This handbook has been designed for the students of Class XI & XII for a quick revision of the various concepts of Biology. Handbook of Biology is a multipurpose quick revision resource with unique format which displays concepts clearly, places them in context and crisply identifies and describes all the factors involved. This book has been divided into 38 Chapters namely Cell: The Unit of Life, Biomolecules, Cell Cycle and Cell Division, The Living World, Biological Classification, Plant Kingdom, Animal Kingdom, Structural Organisation in Animals, Digestion & Absorption, Breathing & Exchange of Gases, Body Fluids & Circulation, Locomotion & Movement, Excretory Products and Their Elimination, Neural Control and Coordination, Chemical Coordination & Integration, Human Reproduction, Reproductive Health, Human Health & Disease, Morphology of Flowering Plants, Anatomy of Flowering Plants, Mineral Nutrition in Plants, Photosynthesis in Higher Plants, Transport in Plants, Respiration in Plants, Plant Growth and Development, Reproduction in Organisms, Sexual Reproduction in Flowering Plants, Principles of Inheritance & Variation, Molecular Basis of Inheritance, Biotechnology: Principles & Processes, Biotechnology & Its Application, Strategies for Enhancement in Food Production, Microbes in Human Welfare, Evolution, Ecosystem, Organisms & Population, Biodiversity & Conservation and Environmental Issues. Each chapter contains Key Notes, Terms, Definitions, and Formulae. The book can be highly useful for not only the students of Class XI & XII but also for the aspirants of Engineering and other Competitive Examinations. The book also contains an Appendix at the end after the chapters.