THE BAK-SNEPPEN MODEL - A SELF-ORGANIZED CRITICAL MODEL OF BIOLOGICALEVOLUTION

Recently, Bak and Sneppen proposed a simple model, the Bak-Sneppen (BS ) model, as a coarse-grained description of biological evolution. It h as attracted a lot of attention from interdisciplinary statistical phy sics community, for its simple model definition but extremely rich pro perties to be explored. The aim of this paper is to give a pedagogical and update review of this fast-developing topic. The emphasis is on t he mechanism by which the BS model approaches the self-organized criti cal state, the universal properties of the system at criticality, and the relation with other topics, such as directed percolation, random w alk, and a few self-organized critical models.