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Content: the flatworms 

The phylum includes free-living worms like the planarian, 
parasitic worms like flukes, 
and tapeworms. Nematoda: the roundworms 

No matter the size, all roundworms have slender bodies that taper at both ends. The internal structureof nematodes is quite complex. Although most roundworms are free-living, there are many parasitic forms. These include pinworms, hookworms, trichinella, and heartworms. Competition for resources is fierce in the micro-world of the nematode. In addition to avoiding larger animals, they might also be trapped by the nematode distroying fungior harpooned by Haptoglossa mirabilis. Annelida: the segmented worms 

Members of this phylum, including the earthworm, 
are free-living animals.