Genetic drift

Definition

Genetic drift is the change in the frequency of alleles (gene variants) in a population due to random sampling of organisms. This process can lead to significant changes in the genetic makeup of small populations over time and can contribute to the evolution of species, highlighting how chance events can impact genetic diversity and population dynamics.

5 Must Know Facts For Your Next Test

1. Genetic drift is more pronounced in small populations, where random events can have a larger impact on allele frequencies than in larger populations.
2. This mechanism of evolution can lead to the fixation or loss of alleles, potentially reducing genetic diversity and increasing the risk of extinction for small populations.
3. Genetic drift can interact with other evolutionary processes, such as natural selection, but it operates independently of an organism's fitness.
4. While genetic drift is random, its effects can result in significant evolutionary changes over time, contributing to speciation.
5. Some conservation strategies aim to minimize the effects of genetic drift by promoting gene flow between populations to maintain genetic diversity.

Review Questions

• How does genetic drift differ from natural selection in terms of its impact on population genetics?
  • Genetic drift differs from natural selection primarily in that it is a random process, whereas natural selection is based on differential survival and reproduction due to advantageous traits. In genetic drift, allele frequencies change due to chance events, particularly in small populations. This randomness can lead to the fixation or loss of alleles irrespective of their effects on fitness, while natural selection consistently favors alleles that enhance survival and reproductive success.
• What are the consequences of genetic drift on small populations, particularly regarding their long-term survival and adaptation?
  • The consequences of genetic drift on small populations include a significant reduction in genetic diversity as certain alleles may become fixed or lost purely by chance. This loss of variation can hinder the population's ability to adapt to environmental changes, increasing the risk of extinction. Small populations that experience genetic drift may also face inbreeding depression, where mating among closely related individuals further reduces fitness and adaptability.
• Evaluate the role of genetic drift in speciation and how it may influence the evolutionary trajectories of isolated populations.
  • Genetic drift plays a crucial role in speciation by fostering divergence between isolated populations. As populations become separated, genetic drift can cause them to accumulate different allele frequencies over generations. This divergence may lead to reproductive isolation if the changes are significant enough, ultimately resulting in the emergence of new species. Additionally, interactions between genetic drift and environmental factors can further shape the evolutionary paths these isolated groups take, impacting biodiversity as a whole.

Related terms

founder effect: The founder effect occurs when a small group of individuals establishes a new population, leading to a reduced genetic diversity compared to the original population.

bottleneck effect: The bottleneck effect happens when a population's size is significantly reduced for at least one generation, resulting in a loss of genetic variation and changes in allele frequencies.

natural selection: Natural selection is the process through which certain traits become more or less common in a population based on their advantages or disadvantages for survival and reproduction.