Figure 1.8: Epidemiologists study how diseases spread. The above map shows where humans
contractedWestNileVirusbetween2000and2006. ItisbelievedthevirusenteredtheUnited
States in New York City in 1999. Notice how rapidly the virus spread across the U.S. ( 13 )
Figure 1.9: Alexander von Humboldt mapped the distribution of plants across landscapes
and recorded a variety of physical conditions such as pressure and temperature. Today,
biogeographers study the diversity and distribution of organisms across Earth. ( 20 )