again to its evolutionary past…. The time has come for biology to enter the nonlinear world (Woese & Fox, 1977). The practical ability to achieve Woese’s vision is now beginning to emerge. Biologists are increasingly able to integrate information across many organisms, from multiple levels of organization (such as cells, organisms, and populations) and about entire systems (such as all the genes in a genome or all the cells in a body) to gain a new integrated understanding that incorporates more and more of the complexity that characterizes biological systems (Box 3.1).

As the biological sciences advanced during the 20th century, separate fields emerged to tackle the complex subsystems that together make up living systems. Genetics, cell biology, ecology, microbiology, biochemistry, and molecular biology each took on various aspects of the challenge. The sheer volume of knowledge generated in each of these subdisciplines made it increasingly difficult for researchers who studied organisms to keep up with the progress being made by researchers studying cells, and those studying molecules rarely interacted with those studying ecosystems. Scientists in each of these specialties

BOX 3.1 The Levels of Complexity of the Biosphere SOURCE: Committee on a New Biology for the 21st Century.