Book excerpt: The branch of biology, which encompasses a comprehensive study of the animal kingdom and explores the structure, classification, embryology, evolution and distribution of animals, is referred to as zoology. In the Linnaean classification system, animals are grouped into the classes of Mammalia, Amphibia, Insecta, Pisces, Aves and Vermes. Some of the major sub-disciplines of zoology are animal physiology, invertebrate zoology, vertebrate zoology, behavioral ecology, etc. This textbook provides comprehensive insights into the field of zoology. Some of the diverse topics covered in this book address the varied branches that fall under this category. It is a complete source of knowledge on the present status of this important field.