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Biology · 2026 · 4 marks
CBSE 2026 · Region 2 · Set 1 · Q30
Below is shown a pond that represents a self-sustaining natural ecosystem with both biotic and abiotic components interacting in a balanced food web.…
Below is shown a pond that represents a self-sustaining natural ecosystem with both biotic and abiotic components interacting in a balanced food web.
Based on the diagram, answer the questions :
(a)
Mention two abiotic components of a pond ecosystem.
(b)
Differentiate between the roles of producers and decomposers in such an ecosystem.
(c)
Draw a simple food chain operating in such an ecosystem and label each trophic level.
OR
(c)
Why is transfer of energy not $\displaystyle 100$% efficient between trophic levels?
Marking-scheme solution
(a)
Water, Soil, sunlight, temperature, organic substances, inorganic
substances
(b)
| Role of producers | Role of decomposers |
| Conversion of inorganic molecules into organic material with the help of sunlight through the process of photosynthesis | Break down of dead and decayed organic material into simpler inorganic substances through the process of decomposition |
(c)
| Food Chain | Phytoplanktons → | zooplanktons → | Fish |
| Trophic Levels | Producers / 1st trophic level | Primary consumer / 2nd trophic level | Secondary consumer / 3rd trophic level |
OR
(c)
Some energy is dissipated and lost as heat to the environment / only $\displaystyle 10$% of
energy being transferred to the next trophic level.
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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.