key term - Disruptive selection

Definition

Disruptive selection is an evolutionary process where extreme traits are favored over intermediate traits, leading to increased diversity within a population. This type of selection can result in the emergence of two or more distinct phenotypes, which may enhance the population's adaptability to varying environments. Disruptive selection often occurs in heterogeneous environments where individuals with extreme traits have a survival advantage over those with average traits.

5 Must Know Facts For Your Next Test

1. Disruptive selection can lead to speciation, where populations diverge into two or more distinct species due to differing selective pressures.
2. This type of selection is commonly observed in environments that present diverse challenges, such as varying food sources or habitat types.
3. Disruptive selection contrasts with stabilizing selection, which favors intermediate traits and reduces variability within a population.
4. Examples of disruptive selection include certain species of African seedcracker finches, where individuals with either very large or very small beaks are more successful at feeding on different seed types.
5. The presence of disruptive selection may indicate that a population is undergoing adaptive evolution as it responds to changes in environmental conditions.

Review Questions

• How does disruptive selection contribute to the diversity of traits within a population?
  • Disruptive selection promotes diversity by favoring extreme phenotypes over intermediate ones, allowing those with distinct traits to thrive in varying environmental conditions. As a result, this can lead to increased variability within the population, as individuals adapt differently to their surroundings. Over time, this process can enhance the chances for speciation as populations diverge based on their adaptations.
• Compare and contrast disruptive selection with stabilizing and directional selection in terms of their impact on population genetics.
  • Disruptive selection differs from stabilizing and directional selection primarily in its effects on trait distribution within a population. While stabilizing selection favors intermediate traits and reduces variability, and directional selection pushes the population towards one extreme trait, disruptive selection encourages the existence of two or more distinct phenotypes. This results in a bimodal distribution of traits rather than a unidirectional trend or clustering around an average.
• Evaluate how disruptive selection could lead to adaptive radiation in a given environment.
  • Disruptive selection can trigger adaptive radiation by creating conditions where extreme phenotypes become advantageous in different niches. As individuals with these extreme traits survive and reproduce more effectively, they can exploit various resources within their environment. This diversification not only enhances the survival of those individuals but also increases the overall biodiversity as new forms emerge, adapting to specific ecological roles or challenges present in their habitats.

Related terms

natural selection:

A process in which individuals with favorable traits are more likely to survive and reproduce, leading to changes in the characteristics of a population over generations.

phenotype:

The observable characteristics or traits of an organism, resulting from the interaction of its genotype with the environment.

adaptive radiation:

The rapid diversification of a species into a variety of forms that adapt to different environments, often following the availability of new resources or habitats.