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.
Flatworms. Flat worms are soft-bodied invertebrate animals from the platyhelminthes phylum. They take in oxygen but have no formal respiratory system. This is because they are very simple animals.They went through such small evolution that they never developed a complex respiratory system.lat worms are soft-bodied invertebrate animals from the platyhelminthes phylum. They take in oxygen but have no formal respiratory system.