EvolutionLesson 3 of 4 in the course Evidence for evolution and common descent

Transitional Fossils: Evolutionary Evidence, Classification, and Limits

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

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Summary

This lesson introduces transitional fossils and explains what they can—and cannot—tell us about evolution.

A transitional fossil is fossilized evidence of an organism that has traits associated with both an ancestral group and a derived descendant group. The combination of traits can help illustrate how characteristics changed over evolutionary time.

All flashcards

What is a transitional fossil?
A fossilized organism with a combination of traits associated with related ancestral and derived groups.
Why does transitional anatomy not establish direct ancestry?
A fossil with transitional traits may be a close relative rather than a direct ancestor.
What does a cladogram represent?
A branching diagram of evolutionary relationships, rather than a ladder of progress.
Why is Archaeopteryx important to the study of bird origins?
It combines feathers and birdlike wings with skeletal features associated with theropod dinosaurs.
What does punctuated equilibrium describe?
Long periods of relative morphological stability interrupted by comparatively brief periods of faster evolutionary change.

Quiz questions

  1. What does a monophyletic group include?Answer: A common ancestor and all of its descendants.
  2. Which combination of traits makes Archaeopteryx informative about bird origins?Answer: Feathers and birdlike wings alongside teeth, clawed fingers, and a long bony tail.
  3. What did oxygen isotope evidence suggest about Ambulocetus?Answer: It could tolerate both fresh and salty environments.
  4. Which feature of Tiktaalik is associated with tetrapods?Answer: Fin bones with basic wrist-like elements that may have supported its weight.
  5. What pattern of change does punctuated equilibrium describe?Answer: Extended stability interrupted by shorter periods of relatively rapid change.

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

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