Darwin's Theory of Evolution by Natural Selection (Edexcel IGCSE Biology: Double Science)

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Darwin's Theory of Evolution by Natural Selection

  • Charles Darwin proposed the theory of evolution by natural selection
  • Darwin's theory states that evolutionary change has occurred, and that natural selection is the process that has driven this change
  • The process of natural selection is as follows:
    • Individuals in a species show variation that is caused by differences in genes
    • Individuals with characteristics that are advantageous in their environment have a higher chance of survival
      • This idea of natural selection became known as ‘survival of the fittest'
    • Surviving individuals are more likely to reproduce and so are more likely to pass on their advantageous alleles
    • Over many generations the advantageous characteristics become more common in the population

Examples of evolution by natural selection

Example 1: snail shell colour

Natural selection example 1, IGCSE & GCSE Biology revision notes

Example 2: peppered moth colour

Natural selection example 2, IGCSE & GCSE Biology revision notes

Examiner Tip

There are many examples of natural selection, and an exam question may present an unfamiliar one for you to explain; it is important to learn the basic stages so that you can apply them to any example provided

  • All populations contain genetic variation
  • Some genetic variants will result in characteristics that are advantageous and increase survival chances
  • Surviving individuals are more likely to reproduce and pass on their advantageous traits
  • Over many generations the advantageous traits become more common in the population

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Lára

Author: Lára

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.