The natural science core course provides a broad foundational treatment of concepts and processes that operate in ecological systems. It covers interactions among water, soils, the atmosphere, and basic life processes (respiration and photosynthesis) in terrestrial and aquatic ecosystems, including the principles of energy flow and the cycling of matter. It covers ecological principles such as population growth and regulation, trophic interactions, ecological networks, and community change. It covers evolution and natural selection. The course draws examples from some of the dominant habitats on earth, including rivers, lakes, wetlands, forests, deserts, and agricultural systems.