Which process leverages atmospheric nitrogen for biological use?

Nitrogen fixation is the process that converts atmospheric nitrogen (N2) into a form that can be used by living organisms, specifically into ammonia (NH3) or related compounds. This is crucial because nitrogen is an essential nutrient for all living things, necessary for the synthesis of proteins, nucleic acids, and other biomolecules.

In nature, certain bacteria play a pivotal role in nitrogen fixation. These bacteria either live freely in the soil or form symbiotic relationships with the roots of specific plants, such as legumes. Through nitrogen fixation, these organisms can take the inert nitrogen gas from the atmosphere and transform it into a biologically available form, indirectly supporting the growth of plants and, subsequently, the entire food chain.

The other processes mentioned do not convert atmospheric nitrogen into a biologically usable form. Combustion involves the burning of materials and does not relate to nitrogen transformation. Decomposition refers to the breakdown of organic matter, while photosynthesis involves the conversion of carbon dioxide and sunlight into glucose, not nitrogen. Thus, nitrogen fixation is distinctly recognized as the key process that facilitates the use of atmospheric nitrogen in biological systems.