Genetic diversity is the number of different alleles of genes in a population.
Genetic diversity enables natural selection to occur.
The principles of natural selection in the evolution of populations.
Random mutation can result in new alleles of a gene.
Many mutations are harmful but, in certain environments, the new allele of a gene might benefit its possessor, leading to increased reproductive success.
The advantageous allele is inherited by members of the next generation.
Over many generations, the new allele increases in frequency in the population.
Directional selection, exemplified by antibiotic resistance in bacteria, and stabilising selection, exemplified by human birth weights.
Natural selection results in species that are better adapted to their environment.
These adaptations may be anatomical, physiological or behavioural.
