With the growing awareness of the critical environmental problems facing the world today, ecology, the scientific study of the complex web of interdependent relationships in ecosystems, has moved to the center stage of academic and public discourse. The term ecology comes from the Greek word oikos ("house") and, significantly, has the same Greek root as the word economics, from oikonomos ("household manager"). Ernst Haeckel, the German biologist who coined the word ecology in 1868, viewed ecology as a body of knowledge concerning the economy of nature, highlighting its roots in economics and evolutionary theory. He defined ecology as the study of all those complex interrelations referred to by Darwin as the conditions of the struggle for existence.

Ecologists like to look at the environment as an ecosystem of interlocking relationships and exchanges that constitute the web of life. Populations of organisms...