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The contractile vacuole allows free-living protists to expel extra water. <b>The contractile vacuole allows free-living protists to expel extra water <br /></b>.
Merge this question into. Split and merge into it. Answer by Neodarwinian. Confidence votes 22.7K. Living in fresh water, a hypotonic environment, causes water to enter the cell of certain protists (protozoa) and would lysis the cell unless there were a way to expel this water. This is what contractile vacuoles do.