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Hi. It's Mr. Andersen. And in this podcast I'm going to talk about coevolution. Coevolution
is essentially when two species head down an evolutionary pathway together. And so insects
and flowers are a great example of that. This bee is taking nectar from the flower. And
in return it's transferring some of this pollen down here to another flower. And so the insect
gets an advantage from that. And the flower gets an advantage from that. And it's worked
so well that half of all animals on the planet aren't' only insects, but are beetles which
are a specific type of insect. And so insects have done very well. And flowering plants
have done very well as well. And so angiosperms or flowering plants make up most of the plants
that you see. Grasses. Big maple trees. Those are all angiosperms. And so they both have
benefitted from this mutualistic relationship. And that's coevolution. And so I wanted to
think of an analogy that would explain kind of how this works. But beware. This is an
analogy. This is not evolution or coevolution at all. But think of those first humans when
they were on the planet. And they were trying to find something to eat. Well once they developed
a primitive spear head and could throw that and kill a mammoth, that gave them an advantage.
It gave them food. It gave them more time to think about technology. And so eventually
we came up with the wheel, which made up more powerful. And more mobile. We could move material
around. And with that extra time and that mobility we started to share ideas. And we
eventually started to print these ideas. And share them. And so technology really took
off to the point where once we had done this, the wheel, the printing press. Then it wasn't
long before we were in space. And so you could say that humans and technology are coevolving
with each other. And they both get advantage from that relationship. So again that's simply
an analogy to kind of explain how it works. And so before we talk specifically about coevolution
and what it is, we should say what it's not. And so convolution is not convergent evolution.
This is sometimes confused by students. Convergent evolution is when you have two species that
aren't related at all and then they end up looking like each other because they live
in a similar niche. Or they fill a similar role. And so if you were to just look at these
quickly, we've got a shark, a dolphin and then this is an extinct ichthyosaurus. You
would say well, they all look very similar. But they're not related at all. Even though
there are similarities, if you look at it. They all have dorsal fins. They all have pectoral
fins that allow them some stability. There are a few key differences. If you were to
look at this, the dolphin is going to have a horizontal caudal tail. And that's because
it evolved from a mammal that walked on land. Where as these evolved from early fishes or
early reptiles. Or if we look at the pill bug here and this pill millipede, excuse me,
they both look the same because that gives them defense. And they can roll up in a ball.
And so that's convergent evolution. And these things normally aren't related at all. Another
quick thing you should understand is coevolution is not between species and their environment.
And so if we look at the peppered moth, remember during the Industrial Revolution the plants
were covered in soot. And so all of a sudden moths that looked like this, dark moths, had
an advantage. Or right now, with global warming, as we start to have spring come earlier and
earlier and earlier. As species start to flower earlier, that's not coevolution with the environment.
It's basically adapting to your environment. And then coevolution is not necessarily between
friends. And so this right here is the rough skinned newt. It's one of the most toxic animals
on the planet. It has a neurotoxin. If you were to eat a newt you would die. If you were
to take a newt, boil it in water and then serve it to people, all the people would die.
It's a nasty neurotoxin. Now they don't bite. And so it's not a big deal. And you might
think why are they so toxic? Well the only thing that preys on the rough skinned newt
is this garter snake. And this garter snake, as it evolved a resistance to that toxin.
It's funny though, they'll eat a rough skinned newt and they'll kind of enter into a coma
where they have to metabolize that toxin before they can move on. And so basically it's coevolution
where the newest developed toxin. The garter snake developed resistance to that. So they
got more toxin more resistance more toxin more resistance more toxin more resistance.
And so again this is not good for both of them. They're on this evolutionary arms race.
Now something unique. Most of the garter snakes around here don't look colored. This bright
coloration. And the ones that eat the rough skinned newt actually get some protection
from the toxins. Start to have a brighter color. And so that's not, excuse me, that
is coevolution. But it's when it hurts both of them. And so basically on the next three
slides I want to talk about some symbiotic relationships that evolved through coevolution.
And they're just radical examples of that. So this right here is an acacia tree. And
this is an acacia ant. And here's a bunch of acacia ants living on an acacia tree. Now
how does this relationship work? Well basically the acacia tree will give off an odor that
attracts female queen acacia ants. And they'll be drawn to that plant. They'll lay their
eggs inside it. And they actually live in the acacia tree. There are hollow sections
of it. These are the thorns. But there are hollow sections where they live. And so they
get a home. And they're even fed. The acacia tree produces these little bodies that are
filled with sugar. And so they have something to eat. So what does the acacia ant provide
to them? Well they provide protection. If you touch an acacia tree these acacia ants
will storm all over you and bite you. So it's very painful. And that's going to keep insects
off and animals from browsing on the leaves. And they'll also trim vegetation around it.
So if a tree starts to grow on to an area where the acacia tree is, the ants will climb
over and they'll cut off those leaves. Or they'll even go in the area around the acacia
tree and kill any plants that start to grow. And so basically this is pretty advanced relationship.
And so it's evolved through step by step interactions where they're each getting an advantage. Old
story is this. An orchid was sent to Darwin. And it had this really long reproductive path
down to where the ovules form. And basically what Darwin formulated is that there must
be some kind of a pollinator, maybe a moth, that has like a really long proboscis that
it could actually fertilize this and help fertilize this plant. Darwin dies. Twenty-one
years later they develop this moth or they discover this moth rather that has this incredibly
long proboscis. And it doesn't usually look like that. Usually it would be wound up in
a moth like this. But this one had evolved this radically long proboscis. And it did
that step by step. Where it first of all had a slightly longer one. And a longer one. And
now the two of them, the orchid and the moth were locked together in this coevolutionary
pathway. And eventually it just kind of got out of, almost out of control. And then my
favorite example is this. When we travel to the Amazon one of the first things you see
right away are these leaf cutter ants everywhere. They're basically cutting little sections
of the leaf off and then returning it to their mound. So you can see them right here. Now
the mound is underground. It will be in an area where there are no trees are around it.
But basically what they're doing is their chewing that leaf down and then they're feeding
it to this. The fungus. And this is the ant, the queen ant. And so basically you'll have
ants that go gather leaves. But you'll also have little worker ants that are living inside
and on the fungus. And what they found is that the fungus never really was infected
with bacteria. It just grew well. We thought these were like perfect farmer ants that would
somehow never be plagued by pests. But when they look closer at a lot of the ants who
worked in and around the fungus, they found that there was this white fuzz growing on
their mouth. And when they looked at that under the microscope they found that there
was a certain type of bacteria, streptomyces bacteria. And what was happening is that it
was actually producing antibiotics which was killing bacteria growing on the fungus. And
the cool thing about that is in humans, and this actually is the same type or we get a
lot of our antibiotics. The cool part of that is that the bacteria that live on the fungus
are never going to evolve a resistance to that antibiotic because this streptomycin
is actually alive. So it's coevolving as well. And so we have all of these coevolutionary
adaptations, groups that are growing. Symbiosis upon symbiosis. And that's one of the reasons
why I love biology so much. It's hard to even think of all these relationships. But again,
that's coevolution. And I hope that's helpful.