Which of the following best describes the nitrogen cycle?

The nitrogen cycle is best described as a transformation of nitrogen through its chemical forms. This process is crucial for maintaining ecosystem health and involves several key steps, including nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.

In nitrogen fixation, atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or related compounds by certain bacteria, making it available for plants. Nitrification follows, where ammonia is oxidized to nitrites (NO₂⁻) and then to nitrates (NO₃⁻), which are again usable by plants. Assimilation involves the uptake of these nitrates by plant roots, integral in synthesizing essential amino acids and proteins.

Ammonification refers to the conversion of organic nitrogen from dead organisms or waste back into ammonia, while denitrification completes the cycle by converting nitrates back into nitrogen gas, releasing it into the atmosphere. This thorough transformation through various chemical forms emphasizes the nitrogen cycle's role in sustaining life and maintaining productivity in ecosystems.

Other options do not accurately capture the essence of the nitrogen cycle. Weathering rocks relates to geological processes rather than biological and chemical transformations of nitrogen. Carbon fixation deals specifically with the conversion of carbon dioxide into organic compounds, which is