Q3 - Biologist: DNA analysis shows that Acacia heterophylla

[Laura Damone]

Question Type:
Strengthen

Stimulus Breakdown:
Conclusion: Seabirds probably caused the dispersal of the A. koa seeds.

Evidence: The seeds traveled from Hawaii to Reunion Island. They don’t germinate after being soaked in seawater. The trees grow in the mountains, not by the shore.

Intermediate Conclusion: The seeds probably didn't float from Hawaii to Reunion.

Answer Anticipation:
This argument supports one cause (birds) by ruling out an alternative cause (floating between islands). To streghthen the argument, we might rule out another alternative cause, or provide information that supports the bird hypothesis.

Correct answer:
B

Answer choice analysis:
(A) This supports the floating hypothesis, but we need to support the bird hypothesis.

(B) This supports the bird hypothesis by showing that there are birds that might go up to the Hawaiian mountains, eat some seeds, then fly over to Reunion and deposit them. Winner winner!

(C) So what? We're worried about how A. koa got from Hawaii to Reunion, not how it ended up in Hawaii in the first place.

(D) More support for the floating hypothesis. Eliminate!

(E) This doesn't strengthen the argument because it doesn't increase the likelihood that birds were loading up on seeds in Hawaii and depositing them on Reunion. That said, it doesn't weaken the argument either. So what if many seabirds don't frequent the land? As long as some go between the two islands in question, the bird hypothesis isn't impacted.

Takeaway/Pattern:
If you're tasked with strengthening an argument that supports its conclusion by ruling out an alternative, make sure you know which option your correct answer needs to support. Chances are high that some wrong answers will support the alternative.

#officialexplanation

[HughM388]

I understand what (B) is apparently saying, but it could just as easily be interpreted to mean that there happen to be species of birds common to both Réunion Island and Hawaii. That hardly suggests they fly between the two islands. Those particular species-in-common could, in fact, be flightless. Penguins are seabirds, too. It's quite plausible that a species of flightless or relatively flightless mountain-climbing bird is native to various Pacific islands.

Having seen the development of LSAT questions over the course of seventy tests, from the very beginning to this one, I have discerned an unfortunate decline in the quality of editing and copy-editing.