Fundamentals of Evolution - Korzh O.P. - 2006

Part II. MACROEVOLUTION

Chapter 12. Evolution of Ontogeny

Evolution, as a process of historical development of organisms, consists in the adaptation of specific organisms to their ambient environments. Phylogeny (historical development) can be conceptualized as a chain of interconnected ontogenies (cycles of individual development). The advancement of the Modern Synthesis has successfully resolved a wide range of issues concerning microevolutionary mechanisms. Heredity and Variability—concepts originally introduced by Charles Darwin—constitute the genetic foundation of evolutionary changes within the elementary evolutionary unit, the population, under METABOLISM/18.html">The Influence of elementary evolutionary factors, as discussed previously. The consequence of such shifts in population Structure is The formation of adaptations, whereby organisms fit specific environmental conditions that ensure the viability of respective species.

At the same time, these mechanisms do not provide a full explanation for all patterns of the evolutionary process. The individual development of organisms, which ensures the realization of the phenotype, remains insufficiently understood. Since the phenotype is the active bearer of life and the primary target of natural Selection, the course of ontogeny is undoubtedly significant for evolution. Today, however, the Organism is often viewed merely as a passive object manipulated by natural selection (according to contemporary views, as an external factor rather than a consequence of the organisms' own activity). As we can see, the Struggle for Existence is thus disregarded. These Perspectives cannot be considered an accurate reflection of the true state of affairs in nature.

Despite an overwhelming amount of research, The problem of mechanisms and GENERAL PATTERNS OF ontogeny is still recognized as one of the most enigmatic in modern natural science. Even pessimists who believe that science as an endeavor is nearing its "end" agree that the process by which a single fertilized Cell transforms into a multicellular organism remains one of biology's enduring mysteries. This issue acquires special significance in the light of evolutionary events, because what matters is not only the status of the organism within certain biological systems, but also all the changes it undergoes throughout ontogenetic transformations. I.I. Schmalhausen was among the first to draw attention to the evolutionary shifts resulting from developmental plasticity in organisms.