Evolutionary Biology is a fast developing subject to encompass animals and plants, past and present. This book on Organic Evolution is an updated exposition of the subject to include the latest concepts theories and observations in a simple and lucid language. Text is divided into five part: Part-I deals with concepts, evidences and theories of evolution. Part-II peeps into the Mechanism of Evolution Part-III provides a systematic approach to the process of Speciation. Part-IV explores the basic patterns of Evolution and Part-V provides an insight into the origin of life fossil- records and history of life on Earth.