Question

Assertion :If the species-area relationships are analysed among very large areas like the entire continents, the value of Z, i.e., slope of line lies in the range of 0.1 to 0.2. Reason: The value of Z, i.e. slope of line of species area relationships lies in the range of 1.6 to 1.2 when analysis is done among small areas.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is D Both Assertion and Reason are incorrect

the great German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with increasing explored area, but only up to a limit. 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

Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the region (whether it is the plants in Britain, birds in California or molluscs in New York state, the slopes of the regression line are amazingly similar). But, if you analyse the species-area relationships among very large areas like the entire continents, you will find that the slope of the line to be much steeper (Z values in the range

of 0.6 to 1.2).

So the correct option is 'both assertion and reason are incorrect'.