lsat 2-4-7

7.     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

答案是d，不明白。。。

OLD: evolved as a protective camouflage

NEW: physiological stress associated with heat absorption

D:  light-shelled snails in a calm inlet with a dark, rocky bottom and many predators-->discredits the camouflage theory but is compatible with heat absorption theory.

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.

This is an inference type of question. There is no argument in the stimulus, but information. Since the question stem ask you to strengthen the new theory, you should only focus on the new theory. Do not let the old theory disturb you while you are trying to decide the right answer.

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

rocky bottom and many predators are information not related to the question.

This against the new theory, in calm inlet, there should be numerous
                 white shell, not dark shelled snails.

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

This against the new theory, in calm inlet, there should be numerous
                 white shell, not dark shelled snails.

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

This against the new theory, in an inlet with much wave action, there should be numerous dark shell, not white shelled snails.

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

This is the right answer, follow what new theory is about.

Light – shelled snail should be numerous in calm inlet.

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

Since new theory claims that shell color is related to physiological stress associated with heat absorption. The difference between Choice D and E is the sand color. We knew from physics that dark color absorb more heat from the sun. White sandy button absorb less heat than rocky dark button. So, this answer did not fit in with new theory.