Practice question

“Drastic ecosystem changes at both higher and lower trophic levels” for collapse of intermediate trophic level species mainly causes. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. The remaining alternatives—“Stability in all trophic levels”, “Increase in primary productivity”, “Reduced predation pressures”—refer to different states, processes, or scales and therefore do not express the same causal relationship. The relevant inference should follow the pathway from resource supply to organismal uptake and then to ecosystem-level flux. Productivity, trophic transfer, decomposition, and nutrient regeneration are connected, but each measures a different part of that pathway.