Gaseous Exchange


 
 
Concept Explanation
 

Gaseous Exchange

Gaseous Exchange in Unicellular Organism

In unicellular organisms, simple diffusion through body surface is sufficient for exchange of gases necessary for respiration because the cell is in continuous contact with the external environment. This exchange occur based on the partial pressure of the gas with in the body and the surrounding. If the partial pressure of  the gas is more in the body then it will diffuse out of the body and vice versa.

Gaseous Exchange in Multicellular Organism: In simple multicellular organisms like poriferans and coelenterates, respiration occurs by simple diffusion because most of their cells are in contact with external environment. But in complex multicellular organisms a respiratory system is needed for effective gas exchange because all cells are not in direct contact with external environment.

Gaseous Exchange in Humans :

In case of humans a special system called as respiratory system is required for the exchange of gases.The system consisist of lungs and trachea. We breath in atmospheric air during inhalation. The partial pressure of oxygen is more in the air inhaled. After reaching the lungs this air get transported to the blood through alveoli. In the same way when the partial pressure of carbon dioxide gas is more in the cells, than it will diffuse out into the blood flowing in the blood capillaries surrounding the cell. Blood then transfer carbon dioxide to the lungs for exhalation.

Sample Questions
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Question : 1

Gaseous exchange in plants take place through ________ and ___________ .

Right Option : A
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Question : 2

Which of the following are correct ?

(a) In unicellular organisms, simple diffusion through body surface is sufficient for exchange of gases necessary for respiration because the cell is in continuous contact with the external environment.

(b) In simple multicellular organisms like poriferans and coelenterates, respiration occurs by simple diffusion because most of their cells are in contact with internal environment.

(c) Humans a special system called as respiratory system is required for the exchange of gases.

Right Option : C
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Question : 3

The actual site of gaseous exchange in respiratory system is

Right Option : C
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