Natural Selection

Natural selection is the process in which individuals better adapted to their environment are more likely to survive up to reproduction and therefore pass on their genes.


It ensures that traits that give an individual an advantage or increase their fitness, are more likely to be passed on to the next generation. This results in the advantageous trait becoming more prevalent or “dominant”. The trait will only remain dominant so long as the environmental conditions favour it. If the environmental conditions change and the trait becomes disadvantageous then it will become less prevalent due to those individuals being less likely to survive until they mate. It is through this process of natural selection that evolution occurs. Over time, the accumulation of many small changes can lead to populations no longer being able to produce fertile offspring with their neighbours. When this occurs a new species has been formed. This is known as speciation.


A famous example of natural selection are Darwin’s finches of the Galapagos Islands. Darwin discovered that the finches’ beaks varied from island to island. While the finches originated from the same species, each species’ beak had adapted differently on each island to better suit their food sources.

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Key Terms

Speciation – The formation of a new, distinct species due to genetic information not being able to transfer between groups of organisms.

Fitness – How good a trait is at leaving offspring to the next generation.

Population – A group of individuals of the same species living in the same area at the same time

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