This book takes a fundamental, biophysical approach toward animal physiology. Shows the progressive changes, modifications, and developments of physiological systems from simple to complex animals. Comparisons show the similarities and differences in how animals function, but stress fundamentally similar adaptations in very different animals. Also, provide comparative physiology of animals, in a strongly environmental context. It provides full analysis of the basic principles of physiological adaptations, in both vertebrates and invertebrates and how they allow integration with the environment, detailed and integrated reviews of how animals sense, react to and cope with particular environments - the marine and freshwater worlds, the particularly challenging seashore and estuarine zones, the different kinds of terrestrial habitat, and the parasitic environment. Integrated with ecological principles and with behavioural responses used by animals in coping with environmental challenges. This book provides a stand-alone core text for undergraduate and graduate courses in comparative physiology, animal physiology, or environmental physiology and environmental biology.