Energy is a common currency of ecological interactions. In this dissertation, I consider ecological energetics at different temporal, spatial and organizational scales. In my first chapter, I examine the energetics and thermoregulation of an enigmatic taxon: dinosaurs. From fossil evidence and assessment of living vertebrates I conclude that many non-avian dinosaurs were likely thermally intermediate, or \u27mesothermic\u27. In my second chapter I detail the empirical evidence gathered to buttress my claim of dinosaur mesothermy. In my third chapter, I show how ecosystem rates of carbon flux, gross primary production and total biomass can be linked to individual body size. In my fourth and final chapter I explore how differences in metabolism and thermoregulation lead to predictable difference in marine predator biogeography, diversity and food consumption at ecosystem scales. A focus on organismal energetics offers insight into ecological interactions across space and time
