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.