- [Voiceover] The amino acid sequence of cytochrome c
was determined for five different species of vertebrates.
The table below shows the number of differences
in the sequences between each pair of species.
So, just to give us some context
for what we're talking about.
We're talking about cytochrome c.
This is a protein.
You might remember it when we studied
the electron transport chain.
You don't really have to know that for this question,
but it's a protein that's found in a lot
of different species, and we're going to compare the
difference in the sequence of amino acids
for that protein in the different species.
So even though you have the same or similar protein,
we call them all cytochrome c,
the sequence might be slightly different
when you go from one species of vertebrate to another.
And the way to read this is
for each of these rows you could say,
all right, this row
describes D. polylepis,
and we can see the number of sequence differences
between D. polylepis and G. gallus.
There's 18 differences.
There's clearly going to be zero differences
between that species and itself.
All right, now let's answer their question.
Using the data in the table,
create a phylogenetic tree on the template provided
to reflect the evolutionary relationships
of the organisms.
Provide reasoning for the placement on the tree
of the species that is least related to the others.
So, looking at these differences,
it's reasonable to say, well, the things
that have the fewest differences in the sequence
of cytochrome c, well, those are probably
most closely related.
And they already gave us a tree here,
so whatever goes here and here
are probably pretty closely related.
They shouldn't have too many differences
in the sequence of cytochrome c.
And these two should be pretty similar.
Shouldn't have many differences.
While this one should have a good number of differences
from any of the other four.
So let's first look at which ones
have very little difference.
And I'm just scanning this chart here
and looking for small numbers.
So you see here, there's only one
amino acid difference, or one sequence.
Well, yeah, one amino acid difference
between cytochrome c in E. ferus and E. africanus.
So I would say that these are fairly closely related.
They probably share an ancestor not too far
in the distant past.
So let me write E. ferus and E. africanus.
So, I'll do it here.
E.
E. ferus.
And E. E. africanus.
I'd do that there.
Now where else do we see some low numbers.
Well, I see this three right over here
and so that's the number of sequence differences
or the amino acid differences
between G. gallus and A. forsteri.
Forsteri, however you pronounce that.
So I would say those are probably pretty closely related.
And so let me write this here.
G. gallus
and A. forsteri.
And who have we not dealt with yet.
Well, we haven't dealt with
D. polylepis yet.
We've dealt with the other four.
So I'll put that here.
D. polylepis.
And you can see when you compare D. polylepis
to any of the other ones,
you see a pretty big difference.
D. polylepis to E. ferus is a 21 difference.
18 difference with G. gallus.
17 difference with A. forsteri
and 20 amino acids are different
in the sequence for cytochrome c
between D. polylepis and E. africanus.
So this has the most differences.
And they say provide reasoning for the placement on the tree
of the species that is least related to the others.
So I'll provide the reasoning.
So, D. polylepis
is most,
is least related, I should say,
is least related
because it has
a large amino acid,
amino acid sequence
difference
from the other four.
From the other, other four.
Or you can say, has the largest.
Maybe I'll write that.
Has the largest amino acid sequence difference
from the other four.
Because even if you were to compare E. ferus to G. gallus,
E. ferus to G. gallus, you still don't get close to 20,
while D. polylepis is pretty close
to 20 difference with all of them.
And so that makes sense, that even these four
share a common ancestor, that you don't
have to go as far back in time
to get to the common ancestor
as you do to get to D.,
the common ancestor with D. polylepis.
All right, let's do part b now.
So that was part a.
Let me label that
That was part a.
Now part b.
Identify whether morphological data
or amino acid sequence data
are more likely to accurately represent
the true evolutionary relationships among the species
and provide reasoning for your answer.
So, morphological data, this is looking at
the morphology of the different species.
And you could say, like, what's the shape
of their backbone or their different bones,
or the shape of different parts of their body,
while amino acid sequence, you're looking at,
well, how are their proteins actually made up.
I, personally, would go with the amino acid data.
So, I, I believe.
I believe,
I believe amino acid
sequence data
are, data's plural, are more likely,
are more likely to accurately represent
the true evolutionary relationship,
are more acc, are more likely to represent
the true evolutionary relationship.
True evolutionary relationship.
And let me provide my reasoning.
You could have convergent morphology.
You can have
convergent morphology
and what that means is, for example,
you could look at a bat's wings and a bird's wings
and say, okay, look, they each have similar morphology,
but they aren't related just because
they both have wings.
Or you could look at a dolphin and a fish,
and you say, okay, they both have flippers.
Maybe they're more closely related,
if you just look at the body type.
But that's convergent.
They actually came from different ancestors,
but then their ancestors,
because they had similar environments,
had a convergent parts, I guess you could say.
Had convergent morphology.
You can have convergent morphology,
morphology,
while having very, while being far apart
on the evolutionary tree.
While being
far apart
on evolutionary,
on evolutionary tree.
Now there's arguments for morphology as well,
'cause you might be looking at.
You know, we're only looking at cytochrome c here.
That might be some type of an anomaly,
or maybe you have some convergence or divergence
for that particular protein that does not
actually gel with what's actually happened
in evolutionary history,
but in general if I can look at the molecular sequences.
If I can look at sequences of proteins,
if I could look at what's going on with the DNA,
I like looking at that,
because that doesn't, that allows you to not be tricked
by the convergent morphology or far apart things,
like bats and birds or dolphins and fish.