Natural selection

Definition

Natural selection is the process by which organisms that are better adapted to their environment tend to survive and reproduce more than those that are less well adapted. This mechanism of evolution explains how species evolve over time, and it connects to various concepts including inherited traits, variation among individuals, and the competition for resources.

5 Must Know Facts For Your Next Test

1. Natural selection was a key concept introduced by Charles Darwin, emphasizing that advantageous traits become more common in successive generations.
2. The mechanism relies on variation within a population, which is often caused by mutations, genetic recombination, and environmental factors.
3. Natural selection can lead to speciation, where populations diverge enough that they become separate species over time.
4. It operates at the level of individuals, but its effects are seen at the population level, shaping the genetic makeup of species.
5. The theory of natural selection challenged existing beliefs about the fixed nature of species, influencing both scientific thought and societal views on evolution.

Review Questions

• How does natural selection contribute to the process of evolution?
  • Natural selection contributes to evolution by favoring individuals with traits that provide a survival or reproductive advantage in their specific environments. Over time, these advantageous traits become more common in the population, leading to changes in the species. This process explains how organisms adapt to their surroundings and can eventually result in the emergence of new species.
• Compare and contrast Lamarck's theory of evolution with Darwin's theory of natural selection.
  • Lamarck's theory suggested that organisms could pass on traits acquired during their lifetime to their offspring, leading to gradual changes in species. In contrast, Darwin's theory of natural selection emphasizes that genetic variations within a population are subject to environmental pressures. While Lamarck believed in the inheritance of acquired characteristics, Darwin proposed that only heritable traits that enhance survival and reproduction are passed on over generations.
• Evaluate the impact of molecular evidence on our understanding of natural selection and evolution.
  • Molecular evidence has significantly enhanced our understanding of natural selection by providing concrete data on genetic variations and evolutionary relationships between species. By analyzing DNA sequences and protein structures, scientists can trace how certain traits have evolved and identify common ancestors. This molecular perspective supports Darwin's theory by demonstrating that natural selection acts on heritable genetic variations, reinforcing the idea that evolution is a gradual process shaped by environmental pressures.

Related terms

Adaptation: A trait that enhances an organism's ability to survive and reproduce in a specific environment.

Fitness: The reproductive success of an organism in passing on its genes to the next generation compared to others in the population.

Descent with Modification: The principle that each generation is modified from its ancestors, contributing to the diversity of life through evolutionary changes.