Marine biologists have long thought

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsStrengthen

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Stimulus

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 more numerous in calmer waters where the snails will absorb more heat from the Sun’s rays.

What this question is testing

Strengthen

Your task

Find the choice that makes the argument's conclusion more likely to be true.

Common trap

Answers that are consistent with the argument but add no real support, or that strengthen a claim the argument doesn't make.

Winning move

Locate the gap between evidence and conclusion, then pick the choice that closes it.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question

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

Answer choices

Opposite4% picked this
Dark-shelled snails in a calm inlet with a dark, rocky bottom
The new theory predicts white shells at the bottom of calm waters.
4%
Opposite3% picked this
Dark-shelled snails in a calm inlet with a white,
The new theory predicts white shells at the bottom of calm waters.
3%
Opposite3% picked this
Light-shelled snails in an inlet with much wave action and a
The new theory predicts brown shells at the bottom of choppy waters (much wave action).
3%
Correct63% picked this
Light-shelled snails in a calm inlet with a dark, rocky bottom
Why this is right
The new theory predicts white shells at the bottom of calm waters, which is what this answer says. The old theory predicts brown shells when the bottom is dark, whereas this answer describes light shells where the bottom is dark. So this matches the prediction of the new theory and goes against the prediction of the old theory.
Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.
63%
Half Scope27% picked this
Light-shelled snails in a calm inlet with a white, sandy bottom
This supports both the New and the Traditional theory. The new theory predicts light shells under calm waters, which matches this answer. And the traditional theory predicts light shells where the bottom is light-colored, which also matches this answer. So this answer only does half of what the question stem asked us for: it supports the New Theory but it fails to undermine the Traditional Theory.
27%

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