What is the purpose of energy pyramids in ecosystem studies?

• A. To explain why photosynthesis occurs
• B. To show rainfall patterns in an ecosystem
• C. To illustrate the decrease of usable energy at higher trophic levels
• D. To compare gene flow among populations

Answer: (C)

Energy pyramids show how energy available to organisms decreases as you move up the food chain. The sun provides energy to producers through photosynthesis, but only a portion is captured and stored as chemical energy. As energy moves from producers to primary consumers to higher-level consumers, organisms use much of it for metabolism, growth, movement, and daily activities, and a large portion is released as heat. Because energy transfer is inefficient, only a small fraction reaches the next level—often around 10%—so higher trophic levels have much less usable energy. This is what the pyramid conveys: the steady decline of usable energy at higher levels. It’s not about explaining photosynthesis itself, rainfall patterns, or gene flow.