There is a rich mathematical literature, going back at least to Vito Volterra, describing the dynamics of populations in ecological time. There are many reasons, however, to place such dynamics in an evolutionary framework, allowing examination of how behaviors and interactions change over longer time scales. Such approaches can inform the description of interactions on the faster time scales and explain why we observe the systems we do; furthermore, they can provide insights about how systems will change in response to changing environmental conditions. General approaches to such questions will be discussed, with specific application to problems of resource use and stoichiometry.