Question

............ system acts as excretory system in echinoderms.

Answer 1

Echinoderms lack specialized excretory (waste disposal) organs and so nitrogenous waste, chiefly in the form of ammonia, diffuses out through the respiratory surfaces. The anus though is located in most echinoderms and is used for the jettison of waste as well. The chief way in which the respiratory system operates though is primarily on an exchange of gases and liquids. This is one example in which a system of an organism provides the multiple functions.