Feedback loops are widespread in nature. It's easily recognized, for example, that overpopulation may result in over-exploitation of resources such as food to the point that population size crashes. In turn, the reduction of population size allows the resource to rebound, allowing the population to once again increase its size—back and forth, oscillating around some average value.
Not so obvious is the feedback loops between an organism's effect
on the environment and the environment's effect on the organism. Organisms
inevitably affect the environment that they live in—sometimes for the better, sometimes
for the worse. The point is, that the population has to live in a changed environment
which affects selection pressures on the population. As the population evolves, its
effect on the environment changes. The result is a feedback loop that might in the long
run finally end in equilibrium. In real life, however, outside influences usually
intervene, and both the organism and the environment are besieged by multiple factors.
Once again, we're reminded that biology often is fun, but it's never
simple!
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Vandermeer, J. 2004. The importance of a constructivist view. Science 303:472-474.