2. Worms

3. Flatworms Bilateral symmetry No coelum Has organs & systems 3 body layers –Ectoderm –Mesoderm –Endoderm Gasses pass in/out by diffusion Anterior end w/ mouth Primitive brain

4. Flatworm Reproduction Asexual –Stretch or break apart –Each half becomes new animal Sexual –Hermaphrodites –Both transfer sperm to one another Web link

5. Flatworm Parasites Tapeworms –Larvae enter through undercooked meat –Hooks attach to inner walls of intestines –Food absorbed through skin –Grow up to 12 meters

7. One Final Look

8. Roundworms Cylindrical bodies w/ mouth and anus Separate male/female –Sexual reproduction 1 st to have body cavity (coelum) –Movement of fluid circulates gas & nutrients Most small in size (few mm) Most free-living

9. Roundworm Parasites Ascaris –Infects pigs, horses, humans –Knots of worms can block intestines (cause death) –Larvae cause respiratory illness –Females: lay 200,000 eggs/day Trichinella –Eat undercooked pork –Larvae burrow into intestines & mature –New larvae pass into blood & form cysts in muscles

11. Segmented Worms Have coelum 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

12. Segmented Worm Reproduction Hermaphroditic Ventral surfaces press together –Mucus holds worms together Sperm released into the mucus & stored in a pouch Worms develop inside pouch

13. Segmented Leeches Live in calm, freshwater Sucker attached to host or prey Release anaesthetic to hide presence Can eat up to 10x own weight Used to help restore blood flow in limb reattachment