Natural selection

Definition

Natural selection is a biological process where organisms better adapted to their environment tend to survive and produce more offspring. This mechanism drives evolution by favoring traits that enhance survival and reproductive success, leading to gradual changes in population characteristics over generations. It plays a crucial role in shaping genetic variation within populations, as certain traits become more common while others diminish.

5 Must Know Facts For Your Next Test

1. Natural selection operates on existing genetic variation within a population, meaning that it cannot create new traits but can only amplify or diminish them based on environmental pressures.
2. The 'survival of the fittest' phrase often misinterpreted; it actually refers to reproductive success rather than just physical strength or fitness.
3. Natural selection can lead to speciation, where populations diverge enough over time that they become distinct species due to adaptive differences.
4. Selective pressures can include environmental factors such as climate, food availability, predators, and diseases, influencing which traits are favorable.
5. Over time, natural selection can contribute to the development of complex traits and behaviors in organisms as they adapt to their specific environments.

Review Questions

• How does natural selection influence genetic variation within a population?
  • Natural selection influences genetic variation by favoring certain traits that enhance an organism's survival and reproductive success. As individuals with advantageous traits are more likely to survive and reproduce, these traits become more common in the population over generations. This process shapes the overall genetic makeup of the population, leading to a higher frequency of beneficial alleles while reducing those that are less favorable.
• Discuss the role of environmental factors in determining which traits are favored by natural selection.
  • Environmental factors play a critical role in shaping which traits are favored by natural selection. Conditions such as availability of resources, climate, presence of predators, and disease can create selective pressures that impact survival rates. For instance, a drought may favor plants with deeper roots that can access water, while a change in predator populations might select for faster prey. Over time, these selective pressures influence the evolutionary path of populations.
• Evaluate how natural selection and genetic drift work together to shape the evolution of a population.
  • Natural selection and genetic drift both contribute to the evolution of a population but operate through different mechanisms. Natural selection systematically favors beneficial traits based on environmental pressures, leading to adaptive changes. In contrast, genetic drift introduces random fluctuations in allele frequencies due to chance events, particularly in small populations. The interplay between these two processes can result in unique evolutionary outcomes; for example, while natural selection may promote certain traits for survival, genetic drift might cause unrelated alleles to become fixed or lost purely by chance, complicating the overall picture of a population's evolution.

Related terms

Mutation: A change in the DNA sequence of an organism, which can introduce new genetic variation into a population.

Adaptation: The process by which a species becomes better suited to its environment through natural selection, leading to enhanced survival and reproduction.

Genetic Drift:

A mechanism of evolution that involves random changes in allele frequencies within a population, which can impact genetic variation independently of natural selection.