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Phylum Nematoda https://www.youtube.com/watch?v=X1YiIiPUQR8 ROUNDWORMS Kingdom Animalia Phylum Nematoda --Unsegmented worms --Pseudocoelom ("false coelom") -- body cavity contains organs Characteristics • Bilaterally symmetric • Body has more than two cell layers, tissues and organs • Body covered in a complex cuticle (protective noncellular layer of roundworms) • Has a nervous system with pharyngeal nerve ring. • Has no circulatory system (no blood system) • Respiration= diffusion Digestive tract with 2 openings: mouth & anus Feeding Free-living - predators Parasites - humans and animals Reproduction: Sexual reproduction, Separate sexes (male & female) Roundworms & Disease Trichinosis (trichinella worm) - cysts within the muscles are consumed (undercooked food) -- worm grows in intestine -- forms cysts in the muscles of the new host -- symptom: terrible pain in muscles https://www.youtube.com/watch?v=DC4ozHnm9bY&index=3& list=PLLACj7guzqJpyi94ecdzg2mzHdVb6NYDR Filarial Worms - found in Tropical regions of Asia -- usually transmitted by mosquitoes -- causes elephantiasis https://www.youtube.com/watch?v=dnWwHthkGkY Ascarid Worms (common roundworm) - lives in intestine - eggs are passed out in the feces Most roundworms infect dogs, but occasionally they find their way into human hosts Hookworms - burrow into the skin from soil - mature in the intestines --hooks used to attach and suck blood https://www.youtube.com/watch?v=8zqSLIUv_oQ C. elegans: A model organism ●first organism to have DNA completely sequenced ●It is a very simple, free living roundworm https://www.youtube.com/watch?v=v4ePpLoS6xw References • • Biology Corner http://www.earthlife.net/inverts/nematoda.html