Match List-I (step of decomposition) with List-II (what happens in it):
| List-I | List-II |
|---|---|
| A. Fragmentation | I. Water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts |
| B. Leaching | II. Humus is further degraded by some microbes and inorganic nutrients are released |
| C. Catabolism | III. Detritivores break down detritus into smaller particles |
| D. Mineralisation | IV. Bacterial and fungal enzymes degrade detritus into simpler inorganic substances |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-III, B-I, C-IV, D-II
Decomposition breaks complex organic matter (detritus) down into inorganic substances like carbon dioxide, water and nutrients. Its important steps are fragmentation, leaching, catabolism, humification and mineralisation, and they work on the detritus at the same time.
(A) Fragmentation — this matches (III) Detritivores break down detritus into smaller particles. Detritivores such as the earthworm cut the detritus into small pieces; no chemical change is needed at this step.
(B) Leaching — this matches (I) Water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. Water carries the soluble nutrients down into the soil, where they settle as salts.
(C) Catabolism — this matches (IV) Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This is the chemical breakdown done by the enzymes of bacteria and fungi.
(D) Mineralisation — this matches (II) Humus is further degraded by some microbes and inorganic nutrients are released. It acts on humus, which is formed by humification and breaks down very slowly.
NCERT Extract:
Decomposition – “… Detritivores (e.g., earthworm) break down detritus into smaller particles. This process is called fragmentation. By the process of leaching, water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism.”
Decomposition – “… Being colloidal in nature it serves as a reservoir of nutrients. The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralisation.”