Why do we need energy?

Hint: Every organism present on this planet, whether it is a plant, animal or a microorganism - requires a continuous supply of energy. This energy obtained from the sun is interconverted to various forms and is utilised by the organism. The plants convert the solar energy into chemical energy which is taken up by the other living beings as food.

Complete answer:
We know that the sun is the ultimate source of energy. We living beings rely on the sun directly or indirectly.
Energy is obtained from the food an organism eats via the processes of digestion, absorption and assimilation in the body. The energy that can be utilised is in the form of ATP.

The energy supplied from the food is used to maintain the essential functions of the body like respiration, water regulation, beating of the heart, maintaining the body temperature etc. These functions are essential in the sense that an organism’s survival depends on them and without these, it may die. These functions are usually involuntary by nature.

Energy is also required to enable organisms to do physical activity. This includes all forms of movements of different body parts as well as locomotion. As the physical activity of an organism increases, the demand for energy that is required by the body also increases.

Energy is required for the growth of an organism. These may be during specific periods like infancy, childhood as well as adolescence when there are several changes taking place in the body of an individual.

Note: Organisms are also capable of storing energy as reserves for times when the resources are limited. Our body is constantly in the process of wear and tear and thus requires a continuous system of repair in place. This, in turn, also requires energy.