Population size, technically the effective population size, is related to the strength of drift and the likelihood of inbreeding in the population. Small populations tend to lose genetic diversity more quickly than large populations due to stochastic sampling error (i.e., genetic drift). This is because some versions of a gene can be lost due to random chance, and this is more likely to occur when populations are small. Additionally, smaller population size means that individuals are more likely to breed with close relatives. In closed populations, individuals will be more closely related to each other compared to individuals in the previous generation. For example, in a hypothetical population consisting of only four individuals, if two pairs each produced two offspring (meaning that four new individuals are present in the next generation), the offspring must either mate with a sibling, a parent, or an individual from the other pair. Assuming they choose the non-sibling/non-parent option, all of the offspring in the third generation must mate with individuals that have the same grandparents or choose to forgo reproduction. Although this example is extreme due to the very small hypothetical population, the same patterns and forces are present in larger – albeit still small – populations. Show Although the mechanism of the loss of genetic diversity due to inbreeding and drift is different, the effects on populations are the same. Both inbreeding and drift reduce genetic diversity, which has been associated with an increased risk of population extinction, reduced population growth rate, reduced potential for response to environmental change, and decreased disease resistance, which impacts the ability of released individuals to survive and reproduce in the wild. When genetic drift occurs in a small population?Typically, genetic drift occurs in small populations, where infrequently-occurring alleles face a greater chance of being lost. Once it begins, genetic drift will continue until the involved allele is either lost by a population or is the only allele present at a particular gene locus within a population.
What are the types of genetic drifts?There are two main types of genetic drift: population bottlenecks and the founder effect.
What results when a small group of individuals establishes a new population far from existing populations?In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall Wright.
What are the two effects that can cause genetic drift in a small population?The founder effect and the bottleneck effect are cases in which a small population is formed from a larger population. These “sampled” populations often do not represent the genetic diversity of the original population, and their small size means they may experience strong drift for generations.
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