What is decomposition? Describe its steps and the factors that affect its rate.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define in one line. Decomposition is the breakdown of complex organic matter (detritus) by decomposers into inorganic substances like CO₂, water and nutrients.
2 · Explain fragmentation. Detritivores such as earthworms break detritus into small particles.
3 · Explain leaching and catabolism.
Leaching: soluble nutrients move down into the soil as unavailable salts.
Catabolism: bacterial and fungal enzymes degrade the detritus.
4 · Explain humification and mineralisation.
Humification: humus forms; dark, colloidal, slow to decay, a nutrient reservoir.
Mineralisation: microbes release inorganic nutrients from humus.
5 · Draw the flow. [Flow chart: detritus → fragmentation → leaching and catabolism → humification → mineralisation → nutrients]
6 · State the factors. Fast: warm, moist, aerobic, rich in nitrogen and sugars. Slow: cold, anaerobic, rich in lignin and chitin.
7 · Link to real life. Vermicomposting uses earthworms to turn kitchen waste into compost.
8 · Close in one line. So decomposition returns nutrients to the soil for producers to use again.
Scoring tip: Keep the five steps in order and name the agent of each: detritivores, water, enzymes, then microbes in the soil.
