Many organisms have pronounced stages (e.g., juvenile and adult stages) where development, reproduction and survivorship vary strongly with the biological environment. Since fitness is the cumulative outcome of these life-history traits, selection in structured organisms has more complexity than unstructured organisms. Physiologically-structured population models provide a good approach to scale from life history experiments to both population and evolutionary dynamics. Using the freshwater zooplankton Daphnia as an exemplar, I will show results from a series of experiments and modeling that illustrate how stage-structure influences population dynamics, and how population dynamics can influence selection among asexual genotypes. More specifically, the interaction between a coupled algal resource and the resource-dependent life-history of Daphnia generates a range of population dynamics that includes alternative states and alternative co-existing limit cycles. This range in population dynamics is predicted to generate a correspondingly wide range of evolutionary dynamics from slow to rapid selection.