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.
Cnidarians are the one of the most simplest of organisms and they do not have a closed or open circulatory system,.Their circulatory system does not have any circulatory vessels. They mostly use diffusion as their means of circulating materials through their bodies.oral does not have a circulatory system. Coral's stomachs mainly serve as the circulatory system because of its gastrovascular system. The many species of fish that live symbiotically with the coral also aid in the circulation of materials, oxygen, and nutrients for coral.