Study the picture given below showing three food chains (a), (b) and (c) and answer the following questions :
(i) Name the type of ecosystems that exist in food chains (b) and (c).
(ii) The first trophic level in all food chains are producers. Why ? What percentage of solar energy do these producers capture for their use ?
(iii) Why are the arrows shown in the diagram in one direction only and not vice versa ? Justify.
Generated by claude-sonnet-4-6 · 2026-06-15 06:42 · grounding rag
Model Answer
(i) Food chain (b) represents a grassland ecosystem and food chain (c) represents a pond (aquatic) ecosystem.
(ii) Producers (green plants/autotrophs) are at the first trophic level because they fix solar energy and convert it into chemical (food) energy, making it available for all other organisms. Green plants capture about 1% of the solar energy falling on their leaves.
(iii) Arrows are unidirectional because energy flow in a food chain is one-way. Energy captured by autotrophs does not revert to the sun, and energy passed to herbivores does not return to autotrophs. As energy moves to each higher trophic level, it is no longer available to the previous level, and some is lost as heat at every step.
Source: Chapter 13, Section 13.1.1 — Food Chains and Webs
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Explanation
- For (i), the textbook caption of Fig. 13.1 explicitly states (a) forest, (b) grassland, (c) pond — learn this directly.
- For (ii), the key figures are autotrophs fix solar energy and 1% capture — both are directly stated in the passage; don't confuse with the 10% law (that's for transfer between trophic levels).
- For (iii), examiners want the phrase unidirectional flow plus the reason: energy lost as heat cannot be recovered by lower levels. Quoting from Fig. 13.4's explanation scores full marks.