>> Sean Carroll: The fact that
lizards differ in leg length
and toe pad size,
depending on where they live,
suggests that these differences
in traits are adaptations
to the lizard's habitats.
>> Jonathan Losos: Here's
a good tree over here.
>> Sean Carroll: To test whether
that is in fact the case,
I came here to help Jonathan
conduct some experiments.
>> Jonathan Losos: Yeah, these
lizards are very cooperative.
>> Sean Carroll: We begin by
comparing the running ability
of two lizards, one with long
legs, the other with short ones.
>> Jonathan Losos:
Let's do some tests.
Let's start with this
little lizard here
and see how fast it can
run up this broad surface.
>> Sean Carroll: All
right, I'll catch him
if he makes it to the end.
>> Jonathan Losos:
All right, here we go.
There he comes.
>> Sean Carroll: Wow.
She's a sprinter.
>> Jonathan Losos: Exactly.
She lives at the bottom of
trees right in the open.
She catches prey on the
ground so she has to run
down quickly to get them.
>> Sean Carroll: The shorter
legged twig lizard is not nearly
as fast.
It seems like a disadvantage.
Why aren't their legs longer?
Jonathan puts a twig lizard on
a thin branch to demonstrate.
>> Jonathan Losos: All
right, let's see how he does.
There we go.
>> Sean Carroll: Looks
pretty comfortable there.
>> Jonathan Losos: Yup.
>> Sean Carroll: Just sort
of scurrying along,
like a balance beam.
>> Jonathan Losos:
This is what they love.
>> Sean Carroll:
Instead of speed,
the twig lizard's legs
provide a firm grasp.
>> Jonathan Losos: All right,
now let's try the other one.
>> Sean Carroll: So
this is the sprinter.
>> Jonathan Losos:
This is the sprinter.
Let's see how she fares
on this little stick.
Look how ungainly she is.
Her legs are too long for this.
So you can see on
these narrow surfaces,
long legs are a disadvantage.
>> Sean Carroll: On twigs, long
legs only increase the chance
of falling so ground lizards
have evolved long legs
and twig lizards, short ones
that enable their lifestyles.
Next, we compare how well two
species can climb the slick
surfaces of leaves.
Anoles have different sized
toe pads on their feet.
We'll see if these help them
navigate different environments.
>> Jonathan Losos: So it's time
for lizard Olympics, part two.
>> Sean Carroll: All
right, I'm game for that.
>> Jonathan Losos: Here
is the ground lizard.
Let's see if he can
hang on and move up it.
[ Background noise ]
>> Oh, no.
>> Sean Carroll:
Couldn't even hang on.
>> Jonathan Losos:
Cannot hang on.
>> Sean Carroll:
Let's try it again.
>> Jonathan Losos: There he
goes, he's getting up there.
He's able to move up
but not very easily.
All right, let's
do another species.
>> Sean Carroll: All right.
>> Jonathan Losos: Take
a look at this guy.
>> Sean Carroll: Oh my goodness.
That's an anole.
>> Jonathan Losos: This
is the big canopy lizard.
Let's see how he does.
>> Sean Carroll: Well,
that's not a fair contest,
he's so huge, there's no way
for him to hold up his weight.
>> Jonathan Losos: What do
you think now, smart guy?
>> Sean Carroll: Okay,
he proved me wrong.
Pretty impressive.
>> Jonathan Losos: He's using
the little, microscopic hairs
on his toe pads to
bond with the surface
and that's what holds him up.
>> Sean Carroll: And
his toe pads are bigger
than other lizards?
>> Jonathan Losos:
Yes, they are, even --
he's a bigger lizard
but even for his size,
he has particularly
large toe pads.
>> Sean Carroll: So
this is an adaptation.
>> Jonathan Losos:
This is an adaption
because he cannot afford
to fall out of the canopy.
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