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Question 3 • CMS 2026-2027 Biology CREDIT RECOVERY

Which of the statements best describes the response of finches to drought on the Galapagos Islands?

Answer

During drought, finches struggled to open harder seeds. All the scraping and pecking wore down their beaks, resulting in a reduced average beak depth.

During drought, only finches with larger-than-average beaks were able to crack the hard seeds that were available. These finches survived while smaller-beaked finches died, resulting in an increased average beak depth in the population.

During drought, finches with smaller beaks (and smaller bodies) had an advantage. With reduced food supplies, larger finches (with larger beaks) were more likely to starve. The result was a decrease in average beak depth.

During drought, individual finches saw that large, hard seeds were the only available food. To crack these harder seeds, individual finches grew their beaks larger, resulting in an increased average beak depth.

Explanation

During droughts, soft seeds became scarce and harder seeds were more available. Finches with deeper, larger beaks were better able to crack those seeds, so they were more likely to survive and reproduce. Over generations, this natural selection increased the population’s average beak depth; individual birds did not grow larger beaks just because they needed them.

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