Based on the CBSE syllabus, this book is meant for students of class 11 of Bihar, Jharkhand and all other state boards following the CBSE syllabus. Difficult biological processes and principles have been explained in simple language. The lucid text is supported by clear, labelled diagrams. Each chapter is followed by a comprehensive exercise section, which includes all types of questions asked in the examination. A large variety of objective questions with their answers is given in the last section of the book which will help students prepare for various competitive examinations.