Using Earth's Resources explains some of the different regions of Earth, such as rain forests, oceans, deserts, and mountains, from which people collect resources to use. Each of the four books focuses on a different region and the specific resources that come from these areas. However, the same key concepts are developed across books to help students focus on the big ideas. The theme explores the natural resources Earth provides and how people use these resources. The theme also develops an understanding of how people can help to conserve and recycle to use these resources wisely. Students use the specific content and vocabulary within each book to discuss and examine these big ideas, or Key Concepts. The Theme Set Program is designed for differentiated instruction. Each Theme includes four books written at four different reading levels.