Respiration in Organism


We can live without food for a week, without water a day or two, but without breathing? Not more than a minute. All of us are alive because we breathe, not just humans, but plants and animals also breathe. But how do we breathe? Let us find out below!

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What is Breathing?

Breathing is a mechanical Process. In breathing, an organism takes in oxygen from its environment and released carbon- dioxide.Breathing involves the transport of oxygen and carbon dioxide between the external environment and the body cells. This process is also called pulmonary respiration.

Organisms carry out external respiration in various ways depending on their size and environment. For example, exchange of oxygen and carbon dioxide happens directly with the environment through any cell membrane. In human beings and some animals, lungs are the chief organs of breathing.

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Types Of Breathing

The process of breathing consists of two types:

  • Inspiration or Inhalation: Taking atmospheric air into the lungs. This process is inhalation. And it depends on the pressure inside to the lungs. When atmospheric air pressure is more than the air pressure in lungs, then air enters to the lungs.
  • Expiration or exhalation: This is the process that involves discharging the air from lungs. When the air pressure in lungs increases and there’s a decrease in the atmospheric pressure then air comes out from lungs into the environment.

Breathing is the combination of Expiration and Inspiration:

Component Inhaled Exhaled Explanation
Oxygen 21% 16%  During respiration cell uses up the Oxygen.
Carbon dioxide 0.03% 4% Production of carbon dioxide occurs as a waste product of respiration.
Nitrogen 78% 78% Cells do not use nitrogen gas.
Water Variable High Some of the water evaporates and is lost as air which is breathed out



Comparison Between Breathing and Cellular Respiration

S.No Breathing Cellular respiration
1.. It is a physical process in which oxygen is taken in and carbon dioxide is given out. It is a biochemical process in which glucose is oxidised to carbon dioxide and water.
2. It consumes energy. It liberates energy.
3. It is an extracellular process It is an intracellular process.
4. Enzymes are not used in this process. Enzymes are used in this process.

How Do We Breathe: Respiration

Breathing is the process that involves taking atmospheric air into lungs, where an exchange of gases and foul air occurs which is eventually expelled out from the lungs. The main muscles during respiration or breathing are Intercostal (external) muscles and diaphragm. Larynx does not contribute to the breathing movements.


  • The muscles of a rib (intercostal) and diaphragm are responsible for intake and output of air from lungs.
  • Inspiration is the result of muscle contraction so it is an active process.
  • During inspiration, the diaphragm and external intercostals muscles contract simultaneously. Muscles move the lateral thoracic walls outward and upward.
  • To take in the air into lungs, the diaphragm must be flattened.
  • Expiration is the result of muscles relaxation so it is a passive process.
  • During expiration, the diaphragm and external intercostals muscles relax simultaneously. Muscles move the lateral thoracic walls inward and downward which result in the exhalation of air.

Breathing rate is lowest while we are sleeping. During normal breathing, the respiratory movements occur about:

Age Rate
Newborn child 32/min
5-year-old 26/min
25-year-old 16/min
50-year-old 18/min

Question For You

Q. When is the breathing rate at its lowest?

Sol: The breathing rate is at its lowest during the night because our body is in rest at night.

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