Answer:
Alexander von Humboldt (German naturalist and
geographer) while working on wilderness of South American Jungles found that at
specific places species richness increased with increasing explored area. But
at such places, this increase in species richness was only up to certain
extent.
A rectangular hyperbola is obtained for
relation between species richness and region. This happens for wide range of
taxa like birds, bats, freshwater fishes and angiosperms. Relationship is of
straight line on logarithmic scale e.g.
[S = species richness; A = area;
Z = regression coefficient (slope of line) and C = Y-intercept] In any type of
taxonomic group or region value of Z conies in between 0.1 to 0.2. This value
is similar e.g. for plants in U.K., birds in California and molluscs in New
York. However if large continents are taken into account for this type of
studies, value of Z differs e.g. it comes in between 0.6 to 1.2. Even the slope
of line is much steeper. When Z value is studied, it comes equal to 1.15 for
frugivorous (fruit eating) birds and mammals of tropical forests of different continents.
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