A-Level Biology AQA Notes

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Genetic Diversity & Adaptation

Genetic diversity is the number of different alleles of genes in a population
Genetic diversity is a factor enabling natural selection to occur
Natural selection is a mechanism of evolution by which individuals better adapted to their environment tend to survive, reproduce successfully and pass on their alleles.
In the process of natural selection: 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. As a result, over many generations, the new allele increases in frequency in the population
Direction selection is a selective force that favours individuals with an extreme form of a trait and selects against phenotypes at the other extreme. E.g. antibiotic resistance. Powerful antibiotics apply a very strong selection force favouring individuals possessing resistance alleles
Stabilizing selection is a selective force that favours the phenotypes closest to the mean value of a trait. E.g. Human birth weight. Babies that tend to the extremes of birth weight have higher mortality rates.
Adaptations may be anatomical, physiological or behavioural.

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