Consider the following statements about the Nitrogen Cycle: 1. Nitrogen gas constitutes 78% of our atmosphere. 2. Nitrogen is completely absent in proteins and vitamins. 3. The cycle ensures that the percentage of nitrogen in the atmosphere constantly increases. Which of the statements given above is/are correct?

Correct Option The correct option is (a). Explanation The Nitrogen Cycle is a critical biogeochemical cycle that circulates nitrogen through the atmosphere, soil, and living organisms. It involves the transformation of nitrogen into various chemical forms, making it accessible to plants and animals while maintaining atmospheric stability. Statement-wise Analysis - Statement 1 is Correct: Nitrogen gas (N2) is the most abundant component of Earth's atmosphere, constituting approximately 78% by volume. However, in this gaseous form, it is largely inert and cannot be used directly by most life forms. - Statement 2 is Incorrect: Nitrogen is a fundamental building block of life. It is an essential constituent of amino acids (which form proteins), nucleic acids (DNA and RNA), vitamins, and chlorophyll. It is strictly required for the synthesis of these biomolecules. - Statement 3 is Incorrect: The nitrogen cycle operates as a closed system in terms of mass balance. While nitrogen fixation removes nitrogen from the atmosphere to the soil, processes like denitrification return nitrogen gas back to the atmosphere. This cycle ensures that the percentage of nitrogen in the atmosphere remains more or less constant, rather than constantly increasing. Key Takeaway: Nitrogen is essential for the formation of proteins and genetic material. The nitrogen cycle maintains a dynamic equilibrium, ensuring the atmospheric concentration of nitrogen remains stable at approximately 78%.

NCERT Class 8 Science — Chapter 2: Microorganisms : friend and foe

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Consider the following statements about the Nitrogen Cycle:

Nitrogen gas constitutes 78% of our atmosphere.
Nitrogen is completely absent in proteins and vitamins.
The cycle ensures that the percentage of nitrogen in the atmosphere constantly increases.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

Correct Option

The correct option is (a).

Explanation

The Nitrogen Cycle is a critical biogeochemical cycle that circulates nitrogen through the atmosphere, soil, and living organisms. It involves the transformation of nitrogen into various chemical forms, making it accessible to plants and animals while maintaining atmospheric stability.

Statement-wise Analysis

Statement 1 is Correct: Nitrogen gas (N₂) is the most abundant component of Earth's atmosphere, constituting approximately 78% by volume. However, in this gaseous form, it is largely inert and cannot be used directly by most life forms.
Statement 2 is Incorrect: Nitrogen is a fundamental building block of life. It is an essential constituent of amino acids (which form proteins), nucleic acids (DNA and RNA), vitamins, and chlorophyll. It is strictly required for the synthesis of these biomolecules.
Statement 3 is Incorrect: The nitrogen cycle operates as a closed system in terms of mass balance. While nitrogen fixation removes nitrogen from the atmosphere to the soil, processes like denitrification return nitrogen gas back to the atmosphere. This cycle ensures that the percentage of nitrogen in the atmosphere remains more or less constant, rather than constantly increasing.

Key Takeaway: Nitrogen is essential for the formation of proteins and genetic material. The nitrogen cycle maintains a dynamic equilibrium, ensuring the atmospheric concentration of nitrogen remains stable at approximately 78%.

Your note

More from Chapter 2: Microorganisms : friend and foe

With reference to microorganisms, consider the following statements: 1. They are classified into four major groups: bacteria, fungi, protozoa, and algae. 2. They can survive only in moderate climates and die in ice-cold or hot spring environments. 3. Some microorganisms are unicellular, while others are multicellular. Which of the statements given above is/are correct?

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Which one of the following characteristics distinguishes viruses from other microorganisms?

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Consider the following statements regarding the habitat of microorganisms: 1. They are found in air, water, and soil but not inside the bodies of animals. 2. They can exist freely as well as grow on other organisms. 3. They are capable of surviving in deserts and marshy lands. Which of the statements given above is/are correct?

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Which one of the following human diseases is caused by a protozoan pathogen?

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Consider the following pairs of microorganisms and their classification: 1. Aspergillus : Algae 2. Paramecium : Protozoa 3. Penicillium : Fungi 4. Spirogyra : Bacteria How many of the above pairs are correctly matched?

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Keep practising Chapter 2: Microorganisms : friend and foe

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Correct Option

The correct option is (a).

Explanation

Statement-wise Analysis

Statement 1 is Correct: Nitrogen gas (N₂) is the most abundant component of Earth's atmosphere, constituting approximately 78% by volume. However, in this gaseous form, it is largely inert and cannot be used directly by most life forms.
Statement 2 is Incorrect: Nitrogen is a fundamental building block of life. It is an essential constituent of amino acids (which form proteins), nucleic acids (DNA and RNA), vitamins, and chlorophyll. It is strictly required for the synthesis of these biomolecules.
Statement 3 is Incorrect: The nitrogen cycle operates as a closed system in terms of mass balance. While nitrogen fixation removes nitrogen from the atmosphere to the soil, processes like denitrification return nitrogen gas back to the atmosphere. This cycle ensures that the percentage of nitrogen in the atmosphere remains more or less constant, rather than constantly increasing.