Discrete time models, one linear and one non-linear, are investigated, both with a herbivore species that consumes a basal food source species. Results are presented for coexistence of the species and to illustrate chaotic behaviour as parameters are varied in the non-linear model. The results indicate the benefit of fertilization in terms of the region of parameter space for which coexistence occurs. Possible extensions from these models for independent investigations are provided alongside classroom exercises.