Question

In 1977, before the drought on Daphne Major, the average beak depth in the finch population was 9.2 mm. Breeding parents that survived the drought had an average beak depth of 9.7 mm. The difference between these values represents:

a. Genetic variation
b. Genetic drift
c. Natural selection
d. Phenotypic plasticity

Answer 1

The difference in average beak depth before and after the drought on Daphne Major, from 9.2 mm to 9.7 mm, represents an example of natural selection.

Step-by-step explanation:

In 1977, a drought on the Galápagos island of Daphne Major caused a significant change in the food resources available to the finch population. The hard seeds that could only be cracked by finches with larger beaks became more common, while the smaller, softer seeds became rare. As a result of the drought, finches with larger beaks (9.7mm on average) survived and reproduced, while many of the finches with smaller beaks did not survive.

Natural selection occurs when environmental pressures, such as food availability, cause differential survival and reproduction within a population. In this case, finches with deeper beaks were more suited to the new environment because they could eat the larger seeds that were still available. Their survival and subsequent reproduction shifted the average beak depth in the finch population, exemplifying evolution in response to a changing environment.