Functions of Ecosystem: Decomposition - Practice Questions & MCQ

• Decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition.
• Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute detritus, which is the raw material for decomposition.
• Decomposition is largely an oxygen-requiring process. 
• The rate of decomposition is controlled by chemical composition of detritus and climatic factors. 
• In a particular climatic condition, decomposition rate is slower if detritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and water-soluble substances like sugars. 
• Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes.
• Warm and moist environments favour decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in build up of organic materials.
• The important steps in the process of decomposition are: 
  • fragmentation, 
  • leaching, 
  • catabolism, 
  • humification 
  • mineralisation

1. Fragmentation of Detritus:

• It takes place with the help of invertebrates like snails and earthworms. 
• As they feed on detritus they are called detritivores. 
• When detritus passes through their alimentary canal it gets fragmented or pulverised. This increases the surface area of detritus. 
• They also add certain growth substances which help in the growth of microbes. 
• A few detritivores are coprophagic, that is they can break down the faecal pellets of animals.

2. Leaching:

• This is the process by which simple and water soluble compounds percolate down to lower layers of soil with moving water.

3. Catabolism:

• During this process certain bacteria and fungi release extracellular enzymes. 
• These enzymes help in converting decomposing detritus to inorganic forms. 
• The enzymes are specific and work on a specific detritus, for example Pseudomonas bacteria decomposes proteins into ammonia and simple nitrogen compounds.

4. Humification:

• Humification means formation of humus which is dark coloured amorphous substance formed from dead and decomposing material. 
• It is highly resistant to microbes because of which it undergoes slow decomposition.
• Humus is a reservoir of nutrients.

5. Mineralization:

• The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralisation.
• It leads to the addition of inorganic substances like , and minerals like NH4+, Ca++, Mg++, K+, etc. to soil.