Question

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?
○ 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.

Explanation:

To determine how the population evolved, we use the definition of evolution: a change in allele frequencies in a population over time. The northern elephant seals had a bottleneck (population reduction) leading to reduced genetic variation (change in allele frequencies). Growth alone doesn't define evolution, and the first two options are wrong as evolution occurred due to allele frequency change. The fourth option matches the evolution definition.

Answer:

D. The population has evolved because there was a change in allele frequencies. (Note: Assuming the fourth option is labeled D; if the original options had labels like A - D with the fourth being this, else adjust the label as per original. Here, based on the options, the correct one is the last option stating evolution due to allele frequency change.)