Natural selection

Definition

Natural selection is the process through which certain traits become more or less common in a population due to the survival and reproduction of individuals with those traits. It is a key mechanism of evolution, driving the adaptation of species to their environments over generations by favoring advantageous traits that enhance survival and reproductive success.

5 Must Know Facts For Your Next Test

1. Natural selection operates on existing variations within a population, meaning it cannot create new traits but can amplify or diminish them based on their impact on survival.
2. The concept of fitness in natural selection is not just about strength; it's about how well an organism's traits help it survive and reproduce in its specific environment.
3. Natural selection can lead to speciation, where populations evolve into distinct species when subjected to different environmental pressures over time.
4. Hardy-Weinberg equilibrium assumes no natural selection occurs; deviations from this equilibrium can indicate that natural selection is at work within a population.
5. Natural selection can be directional, stabilizing, or disruptive, reflecting how environmental pressures can favor specific traits under varying circumstances.

Review Questions

• How does natural selection contribute to the genetic diversity of a population?
  • Natural selection contributes to genetic diversity by favoring individuals with advantageous traits that enhance their survival and reproduction. This process leads to the prevalence of those beneficial alleles in future generations while less advantageous traits may diminish. As the environment changes, different traits may become favored, allowing for ongoing changes in the genetic makeup of the population.
• Compare and contrast natural selection with genetic drift and explain how both influence population genetics.
  • Natural selection is a non-random process where advantageous traits increase in frequency due to survival and reproduction benefits, while genetic drift is a random process that affects allele frequencies through chance events, especially in small populations. Both processes influence population genetics but do so in different ways: natural selection drives adaptation and can lead to significant evolutionary changes, whereas genetic drift can cause random fluctuations that may lead to the loss of genetic variation or fixation of alleles.
• Evaluate the implications of natural selection on Hardy-Weinberg equilibrium in a given population. How would deviations from this equilibrium affect evolutionary outcomes?
  • Natural selection directly challenges Hardy-Weinberg equilibrium, which assumes no evolutionary forces are acting on a population. If natural selection is at play, we would see shifts in allele frequencies as certain traits confer survival advantages, leading to deviations from the expected genotype proportions. These changes can result in significant evolutionary outcomes such as adaptation to environmental pressures, speciation, or even extinction if unfavorable traits become predominant under new conditions.

Related terms

Genetic Drift: A mechanism of evolution that refers to random changes in allele frequencies within a population, often having a more significant impact in smaller populations.

Mutation: A change in the DNA sequence of an organism that can lead to new traits, which may be subject to natural selection.

Fitness: The ability of an organism to survive and reproduce in its environment, often influenced by the traits it possesses.