The primary interaction in biogeochemical cycles involves the transfer of elements and compounds between living organisms and the Earth. Key processes include photosynthesis, respiration, and decomposition. For instance, in the carbon cycle, plants absorb carbon dioxide during photosynthesis and release oxygen. Animals then consume plants, incorporating carbon into their bodies. Ultimately, decomposition returns carbon to the soil and atmosphere, facilitating the cycle's continuity. These interactions are vital for sustaining nutrient availability and supporting life on Earth.