Fundamentals of Evolution - O.P. Korzh - 2006

Part I. MICROEVOLUTION

Chapter 8. Adaptation as a Biological Phenomenon

8.1. Concept and Biological Significance of Adaptation

The term "adaptation" is used in evolutionary theory to denote the adjustment of organisms to specific environmental conditions throughout the evolutionary process. However, its interpretation varies somewhat across different biological disciplines. For instance, physiologists often define adaptation as minor modifications of an Organism resulting from immediate adjustments to temporary environmental changes—such as eye accommodation, acclimatization to cooler or warmer, more humid or drier climates, or high-altitude conditions. Since such changes occur within the reaction norm of a single individual, they are considered non-essential for evolution as a whole, and therefore, adaptations of this kind will not be discussed here.

In ecology, the term "adaptation" is used in at least two Senses: first, in a strictly evolutionary sense, as The process of change and adjustment of organisms to specific environmental conditions; second, as the actual relationship between an organism and its immediate living conditions, or the degree to which an organism fits its specific habitat. So what is it—a process, an evolutionary outcome, or a precondition for the existence of organisms? This chapter is dedicated to answering this question.

A central tenet of modern evolutionary science is that the evolution of organisms is adaptive, meaning it consists in The Development of traits that correspond to their living conditions. Thus, As a result of the historical development of organisms, their entire Organization turns out to be profoundly adaptive (with adaptation being understood in a broad sense).

In our view, adaptation can be most accurately defined as the set of morphophysiological, behavioral, population, and other characteristics of a particular biological species that ensures its specific way of life in a given environment. Consequently, adaptation in the evolutionary sense is not merely minor changes in an organism, nor even isolated properties, but the entire complex of species-specific traits (within the reaction norm) that together ensure the survival of a given species strictly within corresponding ecological conditions.

According to some evolutionary biologists, all evolutionary changes—ranging from The formation of new populations to the complexification or simplification of organization—are essentially just various manifestations of the development of adaptations. From an ecological perspective, any changes in organization that reduce organismal mortality caused by environmental factors are considered adaptations.

The imperfection of adaptations necessitates adaptive evolution driven by natural Selection.

Building on this, evolution can be viewed as the process of adaptation formation—adaptogenesis. All of this defines the place and Significance of the adaptation problem in modern evolutionary theory.

Therefore, adaptations should be understood as the complex of specific characteristics inherent to a particular species that distinguishes it from other organisms. It is precisely this complex that enables the existence of a given species under appropriate conditions; under any other conditions, this same complex will no longer be adaptive. Furthermore, this applies not to isolated traits of a given organism, but to their entire complex, since an individual develops as an integral, unified Structure. For example, due to their size, elephants can be considered sufficiently protected animals, which in itself requires a whole range of adaptations to sustain the organism (such as the development of a trunk used as a hand), taking into account their physiology and even behavior. At the same time, the invention of rifled long-range weapons by humans made these land giants vulnerable. However, thanks to their intelligence, elephants changed their behavior and moved from open spaces, where they were visible from afar, into tropical thickets, where the advantages of long-range rifles were nullified. In this case, behavioral traits take precedence in preserving the species, without requiring changes in Anatomical and morphological features. Similarly, any other organism can be characterized through its strictly species-specific traits.

Even species with very close ecological characteristics cannot be considered identical in their adaptive properties. This is because, In addition to the ecological niche, the adaptive complex encompasses a vast array of other traits, ranging from physiology to the ethological STRUCTURE OF THE population.

As for the Evolutionary Significance of adaptation, the situation is even more complex. Overall, adaptation can be considered, in a certain sense, the outcome of the evolutionary process, whereby a specific species possesses a set of adaptations suited to its living conditions. However, this outcome may prove useless even with minor environmental changes, thereby triggering a new demand for evolutionary change, and the cycle repeats.

In reality, the aforementioned approach is overly simplistic. In truth, adaptation is never absolute; rather, it manifests as a reaction norm that allows organisms to withstand certain fluctuations in environmental conditions (short of catastrophes). If environmental changes exceed the reaction norm of the organisms in question, they face two alternatives: either modify their adaptive complex accordingly, or perish as a biological phenomenon. Therefore, adaptation could be recognized as a species-specific characteristic of particular organisms. Since a universal organism (capable of surviving simultaneously under any conditions) would be the most progressive, adaptation—by restricting a species to specific conditions and limiting its distribution—cannot be considered the ultimate goal of the evolutionary process. Instead, it can be viewed as a necessity without which real species cannot exist, yet one that brakes the overall pace of evolution.

In the evolutionary process, of utmost importance is not the adaptive complex of a given species in general, but the capacity of organisms to adapt to substantial environmental changes or stability. In other words, we must abandon the notion of adaptation as something immutable, established once and for all, and return to the inherent activity of the individual. The phenotype realized in specific microclimatic conditions may differ significantly from individuals of the same species developing under different conditions (the very phenomenon of population polymorphism). Yet, a crucial role in this process is played by The activity of individuals capable of selecting appropriate microclimatic conditions and steering their ontogeny (or the ontogeny of their offspring) along the corresponding pathway.