This book presents a physicist's view of life. The primary life functions of animals, such as eating, growing, reproducing and getting around all depend on motion: Motion of materials through the body, motion of limbs and motion of the entire body through water, air and on land. These activities are driven by internal information stored in the genes or in the brain and by external information transmitted by the senses. This book models these life functions with the tools of physics. It will appeal to all scientists, from the undergraduate level upwards, who are interested in the role played by physics in the animal kingdom.