Question

$CO_2$ and $O_2$ balance in the atmosphere is due to
A)Photosynthesis
B)Respiration
C)Leaf anatomy
D)Photorespiration

Answer 1

Oxygen is the most vital element present on earth which supports all life forms. The atmosphere contains around 21% of oxygen. The carbon dioxide is present in the atmosphere whose composition is around 0.03%. These both gases play an important role in sustaining the living forms.

Complete answer:
To solve this question, we must know about the physiological processes in the living organisms.

All the living organisms require oxygen for respiration. Respiration is the process by which the food or glucose is oxidised or broken down to liberate energy in the form of ATP. The process of respiration involves taking in oxygen and giving out of carbon dioxide. This process is universal to all plants, animals and other living beings (except anaerobic organisms).

If only respiration was the process then the percentage of oxygen in the air would be depleted and carbon dioxide would have been high. An important process is carried out by the plants which utilises carbon dioxide and liberate oxygen is photosynthesis. In this the plants prepare carbohydrates by taking in carbon dioxide from the atmosphere and releasing oxygen.

Leaf anatomy- The structure of the leaf comprises the stomata which allows the exchange of gases for photosynthesis and respiration.

Photorespiration- It is an oxygen utilising process in the plants. It reduces the rate of photosynthesis.

Hence, the correct answer is option (A)

Note: In plants, the respiration and the photosynthesis takes place at the same time. The manufactured food by the photosynthesis is broken down by the process of respiration to liberate energy. The photosynthesis does not take place at night due to the absence of sunlight. So at night plants breathe in oxygen and breathe out carbon dioxide.