Science Assessment

The ground finch is a species of bird. Seeds are the finches’ main source of food. Finches with small beaks can eat only small seeds, but finches with large beaks can eat both small and large seeds. Beak size is inherited.

In 1976 scientists collected data on the size of the beaks of a population of finches that hatched that year. The graph below shows the beak size (in millimeters) of the 1976 sample.

Left: An individual female ground finch. Middle: A drawing showing the part of the finches’ beaks that the scientists were measuring. Right: Graph showing beak size (in millimeters) of ground finches hatched in 1976. 

In 1977, during a long period without rain many plants that produced small seeds died.

To learn how this influenced the next generation of finches; scientists returned in 1978 and measured the beak size of finches that hatched that year. The graph below shows the beak size (in millimeters) of the 1978 sample.

Graph showing beak size (in millimeters) of ground finches that hatched in 1978. 

Do you think the process of natural selection caused the changes in the finch populations between 1976 and 1978?

Write your answer in the form of an argument. Your argument should include: A claim that answers the question, evidence in the form of specific scientific data that supports your claim, and reasoning that uses appropriate scientific principles and justifies why the data counts as evidence for your claim.