In this lecture, we're going to get deeper into evolutionary biology.
And were going to talk about species as being discrete real things in the world.
We're going to talk about the origin of species,
what are the mechanisms by which species arise?
And then we'll start discussing about how to build phylogenetic trees, building the
tree of life. Now again, Darwin's first idea
was descent with modification.
And from that came the notions of phylogenetic trees.
But first you got to understand what are we putting on these trees?
Well, we put species, and groups of species.
And understanding species is a really important concept in
evolutionary biology, but it's also a very difficult concept.
But in essence, species are real
things out in nature.
We, we have to think as biologists and as scientists
that the things that we're studying there are real discrete entities.
And they represent products of an evolutionary history.
and that helps us understand the process itself by which species arise.
But also a very, very imprtant, it helps us classify organisms.
And classifying an organism
is extremely important for all kinds of solving biological problems.
Understanding what species are is very
important in biological science and applied science.
We, we discuss conservation units. People want to conserve species.
They want to conserve groups of species.
They want to go out and describe new species,
so new species are being described all the time.
But you gotta know what a species
is in order to say its a new species. Invasive species, the United States
spends billions and billions of dollars mitigating against invasive species.
So, we need to know what they are, where they come from, what they're related to.
And there are many pathogens and hosts
that we are very concerned about discovering.
In the last lecture
we, we talked about West Nile Virus. And there are many other things that we
use the notion of species in to, to find out what they are and to to describe them.
And, then there's agricultural wild relatives.
We use a lot of wild relatives of a plan, of food crops, to help improve food crops.
A very good example
is that the wild relatives of corn live in the mountains of Mexico.
And they have genes that when planted in, that when bred
into, the cultivated corn in, in Mexico,
prevented disease. And, and therefore enhanced their crops.
So what is a species? This is where
biologists have debates.
And there are a multiple of definitions of species out there.
But there's two real ideas that go across almost all of those definitions.
One, is that these populations or groups of
populations can be told apart by some feature.
So they have a red wing, or a white wing, for instance.
So, these are phenotypic
characters, but also genetics is in,
increasingly being used to help individuate
new, new kinds of species, and
in, individu, individuate populations into species.
Then another big idea that is, constantly talked about, is that
well populations, are different species if they don't interbreed
with other populations that look sort of like them.
So, non-interbreeding is also a very big concept.