Lecture 29 _March 21_ Origin of Animals post

Lecture 29 _March 21_ Origin of Animals post - 3/18/11 !...

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3/18/11 1 Lecture 29: Monday March 21, 2011 Biology 171 Origin of Animals (Metazoa) Announcements This Week in Discussion: Frogs & Phylogenies Revision Session Sunday March 27, 3-5pm 1800 Chemistry On becoming Multicellular Sponges, the earliest Metazoa Cnidaria, the tissue level of organization Bilateria: Protostomes & Deuterostomes Lophotrochozoa & Ecdysozoa Chordates Text Reading Chapter 32 (601-609, 617-620) Chapter 33 (623-625) Chapter 34 (646-655) Why We Care • We are in the animal kingdom – when we study animals, we study ourselves • The evolution, physiology & behavior of many animals are very similar to our own – they make good models for studying disease • We rely on animals for their roles in ecosystems, food, transportation, labor, sport, and companionship What is an animal? Most animals share these characteristics: - are multicellular, heterotrophic, eukaryotes - most have two unique tissues: nervous and muscle -many reproduce sexually - diploid stage is dominant - distinct types of patterns in early development
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3/18/11 2 Metazoa (Animals) are a terminal twig on the Tree of Life The Metazoa evolved 3 billion years after the Frst life forms The Evolution of Animalia Mitotic divisions in early development proceed through a series of embryonic stages
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3/18/11 3 A Few Key Points • All animal phyla evolved in marine environments and most animal phyla remain in marine environments – terrestrial and freshwater animal groups are a very small subset of phyletic diversity (though a very large proportion of species diversity ) • Some animal phyla are sessile for much of their lives and grow by the addition of
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Lecture 29 _March 21_ Origin of Animals post - 3/18/11 !...

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