Science Chapter 06: Respiration in Organisms

Class 07 Science NCERT

Respiration is essential for survival of living organisms. It releases energy from the food. The oxygen we inhale is used to breakdown glucose into carbon dioxide and water. Energy is released in the process.

The breakdown of glucose occurs in the cells of an organism (cellular respiration). If the food is broken down with the use of oxygen, it is called aerobic respiration.

If the breakdown occurs without the use of oxygen, the respiration is called anaerobic respiration. During heavy exercise when the supply of oxygen to our muscle cells is insufficient, food breakdown is by anaerobic respiration.

Breathing is a part of the process of respiration during which an organism takes in the oxygen-rich air and gives out air rich in carbon dioxide. The respiratory organs for the exchange of gases vary in different organisms.

During inhalation, our lungs expand and then come back to the original state as the air moves out during exhalation. Increased physical activity enhances the rate of breathing.

In animals like cow, buffalo, dog and cat the respiratory organs and the process of breathing are similar to those in humans.

In earthworm, the exchange of gases occurs through the moist skin. In fishes it takes place through gills and in insects through the tracheae. In a plant the roots take in air present in the soil. Leaves have tiny pores called stomata through which they exchange gases. The breakdown of glucose in the plant cells is similar to that in other living beings.