The Theory of Natural Selection
Natural selection is a major microevolutionary process that results in the differential survival
and reproduction of individuals of a population that differ in one or more traits.
The main points of the theory are:
- All populations have the reproductive capacity to increase in size, thus threatening their own
survival, forcing a competition for limited resources.
- Individuals of a population share in the same gene pool, but differ in phenotypic details.
- Some alleles promote survival and reproduction and therefore increase in frequency over
generations resulting in individuals that differ in one or more heritable traits (evolution).
- There is a difference in the survival and reproductive success of different phenotypes.
- It acts directly on phenotypes and indirectly on genotypes
- Over time, the alleles that produce the most successful phenotypes will increase in the
population.
- Less successful alleles will become less common.
- Change leads to increased fitness and increased adaptation to environment.
Three possible outcomes for natural selection:
- A shift in the range of values for a given trait in some direction.
- Stabilization of an existing range of values.
- Disruption of an existing range of values.
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