GCSE Biology (AQA)

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Evolution by Natural Selection

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Inheritance, Variation and Evolution Variation and Evolution

Evolution by Natural Selection

3:38 Variation and Evolution
Spec 4.6.2.2
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  • Evolution refers to changes in populations over time.
  • The most commonly accepted theory of evolution is by natural selection, proposed by Charles Darwin.
  • Natural selection explains how evolution occurs through changes in inherited characteristics of a population.
  • Inherited characteristics are traits passed down through genes to offspring.
  • Evolution by natural selection involves steps starting with a mutation, which is a random change in DNA.
  • Mutations lead to variations within a species, though many mutations have little or no effect.
  • Organisms with beneficial traits survive and reproduce more, passing these traits to the next generation.
  • This process is often described as the survival of the fittest, where "fittest" refers to being best suited to the environment.
  • An example of natural selection is the leg length of nous lizards, where lizards with longer legs can escape predators more effectively and are more likely to survive and reproduce.
  • Over time, evolution can lead to the formation of new species as small changes accumulate.
  • According to the theory, all species have evolved from simple life forms that first developed more than 3 billion years ago.
  • Genetic comparisons across organisms show that all life is linked back to a single common ancestor.
  • Life forms have evolved from single-celled organisms to complex multicellular organisms.

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