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Biology · 2026 · 2 marks
CBSE 2026 · Region 5 · Set 1 · Q21
(a) Differentiate between grazing food chain and detritus food chain.
(a)
Differentiate between grazing food chain and detritus food chain.
OR
(b)
Ecological pyramids are widely accepted but they still have some limitations. Write any two limitations.
Marking-scheme solution
Grazing food chain
Detritus food chain
− Starts from producers.
− Starts from Detritus /
decomposers / dead organic
matter.
− It is the major conduit for
energy
flow
in
aquatic
ecosystem
− It is the major conduit for
energy flow in terrestrial
ecosystem
− Less fraction of energy flow
(because food chain is large)
− Larger fraction of energy flow
(because
food
chain
is
smaller)
− It does not take into account the same species belonging to two or more trophic levels.
− It assumes a simple food chain something that almost never exists in nature
− It does not accommodate a food web.
− Saprophytes are not given any place in ecological pyramids even though they play a vital role in the ecosystem.
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CBSE Class 12 Biology past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.