Feb 23 annelids_mollusks 2009

Feb 23 annelids_mollusks 2009 - Metazoan Structure...

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Metazoan Structure Triploblastic metazoans (All animals except sponges and Cnidarians) Three tissue layers Ectoderm “skin” nervous system sensory systems Endoderm digestive tissues secretory tissues Mesoderm muscles Which way to face? - Symmetry No symmetry e.g. sponges Radial sumetry e.g. cnidarians; ctenophores Bilateral symmetry e.g. arthropods Pentaradial symmetey e.g. echinoderms Where the guts fit - Body cavities Acoelomate No body cavity e.g. flatworms Pseudocoelomate Body wall but not gut lined with mesoderm (muscle) e.g. nematodes Coelomate Both Gut and body wall have mesodermal (muscular) lining Protostomes spiral cleavage determinate cleavage mesoderm derived from blastopore lit schizocoelous mouth derived from blastopore Deuterostomes radial cleavage indeterminate cleavage mesoderm derived from walls of developing gut enterocoelous anus derived from blastopore
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Phylum Annelida KEY FEATURES Bilateral Protostomes Metamerism External – body composed of ring-like segments Internal – organs usually repeated along the length of the body
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This note was uploaded on 09/28/2009 for the course BIOL 172 taught by Professor Staff during the Spring '08 term at Hawaii.

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Feb 23 annelids_mollusks 2009 - Metazoan Structure...

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