This book is an exercise in predictive ecology. It draws together a widely dispersed body of empirical relations that relate biological form and process to body size. These relationships are then applied to ecological problems; that is to say, to problems whose solutions require some knowledge about temporal and spatial patterns in the characteristics of organisms and in their abundance.

Although the book is largely based on the work of autecologists and environmental physiologists and is applied principally to the interests of ecologists, it should appeal to anyone interested in the development of a broad, quantitative science of organism function. The book was written for senior undergraduates, who should have some feeling for the goals and jargon of ecology. Nevertheless, the approach and information are original enough that many established scientists will find it interesting too. I hope the book is sufficiently clear that it is also open to the educated (if perseverant) layman.

In writing this book, I have used a simple design. I begin with a sketch of one typical body size relationship (Chapter 1) to show why the subject of this book deserves better recognition and wider use. In brief, these body size relations represent scientific theories and hypotheses, which include many examples of general, quantitative biological laws.