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STD 12 - 12. ecosystem — Biology STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceBiologySTD 12 - 12. ecosystem1 Mark
MCQ
Which one of the following processes during decomposition is correctly described ?
  • A
    Catabolism -Last step in thedecomposition under fully anaerobiccondition
  • B
    Leaching -Water soluble inorganicnutrients rise to the top layers of soil
  • ✓
    Fragmentation -Carried out by organismssuch as earthworm
  • D
    Humification -Leads to the accumulationof a dark coloured substance humuswhich undergoes microbial action at a veryfast rate.
✓

Answer

Correct option: C.
Fragmentation -Carried out by organismssuch as earthworm
c
(c) :Decomposition is the process in which decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients. The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralisation. 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. Humification and mineralisation occur during decomposition in the soil. Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralisation.

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