Decomposition | Class XII

It is the process of breaking down of dead organic matter into smaller organic. molecules and inorganic molecules by Decomposers (bacteria, fungi)

  • DETRITUS: Dead remains of plants and animals is called detritus.
  • DETRITIVORES: Animals that feed on decaying organic matter (detritus). Examples: earthworms, termites, snails etc
Mechanism of Decomposition:
Fragmentation of Detritus: Detritivores feed on detritus —breakdown—increases the surface area of detritus particles for microbial action.
Leaching: Soluble inorganic nutrients dissolve in water — percolate through the soil —removed due to leaching action.
Catabolism: Decomposers (bacteria, fungi) release enzymes — decompose detritus — simpler inorganic compounds.

Humification: Simplified detritus— converted to HUMUS

– Humus is a Dark, Amorphous substance.

– Highly resistant to Microbial Action

– Undergoes Decomposition very Slowly.

– Reservoir of nutrients (due to colloidal nature)

 Mineralisation: Humus is degraded — releases inorganic substances (CO2, H2O etc) and nutrients (Ca2+, Mg2+,K+ etc)

Factors affecting rate of Decomposition:

Chemical composition – decomposition rate will be slow when detritus rich in lignin and chitin and rate increases when detritus is rich in nitrogen and water soluble substances like sugars.


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