Match List I with List II :

List I	List II
A. Productivity	I. Gross primary productivity minus respiration losses
B. Net primary productivity	II. Rate of formation of new organic matter by consumers
C. Gross primary productivity	III. Rate of biomass production
D. Secondary productivity	IV. Rate of production of organic matter during photosynthesis

Choose the correct answer from the options given below:

Core Logic

• Decomposition (A) is the biological process of breaking down complex organic matter into inorganic substances (A-III).
• Detritus (B) acts as the raw material for decomposition and includes dead remains of plants, animals, and fecal matter (B-IV).
• Mineralisation (C) is the degradation of humus by microbes, releasing inorganic nutrients (C-II).
• Humification (D) leads to the accumulation of a dark coloured amorphous substance called humus (D-I).

Step 1: Final Conclusion

The correct matches are A-III, B-IV, C-II, D-I.

Pattern Recognition

Humification explicitly forms 'Humus', which is the 'dark coloured amorphous' substance. D-I is uniquely distinguishing in some options, paired with A-III for Decomposition.

Chapter Mix

Class 12 Biology: Ecosystem

Core Logic

Let's review the shape of various ecological pyramids:

• Pyramid of Energy: ALWAYS upright in all ecosystems, as energy is lost as heat at each step (10% law).
• Pyramid of Number in Grassland: Upright (millions of grass plants support fewer herbivores and even fewer carnivores).
• Pyramid of Biomass in Grassland: Upright.
• Pyramid of Biomass in Sea/Aquatic ecosystems: Generally inverted. The standing crop of phytoplankton (producers) has less biomass than the zooplankton and fish (consumers) they support due to their rapid turnover rate.

Step 1: Final Conclusion

The pyramid of biomass in a sea/aquatic ecosystem is the classic example of an inverted pyramid.

Pattern Recognition

Aquatic biomass pyramid = Inverted. Tree ecosystem number pyramid = Inverted/Spindle. Energy pyramid = Always upright.

Chapter Mix

Class 12 Biology: Ecosystem