Bio; Lecture 21; Survey of the Animal Kingdom

Bio; Lecture 21; Survey of the Animal Kingdom - Principles...

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Principles of Biology 2 BIO U103 March 1, 2007 Echinodrms Deuterostome Radial cleavage Develop a coelom from the archenteron Blastopore becomes the anus No brain or ganglia Really simple structure Common names o Sea stars, brittle stars, sea urchins, sand dollars, sea lilies, feather stars, sea cucumbers, sea daisies Water vascular system . o Unique to echinoderms o Allows water to come into the body o It consists of a network of hydraulic canals, branching into extensions called tube feet o Function in locomotion, feeding, and gas exchange o When water enters the system, the tube feet extend o In sea urchins, they are capable of opening up a bivalve. Secondary radial symmetry o Radial adults develop by metamorphosis from bilateral larvae . o Radial appearance of most adult echinoderms is the result of secondary adaptation to a sessile lifestyle o The larvae are bilateral o Echinoderm adults are not truly radial in their anatomy Thin skin covers an endoskeleton of hard calcerous plates o Most are prickly from skeletal bumps Sea stars o Water enters through the madreporite , enters the ring canal (circular ring below the madreporite—then water enters lateral canals —then water is pushed by muscle contractions of the ampulla , forcing water into the tube feet . o
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Bio; Lecture 21; Survey of the Animal Kingdom - Principles...

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