Question

An amoeba, placed in medium with more salts than usual develops

• A. Many contractile vacuoles
• B. Small contractile vacuole
• C. Large contractile vacuole
• D. No contractile vacuole

Answer 1

The correct option is D No contractile vacuole

In the freshwater environment, water is constantly moving into the Amoeba, because it contains more concentrated solutes than its environment. The amoeba collects the excess water in the contractile vacuole which expels the excess water. As an amoeba moves into the brackish environment, the net water movement into the amoeba will slow (as compared with the freshwater environment). The contractile vacuole will contract less frequently. As the amoeba enters the seawater environment, the net water movement will be from the paramecium to the environment. Water will move out of the cell, and the cell will shrink and so the vacuole. Thus the correct answer is option D.