Ecology is a biological branch that is concerned with the study of the interactions between organisms and their environment. It primarily focuses on the biotic and abiotic components of the organisms' environment. Ecology studies the distribution, biodiversity, biomass and populations of organisms. It also focuses on the competition and cooperation among species. Concepts from this field are often applied in areas such as wetland management, conservation biology, city planning, community health, applied science, human social interaction, etc. It is also applied in natural resource management such as forestry, agroforestry and agriculture. Ecology works to explain the movement of energy and materials via living communities, life processes, adaptations and interactions, the successional development of ecosystems, and the distribution of organism's biodiversity in the environment. This book is a compilation of chapters that discuss the most vital concepts in the field of ecology. Such selected concepts that redefine this field have been presented herein. The textbook is appropriate for students seeking detailed information in this area as well as for experts.