Natural Selection

Definition

Natural selection is a process by which organisms better adapted to their environment tend to survive and produce more offspring. This mechanism drives evolution by favoring traits that enhance survival and reproduction, leading to gradual changes in species over time and explaining the diversity of life on Earth.

5 Must Know Facts For Your Next Test

1. Natural selection was first formulated by Charles Darwin in the 19th century, providing a scientific explanation for how species evolve over time.
2. It operates on existing genetic variations within a population, meaning that only those traits already present can be selected for or against.
3. Natural selection can lead to adaptations, which are traits that enhance an organism's fitness in a particular environment.
4. The concept also applies to human evolution, influencing traits like bipedalism and brain size as adaptive responses to changing environments.
5. Natural selection is one of several mechanisms of evolution, alongside mutation, gene flow, and genetic drift, contributing to the complexity of species' development.

Review Questions

• How does natural selection contribute to the theory of evolution, and what role does it play in shaping human characteristics?
  • Natural selection is a key mechanism behind the theory of evolution, as it explains how species adapt and change over time. It selects for traits that enhance survival and reproductive success in specific environments. In humans, natural selection has influenced traits such as bipedalism and larger brain size, as these adaptations provided advantages for survival in diverse habitats and social structures.
• Compare and contrast natural selection with genetic drift and discuss how each affects evolutionary processes differently.
  • Natural selection is a non-random process that favors beneficial traits based on environmental pressures, leading to adaptations that improve fitness. In contrast, genetic drift is a random process that causes fluctuations in allele frequencies due to chance events. While natural selection systematically shapes populations over generations by promoting advantageous traits, genetic drift can lead to loss of genetic variation and influence small populations disproportionately without regard for adaptive value.
• Evaluate the significance of natural selection in explaining the fossil record and its implications for understanding human evolution.
  • Natural selection provides a framework for interpreting patterns seen in the fossil record, demonstrating how certain traits emerged and became prevalent due to adaptive advantages. The fossil evidence shows a progression of species adapting to changing environments, shedding light on human evolution's path. Understanding this helps explain not only our physical attributes but also behavioral changes influenced by survival challenges faced by our ancestors.

Related terms

Survival of the Fittest: A phrase often associated with natural selection, describing the idea that individuals with advantageous traits are more likely to survive and reproduce than those without them.

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

Speciation:

The evolutionary process through which new biological species arise, often influenced by mechanisms like natural selection that create reproductive barriers.