AP BIOLOGY

Detailed explanation-1: -Northern elephant seals have reduced genetic variation probably because of 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.

Detailed explanation-2: -A bottleneck in population size of a species is often correlated with a sharp reduction in genetic variation. The northern elephant seal (Mirounga angustirostris) has undergone at least one extreme bottleneck, having rebounded from 20-100 individuals a century ago to over 175, 000 individuals today.

Detailed explanation-3: -The drought lake is the best example of the Bottleneck effect because the event was random and the survivors lived due to random chance. A small number of the fish reestablished their population in the lake, their genetic diversity was also reduced.

Detailed explanation-4: -A genetic bottleneck occurs when a population is greatly reduced in size, limiting the genetic diversity of the species. Scientists believe cheetahs (Acinonyx jubatus) have already survived at least two genetic bottleneck events.

Detailed explanation-5: -Bottlenecks cause alleles at low frequency (< 0.1) to become less abundant than alleles in one or more intermediate allele frequency class (e.g., 0.1-0.2). This distortion is transient and likely to be detectable for only a few dozen generations.