Before revision:  We implement our model both with ordinary differential equations (ODEs)  to explore the role of bifurcations in producing the one-way character of differentiation  and with stochastic differential equations (SDEs)  to demonstrate the effect of noise on the system in simulations .
After revision:  We implement our model both with ordinary differential equations (ODEs) to explore the role of bifurcations in producing the one-way character of differentiation , and with stochastic differential equations (SDEs) to demonstrate the effect of noise on the system in simulations .