STD 11 - 8. Cell the unit of life — BIOLOGY STD 11 Science — Question

a
Contractile vacuole is a sub-cellular structure (or organelle) which is found primarily in protists (for eg, Amoeba) and unicellular algae. Contractile vacuole is responsible for excretion and osmoregulation. It absorbs excess water and wastes from a microorganism's cell and excretes them into the environment by contracting. Contractile vacuoles function in a periodic cycle by expanding while collecting water and contracting to release the water.