As energy is limiting in biological systems, the way it is allocated to structures and functions is under selective pressure. The energetic approach provides a way to link ecological, physiological, and nutritional studies. This has become a major basis for research in my laboratory, using echinoderms as the group for investigation. This involves research at all levels of organization, in the laboratory and in the field. We are attempting to understand the ways individuals of different species with different life-history strategies allocate material and energy to survival, growth, and reproduction. The ways in which physical (temperature, salinity, pollutants) and biological (food, sublethal predation) variables affect allocation provide an interesting aspect of the studies. These studies have important implications for aquaculture of sea urchins.