The study of the flow of energy from the sun through and up the trophic levels, expressed in calories. With movement up each trophic level, there is a very great loss of the energy available as food. ‘A more appropriate name for ecological energetics could refer to limitations by a single component of the resource’ (Brooks et al. (1996) Ecoscience 3, 3). See also Kooijman et al. (1999) J. Theor. Biol. 197.