Which process is involved in the nitrogen cycle?

The process involved in the nitrogen cycle that is correctly identified is nitrogen fixation. Nitrogen fixation is essential because it converts atmospheric nitrogen (N₂), which is not directly usable by most organisms, into ammonia (NH₃) or related compounds that plants can assimilate. This process is primarily carried out by certain bacteria and archaea, some of which live in symbiotic relationships with the roots of legumes, while others are free-living in the soil.

Understanding nitrogen fixation is crucial for grasping how nitrogen, a vital nutrient for plant growth and development, enters the ecosystem. Without this process, the nitrogen available to living organisms would be limited, affecting food webs and ecosystem functioning.

Other processes mentioned, while important in their own right, do not specifically pertain to the nitrogen cycle. For instance, photosynthesis is involved in the carbon cycle and is the process by which plants convert light energy into chemical energy. Transpiration refers to the movement of water within plants, playing a role in the water cycle rather than the nitrogen cycle. Cellular respiration, although critical for energy production in living organisms, primarily involves the consumption of oxygen and the release of carbon dioxide, rather than nitrogen.