Which of these is the primary source of energy in an ecosystem?

• A. Plants
• B. Consumers
• C. Decomposers
• D. The Sun

Answer: (D)

Verified step by step guidance

1. Understand that ecosystems rely on energy to sustain life, and this energy must come from an external source.
2. Recognize that the Sun is the primary source of energy for most ecosystems on Earth. It provides the energy needed for photosynthesis.
3. Photosynthesis is the process by which plants, algae, and some bacteria convert solar energy into chemical energy stored in glucose. This can be represented by the equation: $6_{\mathrm{CO}}+6_{H2O}\to {C6H\mathrm{12}O6}_{+6_{O2}}$
4. Plants, as primary producers, capture solar energy and convert it into a form that can be used by other organisms in the ecosystem, such as consumers and decomposers.
5. Therefore, while plants, consumers, and decomposers play crucial roles in the ecosystem, the Sun is the ultimate source of energy that initiates the flow of energy through the ecosystem.