Q4. Distinguish between litter and detritus. (NCERT Exercise 6(e), page 215.)
Detritus is all dead organic matter that is the raw material for decomposition: dead plant remains such as leaves, bark and flowers, and dead remains of animals, including fecal matter (NCERT page 207). Litter is the plant part of it lying on the ground: NCERT Figure 12.1 shows fallen leaves, partly consumed by fungi and bacteria, losing form and becoming litter (page 208). Beyond the NCERT text, the US Forest Service defines litter as recently fallen plant material, such as leaves, needles and fine twigs, on the forest floor, only partially decomposed and still recognisable (Fire Effects Information System glossary, public domain). So all litter is detritus, but detritus also includes dead animals and fecal matter, and material already broken down.
Q5. Distinguish between production and decomposition. (NCERT Exercise 6(b), page 215.)
Production is the making of organic matter (biomass) by producers in photosynthesis, using the sun’s energy; it is the ecosystem’s input, measured per unit area as g m or kcal m (NCERT pages 205–207). Decomposition is the breakdown of dead organic matter (detritus) by decomposers into inorganic substances, carbon dioxide, water and nutrients; it is part of the ecosystem’s output of degradation, and it returns nutrients for reuse (NCERT pages 205–207). Production turns inorganic matter into organic matter; decomposition turns it back.
Q6. Why is humus important for soil, although microbes break it down only very slowly?
Humus is colloidal in nature, so it serves as a reservoir of nutrients; its slow mineralisation by microbes releases inorganic nutrients gradually (NCERT page 208).
Q7. Which steps of decomposition are carried out by (a) earthworms, (b) water, (c) bacterial and fungal enzymes?
(a) Fragmentation; (b) leaching, in which water-soluble inorganic nutrients go down into the soil; (c) catabolism (NCERT page 207).
Q8. NCERT’s Summary lists three processes of decomposition. Which are they, and which two further steps does the text add?
The Summary names fragmentation of detritus, leaching and catabolism (page 214), the three that act together on the detritus. The text adds humification and mineralisation, which occur during decomposition in the soil (page 207).
Q9. Give the two climatic factors that matter most for the rate of decomposition, and say how they act.
Temperature and soil moisture: they regulate decomposition through their effects on the activities of soil microbes. Warm and moist conditions favour decomposition; low temperature and anaerobiosis inhibit it (NCERT page 208).