(A) Alexander Von Humboldt was the naturalist who studied the relationship shown in the graph. He observed that within a region, species richness increased with increase in explored area but only upto a limit.
(B) When the value of z lies between
(i) z = 0.1 to 0.2: for small or average area.
(ii) z = 0.6 to 1.2 : for large area, for example, entire continent.
Z stands for slope of line.
(C) The slope of the line 'b' become steeper when very large areas such as continents are considered for species-area relationship.