In biogeochemical cycles, _______ is continually recycled, typically between living and nonliving forms.

• A. Energy
• B. Water
• C. Genes
• D. Matter

Answer: (D)

Matter is continually recycled in biogeochemical cycles, moving between living organisms and the nonliving environment. Atoms such as carbon, nitrogen, phosphorus, and water are reused over and over through processes like photosynthesis, respiration, decomposition, and weathering. This recycling keeps these essential elements available for future generations of life.

Energy, by contrast, flows through ecosystems in one direction: it enters as sunlight, is converted to chemical energy by producers, used by organisms, and is eventually released as heat. It isn’t recycled back into the system in the same way matter is. Genes are part of matter, but the broader idea here is about how elements and compounds cycle through the environment, not about the persistence of a particular genetic sequence.