Evolutionary biology is a multi-disciplinary subject, where every question and curiosity leads to diversified study. Therefore, it won't be wrong to say that in times to come, through evolutionary biology; much more will be known about our past, present, and future. This is a multi-disciplinary subject that requires detailed attention in every branch of study. This book strives to do the same and helps the reader in grasping every element of the content. Special regard has been given to lucid flow of topics, comprehensible language, and frequent use of diagrams, figures, and examples for better understanding.