Natural selection

Definition

Natural selection is the process through which certain traits become more or less common in a population due to the differential survival and reproduction of individuals with those traits. This mechanism leads to evolution, as advantageous traits are passed down to future generations, shaping the behavior and characteristics of species over time.

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 rather favors those that are already present.
2. The concept was independently formulated by Charles Darwin and Alfred Russel Wallace in the 19th century, fundamentally changing our understanding of evolution.
3. Natural selection can lead to speciation, where populations diverge into separate species due to different selective pressures in their environments.
4. Environmental changes can alter the selective pressures on a population, leading to shifts in traits that are favored over time.
5. Natural selection is not a linear process; it can be influenced by various factors such as mutation rates, genetic drift, and ecological interactions.

Review Questions

• How does natural selection contribute to the development of adaptations in organisms?
  • Natural selection drives the development of adaptations by favoring individuals with traits that enhance their survival and reproductive success in a given environment. Over time, these advantageous traits become more common in the population, leading to changes in behavior, morphology, or physiology that better suit the organisms to their surroundings. This process illustrates how specific environmental pressures shape the characteristics of species through successive generations.
• Compare and contrast proximate and ultimate causation in relation to natural selection.
  • Proximate causation refers to the immediate mechanisms that trigger behaviors or traits, such as hormonal changes or neural processes. In contrast, ultimate causation focuses on the evolutionary reasons behind these traits, explaining how they have been shaped by natural selection over time. Understanding both levels of causation provides a comprehensive view of how behaviors evolve; proximate factors may influence immediate responses, while ultimate factors elucidate their adaptive significance in survival and reproduction.
• Evaluate the implications of sexual dimorphism as a result of natural selection in various species.
  • Sexual dimorphism arises from natural selection when males and females develop distinct physical traits or behaviors based on differing reproductive strategies. For instance, males may evolve larger sizes or elaborate features to attract mates, while females might develop traits that enhance their ability to rear offspring. This divergence reflects how natural selection operates differently on each sex due to their roles in reproduction, influencing everything from mating systems to social structures within species. Analyzing sexual dimorphism provides insights into evolutionary pressures and adaptive strategies shaped by competition and mate choice.

Related terms

Adaptation: A trait that enhances an organism's ability to survive and reproduce in its environment, often resulting from natural selection.

Fitness:

The measure of an organism's ability to survive and reproduce, relative to other individuals in the population.

Gene flow: The transfer of genetic material between populations, which can introduce new genetic variations and influence the process of natural selection.