A diagram that illustrates energy flow across trophic levels, typically showing less energy available at higher levels, is called what?

• A. Energy pyramid
• B. Food web
• C. Hydrologic cycle
• D. Biogeochemical cycle

Answer: (A)

Energy pyramids show how energy moves through an ecosystem from the base up, with the most energy at the bottom and progressively less at higher trophic levels. This pattern exists because a large portion of energy is lost as heat and used for metabolic processes and maintenance, so only a fraction is transferred to each successive level. That is why the diagram commonly looks like a pyramid, narrowing toward the top as you move to higher consumers. The other terms refer to different concepts: a food web maps who eats whom in a community, a hydrologic cycle tracks the movement of water, and a biogeochemical cycle follows the paths of nutrients like carbon or nitrogen.