Question

(a) Name the phenomenon which helps fresh water unicellular organisms (e.g. Amoeba) continuously gain water in their bodies. Also name the mechanism by which these organisms throw out excess water from their bodies.
(b) Give atleast two examples in plants where similar phenomenon is used to gain water.

Answer 1

This process is known as osmoregulation.
The contractile  vacuole of amoeba, slowly fills with water from the cytoplasm and while fusing with the cell membrane it quickly contracts releasing the excess water to the outside by exocytosis. This process regulates the water present inside ameoba. 

Answer 2

a) The phenomenon that helps fresh water unicellular organism such as amoeba to continuously gain water in their bodies is due to osmosis.

These organisms have contractile vacuoles to throw out excess of water from their bodies.

b) i. By the process of osmosis, the plant roots can absorbs water from the soil through root hairs.

ii. In plants, cells, tissues and soft organs like leaves, young shoots, flowers etc maintain turgidity due to osmotic absorption of water.