Osmoregulation :
Amoeba is a fresh water animal, hence water enters into the body constantly by endosmosis. Simultaneously. Amoeba constantly expels out the water with the help of contractile vacuole. It is called as osmoregulation.
Initially, a small CV develops near the nucleus by the fusion of some water droplets and it grows gradually due to further fusion of these water droplets. This process is called as diastole. When the CV attains complete size, it moves towards outside and on contact with plasmalemma it bursts suddenly to release the water outside. It is called as systole
