Adding species to chemical reaction networks: Preserving rank preserves nondegenerate behaviours

We show that adding new chemical species into the reactions of a reaction network (CRN) in such way rank remains unchanged preserves its capacity for multiple nondegenerate equilibria and/or periodic orbits. One consequence is any bounded behaviours which can occur CRN with stoichiometric classes. The main result adds to family theorems tell us enlargements preserve nontrivial dynamical behaviours. It generalises some earlier claims, and complements similar claims involving addition CRNs. gives information on how ignoring species, as common biochemical modelling, might affect allowed dynamics differential equation models demonstrate scope limitations theorem via several examples. These illustrate we use predict multistationarity oscillation CRNs enlarged additional species; but also introduce orbits bifurcations.