Hypotheses is best supported by the statements given?

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When a caterpillar emerges from the egg on a tree branch, it immediately climbs upward until it finds a leaf bud to eat. Biologists thought that this behavior displayed an innate tendency to move in the direction opposite to the pull of gravity. In a recent experiment, a strong light source was placed at the bottom of a tree, and caterpillars, after hatching, climbed downward.

Which of the following hypotheses is best supported by the statements given?

A. Caterpillars have an innate tendency to move in the direction of gravity.
B. Newly hatched caterpillars are unable to see in the dark.
C. Newly hatched caterpillars move towards the strongest light source in the environment.
D. Newly hatched caterpillars move toward the leaf bud nearest to them.
E. The eyes of newly hatched caterpillars become less sensitive to light over time.

I do see a post for this question but thought of highlighting my doubt in a new post.

The correct answer is C.

As per my understanding for these type of questions, correct answer can always be proven by referring to the facts stated in the stimulus.

I went for answer D, as it is stated in the stimulus that " When a caterpillar emerges from the egg on a tree branch, it immediately climbs upward until it finds a leaf bud
to eat"

I highlighted - "until it finds a leaf bud" which implies that - Newly hatched caterpillars move toward the leaf bud nearest to them - Something struck me while I m typing this question and my doubt :wink: - What if newly hatched caterpillar needs to go downwards to find the nearest leaf bud (which is not stated in the stimulus)

Doubt: Please explain how is C right? C is definitely right as we should not question the right answer in GMAT, but please help me understand, with all the details stated in stimulus, how should I think to arrive at the correct answer?

What if the experiment is conducted in night. Then the caterpillar should go down first if it is attracted to strongest source of light. Please Help...

Thanks

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by vk_vinayak » Sun Apr 29, 2012 9:24 pm
Let me take a shot.

P1: When caterpiller emerges from egg, it moves upward until if finds leaf buds to eat.
P2: Biologist thought it was due to tendency to move opposite to gravity
P3: When strong light is placed at the bottom of tree, caterpillar moved downwards.


A. Incorrect. - As per P1, caterpillar moves upward.

B. Incorrect - If it were unbale to see, and when no source of external light is placed, why did it always move upwards. Why not some time upwards, and sometime downwards ?

C. Correct - This can be inferred from the argument. Even the observation in P1 is seen at night, rememebr that moon is the source of light. And when external source of light is placed at the bottom of the tree, caterpillar moved downward. So, we can say that caterpillar reacts to light and move toward the light.

D. Incorrect - If caterpillars moved toward the nearest leaf bud, why did it always move upward when no strong source of light is placed? Even when the source of light is placed, why did it always move downward? Nearest leaf bud could be in any direction.

E. Incorrect - No mention of sensitivity in the stimulus.

Hope it helps.
- VK

I will (Learn. Recognize. Apply)

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by chris@magoosh » Mon Apr 30, 2012 2:38 pm
Scientists' original hypothesis was that caterpillars move away from gravity and therefore climb up. Notice the hypothesis is not that caterpillars climb upward to find a leaf. Indeed, the direction they climb is not based on whether a leaf is above them or not. See, the experiment had a light source placed at the base of the tree. Caterpillars moved towards the light source. Therefore, the theory is they moved towards the light source.

Such behavior is not inconsistent with the initial observation: caterpillars move upwards. Why? Well, light comes from the sky, so they were presumably moving upwards. Now I understand how it is confusing if the caterpillar hatched at night. Would it climb up or down? Well, even at night (remember the moon) there is more light above then below (without any artificial light). With the placement of the artificial light we would have to assume it is brighter than the sun. So that said, that is a slight gap in the question. However, (C) is still the strongest answer.

Hope that helps :).

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by suyashtcs » Mon Nov 09, 2015 8:29 pm
Why not option A is correct...? If caterpillar moves downward with light source...this shows the ability of caterpillar to move with the direction of gravity...Experts can u pls explain?

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by Jim@StratusPrep » Tue Nov 10, 2015 8:00 am
suyashtcs-

A is not correct because in the normal state, caterpillars crawl up, away from gravity.
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