When a freshwater protozoan possessing a contractile vacuole is placed in a glass containing marine watre, the vacuole will

Options

A. increase in number
B. disappear
C. increase in size
D. decrease in size

Answer

D

Explanation

(b) Fresh water protozoans live in hypotonic environment so, for regulation of excess of water which comes in the protoplasm through the process of endosmosis, contractile vacuoles have developed. When these protozoans are placed in marine water, i.e. hypertonic water, the contractile vacuoles become disappear because the proce4ss of endosmosis does not occur and thus, water does not come in the protoplam.