Evolution and nature | Of course, the model of evolution as being driven by environmental change is too simplistic. A better model would incorporate more of the give-and-take of nature. A species in adapting to its niche adopts some other unnecessary characteristic as a side-effect, thereby changing its niche. The species will not be perfectly adapted to its new niche, which will drive further change.
The point is this: A [a species] figures out/ evolves a way to take advantage of [extract energy from] B -- B being either another species, or "everything else" a.k.a. "the environment". The niche for B has therefore changed; a successful B will evolve a way to take advantage of A, changing the relationship from a parasitic one to a symbiotic one. Successful Bs are the only kind there are, given time. (This symbiotic relationship can be viewed as a curious kind of altruism. Seeing A do something that helps B, ask: how is A feeding off B?)
There are no parasitic relationships. How? Because the environment is not static, it's just everything else. (In an entropy diagram we would refer to A as the system, and B, the environment, as the surroundings. It's a convenient line to draw for certain arguments, but not a real one.)