Logical ReasoningDifficulty: Easy

PT143 S4 Q1 Explanation

Among Trinidadian guppies

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

TopicsMost Supported

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Stimulus

Among Trinidadians guppies, males with large spots are more attractive to females than are males with small spots, who consequently are presented with less frequent mating opportunities. Yet guppies with small spots are more likely to avoid detection by predators, only guppies with small spots live to maturity.

What this question is testing

Most Supported

Argument

Here's the situation. Big spots are great for guppy mating — they attract females. But in waters full of predators, big spots get the male killed before he can mate. The small-spotted guppies survive and pass on their genes; the big-spotted ones get eaten.

Anticipate

So big spots help procreation in some environments (safe ones) but actually hurt it in others (dangerous ones). The same trait works for or against the same goal depending on context.

Think of being tall in a crowd. Helps you see over people, but bad if there's a low ceiling. Same trait, different effect by environment.

Goal

An answer that captures this idea: a trait that aids procreation in one environment can undermine it in another.

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

The question
1.

The situation described above most closely conforms to which one of the

Answer choices

  1. Unsupported2% picked this

    A trait that helps attract mates is sometimes more dangerous to one sex

    This says traits attractive to mates are sometimes more dangerous to one sex than another. The stimulus only describes male guppies' large spots — it doesn't compare risk to males vs. females. The stimulus doesn't support a generalization about sex-differential danger.

  2. Unsupported0% picked this

    Those organisms that are most attractive to the opposite sex have the greatest

    The stimulus doesn't establish that the most attractive organisms have the greatest number of offspring. It only says they have more frequent mating opportunities — and even that is reversed in predator-heavy waters where the attractive males die young.

  3. Unsupported2% picked this

    Those organisms that survive the longest have the greatest number

    The stimulus says small-spotted guppies survive in dangerous waters, but it doesn't say survival correlates with greatest offspring count. Many factors affect offspring numbers; the stimulus only addresses survival.

  4. Unsupported1% picked this

    Whether a trait is harmful to the organisms of a species can depend on which

    The stimulus only describes male guppies. It doesn't establish that traits are dangerous depending on which sex has them. It doesn't address what happens when females have spots, or any cross-sex comparison.

  5. Correct95% picked this

    A trait that is helpful to procreation can also hinder it

    Why this is right

    This is supported. Large spots help guppy procreation by attracting mates — but in predator-heavy environments, they hinder procreation by getting the male eaten before he can reproduce. So the very trait that helps procreation in some environments hinders it in others. The stimulus directly supports this generalization.

    Skill tested: Most Supported · how this choice captures the argument's function is the move to repeat next time.

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