Notions of ecology

The notions of ecology concern the study of the relationships that link living organisms to one another and to their environment. They help us better understand how ecosystems function, as well as the balances and imbalances that characterize them. This book has been designed to present, in a progressive and accessible way, the main concepts of ecology. It highlights the components of ecosystems, their interactions, and the processes that ensure their functioning and stability. The aim is to help readers understand how life is organized and maintained at different scales, from local environments to large natural systems. Special attention is given to the exchanges of matter and energy between living organisms and their environment. These flows, essential to ecosystem dynamics, illustrate the deep interdependence that exists in nature and the continuity of ecological processes. This volume is the result of a synthesis of recent work in ecology. It is primarily intended for students in the common core of Earth and Universe Sciences (STU, Geology) and Territorial Planning programs, for whom these concepts provide an essential foundation for understanding current environmental challenges. It is also addressed to students of Life and Natural Sciences, as well as Medical Sciences. Finally, it may support teachers in preparing lectures, tutorials, and laboratory sessions. This work is not fixed. It is intended to remain open and evolving, welcoming any suggestions that may improve its clarity or content, in a spirit of sharing and continuous improvement. Finally, we would like to express our deep gratitude to our teacher, Mrs. Fadhila Hamoudi, whose passion for natural sciences and teaching has influenced generations of students at the University of Science and Technology Houari Boumédiène (USTHB). Her commitment, rigor, and humanity have greatly contributed to inspiring scientific vocations and fostering a love for ecology. This work stands as part of that scientific and human legacy, to which we pay sincere tribute.