Practice question

Herbivores in many aquatic systems consume a larger fraction of primary production than terrestrial forest herbivores. Phytoplankton are small, rapidly renewed, nutrient-rich, and poorly defended by lignified structural tissue, so much of their production is accessible to zooplankton. In forests, a large share of plant production enters wood, roots, and chemically defended leaves and therefore bypasses grazers into the detrital pathway. The comparison concerns consumption efficiency, not necessarily total consumer biomass. Environmental effects are often nonlinear; drought suppresses microbial access to substrates, waterlogging restricts oxygen, and extreme heat can reduce activity despite faster kinetics. Substrate stoichiometry links carbon processing to nutrient demand, so identical mass loss can accompany mineralization in one litter type and immobilization in another. Microbial enzymes act outside cells, making surface area and molecular accessibility as important as the nominal energy content of the dead material. Carbon and mineral nutrients follow different accounting paths: energy is dissipated, whereas atoms may be retained, exported, or recycled into new biomass.