Hi. It's Mr. Andersen and welcome to Biology Essentials video number 20. This
is on biotic and abiotic factors. First thing I should do, I should define the two. Biotic
means living. And so if we're looking at biotic factors we're looking at all the living things
that can affect population or organisms. And abiotic factors are going to be non-living.
Or without life. And so let me give you an example of each. In 1995 wolves were reintroduced
into Yellowstone National Park. And these are the first wolves getting carried into
the park. They stayed in an enclosure for awhile before they actually released them
because they didn't want them to run back to Canada. But that would be a biotic factor.
You're adding an living thing to an ecosystem, Yellowstone National Park. And so that's a
biotic factor. An abiotic factor, this would be a graph of atmospheric carbon dioxide.
They've been studying the amount of carbon dioxide in the atmosphere. This is over the
last 50 years. And you've probably read about that. We've seen an increase of the amount
of carbon dioxide over the last 50 years. And that's causing global warming. So the
temperature is getting warmer and warmer. Now temperature is not alive and so we call
that an abiotic factor. Now both of these, biotic and abiotic factors are going to affect
organisms, populations, ecosystems. And that's what this podcast is really about. And so
the things that I'm going to talk about are factors. Abiotic and biotic. So living and
non-living factors. And how that causes interactions between cells. The example I'll give you is
going to be biofilms that form. And that's as a result of abiotic factors. At the level
of organisms I'm going to discuss the predator-prey relationship. In other words how one organism
can affect the population of another organism. And then finally I'm going to get at a bigger
level. At the ecosystem, population, community level. And I'm going to show you how interconnected
an ecosystem can be. And how food webs, one tiny change in a food web can actually have
huge repercussions throughout that food web. Okay. I want to start at the level of the
cells. How changes in abiotic factors can affect cells. And the example I want to give
you is biofilms. It's a term most people aren't familiar with, but it actually will effect
you more than you might think. Biofilms are formed by bacteria. And so if you have bacteria
by themselves we tend to call those planktonic bacteria. And so that means that they're just
floating, moving by themselves. But if you ever put them in an environment where there
is something that they can attach on to, and then you also have to have flow in general.
And so the flow of the liquid is going to be in this direction. So if you ever have
a flow of liquid and then some kind of a place that they can attach on to, bacteria form
something called a biofilm. And so if we're talking about something to attach on to, flow
or at least some liquid, those are abiotic factors. And how are they going to affect
bacteria? Well bacteria will start to form a biofilm. And so this is one bacteria by
themselves. But once the start to attach, they'll build slime around them, which is
made up of a number of different macromolecules. One big one would be polysaccharides. But
essentially what they'll do is they'll build this slime layer around the bacteria. And
once you have that slime layer around the bacteria you can slough off some of those
bacteria to become more planktonic. But it's really hard to get rid of a biofilm. So an
example of a biofilm would that plaque that forms on your teeth. You can't just get rid
of that. You physically have to scratch it off. Now that might not seem that bad, but
one thing that's going to affect you probably over your life is going to be wounds. And
so chronic wounds, chronic sinusitis, things like that, we're starting to figure out are
actually caused by biofilms. These are bacteria that are actually building a protective home
around themselves. And what make that scary is we normally treat bacteria with antibiotics
and if you apply antibiotics to a biofilm it doesn't do anything. It doesn't get to
the bacteria living on the inside. And so biofilms are a response due to an abiotic
reaction, namely a place and a liquid that kind of goes through that. Next I want to
talk about how organisms can affect other organisms. And this is the predator-prey relationship.
And probably the most famous predator-prey relationship of all when you study biology
is the relationship between the snowshoe hare. And this is a snowshoe hare here. And the
Canada lynx. They both live in Canada or northern North America. And so the cool thing about
this relationship is the Canada lynx feeds just on the snowshoe hare. And the only thing
that can catch a snowshoe hare is a Canada lynx. And so they're linked in this cycle
where the population of the snowshoe hare affects the Canada lynx, which in turn affects
the snowshoe hare population. And so this is a study from 1937, MacLulich. But what
they were looking at was pelts from the Hudson Bay company. Because this is data way back
in the 1800s through 1930. What they were looking at is how many snowshoe hare pelts
they found and lynx pelts. And what they could do is they could approximate the snowshoe
hare population and then the lynx population. And what you find, let me find a color you
can see, is the snowshoe hare population would go up and then go down. And then it would
go up and it would go down. And it would go up and it would go down. So it would cycle
like that. And we see that a lot of times, especially in populations that breed quickly
like rodents or rabbits. But what's interesting is that if you look at the snowshoe hare population,
snowshoe hare population, right as this snowshoe hare population would increase we then start
to see an increase in the lynx population. Why is that? Well they're feeding on them.
And so when the population of snowshoe hares goes up, then there are more of them. So Canada
lynx are able to survive. Able to pass their genes on to the next generation. And so the
lynx population starts to grow. And then as the snowshoe hare population drops off then
the lynx population drops. There's no snowshoe hare to eat. And their population is going
to drop off. And so if I try to trace this what you can see is that there is a predator-prey
relationship. Now lots of times we can't see this in nature. And the reason why is that
there's a lot of other things that might feed on a prey population. But if you look at this,
you can see how the predator population is shifted just a little bit to the right. But
it's clearly responding to that. Now what kind of factor is this? We're looking at a
biotic factor. In other words the biotic factor that is the population of snowshoe hare is
affecting the Canada lynx population and vice versa. Now again it's not always that simple.
Especially as we move up the ecological levels. So now we're looking at the levels of populations,
ecosystems and communities. And what we find is that there's this complex food web and
changes within that food web can have huge repercussions throughout the ecosystem. So
example. Wolves were eliminated from Yellowstone Park. And they were hunted just by humans
to get ride of them because they do have a huge impact on stock. On the number of cows.
They were feeding on cows. And so ranchers got rid of them. And actually the government
got rid of them in Yellowstone Park. So what do wolves feed on if they're not feeding on
cows? They feed on elk. So what happened to the elk population? The elk population went
up. Now it would be hard to predict what happened as a result of that. Let's see how it, I mean
you may want to think, how does that affect coyote populations? Red fox? Beaver? Willow?
Aspen? How would it affect it? Well let me tell you what really happened. As the elk
population went up, elk love to feed especially on young aspen and willow. And so the aspen
populations went down, or excuse me, the willow population went down, aspen populations went
down as well. As a result of that the beavers were pretty much eliminated from Yellowstone
Park because they need aspen and willow to feed on. What happened to the coyote population?
Coyote population went up because the wolves will actually kill coyotes. They see them
as a competitor. As the coyote population went up, they couldn't feed on the elk population
because they're simply too big, but they did have a huge impact by eliminating a lot of
the red fox. And so what had happened was this had been out of flux. As a result of
eliminating that, what we sometimes call the keystone species. So what's happened since
we reintroduced the wolves into Yellowstone Park? The elk population's taken a dramatic
drop. As a result we're seeing increases in these, an increase in these, a decrease in coyote
population. And so we're just talking about biotic factors. Because what happens to beavers?
Well beavers build dams. And that's going to impact the flow of the water. It's going
to slow it down. It's going to create ponds. That's now an abiotic factor. And so you can
see how just one species can have huge repercussions throughout that ecosystem. It's going to affect
biotic factors. It's going to affect abiotic factors. And it's really going to change,
even at the level of the ecosystem, it's going to have some huge changes. Especially when
we remove one large predator. Is that good? Is that bad? Well it has returned balance
to Yellowstone Park. But if you're an elk hunter, it's had a huge impact on their population.
And so what's the right answer? Probably no one right answer. Wolves are probably here
to stay. But it does show you the complexity of life, how it's interconnected and how changes
in one area can affect changes and affect the population throughout. And so those are
abiotic and biotic factors. And I hope that's helpful.