GEOL 102 Historical Geology

Spring Semester 2014
Evolution II: Tempo & Mode, Patterns & Process

With the discovery of evolution by natural selection, biologists from Darwin and Wallace's time onward have documented many different patterns and processes in evolution. Sometimes they refer to "microevolution" (changes within an species) and "macroevolution" (patterns on the larger scale; changes from one species to another, or between different lineages of ancestors and descendants). It is important to remember that "micro-" vs "macro-" is just a matter of scale and perception: at the level of individuals and populations, there is just variability, heritability, and superfecundity.

The most important pattern: the Tree of Life. Darwin and Wallace demonstrated the reality of Divergence through Time and Common Ancestry:

Thus, the basic pattern of the history of living things is a Tree of Life, where the trunk and stems are lineages of ancestors, the branching points representing divergences between lineages, and the tips of the branches living species (or extinct species that died without descendants).

Other important patterns and processes:

Here is Carl Sagan's summary of Darwinian evolution and the Tree of Life, from the TV series Cosmos:

And here is another summary of evolution and how it works (and how it ISN'T like the parody-version of evolution which Creationists claim scientists believe):

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Last modified: 27 February 2014