Practice question

In the tolerance model, early colonists have little direct effect on recruitment of later species. Different species may enter the site, but those able to tolerate progressively lower resources or altered conditions survive and eventually dominate; replacement does not require facilitation by pioneers. Classical succession terminology divides community development into site exposure, arrival, establishment, interaction, environmental reaction, and relative stabilization. Modern ecology treats these as useful descriptions rather than a rigid deterministic program. Local resource conditions, dispersal limitation, life-history trade-offs, herbivory, pathogens, and stochastic events jointly determine which species replace others. Early species often grow rapidly under open conditions, whereas later species commonly persist under lower resources, but the precise pattern varies among ecosystems and disturbance regimes. In this context, the keyed term, Tolerance, 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.