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Student+lab+handout-animals - Kingdom Animalia I The...

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Kingdom Animalia I. The Parazoans: No true tissues, no symmetry A. Phylum Porifera: The sponges All are sessile organisms, and filter feeders. The osculum (central cavity) is lined with choanocytes, which are flagellated cells that set up a water current through the organism. Organization is close enough to choanoflagellates (colonial protists) to suggest evolutionary relationship. Most sponges are hermaphrodites, producing both sperm and eggs. II. The Eumetazoans: Have true tissues and various symmetries A. Phylum Cnidaria (formerly Coelenterata) Radial symmetry Simple body plans-two cell layers surrounding a gastrovascular cavity. -Epidermis: outer layer -Gastrodermis: inner layer lining gastrovascular cavity -Mesoglea: non-cellular jelly between two layers Specialized cells called cnidocytes are unique to this phylum. These contain nematocytes, which are the stinging cells that capture prey. Secrete hypnotoxins to subdue prey. Most harmless to humans, but some strong enough to break human skin and cause problems (fire coral, Portuguese man o’ war). All predatory. Both sexual and asexual (budding) reproduction Primitive nervous systems, nerve nets that carry impulses both ways along the neurons No other specialized structures. Other cellular needs taken care of through diffusion with surrounding water Two body types: medusa (jellyfish plan) and polyp ( hydra -like plan) Class Hydrozoa : Portuguese man o’ war, hydra. Most marine, few freshwater. Class Scyphozoa : Jellyfish. Larval stage are polyps Class Anthozoa : Coral and sea anemones. B. Phylum Platyhelminthes: Flatworms Bilateral symmetry, triploblastic (three germ layers), acoelomates. One opening into gastrovascular cavity Primitive nervous system, anterior brain with two nerve cords running length of body, forming a ladder-like structure. No respiratory or circulatory systems: cell level diffusion Excretion: through cell layers, Flame Cells mostly for osmoregulation with environment Reproduction: Sexual, some regenerate from pieces Class Turbellaria: Mostly free living marine forms, some freshwater forms (like Planaria ) Eyespots detect light.
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