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Download Unsegmented Worms: Flatworms and Roundworms
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Unsegmented Worms: Flatworms and Roundworms Biology 11 Worms • Divided into 2 Groups –Unsegmented • Flatworms • Roundworms –Segmented • Annelids Phylum Platyhelminthes • Platy= flat • Helminth=worm • The Flatworms Characteristics • • • • • Acoelomates (no fluid filled space) Unsegmented body (not divided into sections) Live in aquatic habitat (streams, lake, oceans) Free living or parasitic Cephalization- concentration of sensory organs at one end • Bilaterally symmetrical Germ Layer • 3 cell layers- ectoderm, mesoderm, endoderm • Have a two way digestive system (lack an anus) Class Tubellaria • Free living flatworms • Marine and fresh water (a few terrestrial) • Reproduce asexually by fission and sexually are hermaphrodites Class trematoda • Parasitic flukes • Live as external and internal parasites on fish and other animals • Complex parasitic life cycle involving hosts • Hermaphrodites Class Cestoda • Parasitic tape worms • Live in intestines of vertebrates • Have scolex in “head” section that have sections called proglottids – Contain reproductive organs and fertilization takes place inside – Mature proglottids detach and pass out of the intestine Phylum Nematoda • The roundworms • Found in soil, marine, and fresh water • Cylindrically shaped • Bilaterally symmetrical • 3 body layers- have pseudocoelom • One way digestive system – Have mouth and anus • No circulatory or respiratory system – Fluid in pseudocoelom distributes food and oxygen • Have nerve ring around pharynx (no brain) • Have separate sexes EXTREME HEEBY– JEEBIES AHEAD! Roundworms found in dog poop Inside a chicken’s intestine Feeding • Most are free living carnivores/omnivores • Have pharynx • Can be parasites in plants and animals Respiration and Circulation • Diffusion of gases through body walls Excretion • Metabolic wastes diffuse through body walls • Undigested wastes through anus • Filarial worms • Tropical Asia • Mosquito carries worms from host to host • Cause elephantiasis
