Present book on ecology is to give the reader a better understanding of the way life functions on earth and how it is organized. This book will introduce basic concepts and definitions required to establish a course that is both biological and ecological in approach. You will learn that there are numerous terms in ecology which basically mean the same thing and that there are also a plethora of view on precise definitions. As ecology emerged in the 19th and early 20th centuries many concepts of ecological organization were proposed.