AP BIOLOGY

Detailed explanation-1: -Osmoregulation in unicellular freshwater organisms like amoeba and paramecia involves an organelle called the contractile vacuole, which collects excess water as it accumulates in the cell and pumps it out.

Detailed explanation-2: -So, the correct answer is ‘Contractile vacuole’.

Detailed explanation-3: -The contractile vacuole is required in freshwater amoebae because freshwater has a lower concentration of solutes than the amoeba’s own internal fluids. In freshwater amoeba, if the contractile vacuole is missing, the cell will fill up with water and finally rupture.

Detailed explanation-4: -The contractile vacuole in Paramecium helps in osmoregulation in Paramecium, which helps in survival. The cytoplasm of the Paramecium consists of higher concentration of solutes than the surrounding environment. The cytoplasm absorbs the water by osmosis. The excess water gets collected inside two contractile vacuoles.

Detailed explanation-5: -The contractile vacuole helps in the process of osmoregulation which is the maintenance of water and salt balance. It can be observed in unicellular organisms such as Paramecium and Amoeba. They use contractile vacuoles to collect excess water and expel it out of the body.