Question

How useful is the study of the nature of body cavity and coelom in the classification of animals?

Answer 1

Hint: The two aspects, body cavity and coelom are very important for the classification of animals. The diploblastic and triploblastic animals can be identified keeping these two criteria in mind. A body cavity is a space filled with fluid that does the work of protection for the internal organs. Coelom lies between the intestinal canal and the body wall.

Complete answer:
- There are different phylums of animal kingdom such as Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata and Chordata.
- The body cavity that is lined by the mesoderm is termed as a coelom. The presence or absence of body cavity or coelom is vital for classifying animals.
- The coelomate animals belong to the phylum Annelids, Arthropods, Mollusca, Echinodermata, Hemichordata and Chordata. They possess a cavity filled with fluid between the body wall and digestive tract. The Porifera, Coelenterata, Platyhelminthes and Nematoda are acoelomates that means that they do not possess coelom.
- There is also a term called pseudocoelom where the body cavity is not lined by mesoderm but the mesoderm is present as scattered pouches between the germ layers ectoderm and endoderm. The examples of such animals are Aschelminthes.

Note: There are many advantages of having a coelom. It helps in distribution of hormones, food, wastes and other things from one end to the other end of an organism. Coelom acts as a protection layer for all the internal organs. Coelom also gives rise to the muscles that surround the gut. This enhances the digestion process because muscles help the food to be pushed through the digestive tract.