Which Body System in Hydras Performs the Functions of the Circulatory

Question

Which body system in hydras performs the functions of the circulatory system?
A)Hemocoel
B)Lungs
C)Gastrovascular cavity
D)Coelom
E)Gills

Accepted Answer

Cnidarians,such as hydras,and flatworms,such as planarians,do not have a circulatory system as we have defined it.Instead,they circulate external water within their gastrovascular cavity to move substances to and from their cells.The cells are either part of an external layer,or they line the gastrovascular cavity.In either case,each cell is exposed to water and can independently exchange gases and get rid of wastes.