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Online Course for Teachers: Teaching Evolution

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SESSION 3: What Is the Evidence for Evolution?

Facilitator Notes for SESSION 3

Explore Part C
Note 1: Fossilization is a very rare event, so it's unlikely that scientists would find the direct fossil ancestor of a living species. Vertebrates are more likely to fossilize because they have hard parts (bones and teeth) and because they are more recently evolved. Extinction provides opportunities for existing organisms to diversify into new ecological niches (adaptive radiation). A good example is adaptive radiation of mammals after dinosaurs became extinct.

Explain Part A
Note 2: Do the activity as a "jigsaw" Web quest with three teams. Each team can research one line of evidence (fossil, biogeographical, or anatomical) that Darwin used to support his theory. For each of the three kinds of evidence, teams will identify the key evidence, examples that illustrate how that particular line of evidence supports evolution, and any unanswered questions related to that line of evidence to each other. Then teams will present their findings.

Explain Part C
Note 3: Organisms have many common structures: cells, DNA, proteins, enzymes, biochemical pathways, similarities in different vertebrate forelimbs (homologous structures -- variations on same bones, used for different functions), similarities in vertebrate embryos, and similarities in homeobox sequences for vertebrates and Drosophila.

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