How useful is the study of the nature of body cavity and coelom in the classification of animals?
Coelom is the gap between gut and body wall. Coelom is the characteristic feature of complex or higher animals while lower animals like Platyhelminthes are acoelomate. The absence of coelom indicates that the animal is yet to develop a functional division of labour to carry out various activities. So the coelom characterises complexity of the animals and represents organic evolution. There are three types of coelom (i) Acoelom – It means absence of body cavity which is due to the failure of mesoderm to cavitate during embryogency, so there is no coelom, no peritonium. ex-porifera, colenterata, etc (ii) Pseudocoelom — It means presence of coelom that develops from the blastocoel but not lined by mesoderm, ex-nematodes, etc. (iii) Eucoelom – It means hue coelom, which is lined by mesoderm resulting in tube within -tube design. ex- higher invertebrates, chordates, etc.
