The monograph presents the results of research on the structural and functional organization of biological systems in the conditions of the North .. Data on the diversity of floodplain meadows, the structure and productivity of price populations of some types of medicinal plants. The structural diversity of mycorrhizal associations of herbaceous and woody plants with soil fungi is considered. Information on the species diversity and structure of populations of hardwings, inhabitants of xylotrophic fungi and myxomycetes and the spatial distribution of beetles in tundra biogeocenoses. The results of studies of chronobiological and physiological mechanisms of human adaptation to climatic conditions in the North are presented . The book is intended for botanists, zoologists and human physiologists, university teachers, graduate students and students of biological specialties, agricultural and forestry workers, educational and medical institutions .