AP Board Class 10 Biology Chapter 2 Respiration

The energy that we intake is only available to us after it is broken down through a process known as respiration. In AP Class 10 Biology chapter 2 Respiration, we discuss how the body draws out nutrients from the food taken through the process of respiration.

What is Respiration?

Respiration is a process by which living organisms produce energy from the food consumed. It is a very complex process involving several Biochemical and Physical processes. Following the flowchart shows the sequence of processes that occur during respiration.

AP Board Class 10 Biology Chapter 2 Respiration

Pathway of Air

  • Air enters the body through nostrils. Here, the air is humidified and warmed.
  • Air can also be intake through the mouth.
  • These two openings of the airway meet at the pharynx.
  • The pharynx is part of both digestive and the respiratory system because it carries both food and air. The bottom of the pharynx is divided into two pathways, one for food and the other for air. The epiglottis, a small flap of tissue, covers the air passage when we swallow food preventing the food from going into the lungs.
  • The windpipe channels the air into the lungs.
  • The lower end of the windpipe is divided into two bronchi – each leading to each lung.
  • The bronchi are further divided into smaller branches known as bronchioles.
  • These finally terminate in clusters of air sacs called alveoli in the lungs, which are very small and numerous.

The whole passage from nostrils to alveolus is moist and warm.

Types of Respiration

There are two types of respiration as follows:

  • Aerobic Respiration – Occurs in an adequate supply of air, producing a lot of energy, carbon dioxide and water.
  • Anaerobic Respiration – Occurs in inadequate supply or absence of oxygen to produce energy.

In the next section, let us look at a few chapter questions, to better understand the concepts explained in the chapter.

Class 10 Biology Respiration Chapter Questions

  1. Why does a deep sea diver carry an oxygen cylinder on her back?


Human beings are adapted for terrestrial habitat and hence their respiratory system can utilize oxygen only in the gaseous state. In aquatic habitat, organisms utilise oxygen, which is dissolved in water. As humans cannot utilize dissolved oxygen deep sea divers have to carry oxygen cylinders.

2. Food sometimes enters the windpipe and causes choking. How does it happen?


The epiglottis acts as a door preventing the food from entering the windpipe. When we talk while we eat, the epiglottis fails to stop the food from passing the windpipe which in turn results in choking.

3. What do you mean by Respiratory system?

Solution: Respiratory system mean the passages that transport air to the lungs and to the microscopic air sacs in them, called alveoli (where gases are exchanged between them and blood vessels) and vice versa.

4. What is inspiration(inhalation)?

Solution: When the diaphragm flattens and the volume of the chest cavity is increased, its internal pressure decreases and the air from the outside rushes into the lungs. This is inspiration (inhalation).

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