Logical reasoning PrepTest 136 · Section 2 · Question 11

Incorrect. The argument sticks to talking about the number of species, not the populations of each species. This answer would be correct in an argument that shifted between saying that the number of species is declining and the population numbers of each species are declining.

Incorrect. There's no conditional language in the stimulus, so this illegal reversal answer is incorrect.

Incorrect. While the argument does mention a causal relationship (pollution causing extinctions), it doesn't bring up a reversal of that (which wouldn't make much sense—extinctions causing pollution).

Incorrect. The argument doesn't even believe there is a correlation between pollution and species extinction, instead believing the total number of amphibian species is increasing. So this correlation/causation flaw answer is incorrect.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Biologists have discovered many more amphibian species, so environmentalists are wrong in saying that pollution is decreasing the number of species.

Answer Anticipation:
The argument kicks off by talking about what biologists "have learned," which is a subjective note. They learned that there are "many more" amphibians than previously believed.

From this, the argument states that environmentalists who claim that pollution is causing amphibian extinctions are wrong. In other words, since scientists now know of more amphibian species, the environmentalists' claim that there are fewer species every year due to global warming is wrong.

But that's a bad comparison! The environmentalists are talking about how many species are actually in existence, but the argument rebuts it using the subjective knowledge of species. The total number of amphibian species is a fact that exists outside of the number known to science, so using an increase in the latter to show an increase in the former is flawed.

Answer Explanation:
The premise used by the author of the argument is that the total number of known species increased—a premise about our knowledge of those "objects." The conclusion is that someone claiming the total number of those "objects" has decreased—the amphibian species—is wrong. In other words, there are actually more amphibian species. This answer highlights the jump between the subjective knowledge and objective fact made by the stimulus, so it's the correct answer.

Key Takeaway:
Whenever an argument on the LSAT talks about subjective beliefs or knowledge, see if it uses that to make a determination about reality. Those beliefs don't determine what's real, so they can't be used to form the basis for an argument about objective fact.