Question

How does photosynthesis help to maintain the percentage of oxygen and carbon dioxide in the atmosphere?
(A)By giving off carbon dioxide and absorbing oxygen
(B)By giving off oxygen and absorbing carbon dioxide
(C)By releasing oxygen and carbon dioxide
(D)By absorbing oxygen and carbon dioxide

Answer 1

Hint: Photosynthesis is a mode of nutrition by the Autotrophs (organisms who prepare their own food by combining natural substances). In that process, the plant combines water and minerals from the soil, carbon dioxide from air and in the presence of Chlorophyll traps the sunlight which acts as a catalyst. The product obtained is Glucose, water and oxygen.

Complete answer:
Green plants are autotrophs. They are the group of organisms which can prepare their own food by capturing sunlight and using it to convert water, carbon dioxide and minerals into oxygen and energy rich organic compounds.
During the process of Photosynthesis, the stomata present in leaves intake the carbon dioxide present in air which is a vital component of the food prepared by them. And the gas oxygen is exhaled as a bi-product of this chemical reaction.
However, we should not be confused between a plant's intake of carbon dioxide and oxygen. Autotrophs like all other organisms inhale oxygen for the process of respiration and carbon dioxide is inhaled for nutrition. It is also seen in autotrophs, that during daytime or in the presence of sunlight, the rate of inhaling carbon dioxide increases and similarly, at night the rate of inhaling oxygen increases.
Therefore, it can be said that the activities of Photosynthesis help to maintain the percentage of oxygen and carbon dioxide in the atmosphere by giving off oxygen and absorbing carbon dioxide.

Hence the correct answer is option(B)

Note: Autotrophs are like all other living creatures who have a similar type of respiratory process and the presence of oxygen is inevitable in it. But this act of absorption of carbon dioxide is additional for the process of photosynthesis. During night, when photosynthesis does not happen, the trees leave carbon dioxide like other creatures.