(a) In which groups of non-chordates would you find closed circulatory system ?
(b) Why is closed circulatory system advantageous ?

Explanation

(a) Some annelids (e.g., earthworm) and certain molluscs (e.g., the cuttle fish) have closed circulatory system.
(b) The closed circulatory system has a double advantage over circulatory system :
(i) It generates sufficient blood pressure to maintain far more rapid flow of blood than the open circulatory system. The blood completes its circulation around the body in a much shorter time to supply useful materials to tissues and removal of wastes products from them.
(ii) Arterial musculature and precapillary spincters regulate the flow of blood to the organs according to their needs in closed circulatory system.