November 8-ch 23

November 8-ch 23 - November 8, 2007 Chapter 23 The Annelids...

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November 8, 2007 Chapter 23 The Annelids (Annelida) The segmented worms Bilateral symmetry Coelomate o Fluid filled coelom functions as a hydrostatic skeleton (pressurized fluid provides a framework against which muscles can act) Body divided into a series of repeating units (segmentation) o Allow for complex movement o Hydrostatic skeleton o Segments contain identical copies of nerves, excretory structures, and mucles Many reproduce sexually Some are hermaphroditic Some reproduce asexually by fragmentation o The body breaks into two pieces, each of which regenerates the missing part Three main subgroups o Oligochaetes (earthworms) o Polychsetes (mostly marine) o Leeches (mostly freshwater or terrestrial) The Mollusks (Mollusca) o > 50,000 species o Bilateral symmetry o Coelomate o Mantle (extension of the body wall) o Forms gill chambers o Secretes shell o Most protect body with hard shell o Calcium carbonate o Reproduce sexually o Some have separate sexes, some are hermaphroditic o Three main classes o Gastropods o Bivalves o Cephalopods
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This note was uploaded on 04/10/2008 for the course BIOLOGY 101 taught by Professor Beitch during the Spring '07 term at Quinnipiac.

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November 8-ch 23 - November 8, 2007 Chapter 23 The Annelids...

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