In the species-area relationship (log S = log C + Z log A), what does…

The correct answer is Option (1) → Species richness

Humboldt observed that within a region, species richness increases with the area explored, but only up to a limit. The curve is a rectangular hyperbola; on a logarithmic scale it becomes a straight line described by log S = log C + Z log A. In this equation, S is the number of species found, that is, the species richness.

Option (1) Species richness — Correct. S stands for species richness, the quantity plotted on the y-axis of the species-area graph.

Option (2) Slope of the line (regression coefficient) — Incorrect. The slope of the line (regression coefficient) is shown by Z, not by S.

Option (3) Y-intercept — Incorrect. The Y-intercept of the line is shown by C.

Option (4) Area — Incorrect. The area of the region is shown by A, the quantity on the x-axis.

NCERT Extract:
Patterns of Biodiversity – “… In fact, the relation between species richness and area for a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) turns out to be a rectangular hyperbola (Figure13.2). On a logarithmic scale, the relationship is a straight line described by the equation log S = log C + Z log A where S= Species richness A= Area Z = slope of the line (regression coefficient) C = Y-intercept”

Figure 13.2 Showing species area relationship. Note that on log scale the relationship becomes linear