Respiration in Organisms Class 7 Science Notes - Chapter 10

Breathing vs. Respiration


  • Respiration is the process of gaseous exchange in an organism.
  • Respiration at a cellular level, however, refers to the burning of food to obtain energy.

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  • Breathing is the process of taking in oxygen and giving out carbon dioxide by the organism.
  • Every organism has their own methods to breath.
  • In humans, it is done by the lungs.
  • In organisms like fishes, it is done by gills.

For More Information On Mechanism of Breathing, Watch The Below Video:

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Process of respiration

  • The oxygen in the lungs is taken up by the blood.
  • This oxygen is then transported to all parts of the body.
  • Blood gives up oxygen to the cells and takes up carbon dioxide, which is sent back to the lungs.


  • Diffusion is the process of movement of molecules from the area of its lower concentration to the area of its higher concentration without any application of energy.
  • Diffusion is what happens when you put a drop of ink in water and it slowly mixes with the water uniformly.
  • The same principle is used for the exchange of gases (breathing) in the animals.

Cellular respiration

  • When the cells obtain oxygen from blood, they use up this oxygen to burn the food.
  • Burning of food releases energy which is stored in the form of ATP.
  • Thus respiration at the cellular level is burning of food using oxygen to get energy.

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Aerobic vs. Anaerobic

Aerobic respiration

The type of respiration in which organisms use oxygen for burning food inside the cell is called aerobic respiration.

Anaerobic respiration

Respiration in a cell in the absence of oxygen is called anaerobic respiration.

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How Do We Breathe?

Components of the respiratory system in humans

The respiratory system of the humans have several parts; Nasal chamber, pharynx, larynx, trachea, bronchi, lungs, diaphragm.

The process of respiration in humans

  • Respiration in humans starts with the breathing of air through the nose leading to the oxygen to be transferred into the bloodstream by the lungs.
  • This oxygen is delivered to all the cells, which uses them to burn glucose and generate energy.

Respiration in other organisms

  • Respiration in other organisms is carried out by special organs.
  • Frogs and earthworm use their moist skin, fishes use gills and insects have spiracles.

Gaseous exchange in plants

  • Gaseous exchange in plants occurs through stomata in leaves and through root hair in roots.
  • The woody stems of plants have lenticels too for the exchange of respiratory gases.

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