Figure 4.2 Spatial variation in the environment. As one travels from the west coast to the east coast of the United States, there is tremendous variation in the natural and human-altered habitats.

Photos by (clockwise from top center): USDA Farm Service Agency, © 2012 Google; DigitalGlobe/Getty Images; DigitalGlobe/Getty Images; U.S. Geological Survey, © 2012 Google; USDA Farm Service Agency, © 2012 Google.