Logical Reasoning

PT15 · S3 · Q8 Delta green ground beetles sometimes

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Delta green ground beetles sometimes remain motionless for hours at a stretch, although they are more active in wet years than in dry years.

Conclusion (probably = opinion)

The lower number of beetles observed in 1989 than 1985 probably does not reflect a drop in the population of delta green ground beetles.

Evidence (because)

Delta green ground beetles sometimes remain motionless for hours but are more active in wet years than in dry years.

In 1989, an observer saw ten beetles in nine hours, while in 1985, the same observer at the same location counted 38 in about two hours.

1985 was a wet year and 1989 was relatively dry.

Evaluate

This seems to align with both Anti-Causal and Explain Curious Fact patterns, because there's a comparison in beetle counts between two different years that vary in wetness. The author is rejecting one causal explanation and proposing another.

Curious Fact: Why were there so many more beetles observed in 1985 compared to 1989?

Author's Explanation: It wasn’t due to a drop in population, but rather to the difference in activity levels caused by the wetness of the years.

To strengthen the author's conclusion that the difference in counts isn't due to population changes, we need to rule out the possibility that there was actually a population drop and support the idea that the difference in observed activity levels was due to wetness.

There seems to be an assumption that during the drier 1989, when the beetles would have been motionless for hours, we might have had the same number of beetles present but spotted way fewer.

Goal

Let's find an answer that supports the idea that differences in wetness between the years affect beetle activity and thus observation counts, rather than an actual population decline.

Which one of the following, if true, most strongly supports the conclusion drawn above?

Correct
Because of their excellent camouflage,
Why this is right
This supports the plausibility of the author's hypothesis because it suggests that the observed low number in 1989 is due to the beetles being less active and thus harder to spot when they remain motionless due to a dry year. We know in 1989 that more of them would have been motionless, and so this answer allows us to say that in 1989 more of them would have been almost impossible to see.
Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.
62% picked this
The only habitat of delta
Mixed Impact
This makes it sound like in the wetter years there was more habitat for the beetles. More habitat allows for higher population numbers. Less habitat during the dry years would allow for less population.. This answer strengthens insofar as it makes it sound like wet vs.dry could definitely have a causal influence on how many beetles we observe, but it weakens insofar it sounds like the wet vs. dry would actually lead to higher vs. lower population numbers..
18% picked this
Delta green ground beetles move
No Impact
Knowing that movement is related to reproductive behavior doesn't address why beetles were less observed in 1989. There's no common sense link that gets us from wet vs dry years to "more vs less reproductive behavior", so it's not clear how the wet/dry distinction would interact with this fact, if at all.
5% picked this
Delta green ground beetles are
No Impact
A historical fact about the rarity or discovery of the beetle doesn't help explain the observation discrepancy between wet and dry years discussed in the conclusion.
1% picked this
No predator relies on the
No Impact
The potential lack of predators depending on these beetles for food doesn’t provide information about population or observation discrepancies.
13% picked this

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