Decomposition is the process where decomposers (bacteria and fungi) break down dead plant and animal matter, called detritus, into simple inorganic nutrients. It has 5 steps: fragmentation, leaching, catabolism, humification, and mineralisation. Memory hook: "Fat Ladies Cook Hot Meals" = Fragmentation, Leaching, Catabolism, Humification, Mineralisation.
The 5 steps of decomposition turning detritus into inorganic nutrients. All steps act on the detritus at the same time; warmth, moisture, oxygen, nitrogen and sugars speed it up, while lignin and chitin slow it down.
Your doubts, answered
What are the 5 steps of decomposition in the correct order?
The correct NCERT order is: Fragmentation, Leaching, Catabolism, Humification, and Mineralisation. Remember: these steps do NOT happen one after another in a strict line. NCERT clearly states all steps operate simultaneously on the detritus. NEET often asks the order and the definitions, so learn both.
What is the difference between catabolism and mineralisation?
Catabolism is when bacterial and fungal enzymes break detritus into simpler inorganic substances. Mineralisation is the later release of inorganic nutrients (like carbon, nitrogen, phosphorus) from humus by microbes, so plants can reuse them. Simple hook: catabolism breaks the detritus; mineralisation frees nutrients from humus.
Who performs fragmentation in decomposition?
Detritivores perform fragmentation. The classic NCERT example is the earthworm. They break down large pieces of detritus into smaller particles. This increases the surface area for microbes to act. Note: earthworms do fragmentation, NOT catabolism. NEET set a trap on this exact point.
Is decomposition faster with lignin and chitin or with nitrogen?
Decomposition is SLOWER if detritus is rich in lignin and chitin. It is FASTER (quicker) if detritus is rich in nitrogen and water-soluble sugars. This is a very common NEET trap. Students wrongly think lignin speeds it up. Also, warm and moist conditions with enough oxygen make decomposition faster.
What is detritus and why is it important for decomposition?
Detritus is the dead remains of plants and animals, including faecal matter. It is the raw material for decomposition. Without detritus there is nothing to decompose. The detritus food chain (DFC) begins with this dead organic matter, not with living organisms.
⚠️ The NEET trap ✗ Earthworms break detritus into smaller particles by a process called catabolism. ✓ Earthworms (detritivores) break detritus into smaller particles by FRAGMENTATION. Catabolism is the enzymatic breakdown by bacteria and fungi into simpler inorganic substances. 🧠 Earthworm = Fragmentation. Microbe enzymes = Catabolism. Never swap these two.
Real NEET questions
NEET 2022
Detritivores breakdown detritus into smaller particles. This process is called:
A · Catabolism
B · Fragmentation ✓
C · Humification
D · Decomposition
Solution: Detritivores such as earthworms break detritus into smaller particles; this step is fragmentation. Catabolism is enzymatic degradation, humification is humus build-up, and decomposition is the whole process. So the specific step is fragmentation. (NCERT Ch 12, p.207)
NEET 2022
Statement I: Decomposition is a process in which the detritus is degraded into simpler substances by microbes. Statement II: Decomposition is faster if the detritus is rich in lignin and chitin. Choose the correct answer:
A · Both Statement I and Statement II are correct
B · Both Statement I and Statement II are incorrect
C · Statement I is correct but Statement II is incorrect ✓
D · Statement I is incorrect but Statement II is correct
Solution: Statement I is TRUE: microbes degrade detritus into simpler substances. Statement II is FALSE: decomposition is SLOWER, not faster, when detritus is rich in lignin and chitin; it is quicker when rich in nitrogen and water-soluble sugars. So Statement I correct, II incorrect. (NCERT Ch 12, p.208)
NEET 2026
Match List I (A. Decomposition, B. Detritus, C. Mineralisation, D. Humification) with List II (I. Accumulation of dark coloured amorphous colloidal substance, II. Release of inorganic nutrients by activity of microbes in soil, III. Breaking down of complex organic matter into inorganic substances, IV. Dead remains of plants and animals including fecal matter):
A · A-IV, B-III, C-I, D-II
B · A-III, B-IV, C-II, D-I ✓
C · A-I, B-II, C-III, D-IV
D · A-III, B-II, C-I, D-IV
Solution: Decomposition = breaking complex organic matter into inorganic substances (III); Detritus = dead remains including faecal matter (IV); Mineralisation = release of inorganic nutrients by microbes (II); Humification = accumulation of dark, amorphous, colloidal humus (I). So A-III, B-IV, C-II, D-I. (NCERT Ch 12, p.207)
Solved Ecosystems NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Decomposition is when decomposers like bacteria and fungi break down dead plants, dead animals, and faecal matter (detritus) into simple inorganic nutrients that plants can reuse.
What is the raw material for decomposition?
Detritus is the raw material for decomposition. Detritus is the dead remains of plants and animals, including faecal matter.
Which conditions make decomposition faster?
A warm and moist environment with enough oxygen makes decomposition faster. Detritus rich in nitrogen and water-soluble sugars decomposes quickly, while lignin and chitin slow it down.
Is decomposition aerobic or anaerobic?
Decomposition is largely an oxygen-requiring (aerobic) process. Oxygen availability, along with temperature and soil moisture, controls how fast decomposition happens.
Do the steps of decomposition happen one by one?
No. NCERT clearly states that all the steps of decomposition operate simultaneously on the detritus, not one after another in a strict sequence.
