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Evolution: Natural Selection Finch Beaks

APBIO-K0OYTW

The medium ground finch is a species of bird endemic to the Galapagos Islands that eats by cracking seeds open with their beaks to obtain the food inside. Finch beak size (depth) is controlled by the BMP4 gene, which produces a growth factor known as bone morphogenic protein. In 1977, the Galapagos Islands experienced an intense drought, which severely reduced the population of small seeds and the plants that produced them.

Figure 1 illustrates the changes in the distributions of finch beak depths (size) before and after the drought of 1977. The mean depth is indicated above the caret symbol (^). Rosemary B. Grant and Peter R. Grant. What Darwin's Finches Can Teach Us about the Evolutionary Origin and Regulation of Biodiversity. BioScience. 2003. 53: 965-975. Created for Albert.io. Copyright 2016. All rights reserved.

Which of the following statements BEST explains the trend in finch beak size during 1976 - 1978?

A

Finches with larger beaks must have a higher degree of expression of the BMP4 gene and are better adapted to cracking larger seeds and producing more surviving offspring.

B

Finches with larger beaks are the result of a mutation that prevents expression of the BMP4 gene and are better adapted to cracking larger seeds and producing more surviving offspring

C

Finches that have a higher degree of expression of the BMP4 gene have smaller beaks that are better adapted to cracking small seeds, producing a larger proportion of offspring with smaller beaks.

D

Higher expression of the BMP4 gene leads to better scavenging behaviors, which allows finches to locate seeds more easily, and produce more surviving offspring.