Biology › Evolution and speciation

Evolution and speciation

Unit B19 · 5 lessons.

Notes

Illustrated notes for each topic in this unit, with worked examples and a checklist of objectives.

• Natural selection: variation, selection and allele frequency
  The three sources of genetic variation and which of them makes new alleles, environmental variation and why it is not inherited, selection pressure…
• Evidence for evolution, resistance and genetic drift
  How antibiotic resistance arises and spreads; vertical and horizontal gene transfer; why a prescribed course is finished; pesticide and herbicide…
• Speciation and reproductive isolation
  The biological species concept and the cases it cannot handle, reproductive isolation and gene flow, allopatric speciation by geographical…
• Continuous and discontinuous variation
  Discontinuous variation set against continuous variation on four counts: how many genes control it, whether the environment changes it, how the…
• Artificial selection and selective breeding
  Artificial selection as the same mechanism as natural selection with a different agent choosing, illustrated by disease resistance bred into wheat…