CBSE Class 12 Biology 2025: question 28
Set in the CBSE Class 12 board exam of 2025, paper 57/7/1, section C, question 28, for 3 marks. Try it first; the hints and our step-by-step solution are below.
Q28 · 3 marks · Short answerEcosystem
Name the type of food chains responsible for the flow of larger fraction of energy in an aquatic ecosystem and a terrestrial ecosystem, respectively. Mention any two differences between the two food chains.
Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/7/1.
Hints
Open one hint at a time and try again before the next.
Hint 1
There are two kinds of food chains; one starts with living producers and the other with dead matter.
Hint 2
In forests, most plant matter is not grazed but falls as litter.
Step-by-step solution
Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.
- ½ mark
In an aquatic ecosystem, the Grazing Food Chain (GFC) carries the larger fraction of energy.
- ½ mark
In a terrestrial ecosystem, the Detritus Food Chain (DFC) carries the larger fraction of energy.
- 2 marks
Differences (any two):
Grazing food chain Detritus food chain Begins with producers (green plants) Begins with detritus (dead organic matter) Energy comes from the sun Energy comes from dead organic matter Major conduit of energy flow in aquatic ecosystems Major conduit of energy flow in terrestrial ecosystems
Answer: Aquatic: Grazing Food Chain; Terrestrial: Detritus Food Chain; they differ in their starting point (producers vs detritus) and energy source (sun vs dead organic matter).
Where the marks are
- Aquatic ecosystem: GFC (½ mark)
- Terrestrial ecosystem: DFC (½ mark)
- Any two correct differences (1 + 1 mark)
Revise the chapter
- Chapter: Ecosystem (notes, formulas, where marks are lost and every past question)
- Topic: Energy Flow and Food Chains
More questions from Ecosystem
- 2024 board paper, set 57/1/1, Q20(b) · 2 marksWhy do organic farmers not recommend complete eradication of insect pests ? Explain giving reason.
- 2026 board paper, set 57/5/1, Q21(a) · 2 marksDifferentiate between grazing food chain and detritus food chain.
- Sample paper 2024-25, Q21(A) · 2 marks(i) It was estimated that if an evergreen forest has a GPP of 400 J/m²/day and 150 J/m²/day worth of carbon di…
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