Abstract: The Bak-Sneppen evolutionary model can be used to analyse self-organization on nucleotide content of evolving species. Applying two-parameter Kimura model of substitution enables changes of the nucleotide fractions in time. We established fitness parameter as a deviation of the genomic nucleotide fraction from its equilibrium value (0,25 and the food chain had the same dynamics as in Bak-Sneppen model in spite of its asymmetrical neighborhood. The new findings are: the higher is the value of the threshold fitness, the more frequent are large fluctuations in number of species with strongly differentiated nucleotide content; and it is more often the case that the oldest species, which survive the food-chain competition, might have specific nucleotide fraction making possible generating long genes.