Question

where do contratile vacuoles occur

Answer 1

In certain organisms, usually single-celled organisms lacking a cell wall, there exists a special kind of vacuole, called a contractile vacuole. A contractile vacuole works just the same as the name suggests, in that it expands and contracts. The point of the contractile vacuole is to pump water out of the cell through a process calledosmoregulation, the regulation of osmotic pressure. It occurs in freshwater protists, but mainly in the kingdom Protista as a whole.