*Phylum Nematoda consists completely of Roundworms. *Two types: parasitic and free-living. 90,000 species known; many more exist! *These Roundworms are unsegmented; they have long, narrow, cylindrical bodies that taper to a fine tip in the posterior and a blunt end at the head. Also, they have a cuticle--a tough layer of outerskin--covering their entire bodies. *They are pseudocoelomates. They have a pseudocoelom, an internal body space surrounding the endoderm tissue of the digestive tract and surrounded …showed first 75 words of 208 total…

…showed last 75 words of 208 total…words, Roundworms are cooler than Flatworms]. *Longitudinal muscles; they move side-to-side in a thrash-like motion. *Reproduce sexually. Fertilization = internal, and females deposit more than 100,000 fertilized eggs per day. Zygotes can survive harsh conditions. *Many live in moist soil and in organic matter on the bottoms of lakes and oceans. Play an important role in decomposition and nutrient cycling. *Closely related to phylum Rotifera; they are both VERY small (microscopic) and have a complete digestive tract.