EvolutionLesson 2 of 2 in the course Macroevolution and mass extinctions

Punctuated Equilibrium: Patterns, Mechanisms, and Scientific Context

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces punctuated equilibrium and the pattern of evolutionary change it proposes. Understanding this theory helps explain why many fossil species appear unchanged across long spans of geological time, even though evolution has occurred.

Punctuated equilibrium proposes that a species, once it appears in the fossil record, often remains relatively stable for most of its geological history. This prolonged period of little or no morphological change is called stasis.

All flashcards

Allopatric speciation
Speciation following geographic separation, which limits gene flow between populations.
Peripatric speciation
Speciation when a small population becomes isolated near the edge of a species’ range.
Stabilizing selection
Natural selection that favors traits near an established average.
Saltationism
The proposal that evolution occurs through very large, abrupt changes, sometimes in one generation.
Stasis
A prolonged interval of little accumulated morphological change, despite variation between generations.

Quiz questions

  1. How can geographic isolation help a small population diverge from its parent population?Answer: It limits gene flow, allowing the isolated population to evolve independently.
  2. Who authored the landmark 1972 paper that established punctuated equilibrium as a paleobiological research program?Answer: Niles Eldredge and Stephen Jay Gould.
  3. What distinguishes punctuated equilibrium from saltationism?Answer: Its relatively rapid episodes still involve evolutionary change across many generations.
  4. How does Simpson’s quantum evolution differ from punctuated equilibrium as described in these notes?Answer: It concerns rapid evolution toward higher-level groups and gives less emphasis to stasis.
  5. What is one possible explanation for a gap between fossil appearances of a species?Answer: The species may have evolved elsewhere and later migrated into the region.

Based on the Wikipedia article Punctuated equilibrium, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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