A pond has several varieties of a species of frog that all eat the
same kind of bug. Most of the frogs are fast-growing varieties that need to eat more bugs each day than the slow-growing variety. A drought drastically reduces the number of bugs, and the population of the fast-growing frogs declines drastically while the population of slow-growing frogs declines only slightly. Most of the frogs in the pond are now the slow-growing variety. This is an example of which of the following?
A) evolution
B) mutations
C) acquired characteristics
D) natural selection
E) artificial selection