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.
Earthworm. An earthworm is one of the animals that are classified in the Annelida phylum. Like many other animals, the earthworm has a closed circulatory system. A closed circulatory system means that the blood is confined to blood vessels and its blood recirculates so it gets maximum use. The worm uses its bodies suface area to absorb oxygen from the soil instead for using lungs or gills.