You are studying the regrowth of a clear-cut forest. During your first expedition you observe a beetle species in which 50 percent of the population has a brown exterior coloration and 50 percent has a green exterior coloration. Five years later you return to the same spot to study the beetles. However, you now observe that 75 percent of the beetles have a brown exterior. This is an example of
a. microevolution.
b. macroevolution.
c. species diversity.
d. genotypes.