Through the various biogeochemical cycles, such as the water cycle, the carbon cycle, and the nitrogen cycle, elements and molecules are recycled. Energy, however, cannot be recycled. Instead, energy in ecosystems must be continuously supplied by

Energy in ecosystems must be continuously supplied by the sun as the warmth from the sun allows plants to grow plus photosynthesis depends on the sun's energy also. Animals also depend on the sun for warmth to survive (or else hibernate). Also, the sun powers the water cycle, the carbon cycle and the nitrogen cycle