Abstract: We introduce the standard distribution width of fitness to characterize the global and individual features of an ecosystern described by the Bak-Sneppen evolution model. Through tracking this quantity in evolution, a different hierarchy of avalanche dynamics, the w(0) avalanche, is observed. The corresponding gap equation and the self-organized threshold w(c) are obtained. The critical exponents tau, gamma and rho, which describe the behaviour of the avalanche size distribution, the average avalanche size and the relaxation to attractor, respectively, are calculated by numerical simulation. The exact master equation and gamma equation are derived, and the scaling relations are established among the critical exponents of this new avalanche.

Keywords: 1/f noise; criticality

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