Practice question

Redundancy means that multiple species can perform overlapping ecological functions. If one disappears, another member of the same functional group may partly compensate, buffering ecosystem processes until too many substitutes—or a nonredundant contributor—are lost. Biodiversity–function hypotheses differ in how they assign ecological importance among species. Complementarity emphasizes distinct contributions, redundancy emphasizes overlap and compensation, rivet theory emphasizes cumulative weakening, keystone theory emphasizes particular influential species, and idiosyncrasy emphasizes context dependence. Real communities can display several patterns because functions differ and environmental conditions alter interactions. Richness alone therefore cannot identify mechanism; species traits, relative abundance, functional groups, and the order of species loss must also be considered. In this context, the keyed term, Some species can replace others, identifies the relevant mechanism or quantitative relationship and links the observed pattern to its underlying ecological cause. The distinction is testable by measuring changes in organisms, resources, or process rates through time rather than relying on the label alone.