How did biochemical pathways evolve?
To stress the biological, geological and chemical nature of the processes, they are sometimes called biogeochemical cycles. There are macronutrients as C, H and O which have cycles with an atmospheric store, and some as P and K obtained from the soils. There are micronutrients as Cu, Fe, Co which have soil-based, or edaphic cycles. Nitrogen, a macronutrient, has inorganic pools in both the atmosphere and soil.
A variety of biogeochemical processes controls the links between available and unavailable forms of edaphic nutrients. The qualitative and quantitive nature of nutrient cycles in natural ecosystem is very diverse.