What are respiratory organs in animals? - Learning concepts
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The Animal World

Concept: Respiratory Organs in Animals

Breathing and Respiration:

Before we learn about the respiratory organs in animals, let us have a brief idea about breathing and respiration.

  • The chemical process by which energy is released in the cells due to the breakdown of food is called respiration.
  • The energy released during respiration is utilised to perform all bodily functions.
  • The physical process of inhaling oxygen from the air and exhaling carbon dioxide in the environment is called breathing.
  • The oxygen inhaled during breathing is responsible for the breakdown of food in the cells and subsequent release of energy, i.e., the oxygen we breathe in actually facilitates cellular respiration.
  • The respiratory system in a living organism involves a set of organs working together to help the process of breathing.
  • However, the set of organs is different for different animals based on the complexity of their body. Let us talk about them one by one.


  • Amoeba are single-celled organisms belonging to the group Protozoa. They have a very simple body organisation.
  • They do not have specific organs for the process of respiration.
  • Exchange of gases in amoeba occurs by the process of diffusion across the cell membrane.
  • The oxygen gas dissolved in the surrounding water diffuses through the cell membrane and is utilised by the cells to break down complex food materials and liberate energy.
  • Other members of the Protozoa group who have similar respiratory systems are Hydra and Paramecium.


  • In insects, the air is drawn in and out of the body through openings called spiracles. These openings are present on the body surface.
  • Spiracles take the air to tube-like structures called the trachea located in the abdominal cavity.
  • From the trachea, the air moves into smaller tubes called tracheoles that are present throughout the body.
  • As a result, oxygen gets distributed to all the parts of the insect’s body.


  • Fish and many other aquatic animals have special organs called gills.
  • The gills allow fish to breathe underwater.
  • Through these gills, oxygen dissolved in the water enters the body, and carbon dioxide is expelled from the body by the process of diffusion.


  • Earthworms do not have specialised respiratory organs.
  • They take in the atmospheric oxygen and expel carbon dioxide through their moist skin.
  • Oxygen diffuses through the earthworm’s body surface and spreads across the body via a network of capillaries.


  • Frogs are amphibians, i.e., they can survive both on land and in water. So, their bodies have evolved to breathe both in terrestrial and aquatic habitats.
  • They use their moist skin for breathing in water and lungs to breathe on land.
  • Frogs in the larval stage (tadpole) use gills for breathing.

Mammals and Birds:

  • Mammals are terrestrial and use lungs for breathing.
  • Birds also use their lungs for breathing.
  • Exchange of oxygen and carbon dioxide in the lungs takes place in millions of tiny air sacs.
  • These air sacs are called alveoli in mammals and atria in birds.

Respiratory System of the Human Body:

  • Respiration occurs through the respiratory system which involves a group of organs that help oxygen reach the blood vessels and also facilitate the expulsion of carbon dioxide from the body.
  • The organs of the respiratory system in man are—Nose, Nasal cavity, Mouth, Pharynx (throat), Larynx (voice box), Trachea (windpipe), Bronchi, Bronchioles, Lungs, and Alveoli.
  • Nature-1

The path followed by the oxygen gas as it enters the respiratory system is as follows:


The exchange of gases occurs in the alveoli, from where oxygen is transported to the blood and then carried to the whole body.

New Words:

Diffusion: The movement of oxygen, nutrients, and other molecules across membranes (Note: Membranes are barriers that allow some things to pass and stop others).

Larval stage:A developmental stage in a living organism’s life cycle before it reaches the adult stage.


  • Whales and dolphins breathe through gills.
  • Whales and dolphins are aquatic mammals and breathe through their lungs just like terrestrial mammals. They come to the surface of the water for the exchange of gases.

  • Animals do not have respiratory disorders.
  • Animals are also affected by respiratory disorders like asthma and pneumonia. These disorders are quite common in cats and horses.

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