PT15.S3.Q8 - Delta Green beetles sometimes remain...

cest_la_vie

I picked E because I thought it eliminated an alternative explanation by showing that the population drop was not because the beetles were eaten by their predator. I immediately crossed over A thinking it was totally out of scope. My thought process was: the stimulus talks about the number of beetles "spotted" in 1985 and 1989, so why would their camouflage matter anyway? Is E wrong because it can't explain the "difference" in the number of beetles in those two years? Can anyone explain how A connects to the stimulus?

maco4538

The author states that the beetles are motionless for hours at a time but are more active during wet years than dry years. They use this fact to justify the claim that even though more were spotted in 1985 than in 1989 that the population did not necessarily decline, since 1985 was a wet year and 1989 was a dry year. The assumption here is that the beetles were easier to spot in 1985 than in 1989 (because 1985 was a wet year and 1989 was a dry year.) The only stated difference between the beetle's behavior during wet and dry years is that they were more active in wet years. So, they were easier to spot because they were more active in 1985 than in 1989.

"A" says because of their camouflage that they were impossible to see unless they were moving. Since you could only spot them when they were moving, it make sense that they were spotted more often during years that they were more active than in years that they were less active.

"E" is wrong because it doesn't strengthen the core assumption: beetles were easier to spot in 1985 than in 1989.