Question

Two species of Amoeba X and Y were kept in fresh water and got adapted. Species X developed contractile vacuole. When both were transferred to sea water and got adapted, both X and Y lost their contractile vacuole. From these observations, we conclude that

• A. Both X and Y are marine species
• B. Species Y is marine and X is fresh water
• C. Species X is marine and Y is fresh water
• D. Both X and Y are fresh water

Answer 1

Answer: (C)

To regulate osmotic pressure, most freshwater amoebae have a contractile vacuole which expels excess water from the cell. This organelle is necessary because freshwater has a lower concentration of solutes (such as salt) than the amoeba's own internal fluids (cytosol).

So from the above experiment, we can easily conclude that Amoeba X is marine that's why it had no vacuole and developed contractile vacuole when placed in freshwater while Amoeba Y already had contractile vacuole, that means it is a freshwater amoeba.

So the correct answer is option C.