Practice question

“Number of species present” for species richness refers specifically to. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. The remaining alternatives—“Genetic variation”, “Population density”, “Biomass of organisms”—refer to different states, processes, or scales and therefore do not express the same causal relationship. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.