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5 Cards in this Set
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- Back
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Porifera (pore-IH-fer-ah; 5,000)
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Sponges are all water dwellers, (98% marine) and they are sometimes classified separately from other animals because of their asymmetric bodies and lack of tissue. They are sessile (immobile) andcept in early stages, and collect food particles using sweeping motions of flagellated cells called choanocytes (koh-ANN-oh-sites)
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Cnidaria (nih-DARE-ee-ya; 10,000)
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Also called Coelenterata (se-LEN-ter-AH-tah), they develop to form a diploblastic (two-layered) embryo, and have two serparate tissue layers and radial body symmetry. many have two life stages. the moviel, usually bell-like medusa and the sessile polyp. They all have nematocysts (stinging cells) to capture prey. Examples: hydra, sea anemones, corals, jellyfish, and Portugues man-o-war (which is actually an aggregation of colonia cnidarians)
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Platyhelminthes (PLAT-ee-hel-MIN-theez ; 15,000)
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The flatworms are the most primitive phylum to develop from a triploblastic (three-layered) embryo. They have bilateral symmetry, and are acoelomate (lacking a true body cavity), so the space between their digestive tract and body was is filled with tissue. The are usuall flat-bodied. They have a head and brain, but only one opening which functions as mouth and anus. Most of hermaphroditic, (are both sexes). Example: Tapeworms, flukes, and free-living (non-parasitic) organisms such as the planarians.
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Nematoda (NEM-ah-TOE-dah) 15,000 species
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The roundworms are unsegmented worms that live in a variety of habitats. They are psseudocoelomate; the three tissue layers are concentric, but the body cavity is not lined with tissue derived from the mesoderm (middle embryonic layer). They include both free-living and parasitic species; human parasites include hookworms and the causative agents of elephantiasis, trichinosis, and river blindness. Soil nematodes may be crop pests, while others are beneficial predators on other plant pests, The nematode species Caenorhabdis elegans is a common subject in genetics and developmental-biology labs.
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Annelida (AN-el-LEE-dah; 11,500)
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The annelids are segmented worms and represent the firs lineage of truly eucoelomate (having a body
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