Describe the bottleneck effect.

Describe the bottleneck effect.

• A. It occurs when a population rapidly increases in size.
• B. It describes the introduction of new alleles into a population by migration.
• C. It is the accumulation of mutations in a small population over time.
• D. Gene frequency changes due to re-establishment of a population following a catastrophic loss of most of the population. Founders of the next gene pool are the survivors.

Answer: (D)

The bottleneck effect is a form of genetic drift that happens when a population undergoes a drastic reduction in size. Because only a small group of individuals survives, the new population is founded by these survivors and inherits only a subset of the original genetic variation. This can cause allele frequencies to shift randomly, sometimes reducing overall genetic diversity and altering trait frequencies in the long run. The described scenario captures this: after a catastrophic loss, the next generation is established by the surviving individuals, so the gene pool is determined by those founders. That sampling of the original variation leads to changes in allele frequencies that are not due to natural selection. The other ideas don’t fit as the bottleneck: rapid population growth is the opposite of a bottleneck; migration introduces new alleles into a population (gene flow); and while mutations can accumulate in a small population, the bottleneck centers on the drastic loss of individuals and the resulting sampling effect on allele frequencies rather than mutation accumulation.

The bottleneck effect is a form of genetic drift that happens when a population undergoes a drastic reduction in size. Because only a small group of individuals survives, the new population is founded by these survivors and inherits only a subset of the original genetic variation. This can cause allele frequencies to shift randomly, sometimes reducing overall genetic diversity and altering trait frequencies in the long run.

The described scenario captures this: after a catastrophic loss, the next generation is established by the surviving individuals, so the gene pool is determined by those founders. That sampling of the original variation leads to changes in allele frequencies that are not due to natural selection.

The other ideas don’t fit as the bottleneck: rapid population growth is the opposite of a bottleneck; migration introduces new alleles into a population (gene flow); and while mutations can accumulate in a small population, the bottleneck centers on the drastic loss of individuals and the resulting sampling effect on allele frequencies rather than mutation accumulation.