Question

How animals are classified based on coelom?

Answer 1

The coelom is the fluid-filled body cavity present between the alimentary canal and the body wall.

Classification:

Based on the coelom wall, the animals are divided into three types -

1. Coelomates - The animals having coeloms are called coelomates. Example - from the phylum Annelida to Chordata.
2. Acoelomates - The animals in which the body cavity i.e., the coelom is absent are called acoelomates. Example - Porifera, Coelenterata and Flatworms (Platyhelminthes).
3. Pseudocoelomates - True coelom is not present. The blastocoel is partly filled by mesodermal cells. The body cavity is lined by mesoderm only towards the body wall and mesoderm is not present towards the gut. Example - Roundworms (Aschelminthes).