Disruptive selection

Definition

Disruptive selection is a type of natural selection that favors extreme phenotypes over intermediate ones, leading to increased variation within a population. This process can result in a split in the population, potentially leading to speciation as individuals with extreme traits have a better chance of survival and reproduction in heterogeneous environments. Disruptive selection highlights the importance of environmental factors in shaping genetic diversity and adaptation.

5 Must Know Facts For Your Next Test

1. Disruptive selection often occurs in environments where resources are limited and competition is high, encouraging specialization of extreme traits.
2. An example of disruptive selection can be seen in African seedcracker birds, where individuals with either very large or very small beaks are favored, while those with intermediate-sized beaks struggle to feed effectively.
3. This form of selection can lead to increased genetic diversity as it promotes the survival of individuals with traits that are advantageous in specific environmental niches.
4. Disruptive selection can sometimes initiate the process of speciation, where different subpopulations adapt to varied environments and eventually become reproductively isolated.
5. It contrasts with stabilizing selection, which favors intermediate phenotypes and reduces variation, while directional selection favors one extreme phenotype.

Review Questions

• How does disruptive selection impact genetic variation within a population?
  • Disruptive selection increases genetic variation by favoring individuals with extreme phenotypes, rather than those with average traits. This process encourages a wider range of characteristics within the population, allowing for greater adaptability to changing environments. By promoting survival among those with specialized traits, disruptive selection plays a crucial role in shaping the overall genetic makeup of the population.
• Discuss the ecological factors that may lead to disruptive selection in a population.
  • Ecological factors such as resource availability, habitat complexity, and competition can lead to disruptive selection by creating environments where extreme traits provide a survival advantage. For instance, if food sources vary widely in size or type, individuals with specialized adaptations may thrive while those with intermediate traits may struggle. Such conditions encourage divergence within the population as different individuals exploit distinct niches, ultimately leading to increased variability and potential speciation.
• Evaluate the potential long-term evolutionary consequences of disruptive selection on a species.
  • In the long term, disruptive selection can significantly impact the evolutionary trajectory of a species by fostering diversity and adaptability. As certain traits become more favorable, populations may diverge into subpopulations with specialized adaptations, which can eventually lead to speciation. This phenomenon highlights the dynamic relationship between organisms and their environments and underscores the importance of genetic variability for survival in changing ecological landscapes. Thus, disruptive selection not only enhances immediate survival prospects but also sets the stage for future evolutionary developments.

Related terms

Natural Selection: The process through which certain traits become more or less common in a population based on their impact on survival and reproduction.

Phenotype: The observable characteristics or traits of an organism, which result from the interaction of its genotype with the environment.

Speciation: The evolutionary process by which populations evolve to become distinct species, often as a result of genetic divergence and reproductive isolation.