The gene pools of small populations tend to be reduced compared to those of large populations due to several key factors:
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Genetic Drift: In small populations, random changes in allele frequencies can have a more significant impact. This phenomenon, known as genetic drift, can lead to the loss of genetic variation over generations as certain alleles may become fixed (permanent changes) or lost entirely by chance.
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Inbreeding: Small populations are more susceptible to inbreeding, where closely related individuals mate. Inbreeding increases the likelihood of homozygosity for deleterious alleles, which can manifest as reduced fitness and genetic disorders. This also reduces genetic diversity because fewer different alleles are available in the gene pool.
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Limited Gene Flow: Small populations may be geographically isolated or have limited opportunities for migration. This can restrict the introduction of new alleles from other populations, further reducing genetic diversity.
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Bottlenecks: Small populations can arise from "bottleneck" events—sharp reductions in population size due to environmental events, disasters, or other factors. These bottlenecks drastically reduce the number of breeding individuals and, consequently, the variety of alleles in the gene pool.
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Founder Effects: When a small group of individuals establishes a new population, this founding group may not represent the wider genetic diversity of the original population. The new population will have a limited gene pool as it is based on the alleles carried by these founding members.
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Environmental Factors: Small populations may be more vulnerable to environmental changes and pressures. If they cannot adapt quickly enough due to reduced genetic variation, they may face increased risk of extinction.
Overall, these factors contribute to a greater risk of reduced genetic diversity in small populations, making them more vulnerable to extinction and less adaptable to changing environments.
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