Statement I: Decomposition is largely an anaerobic process, carried out by microbes in the absence of oxygen.
Statement II: Warm and moist environment favours decomposition, whereas low temperature and anaerobiosis inhibit it, resulting in build-up of organic materials.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Only statement II is correct.
Decomposers break down complex organic matter (detritus) into inorganic substances such as carbon dioxide, water and nutrients. The steps are fragmentation, leaching, catabolism, humification and mineralisation. The rate of decomposition depends on the chemical make-up of the detritus and on climatic factors, mainly temperature and soil moisture.
Statement I: Decomposition is largely an anaerobic process, carried out by microbes in the absence of oxygen. — False. Decomposition is largely an oxygen-requiring process. Lack of oxygen (anaerobiosis) slows it down, which is why organic matter piles up where oxygen is short.
Statement II: Warm and moist environment favours decomposition, whereas low temperature and anaerobiosis inhibit it, resulting in build-up of organic materials. — True. Warmth and moisture speed up the activity of soil microbes. Cold and lack of oxygen slow the microbes down, so organic material builds up instead of being broken down.
NCERT Extract:
Decomposition – “… The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralisation. Decomposition is largely an oxygen-requiring process. The rate of decomposition is controlled by chemical composition of detritus and climatic factors. … 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 environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in build up of organic materials.”