the rain forests.
And so what do we measure primary productivity in? Well it's grams of carbon. per meter squared per year. 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. Now how is that carbon being added?
We're taking in carbon dioxide from the atmosphere. We're using light from the sun. And then we're making it into livable material. And so it's easy to measure in an area like this. Just put a quadrant down and Sometimes it's harder if you're in a, this would be a terrestrial area or an ecosystem.
This would be an aquatic area. So when you're in water lots of times it's harder to measure the matter that's being created. So sometimes we'll measure the gases that are being produced.
So we can look at the oxygen that's being produced in an aquatic environment. 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. So primary productivity is going to be just a measure of how much life can be created.
in an area. Food chains measure where this life goes. And so if we start here, on the right side I've got what are called trophic levels. And so we should define what a trophic level is first.
Trophic just means an eating level. And so the lowest level, trophic level 1 we call that, are going to be producers. 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? It's mostly going to be algae.
So what they're doing is converting energy from the sun. And so what we're going into livable material. And so we would call this trophic level 1. Or sometimes we call these producers. Okay.
So if we go to the next level, next level, trophic level 2, these are going to be consumers. And so consumers remember can't make their own food. They have to get their food from somewhere else. And so if we were to do a food chain, the food chain is going to go like that. Now the arrow you should get used to, the arrow is always going to go from what's eaten to what eats it.
And the way I remember this is if you look at the head of the arrow it's like the mouth. So it's like the mouth of Pac-Man. And so whatever is eating is going to be on this side of the arrow. And whatever is eaten is going to be on that side of the arrow. So now we go to the third level.
Third level is going to be, we call these second level consumers. But those are going to feed on these organisms. So algae is eaten by amphipods which are a little crustacean.
Those are fed on on by rainbow smelt. And then if we were to go one more level then we get to the level of Chinook salmon. So this would be the fourth trophic level or we call this a first, second, third level consumer. Now this is a food chain. Food chains are linear.
They go from what's eaten to what eats it to what eats that to what eats that. So it just goes in one direction. But you can imagine that there's a lot more food chains in Lake Ontario than the one that I've just drawn here.
And so if we were to add the other food chains, we would have a Now we get what's called a food web. A food web is going to show all the connections. 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. It's going to show all these interactions. And in any ecosystem this is a fairly simple food web.
It's just showing the major ones. Obviously if we were to include all the different types of algae this would be a massive food web. And so in an ecosystem there's all these connections between the organisms. And it's pretty detailed.
Now each of those have adaptations that allow them to live where they are. In other words the green algae are adapted to this kind of an environment. Same with the diatoms.
Okay. Next thing I need to talk about is growth. And we've mentioned this when we talked about communities and how populations grow.
In general all growth is going to be exponential. So if we were to go with amphipods, they're going to create more amphipods and eventually we get exponential growth. I could use a color that you could actually see.
So we get exponential growth like that. But the problem is as you start to grow there start to be limiting factors. Pretty soon you're too crowded. There's not enough food.
There's competition. There's also going to just be drought. There's going to be meteorological, geological changes that can limit that growth. And so all growth will eventually become, In other words it's eventually going to reach what we call a limit.
In science we call that K or K stands for carrying capacity. So carrying capacity is going to be the maximum level that an ecosystem can support of a specific population. Now it's not going to be linear like this. This is just using a mathematical representation. So we're going to use a mathematical Obviously populations are going to bounce up and down.
And they're going to bounce up and down on this carrying capacity. But in general all populations will undergo that. Let's look at some real populations. So wolves were reintroduced into Yellowstone Park in 1995. So they put some packs there.
This is actually a picture of a pack. So this is a One of the first wolves coming out of the enclosure. They brought them from Canada.
And they left them in an enclosure for months if I remember because they didn't want them just to run back to Canada. So they eventually released them. And let's look at what their population has grown. So blue is all the wolves in Yellowstone Park.
And then the other two bars are just in different areas. But if we look at the population growth, population growth has varied a little bit. But it's gone up and down and up and down and up. And then And so what's it doing? Well you can see that this part was more exponential growth and now it's approaching what's called logistic growth.
In other words there's just a certain number of wolves that you can actually support in Yellowstone Park. If we were to draw in what the K value is, I would say K value so far looks like right about here. Maybe around 140, 150 wolves that Yellowstone Park can support. Now those wolves are moving outside of the park as well. There's competition that happens then.
So this is the same thing. So Here is that growth of wolves. So the wolves are going to be on this side. So their population went up.
They've gone down, up, down. It will probably go up. So it's just going like that. So on this side we've graphed the wolves.
But let's look at what has happened to the elk population. So the elk population is going to be listed on the other side. Something like 87% of what wolves eat are elk. So these two are linked together.
They eat bison. They eat moose. They eat a lot of different things. But in general they're mostly eating elk.
And so if we look at what's happened to the elk population during this time, the elk population started at around, this is in the northern area of Yellowstone Park, started around 16,000. But it steadily dropped off. Okay.
So now it's down to, who knows, 5,000 elk maybe in 2011. So what pressure is that going to put on wolves? Well now there's not a lot of food to eat. And so the wolf population is going to drop off.
As the wolf population drops off they're going to feed on less elk. And so there's probably going to be this predator prey relationship between the two where the elk population will start to make a comeback. It will drop off like that. And then if we look at the wolf population, the wolf population is going to follow that as well. And so we reach what's called an equilibrium.
Now this is great for wolves. Not great if you're an elk hunter in Montana because the population has gone from 16,000 down to like 5,000. So we're going as they move out of Yellowstone Park, as wolves move into that area that's private, like I mentioned at the beginning, there get to be real human issues and impacts with that.
Last thing that I want to talk about relates to humans then. So humans can have huge impacts on an ecosystem and not knowingly we can make big changes. So let me tell you the story of the whitebark pine. Whitebark pine is going to be found in Yellowstone Park. If we look at where it is, here's present day whitebark pine.
So it's usually going to be found in higher areas. But basically it's a sturdy kind of a pine. It can deal with lots of snow and really cold temperatures.
But they'll produce pine nuts during the year. And those pine nuts are gathered up by squirrels. So the squirrels love to grab the pine nuts. They dig and create these middens which are just like a stash of a bunch of these pine nuts.
They'll feed on those during the winter. But sometimes they forget where they are. And a lot of the time those middens are middens, I think, M-I-D-D-E-N-S. are raided by grizzly bears. So grizzly bears will move up into these areas and they'll raid these middens.
And so it's a big part of their food supply before they start to hibernate in the winter. And so what's happening? Well global warming.
So changes to the global climate or climate change is creating warming conditions in Yellowstone Park. And this is projections of what will happen to the whitebark pine population. if we just get a moderate increase in temperature. They can't deal with that and so the white bark pine is going to drop off. As a result of that squirrels aren't going to have any nuts that they can actually stash.
Grizzlies aren't going to have that. And so you can see that this food chain is tied to the environment. Tied into the, in this case it's going to be the overall temperature.
And so human impacts are so fast, so global climate change is so fast that it forces. pressure on all the species within that ecosystem and all those connections. A lot of the ones we don't even know.
And so that's ecosystems. They're really delicate. They also have feedback loops that kind of maintain that equilibrium. But I hope that's helpful.