Question

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 below 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 (^).
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.

Answer 1

The correct option is 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.

The greater expression of BMP4 in the seed feeding finches as an adaptive response to the the drought, resulted in finches with larger - deeper beaks, so that they can feed on larger seeds as the plants that produced smaller seeds perished during drought.

So, the correct answer is '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'