A combination of factors is likely causing the decline of blue spruce trees throughout Michigan. Posted on March 7, 2011 by Dennis Fulbright, Michigan State University Extension, Department of Plant Pathology, and Jill OâDonnell, Michigan State University Extension.
Flatworms lack a respiratory or circulatory system; these functions take place by absorption through the body wall. Nonparasitic forms have a simple, incomplete gut; even this is lacking in many parasitic species. Movement in some flatworms is controlled by longitudinal, circular, and oblique layers of muscle.
Annelids, unlike roundworms (or flatworms for that matter) are segmented. Roundworms only possess a reproduction system as they usually live in an organism's intestines and don't need to digest food. Annelids posses both a reproduction system, and a digestive system as well as a circulatory system. http://wiki.answers.com/Q/What_features_distinguish_annelids_from_roundworms List the defining characteristics for each class of annelid.