The bottleneck effect is used to describe an event where a population decreases. One example involves the northern elephant seal. They have a reduced genetic variation due to a population bottleneck humans inflicted on them in the 1890s. Hunting 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 they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted. Which phrase best explains this change in gene frequency?
Responses
A gene flowgene flow
B speciationspeciation
C genetic driftgenetic drift
D natural selection
C genetic drift
The phrase that best explains the change in gene frequency in this scenario is C) genetic drift.
Genetic drift refers to the random fluctuations in gene frequencies that occur in small populations. In the case of the northern elephant seals, their population size was dramatically reduced to as few as 20 individuals due to hunting, leading to a severe bottleneck effect. When a population goes through a bottleneck event, the genetic variation within the population also decreases because only a small subset of the original genetic diversity is represented in the surviving individuals.
As a result of this population bottleneck, the surviving northern elephant seals had limited genetic variation. Over time, as the population has rebounded and grown to over 30,000 individuals, the limited genetic variation that was present at the bottleneck is still reflected in the current population. This means that the gene frequencies in the population have changed, with certain genes becoming more or less common due to random chance rather than selective pressures. This phenomenon is known as genetic drift.