PrepTest 107

Incorrect. This answer conflates the two viewpoints, bringing in what the opposing point said led to the small goat size with the Biologist's argument. Since the Biologist pivots from this view, we can rule this out.

Incorrect. The stimulus directly contradicts this answer, saying that reproductive success is the only thing that can influence a trait's frequency in the population.

Incorrect. The Biologist accepts that the small goat population is higher on islands, so that's not the part of the opposing point that she disagrees with.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Valid

Question Type:
Must Be True

Stimulus Summary:
A gene's/trait's frequency is influenced only by reproductive success

Answer Anticipation:
There's a lot of complicated and strong language in this stimulus, as well as an opposing point and a conclusion—features we don't normally see in Must Be True questions!

Here, the argument starts with an opposing point. Since the Biologist pivots away from it, we don't have to treat it as true. However, the Biologist does seem to accept that islands have a high frequency of small goats, so that's something we should treat as true.

After this, the Biologist gives us a generalization/principle—only reproductive success influences a gene's/trait's frequency in a population. That's very limiting—nothing else can serve as an influence, including the "evolutionary pressure to ensure a diverse gene pool," as the opposing point claims.

The conclusion more or less restates this generalization, applying it to the specific case of the small goats, so it doesn't really add much that would help us find a correct answer.

Since the generalization/principle is the key statement here that presents information the Biologist accepts as true and isn't repetitive, let's find an answer choice that lines up with it.

Answer Explanation:
The Biologist notes that "only" reproductive success influences a trait's frequency in the gene pool, so evolutionary pressure to ensure a diverse gene pool can't be such an influence. This answer is therefore correct.

Key Takeaway:
The more complicated the stimulus in a Must Be True question, the more important it is to identify key statements that will allow you to home in on concepts that should show up in the correct answers.

Incorrect. This answer conflates the two views and does so in a very strong manner ("cannot . . . unless"). The Biologist doesn't make any claims about what is or isn't necessary for a diverse gene pool to be achieved—she claims only that a push for a diverse gene pool can't influence a trait's frequency.