Question

Identify the correct sequence of steps involved in the process of decomposition.
(a) Humification
(b) Catabolism
(c) Fragmentation of detritus
(d) Leaching
(e) Mineralization

• A. b-d-c-e-a
• B. c-b-e-a-d
• C. c-d-b-a-e
• D. b-d-e-c-a

Answer 1

Answer: (C)

Decomposition is a process in which the physical and chemical breakdown of complex organic matter will take place with the help of decomposers. The basic steps involve-
Fragmentation of detritus - Leaching - Catabolism - Humification - Mineralization.
A) Fragmentation of Detritus: Small invertebrate animals called detritivores or detritophages feed on detritus, e.g., earthworms, termites they bring about its fragmentation.
B) Leaching: Part of water-soluble substances present in the fragmented and decomposition detritus (e.g., sugars, inorganic nutrients) go down into the soil horizon by percolating water and get precipitated as unavailable salts.
C) Catabolism: It is carried out by saprotrophic bacteria and fungi. They secrete digestive enzymes over the fragmented detritus. The enzymes degrade complex organic compounds into simple inorganic substances.
D) Humification. It is the process of decomposition of detritus to form humus. Humus is a dark-coloured, amorphous, more or less decomposed organic matter rich in cellulose, lignin, tannins, resin, etc. and is highly resistant against microbial action. It undergoes decomposition at an extremely slow rate. Humus is slightly acidic, colloidal, and functions as a reservoir of nutrients.
E) Mineralization. It is the release of inorganic substances by saprophytic microbes (e.g.. $CO_2, H_2O$, minerals) from organic matter or humus during the process of decomposition. They are formed along with simple and soluble organic substances when digestive enzymes are poured over organic matter by saprotrophic microbes.