PrepTest 103, Section 3, Question 14
A commercial insect trap consists of a small(79 more words not shown)
Which one of the following,(7 more words not shown)
- AIn households where(25 more words not shown)
- BEven when only(27 more words not shown)
- CAfter eating glucose(33 more words not shown)
- DAfter the manufacturer(29 more words not shown)
- EThe kind of(17 more words not shown)
Reading the argument
My first thought is that the earlier traps may already have killed many of the insects.
If there are fewer insects left to catch, later traps could kill fewer even without any new resistance to the poison. Think of a lake where earlier fishing removed much of the fish population. A smaller catch later wouldn't, by itself, show that the boats had become worse at catching fish. That's a possibility to check about how the decline is being measured, not proof that the researchers are wrong.
The researchers instead explain the decline by resistance developing over successive generations. That could explain it, but is it the only plausible account?
What we’re looking for
For the weakener, I'd look for another reason the traps are eliminating fewer pests. My initial guess concerns a smaller remaining population. The answer could supply a different explanation, so I won't insist that it use exactly the possibility I first imagined.
Working the answers
- ACorrect
The change concerns the bait, not resistance to the poison. Over successive generations, a larger share of the insects naturally avoids eating glucose. Those insects are less likely to eat the poisoned bait in the first place.
That explains why the traps could become less effective even if the pesticide would still kill insects that consumed it. It isn't my initial smaller-population guess, but it gives the same kind of challenge: another cause of the observed decline. We don't need to claim that the insects consciously learned a lesson; the answer describes an increasing proportion with a natural aversion.
- B
This makes pesticide resistance more plausible. Even a few survivors could have offspring resistant to the poison, so resistance could become important over generations. That supports the researchers' proposed process rather than undermining it.
- C
Here the insects actually eat the poisoned glucose, and those from households using the traps regularly die in smaller numbers. That comparison fits the idea that repeated use is associated with greater resistance. It doesn't prove the mechanism by itself, but it supplies no clear alternative explanation like A's avoidance of the bait.
- D
A higher dose failing to improve results doesn't rule out resistance. Resistant insects might survive both concentrations. This fact could also fit other explanations, but it doesn't identify one or show that the insects remain vulnerable to the pesticide. A more directly challenges the proposed mechanism by explaining how insects avoid consuming it.
- E
The existence of other kinds of glucose doesn't establish any change in the insects' response to this trap. We would need information about why the particular bait stopped attracting them or why some other relevant feature changed. Simply identifying other naturally occurring varieties supplies no such connection.
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