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- [Voiceover] All right, Part D.

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To investigate the claim
that exposure to light

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overrides the genetically-controlled
circadian rhythm,

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the researchers plan to
repeat the experiment

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with mutant mice lacking a gene

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that controls the circadian rhythm.

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Predict the observed activity pattern

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of the mutant mice
under L12:D12 conditions

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and under DD, continuous
darkness conditions,

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that would support the
claim that light overrides

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the genetically-controlled
circadian rhythm.

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

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So under some mutant mice,

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mutant mice,

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under, so let me make two columns,

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mutant mice under L12,

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L12:D12, and then

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under continuous, continuous
darkness, what would I expect?

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What would I expect?

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So they predict the
observed activity pattern.

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So the mutant mice, they don't have,

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they have some, they're lacking genes

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that control circadian
rhythm, but under L12:D12,

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they don't need the
genetic circadian patterns,

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the genetically-influenced
ones, because they get the ones

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from their environment,
the light and the darkness.

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

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that somehow makes them
not sensitive to light.

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So I would assume under the L12:D12,

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they would behave, they
would have activity pattern

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similar to non-mutant mice, activity

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same as non-mutant,

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as non-mutant,

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mutant mice,

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non, or inactivity, inactivity

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during L12,

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activity, activity

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during D12.

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That's what I would expect.

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They still could react to the light

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and the darkness the same way

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that a non-mutant mice would.

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Now, what about continuous darkness?

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The non-mutant mice, we said that they,

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they went off of a 24-hour cycle,

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but they still had a cycle
where they were inactive,

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

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for each cycle, but it was close to it.

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

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

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I would guess that a mutant mouse

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that has no, that doesn't have some

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of these genes for circadian rhythm,

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

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it's just gonna be random,

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it's just gonna be much more sporadic.

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So, much, much

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more sporadic,

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sporadic activity,

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activity, fewer,

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fewer continuous,

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continuous,

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or I would say, maybe,
less continuous periods,

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or shorter continuous periods,

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shorter continuous

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periods of activity

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and inactivity,

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activity slash

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inactivity.

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

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So that was my predictions
that I would see

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for mutant mice in either of these.

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So now let's go to Part E.

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In nature, mice are potential prey

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for some predatory birds
that hunt during the day.

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Describe two features of
a model that represents

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how the predator-prey relationship

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between the birds and the
mice may have resulted

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in the evolution

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of the observed activity pattern of mice.

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Well, if the birds hunt during the day,

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if birds hunt

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during day

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a mouse is more likely

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

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Mouse, then,

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then the mouse

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is more likely

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to be eaten,

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eaten if it is

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active during the day,

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if it is active

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during the day.

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And if it is, I guess you could say

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

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that you're just more likely to be eaten

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if you're active when
the birds are hunting.

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

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

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If, actually that should be capital I,

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if, if the mouse

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is more likely

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to be eaten

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by being

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active

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during the day,

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then it is less likely to reproduce,

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then it is less

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likely

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to reproduce.

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

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I would try to put as
much context as possible,

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because you're not exactly sure

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

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to grade this thing, so
you could give more context

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that therefore, the mice

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that are active during,

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therefore, therefore,

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mice that are

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active

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during night,

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they have to be active sometime,

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active during night and inactive

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during day

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will be selected for, will

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be selected for,

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less likely to be eaten, less likely

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to be hunted,

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

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more likely to reproduce,

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reproduce, and we are done.