Practice question

A species–area relationship specifically links the number of species S to sampled area A, commonly expressed as S = cAᶻ or, after logarithmic transformation, log S = log c + z log A. The curve rises because larger areas include more individuals and habitats, but its slope typically diminishes on arithmetic axes. “Richness versus area” directly represents this relationship. Prey killed versus prey density instead describes a predator functional response, while photosynthesis versus light describes physiological resource saturation. Tree richness versus evapotranspiration is an environment–diversity relationship, often used to examine how water–energy availability correlates with plant diversity; it is not a species–area curve because its independent variable is not area. Therefore the item’s wording makes more than one alternative fall outside species–area theory: A, B, and D all represent different relationships, while C is the only literal species–area relation. The keyed choice D can be understood as one non-species–area example, but it is not uniquely defensible. This is an item-construction mismatch rather than a sound single-answer comparison; the key should remain unchanged in the source, but the stem requires revision or a missing graph/context.