The significance of the phosphorus cycle in ecosystems lies in its role as a key nutrient that supports the growth of living organisms. Unlike carbon and nitrogen, phosphorus does not have a gaseous phase and cycles through rock formations, soil, and water systems. It is essential for DNA and ATP synthesis, making it critical for cellular function and energy transfer. Phosphorus availability directly affects primary productivity in ecosystems, influencing the overall health and sustainability of both terrestrial and aquatic systems.