2015 AP Biology free response 1 d e

- [Voiceover] All right, Part D.

To investigate the claim
that exposure to light

overrides the genetically-controlled
circadian rhythm,

the researchers plan to
repeat the experiment

with mutant mice lacking a gene

that controls the circadian rhythm.

Predict the observed activity pattern

of the mutant mice
under L12:D12 conditions

and under DD, continuous
darkness conditions,

that would support the
claim that light overrides

the genetically-controlled
circadian rhythm.

All right, so let me write
this down. So, Part D.

So under some mutant mice,

mutant mice,

under, so let me make two columns,

mutant mice under L12,

L12:D12, and then

under continuous, continuous
darkness, what would I expect?

What would I expect?

So they predict the
observed activity pattern.

So the mutant mice, they don't have,

they have some, they're lacking genes

that control circadian
rhythm, but under L12:D12,

they don't need the
genetic circadian patterns,

the genetically-influenced
ones, because they get the ones

from their environment,
the light and the darkness.

They didn't get, this isn't a gene

that somehow makes them
not sensitive to light.

So I would assume under the L12:D12,

they would behave, they
would have activity pattern

similar to non-mutant mice, activity

same as non-mutant,

as non-mutant,

mutant mice,

non, or inactivity, inactivity

during L12,

activity, activity

during D12.

That's what I would expect.

They still could react to the light

and the darkness the same way

that a non-mutant mice would.

Now, what about continuous darkness?

The non-mutant mice, we said that they,

they went off of a 24-hour cycle,

but they still had a cycle
where they were inactive,

active, inactive, active,
and it was less than 12 hours

for each cycle, but it was close to it.

It was maybe 9, 10, or
11 hours of activity,

followed by 9, 10, or
11 hours of inactivity.

I would guess that a mutant mouse

that has no, that doesn't have some

of these genes for circadian rhythm,

well, for them, it's just gonna be,

it's just gonna be random,

it's just gonna be much more sporadic.

So, much, much

more sporadic,

sporadic activity,

activity, fewer,

fewer continuous,

continuous,

or I would say, maybe,
less continuous periods,

or shorter continuous periods,

shorter continuous

periods of activity

and inactivity,

activity slash

inactivity.

All right, now let's look at Part E now.

So that was my predictions
that I would see

for mutant mice in either of these.

So now let's go to Part E.

In nature, mice are potential prey

for some predatory birds
that hunt during the day.

Describe two features of
a model that represents

how the predator-prey relationship

between the birds and the
mice may have resulted

in the evolution

of the observed activity pattern of mice.

Well, if the birds hunt during the day,

if birds hunt

during day

a mouse is more likely

to be eaten by a bird if
it's active during the day.

Mouse, then,

then the mouse

is more likely

to be eaten,

eaten if it is

active during the day,

if it is active

during the day.

And if it is, I guess you could say

that's one, that's one
feature of our model,

that you're just more likely to be eaten

if you're active when
the birds are hunting.

And then the second one
is, if you're more likely

to be eaten, then you're
less likely to reproduce.

If, actually that should be capital I,

if, if the mouse

is more likely

to be eaten

by being

active

during the day,

then it is less likely to reproduce,

then it is less

likely

to reproduce.

And if I were, if I were
taking the AP test here,

I would try to put as
much context as possible,

because you're not exactly sure

how they're, they're
going to mark this thing,

to grade this thing, so
you could give more context

that therefore, the mice

that are active during,

therefore, therefore,

mice that are

active

during night,

they have to be active sometime,

active during night and inactive

during day

will be selected for, will

be selected for,

less likely to be eaten, less likely

to be hunted,

I guess you could say, and
more likely to reproduce,

more likely to reproduce,

reproduce, and we are done.