Respiration in Plants

1.  What is the common mode of respiration in green plants?

Common mode of respiration in green plants is aerobic respiration.

2.  Name the part of plant that is involved in exchange of gases.

Stomata present on the surface of leaves.

3.  How does exchange of gases occurs in plants?

Exchange of gases in plants takes place by the process of simple diffusion. The large inter-cellular spaces ensure that all cells are in contact with air.

4.  List the factors on which the direction of diffusion of gases in plants depends.

The factors on which the direction of diffusion of gases in plants depends are:
1. Environmental conditions like presence or absence of light
2. Plant requirements.

5.  Explain how the direction of diffusion of gases in plants varies depending upon the environmental conditions and the requirements of the plants.

Exchange of gases at night:

At night in absence of light, the process of photosynthesis slows down. Thus, the requirement of CO₂ reduces.  The major exchange activity during night is therefore removal of carbon dioxide and intake of oxygen for the process of respiration.Exchange of gases at day:

During daytime requirement of CO₂ increases for the process of photosynthesis. The CO₂ produced during respiration also gets used up for photosynthesis, hence there is no CO₂ release. The major exchange activity during day is therefore removal of oxygen and intake of carbon dioxide for the process of photosynthesis.

                                        Respiration in Animals

1.  How do multicellular organisms ensure the process of exchange of gases during respiration?

Multicellular animals have evolved different organs like gills and lungs for the uptake of oxygen from the environment and for getting rid of the carbon dioxide produced.

2.  How do aquatic animals exchange gases?

Aquatic animals use oxygen dissolved in water for respiration.  In these animals, water is constantly taken in and is exposed to the respiratory surface.  As the water moves over the respiratory surface, oxygen diffuses in and carbon dioxide diffuses out of the blood.  Water is then forced out of the body.

3.  Why is the rate of breathing in terrestrial animals slower than aquatic animals?

Amount of dissolved oxygen in water is fairly low as compared to amount of oxygen in the atmosphere (air).  So in order to increase the absorption of oxygen, aquatic animals have faster rate of breathing as compared to terrestrial animals.

4.  What are the characteristics of respiratory organs in animals that ensures efficient exchange of gases?

Respiratory organs of animals show following characteristics:
(i) The structure of these organs is such so as to provide large surface area for exchange of gases.
(ii) Respiratory organs are richly supplied with blood vessels for efficient gas exchange.
(iii) Respiratory surfaces are very thin and delicate to facilitate easy diffusion of gases.

5.  Why are respiratory organs usually placed inside the body of the terrestrial animals?

Respiratory organs are placed inside the body to prevent injury to thin and delicate respiratory surfaces.