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Natural Selection

Human Biology (Year 12) - Evolutionary Mechanisms

Ben Whitten

Natural Selection

The process of natural selection illustrated in an easy to view format.

What is natural selection?

Natural selection is the mechanism that was proposed by Charles Darwin and Alfred Wallace, which can still be utilised in explaining many features which have been observed in living things found in the world today. You may have heard the phrase "survival of the fittest", which applies to the principle of natural selection!

Favourable traits are inherited and become more common in subsequent generations, altering allele frequencies in the gene pool of a population. Depending on the environmental conditions for an organism, their phenotype may confer an advantage or disadvantage, relative to the other individuals of the population. An inherited trait that allows an individual to better survive and reproduce is called adaptation.

What is the process of natural selection?
  1. Variation: The individuals of a population have different characteristics due to sexual reproduction, independent assortment and random segregation, and mutations (chromosomal/point mutations). 

  2. Overproduction: The population produces more individuals than can survive to maturity, creating competition in the population. 

  3. Selection: Individuals in the population are exposed to a new selection pressure, which selects for some individuals over others to survive for longer and reproduces. 

  4. Adaptation: The individuals who survive and reproduce have more common traits in the population/gene pool, with the advantageous allele accumulating over generations.

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