Question

When a fresh-water 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.

Answer 1

When a fresh-water protozoan possessing a contractile vacuole, is placed in a glass containing marine water, the vacuole will:

(b) disappear

Contractile vacuole is responsible to throw excess water that comes from outside to inside the cell. In presence of marine water, due to exosmosis cell start losing water. So, there is a need to preserve water. In that situation, the presence of contractile vacuole will dehydrate the cell. So, contractile vacuole will be disappeared.