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