Question

Which gas in the atmosphere is essential for respiration?

Answer 1

Hint: During breathing, living organisms inhale oxygen and exhale carbon dioxide. This process serves as a medium of obtaining the input and output respectively of the respiration process. During respiration, oxygen is used to break down food to release carbon dioxide and energy.

Complete step by step answer:
Living organisms obtain energy for sustaining their life and doing work from food. The process of the breakdown of the food to produce energy in the cells of the body is known as respiration. In respiration, food is broken down into energy and carbon dioxide with the help of oxygen. This is a kind of combustion process in which the food acts as the fuel.

The oxygen that is required is inhaled by organisms and the waste product of respiration, that is, carbon dioxide is exhaled.

Hence, the gas in the atmosphere that is essential for respiration is oxygen, since it is the driver of the respiration process.

Additional information:
Oxygen is essential for respiration only in certain organisms that undergo aerobic respiration. Other organisms like some bacteria live in environments where there is a scarcity of oxygen. Such organisms perform anaerobic respiration. They usually substitute oxygen with other sources such as sulphur dioxide, etc. Usually, anaerobic respiration is also not as efficient as aerobic respiration and a lot less energy is released.

The human body also undergoes anaerobic respiration when there is excessive working of the muscles, usually during exercise. Lactic acid is broken down in our muscles in the absence of oxygen. The accumulation of lactic acid in muscles causes cramps, fatigue and pain in muscles.

Note: Students must not confuse breathing with respiration. Breathing is only a physical process of inhaling oxygen and exhaling carbon dioxide, but respiration is a biochemical process involving the breakdown of food into energy and carbon dioxide using oxygen.
Students must also be careful about whether the question asks for anaerobes (organisms that perform anaerobic respiration) or not. For anaerobes, oxygen is not the essential atmospheric gas for respiration.