Disruptive selection

Definition

Disruptive selection is a type of natural selection that favors individuals at both extremes of a phenotypic range while acting against the average individuals. This process can lead to increased variation in a population and is a key mechanism in the formation of new species, particularly in sympatric speciation, where populations are in the same geographic area but diverge due to differing ecological niches or resource utilization.

5 Must Know Facts For Your Next Test

1. Disruptive selection can lead to the emergence of two or more distinct phenotypes within a population, increasing diversity.
2. It often occurs in environments with varying conditions that favor different traits, such as different food sources or habitats.
3. In the context of sympatric speciation, disruptive selection can create reproductive barriers as populations adapt to specific niches.
4. Examples of disruptive selection can be seen in certain species of birds where individuals with either very large or very small beaks are favored for different types of food sources.
5. This form of selection is less common than stabilizing or directional selection but plays a crucial role in evolutionary processes.

Review Questions

• How does disruptive selection contribute to increased variation within a population?
  • Disruptive selection contributes to increased variation within a population by favoring individuals at both extremes of a phenotypic trait while selecting against the average. This leads to a wider range of traits in the population, which can enhance adaptability to diverse environments. Over time, as extremes become more prevalent, this can further split the population into two distinct groups, each adapted to different niches.
• Discuss how disruptive selection can influence the process of sympatric speciation.
  • Disruptive selection influences sympatric speciation by promoting reproductive isolation among individuals that adapt to different ecological niches within the same geographic area. As individuals diverge based on their adaptations—such as feeding preferences or habitat use—gene flow between groups may decrease. This reduction in gene flow can lead to the emergence of distinct species, as the populations become more specialized and less likely to interbreed.
• Evaluate the role of disruptive selection in evolutionary theory and its implications for biodiversity.
  • Disruptive selection plays a significant role in evolutionary theory by illustrating how natural selection can drive the divergence of traits within populations. Its implications for biodiversity are profound; by creating distinct phenotypes, it increases the likelihood of speciation events. This mechanism helps explain patterns of biodiversity observed in various ecosystems, as different species evolve to exploit varied resources and niches, thus enhancing the overall complexity and resilience of biological communities.

Related terms

Natural selection: A process where organisms better adapted to their environment tend to survive and produce more offspring.

Phenotype: The observable physical or biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.

Speciation: The evolutionary process by which populations evolve to become distinct species, often influenced by factors such as isolation and selection pressures.