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Phylum Platyhelminthes (flatworms). 18,500 spp. most primitive bilateral animals acoelomate triploblastic minimal cephalization no circulatory system nervous system- ladder-like. Taxonomy. Class Turbellaria (planarians) Class Trematoda (flukes) Class Cestoda (tapeworms).
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Phylum Platyhelminthes (flatworms) • 18,500 spp. • most primitive bilateral animals • acoelomate • triploblastic • minimal cephalization • no circulatory system • nervous system- ladder-like
Taxonomy • Class Turbellaria (planarians) • Class Trematoda (flukes) • Class Cestoda (tapeworms)
Flatworm Physiology • Respiration and excretion via diffusion through the body wall • hermaphroditic w/ internal fertilization • asexual reproduction via fragmentation
fresh water, terrestrial, mostly marine ciliated epidermis evertable pharynx example: Planaria Class Turbellaria (planarians)
11,000 spp. medically important endoparasites of vertebrates eggs void in feces free swimming larvae example: Clonorchis Chinese liver fluke Class Trematoda (flukes)
3400 spp. endoparasites of vertebrates scolex- holdfast proglottids example: Taenia- beef tapeworm Class Cestoda (tapeworms)