Practice question

The tolerance model allows early and late successional species to arrive independently; pioneers neither strongly facilitate nor inhibit later colonists. Species that tolerate lower resource levels or other conditions developing over time eventually persist and grow better, so their life-history traits drive replacement. A disturbance changes the availability of space, resources, and biological legacies, creating opportunities for colonization. Whether succession is primary or secondary depends chiefly on the starting substrate and survival of soil, not simply on the identity of the disturbance. Colonists must arrive, establish, reproduce, and interact with residents; meanwhile they alter nutrient cycling, shade, moisture, and physical structure. These feedbacks create directional replacement, although repeated disturbance or environmental change may interrupt, reverse, or redirect the sequence. In this context, the keyed term, All species can colonize independently, 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.