Aromorphosis

(in Russian, also called arogenez), a morphological and physiological process, one of the main trends in the biological progress of living organisms whereby their organization becomes increasingly complicated in the course of evolution. The term was introduced by A. N. Severtsov, who used the word “aromorphosis” to refer to the most general adaptive changes in organization and functions. Aromorphosis is usually accompanied by an increase in the intensity of the life processes of animals and in the variety of their manifestations (differentiation). These changes are useful and essential when the habitats of the organisms change while the organisms remain stable. Aromorphosis enables qualitative jumps that raise the level of organization of a species and enable it to adapt to life under new conditions, thus helping to enlarge its range. Changes of the aromorphosis type are followed by a period in which individual adaptive changes take place—idioadaptation. The gradual-ness of the evolutionary process is reflected in the alternation of periods of aromorphosis with periods of individual changes in organization at the previous level along with broad adaptive radiation of new groups along the road to adaptation to different conditions of existence. In the foreign literature (B. Rensch, J. Huxley, G. de Beer) these two main trends in the evolutionary process are called anagenesis and cladogenesis. As an example of aromorphosis in the evolution of higher vertebrates Severtsov cites the qualitative jump in the transition from reptilian ancestors to mammals. The four-chambered heart, the alveolar structure of the lungs, diaphragmatic breathing, and other factors raised the level of metabolism in mammals and increased their ability to adapt to changes in living conditions. Bearing young in the mother’s uterus and feeding them milk extended their chances of survival.