Question

When a freshwater protozoan is placed in marine water

• A. The contractile vacuoles become bigger in size
• B. The contractile vacuoles disappear
• C. The number of contractile vacuoles increases
• D. The contractile vacuoles remain unchanged

Answer 1

Answer: (B)

When a freshwater protozoan is placed in marine water, the contractile vacuoles disappear. The function of contractile vacuole is to remove the excess water outside by the process of osmoregulation. In marine water, it is necessary to retain the water inside the body instead of out expelling it out. If contractile vacuoles will not disappear, the cell will get dehydrated.

Thus, the correct answer is option C.