In the open sea (marine ecosystem), the pyramid of biomass is inverted because the standing crop of producers (phytoplankton) is small due to their microscopic size and rapid turnover, yet they support a much larger biomass of primary consumers (zooplankton and fishes).

In terrestrial ecosystems like forests and grasslands, the pyramid of biomass is upright.

Statement (A) is false because decomposition is largely an oxygen-requiring (aerobic) process.

Statement (D) is false because humification occurs before mineralisation (humus is later degraded to release inorganic minerals).

Statement (B) is true: decomposition rate is slower if detritus is rich in lignin and chitin, and quicker if rich in nitrogen and water-soluble sugars.

Statement (C) is true: leaching involves water-soluble nutrients percolating into soil horizons and precipitating out as unavailable salts.

• Standing state: The amount of all inorganic mineral nutrients present in the soil at any given time (A-IV).
• Secondary productivity: The rate of formation of new organic matter by consumers / heterotrophs (B-II).
• Standing crop: The total living biomass or mass of living matter in a trophic level at a particular time (C-III).
• Net primary productivity: Total biomass available for consumption by heterotrophs ($GPP - R$) (D-I).

In nature, food chains are not isolated linear entities. Consumers feed on multiple trophic levels and prey on different species. This network of interconnected feeding relationships is called a food web.