Phylum Nematoda (Chapter 27.2)

1. Phylum Nematoda (Chapter 27.2) Please set up your notebook for Cornell Notes

2. Nematodes • Characteristics • Slender, unsegmented w/ tapered ends • Range from microscopic to 1 meter ling • Most are free-living, some are parasitic • Develop from three germ layers • Have a body cavity b/w endoderm and mesoderm • Pseudocoelomate • Have a digestive tract with two openings

3. Form and function • Feeding • Free living worms are predators with grasping mouth parts • Soil dwelling and aquatic forms eat algae, fungi or decaying organic matter • Respiration, Circulation and Excretion • These processes take place by diffusion

4. Response • Simple nervous system with several ganglia • Numerous sense organs • Movement • Nematodes have muscles that extend the length of the body • Use the pseudocoelom and a hydrostatic skeleton

5. Reproduction • Separate male and female organisms • Reproduce sexually using internal fertilization • Parasitic roundworms have life cycles that involve two or three host or multiple organs in one host

6. Roundworms and Human Disease • Trichinosis  caused by Trichinella • Mate in intestines of host, larva are released into the blood stream to take up residence in various organs, become inactive cysts in muscles cells • Extremely painful • Common hosts are pigs and rats • Human contract by eating undercooked, infected pork

8. Filarial worms  threadlike worms that live in blood and lymph vessels of birds and mammals • Transmitted by biting insects • Cause elephantitis extreme swelling by to buildup of fluid

9. Ascarid worms • Ascarislumbricoides • Mature in intestine and release eggs in feces • Feces can contaminate food or water continuing cycle • Causes malnutrition

10. Hookworms  soil dwelling • Lay eggs in soil • Pierce feet to burrow into skin and enter blood stream • Consume blood causing weakness and poor growth