[Causes and conditions of formation of the aromorphic organization].
Analysis of data concerning the origin of terrestrial vertebrates allows to conclude that the organism undergone the aromorphosis (=arogenesis) not only improves the general degree of organization, but also becomes able to survive in much more complex and diversified environment than its ancestors and, consequently, expands the ancestor's adaptive zone. It was shown that aromorphosis occurs when the ancestral taxon specializes in a narrow adaptive zone having vacant neighboring zone which might be occupied. The aromorphic adaptations are formed very slowly in the course of so-called coherent evolution by accumulation of certain multiply adaptations and by their coordination with each other. In the end, the set of these adaptations overrides the oscillation range of environmental conditions in the ancestral adaptive zone and can be considered as a pre-adaptation to adaptive zone expansion. Some features which are characteristic for the modem 'aromorphic' groups such as Tetrapoda, Avia and Mammalia, appeared independently and asynchronously in many related taxa. However, appearance of a few detached features does not help to widen an ancestral adaptive zone. Taxon becomes really aromorphic only due to the simultaneous formation of all adaptations allowing the expansion of ancestral adaptive zone, i.e. successful exploration and occupation of neighborning adaptive zone.
Severtsov
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AS
D000220:Adaptation, Biological; D000818:Animals; D005075:Biological Evolution; D004777:Environment