Why is water useful to life on the earth?
(i) It maintains ecological balance.
(ii) It sustains life.
(iii) It is necessary for respiration in aquatic organisms.
(i) , (ii) and (iii)
Water maintains all the ecosystems on the earth. Water is considered as an universal solvent and dissolves many salts and gases. It provides the nutrients and minerals necessary to sustain physical life. The water bodies contain dissolved air (oxygen) which is necessary for respiration in aquatic organisms. It is essential for the growth of the plants and essential to carry out photosynthesis (process by which plants make their food).
In animals, water regulates the body temperature. It also serves as the medium for the metabolic functions and other chemical reactions that produce energy in the body.