Question

Northern elephant seals have reduced genetic variation because hunting by humans reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000, but their genes still carry the marks of this near extinction: they have much less genetic variation than a population of southern elephant seals that was not hunted as intensely.

Which of the following best describes how the population has evolved?
The population has not evolved because there was no change in allele frequencies.
The population has not evolved because it has grown.
The population has evolved because it has grown.
The population has evolved because there was a change in allele frequencies.

Answer 1

The population has evolved because there was a change in allele frequencies.

Explanation: the severe bottleneck (down to ~20 individuals) caused genetic drift and loss of alleles, changing allele frequencies. Even though the census size later grew, the genetic makeup was altered—so evolution occurred. Growth alone does not equal evolution.