Question

When a fresh water protozan is placed in marine water

• A. The contractile vacuole disappears
• B. The contractile vacuole increases in size
• C. A number of contractile vacuoles appear
• D. The contractile vacuole remains unchanged

Answer 1

The correct option is A The contractile vacuole disappears

Contractile vacuoles are membrane-bound organelles that pump excess water out of the protozoan. When the freshwater protozoan is placed in a marine environment it loses water due to exosmosis as salt concentration is high outside. The contractile vacuole disappears to prevent the loss of water from the organism because in the presence of contractile vacuoles the cell will be dehydrated.

Thus the correct answer is option A.