In the context of biogeochemical cycles, which component is primarily recycled within an ecosystem?

• A. Sunlight, which is captured and then returned to the Sun in a closed loop
• B. New individuals (organisms), which are continuously reused without replacement
• C. Energy, which cycles repeatedly between trophic levels
• D. Chemical nutrients (matter such as carbon, nitrogen, and phosphorus)

Answer: (D)

Verified step by step guidance

1. Understand the difference between energy flow and matter cycling in ecosystems. Energy flows through an ecosystem and is eventually lost as heat, so it is not recycled.
2. Recognize that sunlight is an energy source that enters the ecosystem but is not recycled within it; it is captured by producers and then lost as heat.
3. Identify that new individuals (organisms) are not reused or recycled; they are produced through reproduction and growth, involving the cycling of matter but not themselves being recycled.
4. Focus on chemical nutrients such as carbon, nitrogen, and phosphorus, which are elements that cycle repeatedly through biogeochemical cycles within ecosystems.
5. Conclude that chemical nutrients are the components primarily recycled within an ecosystem, moving through living organisms and the environment in closed loops.