Practice question

“Fill unused ecological niches” for empty niche hypothesis implies invasive species. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Niche differentiation reduces overlap by separating species along resource, space, or time axes. Such partitioning can stabilize coexistence when each species performs relatively better under the conditions it uses most strongly. The remaining alternatives—“Rely on novel biochemical weapons”, “Benefit from enemy release”, “Depend solely on propagule pressure”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Habitat describes where an organism occurs; niche additionally describes how it obtains resources and affects or responds to other organisms. Distribution therefore provides evidence about a niche but is not identical to it. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.