Biochemical mechanisms of evolution and the role of oxygen

The concept formulated here presumes the existence of specific mechanisms o f evolution that save intermediate (and therefore imperfect) forms of organ isms from elimination by natural selection. A change in the life strategy m ade in situations when the appearance of a new trait worsens, rather than i mproves, adaptation of the organism to the changing environment can be one of these mechanisms. The concept postulates that, in such cases, K-strategy (relatively low rates of reproduction and activity in general but long lif e span) is replaced by r-strategy (high activity and reproduction but short life span). A decrease in the life span upon the K --> r transition is sug gested to be an unavoidable consequence of an elevation of formation of tox ic reactive oxygen species under conditions of increased rates of aerobic m etabolism required for the increased life activity. The phenomenon of giant ism of transgenic tobacco plants that overproduce a mitochondrial heat shoc k protein (experiments done by A. Moore) is assumed to be explained by an r --> K transition. On the other hand, a decrease in the life activity and a considerable increase in life span occurring in a nematode upon mutations inhibiting the CoQ biosynthesis (S. Hekimi) might serve as an example of a K --> r transition.