Chapter Animal kingdom explains the differences in structure and form of different animals. When we look around, we observe different animals with different structures and forms. Over a million species of animals have been described until now, the need for classification becomes all the more important. The classification also helps in assigning a systematic position to newly described species. It also teaches other topics such as Basis of Classification, Classification of Animals and more. There are a few fundamental features that are common to various individuals in relation to the organization of cells, body symmetry, nature of coelom, pattern of different systems such as digestion, circulatory or reproductive systems. These are the fundamental features that form the basis for the classification of animals, some of these are explained in detail in the chapter.