Evolution, natural selection and speciation

Learning objectives

Outline the evidence for evolution provided by the fossil record, by selective breeding of domesticated species, by homologous structures such as the pentadactyl limb, by vestigial organs and by similarities in base and amino acid sequences

Explain natural selection in terms of heritable variation within a population, the overproduction of offspring, competition for limited resources and the greater reproductive success of better adapted individuals

Identify mutation, meiosis and sexual reproduction as the sources of the variation on which selection acts, and explain why characteristics acquired during an organism's lifetime are not inherited

Describe sexual selection and explain how it can favour traits that reduce survival, and use the spread of antibiotic resistance in bacteria and of insecticide resistance in insects as directly observed examples of natural selection

Explain speciation as the splitting of one species into two by reproductive isolation, and (HL) distinguish allopatric isolation by a geographical barrier from sympatric isolation by behavioural, temporal or polyploid mechanisms

(HL) Define a gene pool and allele frequency, apply the Hardy–Weinberg equations p + q = 1 and p² + 2pq + q² = 1 together with the assumptions they require, and distinguish stabilising, directional and disruptive selection by the change each produces in a distribution