Multiple Choice
Why must atmospheric nitrogen ($N_2$) be 'fixed' before most organisms can use it, and which organisms are primarily responsible for this process?
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Nitrogen Fixation
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Why is the nitrogen cycle important to humans?
A
It generates energy directly used by human cells.
B
It converts atmospheric nitrogen into forms usable by plants, which are essential for human food production.
C
It produces oxygen necessary for human respiration.
D
It removes carbon dioxide from the atmosphere.
Verified step by step guidance1
Understand the role of nitrogen in biological systems: Nitrogen is a critical element for living organisms as it is a key component of amino acids (building blocks of proteins) and nucleotides (building blocks of DNA and RNA).
Recognize the challenge of atmospheric nitrogen: Nitrogen gas (N₂) makes up about 78% of Earth's atmosphere, but most organisms cannot use it directly because it is highly stable and unreactive.
Learn about nitrogen fixation: Certain bacteria and archaea convert atmospheric nitrogen (N₂) into ammonia (NH₃) through a process called nitrogen fixation. This ammonia can then be used by plants to synthesize organic molecules.
Understand the importance to humans: Plants absorb nitrogen in forms like ammonium (NH₄⁺) and nitrate (NO₃⁻) to grow and produce food. Humans rely on plants (and animals that eat plants) for nutrition, making the nitrogen cycle essential for food production.
Connect the nitrogen cycle to ecosystems: The nitrogen cycle ensures the continuous availability of nitrogen in forms usable by living organisms, supporting agriculture and maintaining ecosystem balance, which indirectly supports human survival.
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