Marine biologists have long thought that variation in the shell color

Question

Marine biologists have long thought that variation in the shell color of aquatic snails evolved as a protective camouflage against birds and other predators. Brown shells seem to be more frequent when the underlying seafloor is dark-colored and white shells more frequent when the underlying seafloor is light-colored. A new theory has been advanced, however, that claims that shell color is related to physiological stress associated with heat absorption. According to this theory, brown shells will be more prevalent in areas where the wave action of the sea is great and thus heat absorption from the Sun is minimized, whereas white shells will be more numerous in calmer waters where the snails will absorb more heat from the Sun’s rays.

Evidence that would strongly favor the new theory over the traditional theory would be the discovery of a large majority of

(A) dark-shelled snails in a calm inlet with a dark, rocky bottom and many predators

(B) dark-shelled snails in a calm inlet with a white, sandy bottom

(C) light-shelled snails in an inlet with much wave action and a dark, rocky bottom

(D) light-shelled snails in a calm inlet with a dark, rocky bottom and many predators

(E) light-shelled snails in a calm inlet with a white, sandy bottom and many predators

Bunuel · Accepted Answer

OFFICIAL EXPLANATION

This is essentially a suppressed premise question; we are asked to supply a premise (evidence) that would favor the new theory over the traditional theory. The old theory predicts that if there are predators in an area then the shells should have the same color as the seafloor. The new theory, based on heat absorption, predicts that 1) brown shells will be more prevalent in rough waters, and 2) white shells will be more numerous in calm waters. Now we work through the answer-choices, looking for one that contradicts our summary of the old theory and supports our summary of the new theory.

Choice (A) has predators, a dark seafloor, and, as the old theory predicts, dark-shelled snails. It thus supports the old theory. Additionally, it has dark shells in calm waters which contradicts the new theory. Eliminate (A).

Next, choice (B) contradicts 2) of the new theory. Eliminate (B).

Next, choice (C) contradicts 1) of the new theory. Eliminate (C).

Next, choice (D) satisfies 2) of the new theory—light-shelled snails in calm waters. It also directly contradicts the old theory, which predicts that with many predators and a dark bottom the shells should be dark. So the answer is probably (D), but it’s prudent to check the last choice since we are looking for the best answer.

Choice (E) satisfies 2) of the new theory, but it also satisfies the old theory, which predicts that with many predators and a light bottom the shells should be light. Eliminate (E).

The answer is (D).

Skywalker18 · Answer

Marine biologists have long thought that variation in the shell color of aquatic snails evolved as a protective camouflage against birds and other predators. Brown shells seem to be more frequent when the underlying seafloor is dark-colored and white shells more frequent when the underlying seafloor is light-colored. A new theory has been advanced, however, that claims that shell color is related to physiological stress associated with heat absorption. According to this theory, brown shells will be more prevalent in areas where the wave action of the sea is great and thus heat absorption from the Sun is minimized, whereas white shells will be more numerous in calmer waters where the snails will absorb more heat from the Sun’s rays.

Evidence that would strongly favor the new theory over the traditional theory would be the discovery of a large majority of 
Type- strengthen
Pre-thinking- 1. dark-colored shells on a light-colored seafloor with great wave action 
2. light-colored shells on a dark seafloor with less wave action

(A) dark-shelled snails in a calm inlet with a dark, rocky bottom and many predators- incorrect, strengthens the old theory(camouflage)

(B) dark-shelled snails in a calm inlet with a white, sandy bottom- incorrect, weakens the new theory since we have dark-shelled snails in a calm waters

(C) light-shelled snails in an inlet with much wave action and a dark, rocky bottom- incorrect, weakens the new theory since we have light-shelled snails in water with much wave action

(D) light-shelled snails in a calm inlet with a dark, rocky bottom and many predators- Correct

(E) light-shelled snails in a calm inlet with a white, sandy bottom and many predators- incorrect, strengthens the old theory(camouflage)

Answer D

Marine biologists have long thought that variation in the shell color

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Marine biologists have long thought that variation in the shell color

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