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 long
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 due to buildup of fluid

9. Ascarid worms
Ascaris lumbricoides
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

11. Pinworms  most common parasitic infection in US
Adults live in large intestine
Migrate to anal region to lay eggs
Results in intense itching that spreads eggs to clothes and bedding