#19 - A recent study examined the daytime and nighttime

[srr021]

Hello,
The explanation for B still doesn't make sense to me. If B were the case, it seems that it would be opposite case with regards to activity among the lemurs. It seems to me like it would make more sense for the lemurs in the deciduous areas to be more active during the day time so as to avoid the birds. The explanation provided for B seems to me that it assumes that still animals are less easily seen, so they fall victim to their predators less often. I didn't think this was an okay assumption to make.

[evelineliu]

Hi there,

This is a paradox question, so we need to look for the central mystery, then find an answer choice that provides a solution. The stimulus describes two sets of lemurs: (1) lives in rain forests with year-round foliage, and (2) lives in forests where leaves fall off the trees in winter. For some reason, the second group is much more active during the night than the first group. The only difference we know is that the second group lives where the leaves are gone in the winter, but the first group lives where the leaves are there year-round. There must be something about the foliage that makes the second group more active at night, so the correct answer will probably tie the increased nighttime activity to the missing leaves.

(B) solves the mystery. If both sets of lemurs have high-flying predators during the day, then the first group is a little safer during the winter because it is protected by the leaves. They would be able to get more done during the day and rest at night. The second group, however, is exposed with all the leaves gone, so they would probably be more likely to avoid going out during the day. They would instead wait until night to have increased activity.

The answer choices in resolving the paradox questions will introduce a new idea to solve that mystery. Even if you felt uncomfortable making the leap for (B), the other answer choices do not resolve the paradox.

• (A) would give both groups equal competition during the day, so that should result in about equal activity at night.

• (C) puts both groups at equal risk during the day, which would also suggest equal activity at night.

• (D) brings up a difference between the two groups, but no connection between size and nighttime activity.

• (E) does not help because giving the second group a more limited diet does not explain why they would be more active at night.

Best,
Eveline

[leejohnm123@gmail.com]

I found answer choice B to be inadequate mainly because it seemed to me that it would not explain why the lemurs in the rain-forest would increase their nocturnal activity in the winter at all given that canopy coverage is consistent all-year round. B doesn't specify that the birds are more active predators in the winter, so while it might explain the difference between lemur populations nocturnal activity, it seems to require an assumption about the birds activity in winter (or potentially some other assumption) in order to explain the rain-forest lemurs' change in activity in winter.

[Luke Haqq]

Hi leejohnm123!

You raise a good point that seems accurate. However, whether or not there is an additional assumption isn't necessary for arriving at the correct answer choice. You comment,

I found answer choice B to be inadequate mainly because it seemed to me that it would not explain why the lemurs in the rain-forest would increase their nocturnal activity in the winter at all given that canopy coverage is consistent all-year round.

It's possible that lemurs in general are more nocturnal in the winter. That could be an unstated assumption. But even assuming that's the case, we're still left with an unresolved paradox as to why one population's nocturnal activity "was significantly more pronounced" in the winter in comparison with the other population. Answer choice (B) resolves this paradox, by indicating that a reason for this comparatively greater activity can be explained by high-flying predatory birds. This explains why the nocturnal activity of the lemur population in the deciduous forest would be comparatively greater, for they lose canopy cover in the winter months. To resolve the paradox about that comparative difference, it's not essential to know why lemurs in general might be more nocturnal in the winter.

[BrickCityLad]

Hello - thank you for all your help here!

I picked (A) for the reason that if both populations are competing with other animals for food in the daylight, it would make sense that they become more nocturnal to find food when their primary competitors are not active (as mentioned in the answer choice). The degree change you mentioned above would be explained by the fact that in deciduous rainforests there is more daylight (and thus more of an "aid" to their competitors).

As I write this, I understand that the assumption that I'm making here is more daylight => more opportunity to forage for food competitors. In that case, why is it OK that we are assuming a degree change in nocturnal activity between the lemurs but not here? Only because it's mentioned in the stimulus?

And if that is part of the reason that (A) is wrong - why is it OK that in correct answer choice (B) we are OK to assume that a degree change contributes to the difference (i.e. more daylight in deciduous rainforests => more opportunities for predation => more nocturnal activity).

Hopefully these questions make sense. Thank you!

BrickCityLad

[Jeff Wren]

Hi BrickCityLad,

First, if you haven't already done so, I'd recommend reading the earlier explanations to this question.

The word "daylight" can refer either to "natural light from the sun" or to "the period during a day when there is light." In other words, "during daylight" would mean during daytime (i.e. from sunrise to sunset).

In Answer A, the phrase "during daylight" simply means during the daytime (as opposed to nighttime). The actual amount of daylight that one can see is irrelevant to it being daytime/daylight hours. For example, just because you may be standing in the shade of a tree does not mean it isn't during daylight.

For A, the fact that the competitors are active during daylight hours does not mean that the more daylight there is or the brighter/sunnier it is, the more active the competitors are.

As you stated, you are making an assumption that more daylight means more opportunity, which is not an assumption that you should make here.

The differences in the amount of nocturnal activity between the two groups of lemurs is stated as a fact in the stimulus. Our goal in Resolve the Paradox questions (like this one) is to find an answer that explains these facts, not to disprove them.

As for Answer B, the key difference is that the birds fly above the forest and rely on their eyesight to see the lemurs during the day. In the rain forests, where the trees do not lose their leaves, the trees provide cover for the lemurs even during the winter. (If you've ever flown over a dense forest and looked down, all you can see is the tops of the trees.) For the deciduous forests during the winter, the birds can probably see the lemurs much more clearly if the lemurs were out and actively moving around since there is very little cover provided by the trees.