In this Lab we will extend our understanding of systems to problems where there are two interacting variables. Examples include predator-prey problems, two-species competition problems, epidemic models, non-linear oscillators, lasers and love affairs! By adding one more degree of freedom we can (sometimes) get a lot more behavior. Nevertheless, the tools we developed for understanding 1-D systems will help us a long way in understanding 2-D systems. Most important, by the time we are done you will understand the importance and beauty of the Phase Plane and never want to plot anything against time again.... Again, the goal is to develop global understanding of the behavior of your model and when you are in 2-D the most important trick to remember is to plot your variables against each other.