Question

Identify the correct statement

• A. 90% of CO2 is found in atmosphere
• B. 90% of CO2 is found in oceans
• C. Nitrogen is very less in living organisms
• D. Phosphorus cycle is an example for sedimentary cycle

Hint:

Although nitrogen is abundant in the atmosphere, it is present in very low concentrations in living organisms, as it needs to be fixed first before it can be used.

Answer 1

The Correct Option is C

The correct statement is Option (C): Nitrogen is very less in living organisms.

Explanation:

• Option (A) – Incorrect: The atmosphere contains only about 0.03% of CO₂, not 90%.
• Option (B) – Incorrect: While CO₂ is present in oceans, it does not make up 90% of the Earth's CO₂ content.
• Option (C) – Correct: Nitrogen, although the most abundant gas in the atmosphere (78%), is present in living organisms in small amounts because it is not readily used in its gaseous form. It needs to be fixed into a usable form (like ammonia) by certain bacteria for incorporation into proteins and nucleic acids.
• Option (D) – Incorrect: The phosphorus cycle is an example of a sedimentary cycle, involving the movement of phosphorus through rocks, water, and living organisms, but it is not directly atmospheric like other cycles.
• Option (E) – Incorrect: The burning of fossil fuels does increase CO₂ in the atmosphere, contributing to the greenhouse effect and climate change.

Thus, the correct answer is Option (C), as nitrogen is indeed present in lower amounts in living organisms.