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chapter30%20-%20proteostomes%20Spring%202008%20_1_

chapter30%20-%20proteostomes%20Spring%202008%20_1_ - The...

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The Animal Kingdom: Bilateria - The Protostomes Chapter 30 Cephalization evolved with bilateral symmetry; sensory structures; nerve cells in head form a brain, nerve cord extends toward the rear
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Protostomes Characterized by Bilateral symmetry spiral and determinate cleavage Initial development of mouth from blastopore Three body layers (triploblastic) Contain a-coelomate, pseudo-coelomate and coelomate members
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Phylum Platyhelminthes ( acoelomate flatworms) No organ for circulation or gas exchange Gastrovascular cavity (digestive system) with one opening (mouth) Many are hermaphrodites Beginnings of cephalization (head) with concentration of sense organs and nerve cells (simple brain) at anterior end
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