Question

How can the symmetry and the nervous system be described in echinoderms?

Answer 1

Ans. Symmetry: Echinodermata is the class which is known for its radial symmetry. The radial symmetry represents by the equal distribution of body structure around a central point. But this is present only in adult echinoderms including Cniderians. However in the larval stage is bilateral and the adult shows the secondary radial symmetry. Some exceptions are there having lateral symmetry of body. Poriferans do not have defined symmetry.

Nervous system: There is no formation of head in the Echinodermata that is they do not present cephalization. There is presence of a diffused meshwork of nerves and neurons. There is a neural ring surrounding the mouth and a radial nerves splitting into branches along with the pentaradial symmetry of the body of echinoderms.