Natural selection

Definition

Natural selection is the process by which organisms that are better adapted to their environment tend to survive and reproduce more successfully than those that are less well adapted. This mechanism of evolution explains how species evolve over time, as advantageous traits become more common in successive generations. It emphasizes the role of environmental pressures in shaping the genetic makeup of populations.

5 Must Know Facts For Your Next Test

1. Natural selection was first formulated by Charles Darwin and Alfred Russel Wallace in the mid-19th century.
2. It operates on existing variations within a population, meaning that it does not create new traits but rather favors those that already exist.
3. The process involves four main components: variation, competition, survival, and reproduction.
4. Natural selection can lead to the development of complex traits and behaviors over long periods through gradual changes.
5. It is a key mechanism of evolution and is supported by evidence from various fields, including genetics, paleontology, and ecology.

Review Questions

• How does natural selection contribute to the process of evolution?
  • Natural selection contributes to evolution by favoring individuals with advantageous traits that increase their chances of survival and reproduction in a given environment. Over time, these traits become more prevalent in the population, leading to evolutionary changes. This process results in the adaptation of species to their surroundings and can eventually lead to speciation as populations diverge based on selective pressures.
• Evaluate the role of genetic variation in the effectiveness of natural selection.
  • Genetic variation is crucial for natural selection because it provides the raw material upon which selective pressures act. Without variation, there would be no differences among individuals for natural selection to favor. The greater the genetic diversity within a population, the more likely it is that some individuals will possess traits suited to changing environments, allowing for ongoing adaptation and resilience against environmental challenges.
• Synthesize how natural selection interacts with other evolutionary mechanisms like genetic drift and gene flow.
  • Natural selection interacts with genetic drift and gene flow to shape the evolutionary trajectory of populations. While natural selection consistently favors advantageous traits, genetic drift can cause random changes in allele frequencies due to chance events, particularly in small populations. Gene flow introduces new genetic material from other populations, which can alter the effectiveness of natural selection by providing additional variations for the environment to act upon. Together, these mechanisms create a dynamic interplay that drives evolutionary change.

Related terms

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

Genetic Variation: The diversity in gene frequencies among individuals within a population, which is essential for natural selection to occur.

Speciation: The evolutionary process by which new biological species arise, often as a result of natural selection acting on populations over time.