Question

Entamoeba histolytica differs from Amoeba in absence of

• A. Pseudopodia
• B. Contractile vacuole
• C. Nucleus
• D. Ectoplasm

Answer 1

The correct option is B Contractile vacuole

Contractile vacuoles, common in freshwater Protozoa, eliminate water that moves into the cells by osmosis. The contractile vacuole is present in amoeba but absent in Entamoeba because Amoeba lives in water and needs osmotic regulation. The contractile vacuole is basically a water bubble within the endoplasm of A. proteus. Its function is to regulate the water content of the cell. It is also a means of excreting its waste from the cell (out through the cell membrane) via diffusion. E. histolytica doesn't need to have a contractile vacuole as it lives in an isotonic environment. Since the osmotic concentration of its body remains equal to its surroundings entry of water through osmosis will not happen. Therefore, there is no need of contractile vacuole. Thus, the correct answer is B.