Ecology

Thomas Kuhn's concept of paradigm, introduced in The Structure of Scientific Revolutions (1962), changed the common view of how science progresses. A paradigm is a set of overarching principles and methods shared by a scientific community within which its adherents conduct "normal science." Science advances by changing its paradigms in revolutions.

The earliest putative ecological paradigm, the Clementsian organismic paradigm was a descendant of the traditional design or balance-of-nature concept, presuming a stable or equilibrium state as a norm. It is associated with Nebraska botanist Frederic E. Clements, who developed a concept of community or "association" as an organism or superorganism (1916). Clements envisioned the community as developing to converge on a "climax" or a stable endpoint determined by climate. This paradigm dominated early-twentieth-century ecology in America and was evident in major animal ecology references and general textbooks.

Some scholars describe a "revolution," or paradigm change, in ecology in the 1950s, with the revival and widespread acceptance of the "individualistic concept" of H. A. Gleason (1939). The shift from Clementsian ideas of equilibrium, homogeneity, and determinism to Gleasonian ideas of nonequilibrium, heterogeneity, and stochasticity greatly increased the difficulty of ecology and has dominated its recent development.

Another paradigm in ecology, population regulation, has a long natural-history tradition and was introduced into ecology in the 1920s, described by some as the "Golden Age" of theoretical mathematical ecology. Raymond Pearl resurrected the earlier "logistic curve" dN rN (K N) and introduced it as a "law" of population growth. The equation includes r as the rate of population growth, K as the limiting maximum population, N as the number of individuals, and d signifying change. Subsequently the physicist Alfred J. Lotka, who joined Pearl's laboratory, and Vito Volterra, a mathematician, expanded the logistic to two species cases, especially competition. Mathematical population ecology persisted in the face of extended criticism and subsequent concerns about the basic equation. It remains to the present in much-elaborated forms with the assurance that populations at some scale are regulated but the mechanisms remain elusive.