Complexity principle of extremality in evolution of living organisms by information-theoretic entropy

We consider evolution from a multiorgan (multistage) organism, which has a number of identical organs (e.g. a trilobite with many pairs of legs), to another organism, which has one organ modified (specialized) into a different part of the body (e.g. claws of a crab) at the expense of reduction in the number of non-modified organs. We observe that in early stages of evolution multiple organs (pairs of legs) may be created, and that extra organs may rapidly be reduced during later stages. We ask: Why do extra organs evolve during early stages of evolution? To answer the question we construct and then analyze a simple although basic model of evolution based on information-theoretic entropy. We show that an extremality principle is valid in which the increase in number of identical organs is led by the gradient of information entropy increasing with the number of these organs. On the other hand, the reduction in number of these organs, observed for later stages of evolution, results from catastrophes between submanifolds of evolution, the surfaces on which modifications (specializations) of organs may occur. Our conclusion is that modification (specialization) of organs, while in principle consistent with the entropy principle of extremality, may lead evolution to a region of catastrophes, and that these catastrophes may explain extinction of some species. The same mathematical model is applied for explanation of parallel evolution of animals and for some evolution problems of flowers.