Lesson 2: The Woesian Revolution

What is the current tree of life model?

In this lesson, students take an in-depth look at the current molecular three-domain tree of life, a recent and significant scientific development. First, to model how molecular evidence is used to formulate a tree of life, students examine similarities and differences between simulated DNA sequences of a diverse set of organisms to determine relatedness. Students then engage in an important conversation about the use of the term “prokaryote” and how it can be problematic in light of Woese’s discovery of archaea and the new tree of life model. Finally, students read a news article about Carl Woese’s discovery of archaea and discuss different aspects of the nature of science illustrated by the story. Through these activities, the following nature of science concepts are addressed: new technologies advance scientific knowledge and science is subject to changes based on new evidence and/or reinterpretation of existing evidence.

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