BiologyCode 9700
Natural and artificial selection
What this topic asks you to be able to do
- explain that natural selection happens because populations are able to produce large numbers of offspring, which then compete for resources; during the ‘struggle for existence’, the best-adapted individuals are the ones most likely to survive, breed and pass their alleles on to the next generation
- explain the ways in which environmental factors may act as directional, disruptive and stabilising forces of natural selection
- explain in what ways selection, the founder effect and genetic drift, including the bottleneck effect, may change the frequency of alleles in populations
- outline the process by which bacteria acquire resistance to antibiotics, taken as a case of natural selection
- use the Hardy–Weinberg principle to work out the frequencies of alleles and genotypes in a population, and state the conditions that must be met for the principle to apply
- describe the principles behind artificial selection, also known as selective breeding
- outline these examples of selective breeding: dairy cattle bred to give a higher milk yield; maize varieties made vigorous and uniform through inbreeding and hybridisation; and wheat and rice varieties given resistance to disease