Ecosystems: major concepts, how they are structured and how they work; examples and types of ecosystems. Energy flow in ecosystems: energy in the environment, productivity; food chains and trophic levels; pyramids in ecology. Biogeochemical cycles: quantitative studies and models of the biogeochemical cycles: nitrogen cycle, phosphorus cycle, sulfur cycle, carbon cycle, water cycle; sediment cycle, mercury cycle. Limiting factors. Resources: air, water, soil, minerals and waste. Biodiversity: living resources. Energy resources. Populations and communities: properties and structures of human population; interactions between two species; the habitat concept; ecological niches; diversity. The human population: growth, urbanization and regulation. Environmental economics and politics. Development and growth of ecosystems; evolution of the biosphere.