Question

When fresh water protozoan placed in marine water then ,why its contractile vacoule disappear?

Answer 1

Contractile vacuole's job is to throw excess of water coming from outside to inside. In marine water, due to ex osmosis cell start loosing water anyway, means now there is need to preserve water not to throw it away...that’s why contractile vacuole will disappear because presence of contractile vacuole will dehydrate the cell.