Sexual selection

Definition

Sexual selection is a form of natural selection where individuals with certain inherited traits are more likely than others to obtain mates. This process can lead to the development of features that enhance an individual's attractiveness or competitive ability, influencing the genetic structure of populations over generations.

5 Must Know Facts For Your Next Test

1. Sexual selection can result in pronounced differences between males and females, known as sexual dimorphism, where males may develop extravagant traits to attract females.
2. The concept was first introduced by Charles Darwin in 'The Descent of Man,' explaining how certain traits evolve not for survival but to increase mating success.
3. Mate choice can lead to runaway selection, where a preference for certain traits becomes more exaggerated over generations, potentially leading to extreme physical characteristics.
4. Intrasexual competition often results in physical adaptations such as larger body size or weapons (like antlers) in males to compete for female attention.
5. Sexual selection can affect allele frequencies in populations, causing specific genes associated with attractive traits or competitive abilities to increase in frequency over time.

Review Questions

• How does sexual selection differ from natural selection, and what implications does this have for population genetics?
  • Sexual selection focuses specifically on traits that enhance reproductive success rather than overall survival. While natural selection might favor traits that help an organism survive in its environment, sexual selection emphasizes traits that improve an individual’s chances of attracting a mate. This distinction can lead to increased genetic variation within populations as certain traits are favored for mating even if they don't contribute to survival, impacting allele frequencies and the genetic makeup over generations.
• Discuss the role of mate choice in shaping sexual dimorphism within a species, providing examples.
  • Mate choice significantly influences sexual dimorphism as individuals select partners based on particular traits. For example, in peafowls, females often prefer males with larger and more colorful tail feathers. Over time, this preference leads to males evolving more extravagant features to attract mates. As a result, the physical differences between male and female peafowls become pronounced, showcasing how mate choice drives the evolution of distinct sexual characteristics within a species.
• Evaluate how intrasexual competition can impact genetic diversity within a population and its evolutionary trajectory.
  • Intrasexual competition influences genetic diversity by favoring certain traits that enhance competitive abilities among individuals of the same sex. For instance, if larger size is favored for males competing for mates, this could lead to a decrease in genetic diversity as only those with advantageous traits reproduce. Over time, this can shape the evolutionary trajectory of the population by favoring specific alleles associated with competitive success while potentially diminishing other genetic variations. As competition intensifies for mates, it can create selective pressures that impact the population's adaptability to environmental changes.

Related terms

mate choice: The process by which one sex selects a mate based on specific traits, often leading to the evolution of elaborate characteristics in the chosen sex.

intrasexual competition: A form of sexual selection where individuals compete with members of the same sex for access to mates, often resulting in the development of larger size or aggressive behaviors.

dimorphism: The difference in size, shape, or color between males and females of the same species, often resulting from sexual selection pressures.