In 1986, a nuclear power accident in Chernobyl, USSR (now Ukraine), led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since. Based on your understanding of evolutionary mechanisms, which of the following most likely occurred in the rodent populations following the accident?
a. Mutation caused genetic drift and decreased fitness.
b. Mutation caused the fixation of new alleles.
c. Mutations caused major changes in rodent physiology over time.
d. Mutation led to increased genetic variation.
Answer: D