In biology and chemistry, ODE system is a good way to represent some of their special properties. In this article we mention about some tools from graph theory to deal with ODE systems and two models designed to fulfill some biological properties. My results are Theorem 2.10 and Theorem 2.11 in section 2 coming from the ideas in (Fiedler, Mochizuki, Kurosawa, Saito,2013). The Theorems can reduce an ODE system to subsystems which makes a system easy to analyze.
