Q.Define decomposition and describe the processes and products of decomposition.
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Start your 14-day free trial to unlock the full solution →Decomposition is the natural breakdown of dead organic matter into simpler substances, driven by detritivores and decomposers, and it releases nutrients back into the ecosystem.
Decomposition is one of the most fundamental yet often overlooked processes in an ecosystem. When you think about a forest floor covered in fallen leaves, a dead animal lying in a field, or even a rotting log, what you are witnessing is decomposition in action. It is the process by which the complex organic compounds present in dead plants, animals, and their waste products are broken down into simpler inorganic substances. Without decomposition, the nutrients locked inside dead bodies would never return to the soil, the air, or the water. Life would grind to a halt because new plants would have no raw materials to build themselves from.
The NCERT textbook explains that decomposition is not a single event but a sequence of overlapping processes. It involves both physical fragmentation and chemical alteration. The entire process is carried out by two main groups of organisms: detritivores (like earthworms, millipedes, and beetles) and decomposers (primarily bacteria and fungi). Detritivores do the initial heavy lifting by physically breaking down the dead matter into smaller pieces, which increases the surface area available for decomposers to work on. Decomposers then perform the actual chemical breakdown, secreting enzymes that digest the organic material externally and then absorbing the simpler products.
The rate of decomposition is not constant. It is heavily influenced by the chemical composition of the detritus and the prevailing environmental conditions. For instance, a dead leaf with a high lignin content will decompose much more slowly than a soft, fleshy fruit.
The NCERT identifies three key sequential processes that constitute decomposition:
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Fragmentation: This is the physical breaking down of detritus into smaller particles. Detritivores like earthworms and termites chew, grind, and tear the dead material. This step is crucial because it exposes a much larger surface area of the detritus to the action of decomposers. Without fragmentation, decomposition would be excruciatingly slow.
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Leaching: As water percolates through the fragmented detritus, it dissolves and carries away water-soluble inorganic nutrients like calcium, potassium, and magnesium. These nutrients then enter the soil solution, where they can be taken up by plant roots. Leaching is a purely physical-chemical process, not a biological one.
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Catabolism: This is the core chemical step. Decomposers (fungi and bacteria) secrete extracellular enzymes that break down complex organic polymers like cellulose, lignin, proteins, and fats into simpler, soluble monomers. For example, cellulose is broken down into glucose, and proteins are broken down into amino acids. These simpler compounds are then absorbed by the decomposers for their own energy and growth. …
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