This book is an invitation to biologists to dust off their elementary physics and think about biological processes in Newtonian terms. In his clear straightforward text, Colin Pennycuick demonstrates how physical laws operate at all levels, from cells to ecosystems, and shows how to apply them with precision. Rediscovering the nature of physical properties can lead to new insights and understanding. Pennycuick writes in a clear, accessible style, with many examples taken from the familiar world of zoology. One chapter deals with fractal geometry, a new way of measuring size, shape, and scale. A new feature of Pennycuick work is the extension of the biomechanical approach to ecosystem dynamics, the subject of the last two chapters. Students of animal behavior, ecology, and applied physics will enjoy working through the ideas in this stimulating volume.