He begins with a description of how life on the planet is ordered from large to small in biomes, ecosystems, communities, population, and individuals. He describes the major terrestrial and aquatic biomes on the planet. He then describes interactions at the ecosystem level with food webs. He also explains the importance of niche, keystone species, and the edge effect.
Transcript provided by YouTube:
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 co