Question

Why marine protozoa donot have contractile vacuole?

Answer 1

contractile vacuole os ised ro store and remove the excess water due to endosmosis. marine protozoa have hypertonic external environment . so they doesn't have contractile vacuole

Answer 2

Marine protozoa donor have contractile vacuole because they are surrounded by a hypertonic medium or sea water. Contractile vacuole is used to remove excess waste which otherwise may cause the cell to burst.This waste comes from the process of endosmosis.But since they are surrounded by a hypertonic medium they don't have the problem of endosmosis and hence donor have contractile vacuole.  Hope this helps