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

Spec point — 4.38 · explain Darwin’s theory of evolution by natural selection

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

Example 2: peppered moth colour

Exam Hint 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, **which may be caused by mutations
• 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 alleles to their offspring
• Over many generations the advantageous alleles become more common in the population