The Evolution of Animals
Please see the extensive Web links on the Biology 404 HOL Chapter 4 Website
These include a link to Dr. Pamela Gore's helpful lecture notes on the Precambrian-Cambrian Transition.
1. How are sponges like the single-celled protists known as choanoflagellates and, if they are so are similar to choanoflagellates, why are they considered members of the clade, Metazoa?
2. Compare and contrast a sponge, cnidarian, and a worm, such as a flatworm.
3. What are Hox genes? How are they used by animals?
4. The Vendian, or Ediacaran, fauna of Precambrian animals were quite different from Cambrian animals, so much so that Adolf Seilacher proposed that they represent a separate radiation of multicellular animals, he called the Vendozoa. Is this view generally held and, if not, why not?
5. Explain how the "Cambrian Explosion" could represent when metazoans got large, or got skeletons, instead of when they first appeared.
6. We are fortunate to have the Burgess Fauna (in Canada and elsewhere) preserved because it gives us a more complete idea of what soft-bodied animals were present during the Cambrian. List several Cambrian fossils that are more commonly preserved even without such fortunate conditions. List several more that we would not know about without the Burgess Fauna.
7. List two hypotheses that might account for the Cambrian Explosion, along with some evidence for each hypothesis.
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