Practice question

A detritus food chain starts with dead plant material, carcasses, feces, or dissolved organic matter rather than living producer tissue. Microbes condition and enzymatically digest this material, and detritivores consume detritus plus its microbial community; predators then feed on detritivores. The pathway dominates in many forests, streams, and soils because only a minority of primary production is grazed alive. It remains energetically dependent on earlier primary production, but its immediate resource base is nonliving organic matter. Thermodynamic constraints set broad patterns, but species traits, defenses, body size, habitat structure, and disturbance determine the efficiencies observed in a particular ecosystem. 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.