2. System Any size group of interacting parts that form a complex whole.
3. Key Concept How is Earth a system? Its aim is to understand Earth as a system made up of numerous interacting parts, or subsystems.
4. Key Concepts What is a system? Any size group of interacting parts that form a complex whole.
5. Key Concept Where does the energy come from that powers Earth’s systems? One source is the sun, which drives external processes that occur in the atmosphere, hydrosphere, and at Earth’s surface. Earth’s interior is the second source of energy.
6. Key Concept How do humans affect Earth’s system? Our actions produce changes in all of the other parts of Earth system. Significant threats to the environment include air pollution, acid rain, ozone depletion, and global warming.
7. Key Concept What makes a resource renewable or nonrenewable? Renewable resources-plants, water, and solar energy-can be replenished over relatively short time spans. Nonrenewable resources –fuels of oil, natural gas, and coal- are created slowly over millions of years.
