[Biology Class Notes] on Functional Significance of Respiration Pdf for EXAM

What is Respiration?

The cell is the basic unit of life in our body. They carry out almost all the functions in the body such as nutrition, excretion, transport, and reproduction. To perform all these functions, cells require energy. This energy is provided by the food that we eat. The food has energy stored in it in the form of various macromolecules. This energy is released by the process of respiration. For respiration, we breathe in oxygen. The oxygen we inhale is transported to different parts of the body and ultimately the cells. Inside the cells, oxygen helps in the breakdown of food consequently releasing energy. This process of breakdown of food to obtain energy is known as cellular respiration.

Thus, to perform various activities energy is required. The energy is acquired by the process of respiration which is obtained by the breakdown of food.

Why Do We Respire?

We respire to live by obtaining energy and other necessary gases, heat, which are crucial for the survival of a being. Our body is in constant need of oxygen. It is the major element that brings about the breakdown of molecules. Inside the cells, the food is broken down into water and carbon dioxide with the help of oxygen.

• When food is broken down in the presence of oxygen, the process is called aerobic respiration.

• When the food is broken down in the body in the absence of oxygen, it is called anaerobic respiration.

During the process of manufacturing energy molecules- ATP, waste bi-products are generated within the cell. The gaseous waste generated during respiration is Carbon dioxide. This waste in the form of carbon dioxide is also expelled from the body by the process of respiration.

Respiratory Organs of the Animals

Humans have a specialized and highly developed organ system for respiration that comprises the lungs. But various other animals respire through various other respiratory organs, which we will discuss in detail.

Respiration is a process of exchanging gases and it remains similar in all organisms. Ode of respiration could be external or internal, or it may be aerobic or anaerobic. Following are the classes of organisms depending on their mode of respiration-

1. Respiration through Plasma Membrane

All unicellular organisms respire through their plasma membrane. In these organisms, the exchange of gases takes place through the surface of the cell. They take in oxygen from the surrounding and give out carbon dioxide from the cell surface or the plasma membrane by the process of diffusion. 

Example- Amoeba

 

2. Respiration through Skin

Tapeworms, earthworms, and leeches respire through their skin. The skin of Earthworms is very thin and moist and many blood cells are spread on this skin. These blood cells are also known as capillaries. These capillaries carry out the gaseous exchange. This is why earthworms die of suffocation when their skins dry up.

 

3. Respiration through Trachea

In some insects, the transportation of gases or the gaseous exchange takes place with the help of special fine tubes called tracheae. Oxygen enters through spiracles into the tracheal tubes, diffuses into the body tissue, and reaches every cell in the body. Finally, the Carbon dioxide released from the cells goes into the tracheal tubes and comes out through spiracles. 

Examples- Cockroaches, grasshoppers, etc.

 

4. Respiration through Gills

Most of the aquatic animals like fish and prawns breathe through special respiratory organs called gills. Gills are projections of the skin that contain blood vessels that help in the exchange of gases. They take up the oxygen dissolved in water. To carry out respiration, fishes gulp water through the mouth and pump it over the gills. Through the gill slits, water passes into the gill chamber and in each chamber, the water passes over the filaments. They absorb oxygen from the water and replace it with carbon dioxide.

 

5. Respiration in Amphibians

Amphibians are peculiar organisms; they use more than one organ of respiration during their lifecycle. They have gills in their tadpole phase for respiration and as they mature, they respire through lungs as well as skin. 

Example– Frogs.

 

6. Respiration through Lungs

Many mammals, amphibians, and birds respire through lungs. Lungs are air-filled sac-like structures in the chest cavity that are connected to the outside by a series of tubes and small openings.

Example- Humans, birds, monkeys, etc.