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Q.Observe the contents 1, 2, 3 and 4 of soil samples I, II and III shown in the graph. If the temperature and moisture of all soil samples are identical, which soil sample(s) will show faster decomposition ? (A) Soil Sample I (B) Soil Sample II (C) Soil Sample III (D) Both Soil Samples II and III

CBSECBSE Class XII Board 2026MCQ· 1mImportance★★★★★
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Decomposition proceeds fastest in the soil sample with the largest population of detritivores and decomposers; based on the standard NCERT-style version of this question, that is Soil Sample II — though the platform does not have the original graph on file to confirm the exact values.

When organic matter — dead leaves, animal waste, plant litter — falls to the ground, it doesn't simply vanish. It is broken down through decomposition, a process driven by two groups of organisms working in concert: detritivores (earthworms, millipedes, woodlice) that physically fragment the material, and decomposers (bacteria and fungi) that chemically break down complex molecules into simpler nutrients the soil can absorb.

The speed of decomposition hinges on several factors. Temperature and moisture create the physical environment — warmth accelerates microbial activity, moisture keeps organisms hydrated and mobile. But given that all three soil samples in this question share identical temperature and moisture conditions, the deciding factor becomes the population of organisms doing the actual work — the contents 1-4 plotted in the source graph.

Note

This platform does not have the original graph's numeric values on file, so the exact readings for contents 1-4 across Soil Samples I, II and III cannot be reproduced here. The reasoning below follows the general principle the question tests, applied to the typical pattern this style of NCERT question uses. …

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