Solid Waste Management in Maldives

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Marine Biology 3 (BIO 205) 1 Introduction  Members of the Phylum Chordata include animals with which we are probably most likely familiar (including fish, birds, reptiles, amphibians and beasts like ourselves)  As unlikely as it seems, based on embryological evidence, the echinoderms appear to be the mostlikely ancestors to the early chordates  Primitive stemmed echinoderms are thought to have shifted from arm-feeding to filter-feeding acquiring a body plan similar to urochordates Characteristics of Chordates 1. Bilaterally symmetrical 2. Coelomate deuterostomes (coelom lost in some groups) 3. Pharyngeal gill slits present at some stage in development 4. Dorsal notochord present at some stage in development 5. Dorsal hollow nerve cord 6. With an endostyle or thyroid gland 7. Muscular, locomotor, postanal tail at some stage in development 8. Gut complete, usually regionally specialized 9. Ventral, contractile blood vessel (or heart) 10. Gonochoristic or hermaphroditic development variable Marine Biology 3 (BIO 205) 3 1- Bilaterally symmetrical  Only the midsagittal     plan divides the body in to two mirrored images (left and right) Anterior-head end Posterior-tail end Dorsal-back Ventral-belly or front Marine Biology 3 (BIO 205) 4 Body Cavity  Coelomate  A fluid-filled body cavity completely lined with mesoderm (the coelom) separates the digestive tract from the outer body wall  The mesenteries connect the inner and outer mesoderm layers and suspend the internal organs in the coelom Marine Biology 3 (BIO 205) 5 Body Cavity  Pseudocoelomate  A fluid-filled body cavity separates the digestive tract and the outer body wall  This cavity (the pseudocoelom) is not completely lined with mesoderm Marine Biology 3 (BIO 205) 6 Body Cavity  Acoelomate  No body

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