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Worms Flatworms ectoderm mesoderm • Bilateral symmetry • Have organs & systems – Primitive brain – Pharynx: mouth tube • 3 body layers – Ectoderm – Mesoderm – Endoderm Able to “regenerate” endoderm http://www.youtube.com/wat ch?v=0L_mJoG4nts • Gasses pass in/out by diffusion • Reproduction: – Asexual: stretch and break apart – Sexual: “fencing” Flatworms • Bilateral symmetry • Have organs & systems – Primitive brain – Pharynx: mouth tube • 3 body layers – Ectoderm – Mesoderm – Endoderm • Gasses pass in/out by diffusion • Reproduction: – Asexual: stretch and break apart – Sexual: “fencing” Flatworm Parasites Larvae not killed in cooking process • Tapeworms – Larvae enter through undercooked meat – Larvae grow – Scolex (head with hooks) attach to wall of intestines – Food absorbed through skin – Grow up to 12 meters – Eggs released in poop – Contaminated poop water consumed Roundworms (Nematodes) • Protostomes; Bilateral symmetry • Small in size (few mm) • Nerves control longitudinal muscles • What’s new? – Mouth and anus – Pseudocoelum: body cavity to aid with circulation & digestion • Separate male/female • Some free-living; Many parasites Roundworm Parasites • Hookworms – Larvae enter through bare feet walking in contaminated water – Migrate into lungs – Migrate into esophagus and swallowed into stomach – Larvae mature inside intestines – Mating occurs inside host – Eggs exit the host in poop https://www.youtube.com/watc h?v=DxL2qHBetvI Egg • What’s new? – Coelum: cavity to aid with circulation & digestions – Completely surrounded by muscle • Several organ systems – Complex digestive system – Circulatory sys: 2 blood vessels – Nervous sys: Primitive brain and nerve cord – Muscular sys: Circular & longitudinal muscles • Gas exchange through skin • Eat organic waste Segmented Worms (Annelids) Longitudinal muscles Circular muscles Segmented Worm Reproduction . .. . . .M F F M. • Hermaphroditic • Ventral surfaces press together – Mucus holds worms together – Sperm transferred to each – Sperm pouch forms – Sperm & eggs enter pouch as worm backs out – Baby worms develop inside pouch Segmented Leeches • Live in calm, freshwater • Suckers attach to host • Release anaesthetic to hide presence • Can eat up to 10x own weight Segmented Leeches • Live in calm, freshwater • Suckers attach to host • Release anaesthetic to hide presence • Can eat up to 10x own weight • Medicinal use: – Help restore blood flow when body part is severed and reattached Ouch! blood blood