Answer:
1. <em>Carbon dioxide</em>: a trace gas
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It is required for photosynthesis.
2. <em>Nitrogen</em>: most abundant gas in the atmosphere
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It is incorporated as a major component of proteins and DNA.
3. <em>Oxygen</em>: second most abundant gas in the atmosphere
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It is required for aerobic cellular respiration.
Explanation:
Gases that are less abundant in the atmosphere are called trace gases. Carbon dioxide gas is the product of respiration in animals which is then used by the plants for photosynthesis. It is present in the environment at very small concentration ( 0.04%).
Nitrogen and Oxygen both are present in the atmosphere at high proportions. Nitrogen covers 78% of the total gases volume whereas oxygen is about 28% in the atmosphere. It is vital in many biochemical processes that sustains life on Earth; for example, it is used in the production of nitrogen bases (purine and pyrimidine) and amino acid which are required for DNA and protein synthesis. Likewise, oxygen is an oxidizer which is required for aerobic cellular respiration.
