Hi. It’s Mr. Andersen and this is environmental science video 7. It is on ecosystem ecology.
Ecosystems are large areas on our planet that contain both living and nonliving material.
A great example could be these giant kelp forests. The kelp are producers. So they are
taking energy from the sun and converting that into food, which is eaten by herbivores
like this sea urchin, which in turn are eaten by carnivores like this sea otter. Now the
problem with the sea otter is if it dies due to hunting or predation, then the sea urchin
populations will take off. Sea urchins feed on kelp by trimming the bottom and sometimes
the kelp will simply float away. And so if you have too many sea urchins you get what
are called urchin barrens where there are no kelp. And therefore the whole ecosystem
kind of folds in on itself. And so we like to think of the otter as a keystone species.
Just like on this arch, this keystone at the top holds everything else in place. You can
think of each of these stones now as a different species. If we remove that keystone species
then the whole things folds in on itself. In other words some species are actually more
important than others. Before we get to ecosystems we should understand how life is organized
from the very small, one individual for example, sea urchin. It is in part of what is called
a population, or all of the sea urchins in an area. We then take all of the populations
together. That is a community. We then add the non living material. That is an ecosystem.
And then we even have larger areas which are called the biomes. What is larger than the
biomes? That is going to be the biosphere. That is going to be our planet. And so before
we get to ecosystems we will start by studying the major biomes, both terrestrial or land
based and aquatic. We will then move on to the interactions at the ecosystem level. So
that is going to be all of the producers and consumers interacting. A good way to study
that is going to be with their food webs. We are also going to add abiotic or non living
material. We will then jump to individuals and the role of a niche. That is going to
be the job that an individual has. We will then move to the importance of keystone species,
diversity. And then finally edge effects in keeping that ecosystem healthy. And so let’s
start with terrestrial biomes. A desert could be an example. A boreal forest could be an
example. Now there is really only two properties that determine what biome we are going to
have. That is going to be the temperature, average temperature and the average precipitation.
So you could be given a map and just told what is the average temperature and precipitation.
You could make a pretty good guess as to what the biome is going to look like. And so if
we graph those on a graph where we have precipitation on the y, so that is going to be the amount
of annual precipitation from 0 to 400 centimeters per year. And then we look at temperature
from the very cold on the left, -10 degrees celsius as an average up to 30 plus degrees
celsius. You could kind of guess as to what biome are we going to find where it is really,
really hot and where it is really, really moist. You could even point to it on a biome
map. It is going to be the tropical rainforest. And so what you can do on this map is just
read precipitation, temperature. That tells you the biome. If we were to go in Africa
right here and then move to an area where it is still hot but we have less precipitation,
that is going to be a tropical forest or savannah. You are probably familiar with that. If we
keep moving up, so we have even less precipitation then we are going to get into a subtropical
desert. And you can see those at this latitude and at this latitude right here. If we keep
going across from Africa though, lets go up here, we are then going to have temperate
grasslands. Sometimes we have temperate deserts. You can see we have a lot of those in the
midwest of the United States. If we keep going then we are going to get to temperate seasonal
forests. If we keep going then we go to the boreal or northern forests. And then we eventually
get to the tundra. So these are the major biomes. We could fill in a couple of other
ones. So right here in the mediterranean we are going to have woodland shrub lands. We
would have that over in California as well. And then if we go up here we will have these
temperate rainforests where it is cooler but they receive tons and tons of precipitation
throughout the year. And so you can see those are those the major biomes. If we start looking
at aquatic biomes it is not temperature and precipitation, because water exists. And so
it is going to be salinity, the amount of salt, the depth within that water and then
the flow of the water. And so the first way to divide the aquatic biomes is to those that
are freshwater and those that are going to be saltwater. If we look at those that are
freshwater you are probably familiar with almost all of these. Wetlands are areas where
we are going to have water for a large portion of the year but we still have vegetation in
that area. We could move from there to areas that are kind of the boundary between fresh
and salt water. So a salt marsh is going to be an area where we have water flowing in.
So we could have a mix of freshwater and saltwater. Estuaries are like this. Or we could have
mangroves. Those are areas, mangrove is kind of based on a tree that can grow in salt water
and those are important as a border between marine and terrestrial systems. And then as
we move out to the ocean itself we have intertidal zones. So that is going to be when the tide
comes in and out. That thin area along the coast. Coral reefs you are probably familiar
with. And open oceans. Open oceans are really not a super productive ecosystem out in the
middle of the ocean. Only near the top where we get a certain amount of light. So now we
are going to go from biome to ecosystems. So this is going to be a smaller area but
it is still really big. One of the most famous ones in the world is the Greater Yellowstone
Ecosystem. It is really just south of me. I live right here. And so it is bordered by
Montana, Idaho, Wyoming and Wyoming. But it is not just Yellowstone National Park that
makes up the ecosystem, it is going to be this whole area around it, which is going
to contain the national park. But also national forest and private land as well. It is a really
large area. Also includes all of the abiotic or nonliving material. So for example the
temperature, the pH of this water, the flow of the water are all considered when we are
thinking about the ecosystem. Now let’s go to the parts of the ecosystem. So everything
is built on these producers. And so those things that do photosynthesis. If we look
at a terrestrial versus an aquatic we are going to find the same kind of transition.
We have the plants at the bottom. The herbivores. Then we have carnivores and carnivores on
top. So we have these different levels of consumers as we move up. They are organized
in what is called a food chain. And the arrow is going to show where the energy is going
or where the food is going. So food goes from the plant to the insect itself. Students sometimes
confuse which way the arrows go. And here is an easy way to remember that. So just think
of the arrow as the mouth of what is eating it. So this is a mouth of a fish. We know
that the arrow always goes from the food to what is eating it. Or the organism to what
eats that organism. If we organize all the food chains in an area then we have a food
web. And so it is going to have producers on the bottom and then it is going to have
the consumers above that. Different levels of consumers. If you look we have aquatic
and terrestrial all mixing in. Some terms that you may be familiar with are herbivore.
Herbivore is going to be something that just eats plants. We have carnivore, something
that just eats other living things. But we also have an omnivore. That is going to be
something that eats plants and other living things. Keystone species remember is going
to be a species that keeps everything kind of in check in that ecosystem. And I am really
leaving off a bunch, which is going to be all the decomposers. So as material dies we
have to recycle that. So that is going to be decomposers. An example are detritivores
that can eat large bulk amounts of dead material. What is the niche? Now we are at the level
of an individual. So a niche you can think of as like the job of an individual. So if
we take this squirrel and say how does the squirrel preform over different temperatures,
well we are going to get a distribution like that. There are going to be areas where it
can survive. Outside that would be areas where it dies. If it is too cold or if it is too
hot. As we move closer to the middle we get areas where it can survive and grow. And finally
where it can survive, grow and reproduce. And so the environment has a lot to do with
a niche. But also what we are using as a food source. So this dung beetle for example exploits
a niche by taking dung, rolling it up and using that as an eventual food source. What
else determines it then? Not only the environment but the resources, the food that you need.
Or the space you need to live in. And so we can represent that on this graph as here is
the two resources I need and that is going to be my fundamental niche. That is where
this squirrel could live. Now what you will find is that it actually does not fit that
way. You have what is called a realized niche where it could live in all of those areas
but it only lives in the small area. And the reason why, you are probably guessing is that
there are other niches outside that. There is competition going on. Species diversity
is actually good. It is good to have all of these different species. So let me use this
model to show you how that works. Imagine we have species that are just cold tolerant.
They love the cold. Warm tolerant, they love the heat. Or a nice diverse mix of the two.
And so let’s say we apply some cold weather. What happens? All those that are not cold
tolerant die. You can see the warm tolerant are going to be most affected. You are going
to see the diverse species in the middle. And the cold ones are doing fine. But let’s
say we change it up now and it is really hot. Then we are going to have this impact. And
so right here by having a diverse population, this does not have to deal with just temperature,
but it can be resources you are feeding on, the more species we have the healthier that
ecosystem is going to be. That even applies at the individual level. So a raccoon is what
is called a niche generalist. It can eat lots of different food resources. It can live in
lots of different areas. Where as a koala can only eat Eucalyptus leaves. Which of these
do you think is more susceptible to change in that environment? Definitely is going to
be the koala since it is only feeding on one thing. If that resource is impacted it is
going to be impacted as well. The edge effect also affects the health of an ecosystem. Edge
effect is going to be a boundary between two ecosystems. It actually can be a healthy area.
So if it develops over a long period of time what you will get is this transition from
here into the forest. And so that is an area where we can actually support more species.
The problem is that humans lots of times will just create an edge, so we make a trail or
we make a road. And now what happens is there is not this natural boundary and that can
damage the health of the ecosystem. The size of the edge is always going to be the same.
And so watch what happens when I take this shape. Think of this as a protected area.
So the edge will always remain the same. But watch what happens when I shrink the protected
area. The edge becomes a larger proportion. Let me even shrink it up even more. And so
that edge becomes the largest thing. And so if we are trying to protect an ecosystem,
protect an area, it is important that we have the largest area with the healthiest edge
that we possibly can. And so did you learn the following? Can you pause the video now
and fill in the blanks? Well I hope so, but I could work through it. It goes from individual
to population to community to ecosystem to biome. Major examples are terrestrial and
aquatic. Could you list some of those? We have interactions between producers and consumers.
Keystones species, diversity and then the edge effect can affect the health of the ecosystem.
And then remember the niche is the role of an individual. It is kind of like its job.
I hope you learned that. And I hope that was helpful.