AS and A2 Biology

• 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.