It’s function is to regulate the water content of the cell. It is also a means of excreting it's waste from the cell (out through the cell membrane) through diffusion. Amoeba regularly moves to the surface of the water, when it needs to discharge wastes and excess water. This is done via osmosis, where there is a semi permeable membrane that lets the flow of materials through the cell. Without the contractile vacuole, the amoeba may burst.
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