Practice question

“Keystone species” for species group whose removal triggers cascades. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Species management must identify the demographic stage and ecological process that most strongly limits population growth. Prevention, early detection, removal, habitat manipulation, and biological control act at different points in an invasion or recovery trajectory. The remaining alternatives—“Indicator species”, “Generalist species”, “Specialist species”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Effective control reduces propagule pressure or population growth without causing unacceptable non-target effects. Repeated monitoring is necessary because seed banks, dormant stages, recolonization, and density-dependent compensation can reverse short-term gains. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates.