key term - Genetic bottleneck

Definition

A genetic bottleneck is an event in which a significant percentage of a population is suddenly reduced, leading to a loss of genetic diversity. This phenomenon can occur due to various factors such as natural disasters, habitat loss, or drastic environmental changes, and it results in a smaller gene pool that can affect the evolutionary trajectory of the surviving population. In the context of anatomically modern humans, genetic bottlenecks are crucial for understanding how early human populations adapted and evolved, particularly during periods of climatic change and migration.

5 Must Know Facts For Your Next Test

1. Genetic bottlenecks can result from sudden events such as volcanic eruptions or pandemics that drastically reduce population size.
2. An example of a genetic bottleneck is observed in the northern elephant seal, which was hunted nearly to extinction and now has low genetic diversity due to its small founding population.
3. In humans, genetic bottlenecks may have occurred during periods of migration out of Africa, impacting the genetic structure of populations that settled in different parts of the world.
4. The loss of genetic diversity due to a bottleneck can make populations more susceptible to diseases and reduce their ability to adapt to environmental changes.
5. Studying ancient DNA can provide insights into historical genetic bottlenecks and help trace the lineage and adaptation processes of anatomically modern humans.

Review Questions

• How does a genetic bottleneck affect the genetic diversity of a population?
  • A genetic bottleneck significantly reduces the size of a population, which leads to a loss of alleles and genetic variation. This decreased diversity can limit the ability of the population to adapt to environmental changes or survive diseases, as there are fewer genetic traits available for natural selection to act upon. Consequently, the surviving population may exhibit inbreeding and increased vulnerability over generations.
• What are some historical examples of genetic bottlenecks in human populations, and what were their consequences?
  • One historical example is the migration of early humans out of Africa, where small groups faced environmental challenges that could have led to genetic bottlenecks. Another example is the impact of the Black Death in Europe, which decimated populations and resulted in reduced genetic diversity among survivors. These events had long-lasting consequences on the genetic makeup and health of subsequent generations.
• Evaluate the role of genetic bottlenecks in shaping human evolution and adaptability through history.
  • Genetic bottlenecks have played a crucial role in human evolution by influencing the gene pool available for adaptation. During periods of significant environmental change or migration, those populations that survived often had limited genetic variation, which could lead to both challenges and opportunities for evolution. While some groups may have become more vulnerable due to reduced diversity, others might have developed unique adaptations that allowed them to thrive in new environments, ultimately shaping the course of human history.

Related terms

founder effect: A reduction in genetic diversity that occurs when a small group of individuals becomes isolated from a larger population and forms a new population.

genetic drift: The random fluctuations in allele frequencies in a population due to chance events, often having a more significant effect in smaller populations.

population genetics:

The study of genetic variation within populations and the mechanisms that drive changes in allele frequencies over time.