Which statement best describes nitrogen cycle steps?

Which statement best describes nitrogen cycle steps?

• A. Nitrogen is rarely cycled; once fixed, it never returns to the atmosphere.
• B. Plants receive nitrogen from soil as inorganic nitrate; animals obtain nitrogen by consuming living or dead organisms; bacteria and other organisms help cycle nitrogen back to the atmosphere.
• C. The nitrogen cycle does not involve decomposition.
• D. Nitrogen is never reintroduced into the atmosphere by biological processes.

Answer: (B)

Nitrogen moves through ecosystems in a cycle that involves uptake by plants, transfer through the food web, and return to the atmosphere through microbial processes. Plants absorb nitrogen from the soil in inorganic forms, mainly nitrate (and also ammonium), and use it to build proteins and other essential compounds. Animals obtain nitrogen by eating plants or other animals, continuing the flow through the ecosystem. Microbes drive the cycle by transforming nitrogen between forms—including decomposition releasing ammonium, nitrification turning ammonium into nitrate, and denitrification returning nitrogen gas to the atmosphere. This description captures how nitrogen is taken up, moved through organisms, and re-released to the air. The other statements misrepresent the cycle: nitrogen does recycle and can return to the atmosphere via denitrification; decomposition is a key step that releases forms of nitrogen for reuse; and biological processes do reintroduce nitrogen to the atmosphere.

Nitrogen moves through ecosystems in a cycle that involves uptake by plants, transfer through the food web, and return to the atmosphere through microbial processes. Plants absorb nitrogen from the soil in inorganic forms, mainly nitrate (and also ammonium), and use it to build proteins and other essential compounds. Animals obtain nitrogen by eating plants or other animals, continuing the flow through the ecosystem. Microbes drive the cycle by transforming nitrogen between forms—including decomposition releasing ammonium, nitrification turning ammonium into nitrate, and denitrification returning nitrogen gas to the atmosphere. This description captures how nitrogen is taken up, moved through organisms, and re-released to the air.

The other statements misrepresent the cycle: nitrogen does recycle and can return to the atmosphere via denitrification; decomposition is a key step that releases forms of nitrogen for reuse; and biological processes do reintroduce nitrogen to the atmosphere.