Which of these statements best defines pyramid of energy?

Step 1: Analyze the question We are asked to pick the statement that best defines a pyramid of energy.

Step 2: Explain the concept A pyramid of energy is a diagram that shows how much energy is available at each trophic (feeding) level of an ecosystem, usually over a given time. The base is the producers (plants), followed by primary consumers, secondary consumers, and so on. Each level is smaller than the one below it because energy is lost as heat through respiration, movement, and waste. Only about 10% of the energy passes on to the next level. This is why the pyramid is always upright.

Step 3: Evaluate the options

• A. Energy flow from one trophic level to another: This matches the idea of the pyramid. It represents the transfer of energy from producers to consumers level by level. Note that "tropic" in the question is a typo for "trophic". ✔
• B. Energy flow from one habitat to another: Wrong. The pyramid concerns feeding levels, not habitats.
• C. The amount of energy in a given area: Too general. It does not mention trophic levels.
• D. The loss of energy from one organism to another: This describes only the energy loss, not the pyramid as a whole.
• E. The rate of energy flow in an area: Energy pyramids can be expressed as rates (e.g. kJ/m²/year), but this does not mention the trophic structure, so it is less complete than A.

Step 4: Answer It is the only option that ties the pyramid to the flow of energy between trophic levels.

Exam tip: Remember "Pyramid of energy = energy at each trophic level." Pyramids of energy are never inverted, unlike pyramids of numbers or biomass, which can sometimes be. Also, watch the 10% rule: roughly 90% of energy is lost at each step.