Hi. It's Mr. Andersen and welcome to biology essentials video number 47. This
is on ecosystems. And we happen to live next to one of the most famous ecosystems on the
plant. That's the greater Yellowstone ecosystem. So we live right here in Bozeman, which is
about 60 miles north as the 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.
So remember BBECPO 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 at 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 1970s 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. 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 lands 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 effected 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. Basically a feeding chain. And
if we get more complex that's called a food web. But remember every organisms that's living
in an ecosystem is adapted to that environment. And those specific constraints. Now some times
there will be impacts on a 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 layed down by the producers in their
area. 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 then 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 were 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. 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 let's say one
meter area like that, in one year, it's the amount of carbon that would be added. Now
how's 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 measure that. Sometimes
it's hard if you're in a, this would be a terrestrial area or 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 well 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 one 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 into livable material. And so we would call this trophic level one.
Or sometimes we call these producers. Okay. So if we go to the next level, the 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's 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 PacMan. 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. The
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 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'd call this
a 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 then
the one that I've just drawn here. And so if we were to add the other food chains, 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 the 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 logistic. 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. 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 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 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 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 the wolves are moving outside of the park as well. There's competition
that happens then. So this is the same thing. 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 populations started at around, this is in the northern
are of Yellowstone Park. They started around 16,000 but it's steadily dropped off. Okay.
So now it's down to who knows, 5000 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 the predator-prey relationship between the two, where the elk
population will start to make a comeback. It'll drop off like that. And then if we look
at the wolf population, 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. And
so 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 an make big changes. So let 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 that 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 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 whitebark 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, 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 is 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.