Photographs of Earth taken from space show that our planet is a single sys-tem. When students observe Earth from this perspective, they can readilysee oceans, clouds, and continents that are lit by sunlight, the energy thatsupports life on Earth. We do not know of any other planet that has waterand an atmosphere like Earth’s. (However, the components alone—solids,liquids, gases—without continuous changes in temperature, composition,and chemistry, might not support life as we know it.) To understand the waythe Earth system works, students first must learn what these components areand then examine ways that they interact and change. To do this, they willbuild terrariums as models of Earth. Throughout these four units, studentswill learn how scientists study Earth’s system to understand human-inducedand natural changes.