The Evolution of Physiological Systems

So far in this book I have treated genetic evolutionary change as if it were a passive response to the four processes illustrated in Figure 4.1 . Actually, any theory of Natural Selection implies that genetic evolutionary change feeds back and alters the process of Differential Survival. In Figure 5.1 I have illustrated the main ways in which this feedback is accomplished in animals. In plants, of course, behavioral and social change are omitted. All of these ways are interdependent to some extent, but it is appropriate to begin with the lowest level of organization, that of change in physiological systems, or organic evolution.