Logical Reasoning

PT139 · S1 · Q15 To reduce the mosquito population

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To reduce the mosquito population in a resort area, hundreds of trees were planted that bear fruit attractive to birds.

Given that ...

Hundreds of fruiting trees were planted in the hopes that birds would be attracted to the area.

and that ...

As the trees matured, the summer bird population in the area greatly increased, and the birds ate many mosquitoes.

How can it be that ...

Since the trees were planted, the mosquito population has gotten bigger?

Evaluate

There might be something unrelated to the trees that has caused the mosquito population to grow over the same time period since the trees were planted.

For example, maybe the trees were planted 10 years ago, and during the last 10 years there have been more tropical storms than usual, and tropical storms leave lots of standing water where mosquitoes breed.

Maybe people who live in that area have started installing more bird baths in their yard, and the standing water of a bird bath help mosquitoes breed.

Or the uptick in mosquitoes could be related to the trees or the birds themselves (the two variables that have changed).

Goal

Look for an answer that helps us do any of these things: - these trees do something that boosts the mosquito population - this influx of birds does something that boosts the mosquito population - something that boosts the mosquito population changed, around the same time as when the fruit trees were planted

15.

Which one of the following, if true, most helps to explain the apparently paradoxical result?

  1. Most of the species of

    No Impact / Cheats Paradox

    At its best, this answer would explain why the mosquito population didn't decrease. But we need to explain why the mosquito population did increase. The fact that new birds aren't eating mosquitoes doesn't explain why there are more mosquitoes. That would just explain why there's the same number of mosquitoes as before. We also want to be careful about telling ourselves a causal story that would go against one of the background facts. If we read this and thought, "Oh, so the birds didn't do anything to limit mosquitoes!" we'd be cheating the stated fact that "as expected, the birds ate many mosquitoes". We need to be thinking, "Even though the birds did eat a bunch of mosquitoes, what is causing the mosquito population to enlarge so much that even with birds snacking on them there are still more mosquitoes than before?"

    6% picked this

  2. The species of birds that

    No Impact

    This has the same effect and same problems as (A). 1. It doesn't change the fact that some of the birds are eating many mosquitoes 2. it doesn't explain why the mosquito population would go up. It would only explain why the new birds have failed to decrease the mosquito population.

    11% picked this

  3. Correct

    The birds attracted to the

    Why this is right

    This does the 2nd of the three possible things we were looking for: - these trees do something that boosts the mosquito population - this influx of birds does something that boosts the mosquito population - something that boosts the mosquito population changed, around the same time as when the fruit trees were planted These birds eat the insects that prey on mosquitoes (way more than they eat mosquitoes). Throughout LSAT questions, if we're trying to explain why an animal population is increasing, we end up talking about one of these things: - fewer predators - less disease - more food - better habitat - easier to mate If the birds get rid of the mosquitoes' predators, then the mosquitoes will be able to grow in population (even if many of them get eaten by birds).

    Skill tested: Paradox · how this choice captures the argument's function is the move to repeat next time.

    79% picked this

  4. Since the trees were planted,

    Opposite

    This deepens the paradox. This is giving us the 3rd type of idea, but going the wrong way with it. - these trees do something that boosts the mosquito population - this influx of birds does something that boosts the mosquito population - something that boosts the mosquito population changed, around the same time as when the fruit trees were planted This answer is saying that around the same time as when the fruit trees were planted, something happened that lowers the mosquito population. The weather got drier and dry weather suppresses mosquito population. Had this answer said, "Since the trees were planted, the annual precipitation has been above average", it could have worked.

    2% picked this

  5. Increases and decreases in mosquito

    Unclear Impact

    It's possible that the increase in mosquitoes since the fruit trees were planted is unrelated to the fruit trees and is just the crest of a normal cyclical wave in mosquito population. But this answer isn't nudging us enough in that direction. For all we know, the increase in the mosquito population that's happened since these trees were planted occurred during the normal low point of the mosquito population cycle (which would be even more alarming). Since we don't know where we're at in the population cycle, we can't tell whether this answer is really giving us a way to explain the recent increase in mosquitoes.

    2% picked this

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