Before revision:  By allowing the model bacteria to evolve growth rate in the feast period with a trade-off with the growth yield and the death rate , the bacterial population tends to increase the growth rate by changing the counterpart of the trade-off , even though that tends to decrease the total population size . Analysis showed that , under the repeated feast-famine cycles, the ratio between the growth rate and the death rate becomes the effective fitness of the population.
After revision:  By allowing the model bacteria to evolve growth rate in the feast period with a trade-off with the growth yield and the death rate , the bacterial population tends to increase the growth rate by changing the counterpart of the trade-off , even though that tends to decrease the total population size due to the trade-off. Analysis of the model shows that the ratio between the growth rate and the death rate becomes the effective fitness of the population.