Researcher: Over the course of three decades, we keptrecords of the average beak size of two populations of the same ...

Steven on April 24, 2018


Hi Can you please explain this question? Thanks

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Anita on April 24, 2018

Absolutely. This question depends on an understanding of evolutionary survival - that the least advantaged in a species may die off if they can't get food, are preyed on easily, etc. So the prompt tells us that in a study, the birds in a cage stayed the same, but the birds in the wild grew smaller beaks. In this one, it's often easier to guess what the answer would be - that there is something in nature that is causing birds with bigger beaks to die off, or allowing birds with smaller beaks to live longer/have more offspring/etc. That is, there is something favoring small-beaked birds.

Off to the answers.

A: If it were true that there were a difference in the difficulty of which birds to catch, that would have been the case at the beginning of the study, too, so this doesn't make sense. It also doesn't explain why the wild and captive versions are different, when the captive ones were caught from the wild.

B: Same problem, but even more confusing because that would mean we would see more big-beaked birds.

C: Bingo! This is what we were looking for. The food situation in the wild is favoring small-beaked birds, so they're winning the genetic lottery right now.

D: We're concerned about beak size, not body size.

E: That would be great - you always want to measure multiple times, but it doesn't explain the phenomenon.

Does this help?