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More on Punctuated Equilibrium
Punctuated equilibrium is an important but often-misinterpreted model of how evolutionary change happens. Punctuated equilibrium does not:
Punctuated equilibrium predicts that a lot of evolutionary change takes place in short periods of time tied to speciation events. Here's an example of how the model works:
Evolution appears to happen in sharp jumps associated with speciation events.
We observe similar patterns in the fossil records of many organisms. For example, the fossil records of certain foraminiferans (single-celled protists with shells) are consistent with a punctuated pattern.
However, it is also important to note that we observe examples of gradual, non-punctuated, evolution in the fossil record too. The question that needs answering is: what are the relative frequencies of punctuated and gradual change?
Foraminiferan micrograph courtesy of the National Collection of Foraminifera © Smithsonian Institution
Foraminiferan graph after Malmgren, Berggren, and Lohmann (1983)
Read more about peripatric speciation.
Diversity in Clades
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Spanish translation of Understanding Evolution For Teachers from the Spanish Society of Evolutionary Biology.