EVOLUTION notes

Evolution explains how the great variety of life on Earth came about. This section covers the definition of biological evolution, the difference between a hypothesis and a theory, and why the Theory…

Four lines of evidence support the Theory of Evolution: the fossil record, biogeography, modification by descent (homologous structures) and genetics. For each one, it is important to know what it…

Variation is the differences between individuals of the same species. It is the raw material for natural selection. This section covers the definitions of a species and a population, the five…

Ideas about how species change have developed over the last 200 years. Three main ideas are covered, in the order in which they were proposed: Lamarckism, Darwinism and Punctuated Equilibrium. The…

Lamarckism is the explanation of evolution proposed by Jean Baptiste de Lamarck (1744–1829). He used two "laws": the law of use and disuse and the law of the inheritance of acquired characteristics…

Darwinism is Charles Darwin's (1809–1882) theory of evolution by natural selection. The theory is a sequence of steps that can be applied to any example, such as giraffes, insects that resist…

Punctuated Equilibrium was proposed by Niles Eldredge and Stephen Jay Gould in 1972. It explains the speed at which evolution takes place. It does not replace natural selection: it describes when…

In artificial selection, humans choose which organisms breed, based on the characteristics they want. This section gives an example with a domesticated animal and an example with a crop, and…

This section covers the biological species concept, how speciation and extinction affect biodiversity, and how new species form through geographic isolation, with examples such as the Galapagos…

Reproductive isolation mechanisms keep species separate, because they stop different species from interbreeding to produce fertile offspring. This section outlines the five mechanisms. Reproductive…

Natural selection is still happening today. This section explains four examples of evolution in present times: resistance to insecticides in insects, antibiotic-resistant tuberculosis bacteria, HIV…

This section covers the evidence that living hominids, including humans, share common ancestors: where the family Hominidae fits on a phylogenetic tree, the characteristics that humans share with…

The Out-of-Africa hypothesis states that modern humans originated in Africa and then migrated to other continents. This section covers the fossil and genetic evidence for the hypothesis, a timeline…