4-Animal-Diversity-33 - BIOL 211B, February 7, 2008 LOWE...

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211B , February 7, 2008 A NIMAL D IVERSITY : I NVERTEBRATES L OWE ( FROM THE NOTES OF CHARLES GALT) C H 33 ( ) {CPG file: F:\Eudora Files\attach\01b-Animal-Diversity-331.wpd, February 7, 2008} PARAZOA 1. Phylum Porifera ( pore-bearing ), Sponges : no symmetry, asymmetric, "spongy", mostly marine, "sponge divers", organization as cells, no true tissues, lots of pores in body and cells have flagella that pump water through and filter out particulate food, suspension or FILTER FEEDING; very primitive: no nerves, no muscles, no respiratory system, no circulatory system, etc. NO tissues/organs; FW and esp marine. Collar cells (choanocytes) (function?), porocytes, amoebocytes, etc. RADIATA (ACOELOMATE) 2. Phylum Cnidaria nettle-like -- jellyfishes, sea anemones, corals 1. Radial symmetry, meet environment from all sides, good general approach, but not well specialized 2. Diploblastic: Two tissue layers with solid jelly in between (no cavity): ectoderm, endoderm; so no real mesoderm, though some cells in mesoglea 3. sac-like gut, mouth = anus; gastrovascular cavity (a digestive cavity, but is NOT a ‘body cavity’) 4. No body cavity, so is acoelomate 5. Have tentacles with stinging cells -- cnidocytes or nematocysts -- for defense and food acquisition 6. Two basic body forms, the medusa ( planktonic , jellyfish) and the polyp ( Hydra , hydroids, sea anemone, corals, often colonial), ~ inverses of each other 7. Life history: not true alternation of generations as in plants (N, 2N); these are all diploid, but zygote > larva > polyp/hydroid > (asexually produced) buds > medusae > gonads egg/sperm > zygote, etc. 8. very primitive nervous system, muscular cells, not true organ systems 9. Taxonomy, classes: 1. Class Hydrozoa -- polyp/medusa form both conspicuous; polyps=hydroids, benthic, usually colonial; medusa solitary, planktonic, mostly marine, but some freshwater 2. Class Anthozoa -- polyp form only; all marine; sea anemones and corals, sea fans, etc. Corals in news recent years for their 'bleaching', a probable response to some form of environmental pollution: warming, UV from ozone hole, etc. 3. Class Scyphozoa -- all marine, planktonic, medusa dominant, though polyp present in most 3. Phylum Ctenophora , comb jellies, radial, gelatinous, colloblasts instead of nematocysts, on feeding tentacles, with complete gut (i.e., with anal pores), ciliary locomotion, mostly planktonic , marine; one species was ballast-water invader to Black Sea from Atlantic Coast; disrupted food web and anchovy fisheries 4. Two main evolutionary paths now: show simple development model to illustrate these 1. Protostomes (we'll see more later where name comes from, but it means ‘first mouth’ , meaning that the first opening of the larval gut gives rise to the mouth): Molluscs, Annelids, and others in the Lophotrochozoa and Ecdysozoa (Nematoda, Arthropoda) 2. Deuterostomes (‘ second mouth ’, first opening of larval gut gives rise to anus, and mouth
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4-Animal-Diversity-33 - BIOL 211B, February 7, 2008 LOWE...

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