Natural and artificial selection — common mistakes

For Paper 4, always be precise with your terminology. When discussing natural selection, ensure you mention 'selection pressure', 'differential survival and reproduction', and 'change in allele frequency'. For artificial selection, highlight 'human intervention', 'desired traits', and the crucial consequence of 'reduced genetic diversity' and its implications (e.g., inbreeding depression, susceptibility to disease).

The primary distinction lies in the selective agent. In natural selection, the environment acts as the selective agent, favouring individuals best adapted for survival and reproduction. In artificial selection, humans are the selective agent, choosing individuals with desired traits to breed. Both are covered in our free revision course and practice past papers.

Artificial selection significantly reduces genetic diversity. By repeatedly selecting for specific desired traits, many other alleles that are not chosen (or are linked to undesirable traits) are lost from the gene pool. This makes the population less adaptable to new environmental challenges or diseases and increases the risk of inbreeding depression.

Yes, over extended periods, natural selection is a key driver of speciation. If populations become geographically or reproductively isolated and experience different selection pressures, they can diverge genetically to the point where they can no longer interbreed successfully, thus forming new species. Find more detailed explanations in our premium lessons and past paper solutions.

There are three main types: 1. Stabilising selection, which favours intermediate phenotypes (e.g., human birth weight). 2. Directional selection, which favours one extreme phenotype (e.g., antibiotic resistance). 3. Disruptive selection, which favours both extreme phenotypes over the intermediate one.