By Rebecca L. Johnson
The Biosphere: Earth’s Life Zone introduces students to the thin realm of air, water, and land on our planet’s surface in which organisms live. Students learn that Earth’s surface is a patchwork of biomes—deserts, forests, grasslands, rivers, lakes, oceans—that vary with latitude and elevation and are characterized by the major vegetation of ecosystems within their boundaries. By examining a variety of land and water biomes, students come to understand the hierarchy of organization within the biosphere. They learn that living things interact with each other and with their nonliving environment. They learn that the parts of Earth—the air, water, land, and living things—are connected through global cycles of water, oxygen, and carbon and the one-way passage of energy through food webs. At the end of each two-page spread, a brief statement called The Bottom Line reinforces students’ understanding by summing up the key ideas about the biosphere covered in those pages.