When a freshwater protozoan possessing a contractile vacuole, is placed in a glass containing marine water, the vacuole will (a) increase in number (b) disappear (c) increase in size (d) decrease in size.
Option D Amoeba is a fresh water protozoan containing contractile vacuole that is meant for osmoregulation. When Amoeba is placed in a marine water, then the water from the contractile vacuole will move out resulting in decrease in size of it. Contractile vacuole will increase in size if it is placed in hypotonic solution. Water will enter into contractile vacuole, thus increasing its size and ultimately it will burst and disappear.