Early humans became keen observers of nature by tracking prey, identifying edible plants, and noting the time of year when different plants could be gathered. Humans began to learn about the relationships between living things and the environment. As the field of ecology grew, its focus went beyond the simple cataloging of living things in the world. Ecologists also became interested in understanding how living things function and how they interrelate with one another and with the environment. With the help of content-rich infographics, diagrams, and full-color nature photographs, readers will learn how living things are classified, the environments in which they live, what ecosystems and biomes are, and the place and role of humans within the biosphere.