PrepTest 141, Section 2, 22. Because the native salmon in Lake Clearwater…

How will the right answer fit in terms of support and conclusion?

Only the right answer will add support for the conclusion in the passage.

Highlight the main conclusion in the passage, if there is one:

each has adapted genetically to its distinct habitat.

[BACKGROUND]. [SUPPORT]. Since [SUPPORT], Some researchers hypothesize that [CONCLUSION].

So we have a clear cause-and-effect argument on our hands. It says the fish were “genetically uniform”, then they split into two different habitats, and now the two groups “differ genetically”. Just because it went down in that order doesn’t mean the “distinct habitat” caused the “adapted genetically” thing, but the right answer will convince us it did.

Map the wording of the answers to the wording of the passage:

(A) Neither of the two populations of sockeyes has interbred…

Beautiful! This answer is ruling out a possible alternative cause, which is the most common way the LSAT will strengthen cause-and-effect arguments. If it wasn’t interbreeding, it’s more likely that the habitats were the cause.

(B) When the native salmon in Lake Clearwater were numerous…

Stop. This answer takes place at a time before the argument even gets started. I would only read this all the way through if I didn’t already have a strong piece of support like we got in (A).

(C) …part of the time in shallow water and part in deeper water.

So what? This isn’t specific to the fish in the argument, and the passage doesn’t have anything about splitting time between habitats in it.

(D) One of the populations is virtually identical genetically…

Cool, so only one of the two groups has “adapted genetically”. But that doesn’t help us with whether the habitat is the cause or not.

(E) The total number…is not as large…

There is no comparison of population sizes in the passage, which only mentions numbers of fish in the opening background info. This info doesn’t map to the possible cause-and-effect between habitat and genetics.

(A) is the correct answer.

Common pattern/s in this question: Recognizing cause-and-effect really makes this one less difficult. For extra credit, you’ll know you have a winner when you’re looking for support for cause-and-effect and you see an answer that rules out another alternative.