This introductory chapter presents some general background to theoretical work in energetics. I start with an observation that feeds the hope that it is possible to have a theory that is not species-specific, something that is by no means obvious in view of the diversity of life! A brief historical setting follows giving the roots of some general concepts that are basic to Dynamic Energy Budget (DEB) theory. I will try to explain why the application of allometry restricts the usefulness of almost all existing theories on energetics. This explanation is embedded in considerations concerning philosophy and modelling strategy to give the context of the DEB theory.

Energy and mass fluxes

Hope for generality

Growth curves are relatively easy to produce, which may explain why the literature is full of them. Yet they remain fascinating. When environmental conditions, including temperature and food availability, are constant and the diet is adequate, organisms ranging from yeasts to vertebrates follow, with astonishing accuracy, the same growth pattern as that illustrated in Figure 1.1. This is amazing because different species have totally different systems for regulating growth. Some species, such as daphnids, start to invest, at a certain moment during growth, a considerable amount of energy in reproduction. Even this does not seem to affect their growth curve. So one wonders how the results can be so similar time and again. Is it all a coincidence, resulting from a variety of different causes, or do species have something in common despite their differences? Are these curves really similar, or is the resemblance a superficial one?