Today, as never before, the application of knowledge of Ecology in our everyday life has become of paramount importance. Our very survival depends on these. Most of us are however blissfully unaware of the looming environmental catastrophe, though, the cliche words like ecosystem, sustainable development, and ecotourism are flying about. Few are really conscious about the logistics and the energy required to put ecological knowledge into practice. The aim of this small book is to bring within the reach of educated laymen, both the science as well as the philosophy of Ecology in simple and non-technical English. The first seven chapters of the book explain in simple English, with minimum technicalities, the basic principles of ecology and how the animals and the plants of the entire world are mutually dependant for their survival and flourishing.