- [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,
reproduce, and we are done.