Practice question

Decomposers break down dead organic matter through extracellular enzymatic depolymerization, uptake, and metabolism. Fungi and bacteria convert part of the substrate into microbial biomass, respire carbon as CO₂, and mineralize nutrients into forms such as ammonium and phosphate. They therefore couple energy dissipation to nutrient recycling. Decomposition is not simply storage or mechanical fragmentation: some products persist as humus or mineral-associated organic matter, while soluble nutrients become available to producers or vulnerable to leaching and gaseous loss. Real communities are networks rather than isolated chains, so omnivory, detrital links, and changes in interaction strength modify the simplified trophic sequence. Energy budgets must distinguish stocks from rates: standing biomass can remain high or low even when production and transfer through that compartment are rapid. Matter can cycle repeatedly through producers, consumers, and decomposers, whereas usable energy requires continuous external input because respiration degrades it to heat. The amount reaching a consumer level depends jointly on resource production, the fraction consumed, assimilation efficiency, and conversion of assimilates into new biomass.