1. Breaking down of complex organic matter into simple inorganic substance like CO₂, H₂O and Nutrients is called decomposition.

2. Decomposition steps are

• Fragmentation – It is the breaking down of detritus into smaller particle by the detritivores like earthworm.
• Leaching – Precipitation of water soluble or inorganic nutrient into soil horizon.
• Catabolism – It is the degradation of detritus into simple inorganic substances by the action of micro organism.
• Humification – It is the accumulation of dark coloured amorphous substance called humus. Humus serve as the reservoir of nutrients.
• Mineralization – The degradation of humus & release of nutrients from it by microbes is called mineralization.

3. Decomposers split the complex detritus into simple inorganic compounds while doing so they also bring about nutrient cycling. The degradation of detritus into simple organic substances by micro organism involves catabolic process. Without micro organism the earth would have been filled with dead organisms.