(A Level) Selective breeding, evolution and speciation

Learning objectives

Describe how artificial selection works: breeders choose parents with the desired characteristics, cross them and repeat over many generations, raising the frequency of the chosen alleles.

Outline how breeders have given wheat and rice varieties disease resistance, crossed inbred lines of maize to obtain vigorous, uniform hybrids, and raised the milk yield of dairy cattle.

Outline evolution as a gradual change in a population's gene pool over many generations that can lead to new species arising from existing ones.

Discuss how the number of differences between the DNA base sequences of species indicates how recently they shared a common ancestor.

Explain how speciation follows genetic isolation, either by geographical separation (allopatric speciation) or by ecological or behavioural separation within the same area (sympatric speciation).