Practice question

“Zebra mussel” for which species is considered invasive due to ballast water discharge from ships. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. 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. The remaining alternatives—“Cane toad”, “Nile perch”, “Achatina fulica”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Management outcomes depend on scale and context: suppressing abundance at one site does not guarantee regional eradication when dispersal reconnects treated and untreated populations. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.