Mammals are a comparatively recent group in terms of their evolutionary history, yet they have successfully settled in significant numbers in virtually every type of habitat on Earth. Their success is linked to their ability to extract nutrients in the gut, circulate and supply tissue with essential materials, control their own internal environment, obtain data on external environments and communicate accurately, move and maintain posture, and integrate body systems. This book explains the function of the organs involved and how the tissue structures allow these life processes to occur. The processes are explained through photomicrographs, electronmicrographs and photographs interpreted by drawings, flow diagrams, graphs and notes.