The fast and slow analysis of the heart model from Chapter 24 can be applied in a more general context. In particular, the fast-slow analysis applies when two systems (or populations) interact and where the reaction time of one is much faster than that of the other.

To illustrate how this works, consider first an example that is suggested by the article from Reading 24.1: The example considers the coevolution of pocket gophers and their mite parasites. The mites can be considered to be the fast system and the gophers the slow system, inasmuch as the generation time for mites can be as short as a few days or weeks, while gophers typically have one or at most two litters per year. The point is that the fast generation time of the mite allows the latter to adapt quickly (relatively speaking) to environmental changes, while the adaptation time of gophers is much slower. To be slightly more specific, take g(t) to denote some property of gophers under consideration at time t, and take m(t) to denote some property of mites. [For example, g(t) might represent the fraction of gophers with some particular blood type, and m(t) might denote the fraction of mites that preferentially feed on that blood type.]