Ecosystem Diversity


Hi. It’s Mr. Andersen and this is environmental
science video 9. It is on ecosystem diversity. A model we have talked a lot about so far
is this idea that the earth provides life support for the society of humans which is
driven by economy. Now economics is the choices that we are making but economy, if we put
a monetary value on it is going to be a really large number. It is 75 trillion dollars. That
is the world gross product. That is what we make, products, and also what we do, the services.
It is a huge number but it is actually small compared to what is called ecosystem services.
That is what the planet does, what the planet makes and what the planet does for us. And
it does that for free. In other words it makes oxygen. It makes soil. It recycles nutrients,
filters water. And so it is doing that for free. And it is more efficient the more diverse
the ecosystems on our planet are. The more diversity we have the better it is for ecosystem
services. And as we degrade ecosystems we are going to have to take on some of that
cost. Biodiversity is a measure of the variety of life on our planet. One way to measure
that is the variety of species on our planet. How do we increase the number of species?
We do that through speciation. The mechanism by which that occurs is evolution by natural
selection. Now how do we decrease the number of species? That is through extinction. That
is one way to measure biodiversity. What is another way to measure it? We could measure
genetic diversity. Or we could measure ecosystem diversity. All of the different ecosystems
that we have on our planet. And that lends itself to this idea of ecosystem services,
what the world can do for us. And it really does things in four different areas that we
will talk about in this video. Supporting us, provisioning us, regulating the planet
and there is also cultural significance as well. So we can measure biodiversity on our
planet in one of three ways. We could measure the different types of ecosystems that we
have. The different species that we have. Or the different genes that we have within
those individuals. But if we take species, as an example because that drives everything
else, how did we get the variety of species on our planet? That is through evolution.
So Darwin pointed out that all life on our planet shares one common ancestor. A branching
tree of life. Now that is not super accurate. Let me show you a scientific one. This is
a cladogram that is showing how dolphins, whales, hippos, dogs are all related. And
so they are looking at genetics similarities. But what you find is this cladogram that is
branching out, just like this tree of life. And so there are going to be areas where it
branches. And so one becomes two. We call that speciation. One species becoming two
species. And that is how we increase the number of species on the planet. Now how do we decrease
the number of species? You can see that on this cladogram as well. Some of these are
fossils and that is because they are extinct. In other words they are grayed out on this
cladogram. That is when one species becomes zero species. It takes a lot longer for speciation
to occur then extinction. So what is the major mechanism of speciation? It is evolution through
natural selection. If you are not sure how that works imagine we have some bacteria.
And here is different types of bacteria. They have varying levels of resistance to an antibiotic.
And so let’s say you take an antibiotic. Which of these are going to be killed? Well
the ones that are least resistant. So once we take the antibiotic, this is after selection
or after that selective process. And so now where is our final population. It is evolving
over time. And that is how humans have become better adapted to their environment. But if
we look at speciation, how does that occur? Well imagine we have a group of fish that
are in a pond. And they are interbreeding with each other, we will call them one species.
And they somehow get separated. Maybe it dries up and now we have two ponds. And so what
happens over thousands and thousands of years is that they each are going to adapt to their
environment. And so they are going to be perfectly adapted to that. So maybe there are changes
in size, changes in coloration, changes in behavior. And so they are now becoming two
species. How do we know that? Let’s say that we put them back together again, let’s
say the pond grows again. If they quit interbreeding with each other now we know that two species
have evolved. Now this takes a long time for this to occur but let’s say the climate
changes. Let’s say the environment changes and all of that species goes away. That is
called extinction. It is going from that one species to zero species. And this occurs,
we can look back in the geologic time, it occurs all the time. And so we have had five
mass extinctions over time. So we are looking back here, millions of years in the past,
and this is extinction rates. And so there are lots of different causes. The one you
are probably familiar with is the asteroid impact that caused this extinction of the
dinosaurs. Now most scientists would argue that we are on the verge of what is called
the sixth mass extinction. In other words we are seeing extinction of species at a rate
that we have never seen in the past. Now who is causing that? That is humans that are causing
it. And it is a big deal because the earth provides these ecosystem services, services
that we need. If we were to say what are those? They are in these four areas. And lets go
through each of those. First of all they support us. They support us through number one production.
In other words plants and the process of photosynthesis makes food and it also makes oxygen that we
breathe. It also is making the soil that we use to grow our crops. And is also recycling
nutrients. These are all ecosystem services, things that the earth does for free that we
utilize. We could also look at provisioning services, so they are making the provisions,
the food that we eat. So seafood comes from the sea. Water we are getting. Lumber. We
could look at minerals or even energy from the sun. So that is all provided from the
planet itself at no cost to us. We could also look at regulation. So filtration of water
occurs naturally. We do not have to filter the water. The ecosystem is doing that. Now
if the ecosystem is gone and we have to make water filtration it is going to cost us a
lot more. Decomposition. We could talk about carbon sequestration or climate regulation.
These are all services that the ecosystem provides. And it also provides cultural significance.
Be it historical, spiritual, maybe educational or recreational. Think about if we put a monetary
value on ecotourism that comes from that area, it is hugely valuable. And so it is important
that we protect the diversity from a monetary prospective. Not just because it is the right
thing to do but it makes sense monetarily. And so did you learn the following. Could
you pause the video and fill in all the blanks? If not, let me do it for you. And so biodiversity
is a variety of life. We can measure that in the variety of species. Also genes and
ecosystems. So how do we increase the number of species? Speciation, evolution through
natural selection. How do we decrease it? Through extinctions. Ecosystems provide ecosystem
services that could be supporting us, provisioning us, regulating and cultural services. So I
hope you got that and I hope that was helpful.

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