QUESTION TEXT: To reduce the mosquito population in a …
QUESTION TYPE: Paradox
PARADOX: We planted trees to attract birds. The birds eat mosquitos, but there are more mosquitos than ever.
ANALYSIS: Mosquito population depends on many factors. It’s the number of births minus the number of deaths. You have to look at all the causes of birth rate and death rate.
So yes, birds kill some mosquitos. But maybe the birds and fruit also attracted animals that mosquitos
feed on.
The right answer says that the birds eat the mosquitos’ predators, reducing the mosquitos’ death rate.
Several of the wrong answers mentioned that not all the birds eat mosquitos. This doesn’t matter, because some birds eat mosquitos. That would normally reduce population, not increase it.
___________
- It doesn’t matter if most birds don’t eat mosquitos. Some of the birds do eat mosquitos. We would expect that to reduce the population, not increase it.
- This is practically the same as A. It doesn’t matter if all the birds eat mosquitos, as long as some of them did. We would expect the birds to decrease the population of mosquitos as long as some birds ate mosquitos. Instead the mosquito population increased.
- CORRECT. If this is true, then mosquitos got lucky. The birds ate their predators. So while a few mosquitos die from birds, many more survive due to lack of predators.
- This makes things even weirder. We would expect the dry weather to kill mosquitos. Instead, there are more mosquitos.
- This is just a useless fact. We don’t know what part of the cycle we’re in. If we are in an increasing part of the cycle, this could explain things. If we are in a decreasing part, this makes things more confusing.
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Polly Berman says
Hi I just wanted to clarify something.
So let’s say 100 birds were attracted between species A and B. If 90 of the birds were A and 10 were B, but 90 of the birds did not eat mosquitos and 10 did, we would still have SOME decrease in mosquitos right? which would not increase the amount of mosquitos.
I just wanted to make sure I’m understanding why B is incorrect, since I kind of got lucky in guessing between B and C.
Thanks!!
FounderGraeme Blake says
We can’t be certain. As the argument points out, the birds ate mosquito predators, so the mosquito population actually increased. But, if you frame this as “there would be some mosquitos eaten, right?” then yes, some mosquitos would be eaten.
The argument actually addresses this: “As expected, the birds ate many mosquitos”. So B isn’t adding anything to what the argument already said.
Note: This is an old comment but I wanted to clarify the point.