This 10-chapter guidebook, designed to supplement a basic textbook in biology, provides lessons that demonstrate the application of biological principles and concepts. Chapter 1 is an introduction. Chapters 2 to 5, organized around the key concept of homeostasis, discuss the evolution of the external environment of earth compared to the internal environment of life forms (chapter 2), examine ecological principles (chapter 3), and discuss systems developed by different organisms to obtain nutrients from their external surroundings and to process these raw materials into a form suitable for the maintenance of their internal milieu. Chapter 6 discusses different sensory systems present in organisms which enable them to function effectively in their environment. Chapters 7 and 8 discuss survival of the species and how a species passes on a particular environment and structure to its offspring. Chapter 9 examines how life forms function in extreme abiotic environments (the ocean and outer space) as well as diseases. Each chapter includes an introduction (providing an overview of themes and ideas for instruction), a list of performance objectives, a brief content overview, activities, suggestions for additional activities, and an annotated list of resource materials. Pages which can be duplicated for student use are also included. (JN)