The study provides an entropy assessment from an ecological perspective indicating parasite-host evolutions between bacteriophage lambda and Escherichia coli during induction. The bell-shaped time course of the information entropy indicates that a forward mutation of "lambda -resistant" hosts takes place, since no Loss of cellular viability occurs for the second growth phase of reinduced (i.e. recovered) cells. In addition, no back mutation to obtain a maximal complexity (i.e. lambda -resistant and sensitive species coexistence) or original ecology (i.e. original lambda -lysogen) for the evolution occurs. Thus, a genetic polymorphism of species in a balanced equilibrium can not be established. This point obviously clarifies certain hypothesized results shown in previous work. In addition, virulence reduction of phage lambda enhances total survival of host cells and parasitic lambda species, thus a moderate induction performance is resulted.