Different measures of this quantity are unified as a series of values that depend on an order parameter q called the Hill number. (10[1])R. H. Whittaker (-5[1])introduced a set of terms that defines the beta form of this quantity as the ratio (10[1])between its local and regional forms, (10[1])which are respectively denoted (10[1])alpha and gamma. Historical perturbations such as glaciation have been proposed to explain a phenomenon in which this quantity increases as latitude approaches zero. (10[1]-5[1])This quantity is measured (-5[1])by the (10[1])Simpson (-5[1])index, (10[1]-5[1])which accounts (10[2])for (10[1])richness (10[2])and (10[2])evenness. (10[3])Human activity (10[4])threatens (10[1])regions (10[2]-5[1])with high values (10[1])of this quantity known as its “hotspots,” (10[3])which include (10[1])the Amazon (10[1])rainforest. (10[1])For 10 points, name this measure of how many different species reside in an area. (10[2])■END■ (10[4])