In the species-area relationship equation - \( \log S = \log C + Z \log A \), ‘Z’ denotes:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Slope of the line
The species-area relationship is a rectangular hyperbola. On a logarithmic scale it becomes a straight line:
\( \displaystyle \log S = \log C + Z \log A \)
Here S is species richness, A is area, C is the Y-intercept, and Z is the slope of the line (the regression coefficient). The value of Z lies between 0.1 and 0.2 whatever the group or region. For very large areas, such as whole continents, the slope is steeper.
(1) Y-intercept — Incorrect. This is C, the point where the line cuts the Y axis.
(2) Species richness — Incorrect. This is S.
(3) Slope of the line — Correct. Z says how fast species richness rises as the area grows.
(4) Area — Incorrect. This is A.
Note: A similar question was also asked in CUET (UG) 2025 on 27-05-2025 (Slot 2) and on 14-05-2025 (Slot 2).
NCERT Extract:
Patterns of Biodiversity – “… 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”