Question

The diagonostic character of echinoderms is

• A. Presence of canal system
• B. Presence of ambulacral system
• C. Presence of parapodia
• D. Presence of flame cells

Answer 1

The correct option is B Presence of ambulacral system

Echinoderms are the organisms which have radial symmetry. They are generally marine. The body cavity contains a system of water-filled canals. This is the unique feature of echinoderms. This type of system is called as the ambulacral system. It connects with the tube feet. The canals in the tube feet are the extensions of the body wall that generally protrude through holes in the skeleton. The regions with such pores are called as ambulacra. The water-vascular system consists of a circular passageway which is called the ring canal. This canal surrounds the digestive tract and five radial canals. Each radial canal underlies an ambulacral area. The ring canal is connected to a porous plate in body wall which is known as the madreporite. Sea water enters the system through the madreporite, which is regulated by the animal and thereby the circulation occurs. The tube feet are very thin-walled. This makes the surface of the tube feet suitable for the diffusion of oxygen into the body cavity and the diffusion outward of carbon dioxide and wastes.

Thus, the correct answer is option A.