Darwin's Theory of Evolution by Natural Selection (Edexcel IGCSE Biology) : Revision Note
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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
Example 2: peppered moth colour
Examiner Tips and Tricks
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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