Question

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

• A. Disappear
• B. Increase in size
• C. Decrease in size
• D. Increase in number

Answer 1

The correct option is A Disappear

Fresh water protozoans live in hypotonic solution. Therefore, to regulate the excess water which comes into the protoplasm through the process of endosmosis, contractile vacuoles are formed.
When these protozoans are placed in marine water i.e., hypertonic water, the cell start to lose water through the process of exosmosis. Therefore, due to this loss of water, the contractile vacuoles disappear inside the cell.