The amoeba lives in fresh water bodies like lakes, slow moving streams and ponds. Amoeba excretes excess carbon dioxide, water and ammonia. Ammonia is excreted across the cell membrane although it can also be excreted by the contractile vacuole when it dissolves in water.
Carbon dioxide is excreted by diffusing across the cell membrane. Osmoregulation is achieved by the contractile vacuole. The excess water collects in the contractile vacuole and then it migrates and fuses with the cell membrane hence releasing the water to the outside.