Metazoa_Overview

Metazoa_Overview - BIS2C: lectures on Metazoa Fall 2009...

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BIS2C: lectures on Metazoa Fall 2009 Peter Wainwright 1. From simple to complex: origins of animal multicellularity How it works: regulatory/developmental innovations The big pattern: body plans, adaptive radiation and diversity The metazoan tree: organizing 30 major lineages and their history 2. Sponges Key points: Monophyletic- yes/no Number of species- Distribution- marine (mostly) or freshwater (few) at all depths Key characteristics- flagellated cells called choanocytes, spicules made of calcium carbonate, silica and/or collagen fiber skeleton Size- few mm to over 2 m Reproduction- sexual or asexual Sponges represent the first group that experiments with multicelularity Key point is surface are to volume ratios for single-celled organisms Sponges are sessile, so must bring food to themselves. They use some complex plumbing, plus cells with flagella, to make this work. Diversity of sponges Sponges and humans 3. Cnidaria and Ctenophora: diploblasty as a lifestyle Key points: Monophyletic- yes/no Number of species- Distribution- marine (mostly) or freshwater (few), mostly shallow marine Key characteristics- polyp and medusa individuals,  extremely variable,  diploblastic (2 tissue layers only), cnidocytes with nematocysts  (stinging cell organelles), no coelom Size- few mm to coral reef Reproduction- sexual or asexual Discuss radial symmetry Diploblastic Cnidocyte is a key innovation for protection and food acquisition Life cycle evolution is a key component of diversity of the group Discuss the major clades briefly, including ctenophora
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End with a brief discussion of coral reefs 4. Bilaterians and their major clades: reorganizing body plans What are the advantages of a bilaterian body plan? Replication of parts
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Metazoa_Overview - BIS2C: lectures on Metazoa Fall 2009...

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