African woman or group of women who was the ancestor of all modern humans outside of Africa. She are also our last common ancestor. Examples of a group that has exhibited the founder’s effect & another that has undergone a genetic bottleneck. (fouder the Amish, French-Canadians; Genetic bottleneck, cheetahs; California condors. ) Founder effect, one form of genetic drift, occurs when a small group( fewer than several hundred members) of a large population migrates to a new region and is reproductively isolated. The new region is either unoccupied or occupied by species with which the small group cannot breed.
Because the founding population is so small, there is a very good chance that its genetic compostion is not representative of the parent population’s. Thanks to the founder effect, as the founding population grows its genes pool diverges even further from the source. Population bottlenecks occur when a population’s size is reduced for at least one generation. Because genetic drift acts more quickly to reduce genetic variation in small populations, undergoing a bottleneck can reduce a population’s genetic variation by a lot, even if the bottleneck doesn’t last for very many generations.
This is illustrated by the bags of marbles shown below, where, in generation 2, an unusually small draw creates a XXXXX. An example of a bottleneck: 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. Their population has since rebounded to over 30,000—but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.
Founder effectsA founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have:reduced genetic variation from the original population. a non-random sample of the genes in the original population. For example, the Afrikaner population of Dutch settlers in South Africa is descended mainly from a few colonists. Today, the Afrikaner population has an unusually high frequency of the gene that causes Huntington’s disease, because those original Dutch colonists just happened to carry that gene with unusually high frequency.