Read the following passage from the biology department at university of california, berkeley.

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?
a. the population has not evolved because there was no change in allele frequencies.
b. the population has not evolved because it has grown.
c. the population has evolved because it has grown.
d. the population has evolved because there was a change in allele frequencies.
mark this and return

Answer : Option D) The population has evolved because there was a change in allele frequencies.

Explanation : In the given case study, the population has observed to be evolved through genetic drift. The initial allele frequency was changed in these seals because a of lost genetic variation. As the population seemed to increase there was very less genetic variation seen, as only initial population with its alleles has been able to survive.

The correct answer would be D.The population has evolved because there was a change in allele frequencies.

The original population has evolved as the allele frequency has changed a lot.

The population has evolved as a result of genetic drift particularly a bottleneck effect.

In this effect, the population size reduces drastically due to which the genetic variation of a population reduces a lot. For example, the population size of elephant seal reduced to as few as 20 individuals. Thus, the genetic variation is only contributed by 20 individuals.

So, when this population increases in size, the genetic variation cannot increase much as compared to the population which has evolved from a larger population say of 10,000 individuals.

the answer is a or when it says crossing over