Question

Contractile vacuole in protozoan Amoeba is meant for

• A. Respiration
• B. Excretion
• C. Locomotion
• D. Osmoregulation

Answer 1

The correct option is D Osmoregulation

Amoeba is a eukaryotic shapeless mass of cytoplasm with suspended nucleus and other organelles. It is characterized by formation of cytoplasmic extensions, known as pseudopodia that serve in locomotion and phagocytosis. Thus, option C is incorrect. The waste products of Amoeba are disposed off in surrounding water by the process of simple diffusion through its cell membrane/ body surface. Amoeba exhibits cutaneous respiration wherein exchange of gases takes place via cell membrane which is the general body surface of organism. This makes option A incorrect.

Contractile vacuole serves in osmoregulation to counteract the constant inflow of water from surroundings into the body by the process of osmosis through the general body surface. Owing to higher solute concentration of cytoplasm as compared to the surrounding watery medium, water enters the body, which in turn causes increase in size of contractile vacuole. The endoplasm of contractile vacuole contains urea, carbon dioxide and excess water which are then disposed off in surrounding water. Thus, contractile vacuoles serve in both excretion and osmoregulation, though osmoregulation is its primary function. This makes option B incorrect and D correct.