Patterns of Biodiversity

Latitudinal gradients

· The plants and animals are not distributed evenly worldwide. The diversity of living forms decreases as we go from the equator towards the poles. A huge amount of plants and animals are concentrated in the tropical region because of the following reasons.

· Tropical environment is less seasonal and almost constant and predictable as compared to temperate environment.

· Tropics receive the major part of the solar energy, which contributes to great productivity.

· Speciation is dependent upon time. Tropical areas have remained undisturbed for millions of years unlike temperate regions, which have experienced frequent glaciations in the past.

Species-Area relationships

Alexander von Humboldt observed that biodiversity increases with increase in explored area. This relationship can be given by,

log S = log C + Z log A

where,

S = Species richness

A = Area

Z = Slope of the line (regression co-efficient)

C = Y-intercept

Value of Z is found to lie in the range of 0.1 to 0.2 for comparatively smaller areas such as countries while for very large areas such as entire continents, the slope of the line is much steeper with Z value lying from 0.6 to 1.2.