Habit and habitat:
Most members are parasitic. Some of them lives as parasites of plant roots or grains (Wheat. paddy) Intestine, blood and other organs of different animals. some are free living they live in soil and water. On the basis of number they are second largest phylum of animal kingdom.
Fig: Ascaris lumbricoides
- Body cylindrical, covered with thick cuticle and bilaterally symmetrical.
- Complete digestive system (Mouth and anal opening present).
- Body cavity uncovered, there is no true coelom.
- Circulatory and respiratory system absent.
- They are generally unisexual.
Example: Ascent lumbricoldes (Round worm) Ancylostoma duodenale (Hook worm) Enterobtus vermtcularts (pin worm) Rhabditis- free living, Live in soil.