Practice question

Amensalism is represented as (-,0): one species experiences reduced growth, survival, or reproduction while the other has no measurable fitness change. Classic examples include antibiosis, in which a microorganism releases a compound that suppresses another species as an incidental metabolic effect, and shading where a large plant inhibits a smaller neighbor without being influenced by it. The unaffected status must be evaluated empirically, since hidden benefits or costs can alter classification. (+,0) is commensalism, (-,-) is competition, and (+,+) is mutualism. Amensalism therefore differs from interactions involving either reciprocal harm or a direct benefit to the inhibiting organism. The alternatives can be separated by asking what changes for each participant and which process causes that change. That approach is more reliable than treating familiar examples as fixed labels, because many interactions shift with environmental context. From an evolutionary perspective, traits persist when their net effects improve inclusive or direct fitness under prevailing conditions. The ecological terminology therefore summarizes both an immediate mechanism and its likely consequences across generations.