Genetics

Evolution and natural selection

Antibiotic resistance is an example of natural selection in action: bacteria with a random mutation that allows them to survive antibiotics reproduce, passing on resistance — a major public health threat.

Evolution and natural selection

Selective breeding (artificial selection) is when humans choose which organisms reproduce to pass on desired characteristics, e.g. breeding cattle for more milk or dogs for temperament.

Evolution and natural selection

Darwin gathered key evidence for evolution on the Galápagos Islands, where the variation among finches (especially their beak shapes) — collected during the 1831–36 voyage of HMS Beagle — helped inspire his theory of natural selection.

Evolution and natural selection

Charles Darwin and Alfred Russel Wallace independently developed the theory of evolution by natural selection; Darwin published On the Origin of Species in 1859.

Evolution and natural selection

Extinction occurs when every member of a species dies and no more can reproduce; it can be caused by environmental change, disease, competition, or predation.

Evolution and natural selection

The fossil record shows that organisms have changed over time — transitional fossils provide evidence that species evolved gradually from common ancestors.

Evolution and natural selection

Random mutations in DNA are the ultimate source of new genetic variation; natural selection then acts on this variation.

Evolution and natural selection

Mutualism is a close relationship between two different species in which both organisms benefit, e.g. bees getting nectar while pollinating flowers.

Evolution and natural selection

Natural selection works because: (1) individuals in a population vary; (2) some variation is inherited; (3) more offspring are produced than survive; (4) individuals with favourable traits are more likely to survive and reproduce.