The Theory of Natural Selection

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.

• 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.