Green plants in a terrestrial ecosystem capture only about 1% of the sunlight that falls on their leaves. Considering this, and the 10% energy transfer rule between trophic levels, explain why a large land area is needed to sustainably support a population of top-level carnivores compared to a population of herbivores of the same body mass.
Generated by claude-sonnet-4-6 · 2026-06-26 00:59 · grounding rag
Model Answer
Green plants capture only 1% of sunlight that falls on their leaves, converting it into food energy. When this energy passes from one trophic level to the next, only 10% is transferred; the rest is lost as heat, digestion, and respiration.
Consider a simplified food chain:
Plants → Herbivores → Carnivores (top-level)
- If plants capture 1000 J, herbivores receive 100 J (10% of 1000 J).
- Top-level carnivores receive only 10 J (10% of 100 J).
So a herbivore population receives 10 times more energy than a carnivore population from the same plant base. To sustain a population of top-level carnivores of the same body mass as herbivores, a much larger land area is needed to grow enough plants to support the additional trophic levels through which energy is progressively lost.
Source: Chapter 13, Section 13.1.1 — Food Chains and Webs
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Explanation
- Examiners expect you to use both facts: 1% solar capture by plants AND 10% energy transfer rule.
- Show the numerical logic (even roughly) — it makes the answer concrete and earns marks.
- Key phrase to use: "energy is lost as heat at each trophic level."
- The conclusion must clearly state that carnivores are further from the energy source, so more producers (= more land) are needed to sustain them.
- Do not just describe food chains generally — the question asks you to explain why, so you must link the energy losses to the land-area requirement explicitly.