The diversity of life on Earth is because of the following reasons: 
- Natural selection acted on phenotype that were the result of new mutation in a population. 
- Natural selection acted on isolated populations separately, allowing for those populations to diverge over time allowing for speciation. 
Natural selection
- Natural selection can be defined as the differential survival and reproduction of those organisms that have beneficial traits over others. 
- Those organisms have beneficial phenotype suitable for the environment survive in the adverse environmental conditions.
- The beneficial traits pass on from parents to offspring this leads to the speciation. 
Learn more about natural selection: 
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