As much as possible the mutual interactions between organisms and their physical and biotic environment are approached from a nature philosophy point of view by illustrating the generally valid laws and relationships, rather than through the classical nature historical approach of description and classification of facts. The following concepts and aspects are introduced: relationships and interactions between organisms and their physical environment; exchanges of radiation, heat, mass and momentum with special reference to morphological and physiological adaptations. Fundamental ecological principles and concepts; structure, function, dynamics, development and evolution of ecosystems (individual, population, community, abiotic units), energy flow and biogeochemical cycles; ecosystem types, ecosystem management, and systems ecology. The course materials are structured and introduced along the line of hierarchical organisation levels. After the Preface, and The physical environment of energy and climate; the student is introduced to: Adapations of (individual) plants and animals to their environment; General characteristics of populations; Growth of populations; Communities: general characteristics, competition and predation; Structure and dynamics of communities; Landscapes; Ecosystems and ecosystem productivity; Nutrient cycling; Biogeochemical cycles; Biodiversity. The sustainable exploitation of ecosystem products and services, as well as the impact of mankind on ecosystem sustainability are covered. The course is ending with a discussion of the relationships between energy, ecology and economy within the framework of the human civilisation and development.