How did the drought lead to an increase in beak size in the medium ground finch population? The Grants reasoned that prior to the drought, the finch population fed primarily on small seeds that they could open easily. Although larger, tougher seeds were available, they were not typically eaten, not even by finches with larger beaks. During the drought, only a limited number of small seeds were produced, leaving mostly larger, tougher seeds available for food. Finches that were unable to eat the larger seeds died of starvation.
Based on their observations and the data they collected, the Grants concluded that evolution by natural selection had occurred in the medium ground finch population. The increase in the average beak size of the offspring was a direct result of the change in the food supply during the drought.
In order to have reached this conclusion, the Grants must have either assumed or proven that several other facts about the finch population were true. Which statements represent information that must be true in order for the Grants conclusion to be correct?
Select the three statements that must be true.
a. An individual finch's beak size can change depending on the size of the seeds it eats.
b. Beak size varies among the birds in the finch population under study.
c. Birds that could eat larger, tougher seeds survived and reproduced during the drought.
d. Beak size is an inherited trait in the finch population under study.
e. The drought caused a mutation that led to larger beak sizes in the finch population.