The present publication is divided into three sections i.e. Cytology, Genetics and Evolution. In the Cytology section, many new informations have been added in the structure and physiology of plasma membrane, mitochondria and chromosomes. Examples are chosen both from animals and plants to focus on the genetics concept. Attempt has been made to include the recent work conducted by scientists in the field of Evolution, which has increased our knowledge many fold. The book is designed to satisfy the present day syllabi of various India Universities.