Practice question

Food-web connectance is the proportion of realised feeding links among all possible links. As species richness increases, the number of possible pairwise interactions rises approximately with the square of species number, whereas each consumer usually interacts with only a limited subset. Consequently connectance often decreases with richness even if the absolute number of links increases. The pattern depends on sampling and web definition, so it is an empirical tendency rather than an inviolable law. Mechanistic interpretation connects individual physiology and species interactions to population change, community composition, and ecosystem-level fluxes. Reliable inference requires the complete experimental design, definitions, units, and statistical evidence; missing labels cannot be reconstructed from an answer key alone. Net primary production equals gross primary production minus plant respiration and represents biomass or energy made available for growth and consumers. Rates must be compared on the same area, biomass, leaf-area, and time basis because changing the denominator can reverse an apparent ecosystem ranking.