Basics of Evolution - Korzh O.P. - 2006

Part I. MICROEVOLUTION

Chapter 8. Adaptation as a Biological Phenomenon

8.3. Adaptation as an Essential Feature of the Organization of Life

One of the leading Features of the Organization of life is its adaptability, which is directly related to Structure/149.html">The problem of teleology and expediency.

All properties of any Organism have an adaptive significance and correspond as closely as possible to environmental requirements.

This applies to all Levels of organization of living matter—from the cellular to the ecosystem level—confirming the expediency of living organism adaptations. The vast majority of adaptive traits we discussed earlier pertain to the organismal level.

It is clear that within a single organism, all its parts are mutually adapted to perform specific Functions. An example of such adaptability at the Molecular and genetic level is THE PRINCIPLE OF complementarity, which underlies chromosome duplication, METABOLISM/31.html">Transcription, Translation, and so forth. Enzymes interact exclusively with their specific substrates. Any living matter relies on the principles of mutual adaptation, meaning the surrender of independence by individual parts and their subordination to the biological rhythms of the entire system.

The Emergence of multicellularity inherently necessitated the mutual adaptation of Cells for coexistence. Moreover, THE ORIGIN OF living matter can be viewed to a certain extent as a consequence of the mutual adaptation of macromolecules for coexistence within a single Cell.

According to A.M. Severtsov, the evolution of organisms is adaptive and consists in The Development of traits that correspond to the specific environment in which the organism exists. Furthermore, almost all Organs of any organism acquire adaptive properties, including internal ones that are not directly related to the environment. The individual parts of a single organ also mutually adapt (for example, the PARTS OF THE eye). The central and peripheral nervous systems, nerves and Muscles, individual cells, and so on, are all coordinated.

This also applies to so-called physiological adaptations: the transition of plants from C-3 to C-4 Photosynthesis, the acquisition of toxicity or inedibility by an organism, The formation of electric organs in certain fish, etc. - all these are adaptations of organisms at the physiological level to specific living conditions (therefore, we will no longer focus on the mutual adaptation of individual parts of an organism to perform their immediate functions).

There remains another group of adaptations that deserves special attention: complex adaptations. They are complex because they form a multi-component, intricate mechanism with numerous factors without which it cannot function.

Thus, an example of a complex adaptation is found in the bombardier beetle (Brachinus crepitans). It is believed that its defensive apparatus, located at the end of the abdomen, evolved from mucous glands that initially produced lubricating mucus. The apparatus itself consists of several glands, a storage reservoir for hydroquinone and hydrogen peroxide, and a combustion chamber (Fig. 8.12). When threatened, the mixture of substances from the reservoir is forced into the combustion chamber, where the enzyme peroxidase is added. In the presence of this enzyme, hydrogen peroxide oxidizes hydroquinone, converting it into toxic quinone. The entire process is accompanied by the release of molecular oxygen, which expels the liquid from the chamber and sprays it. When the secretion contacts the Skin, it causes inflammation, and while the enemy recovers, the bombardier manages to leave the "battlefield".

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Fig. 8.12. Bombardier beetle (Brachinus crepitans) and its defensive apparatus (drawn by O.V. Karnaukhov):

1 - hydrogen peroxide-secreting gland; 2 - reservoir; 3 - combustion chamber; 4 - enzyme-secreting gland; 5 - valve; 6 - outlet orifice

Such an adaptation is considered complex because it fails to work if even a single component is missing. For instance, in the absence of a storage reservoir, hydrogen peroxide—which is toxic in its own right—would harm the beetle. Without peroxidase, all Other components of the adaptation are equally useless, making it difficult to explain the emergence of the entire adaptation in a few stages. It is believed that the bombardier's defense mechanism could have formed through the combination of favorable Mutations.

Fig. 8.13. Evolution of the eye (1 - after E. Hadorn, R. Wehner, 1989; 2 - after Yu.I. Polyansky, 1987; 3-6 - after A. Romer, T. Parsons, 1992):

1 - eye of a turbellarian (Planaria gonocephala) with a pigment cup; 2 - eye of a pelagic polychaete (Alciope); 3 - eye of a frog (Rana); 4 - eye of a horse (Equus); 5 - eye of a fish (Salmo); 6 - eye of a bird (Columba)

The origins of adaptations such as carnivory in plants or the vertebrate eye are somewhat easier to explain. In this case, it is straightforward to trace the phylogenetic Stages of the respective adaptation's formation (Fig. 8.13). Overall, we can classify almost all specialized organs of highly developed animals and plants that function only in the presence of all components as complex adaptations. These include The structure of flowers adapted for pollination by specific insects or other pollinators (the presence and arrangement of nectaries, coloration and structure of petals, length and arrangement of stamens and pistils, etc.), the structure of a horse's limb, and a bird's wing. In many cases, the direct organization of a given adaptation depends on the specifics of its function. For example, the structure of a bird's wing varies depending on its flight characteristics (forest vs. aquatic bird, various soaring techniques, and other details). In all the Examples provided, the main evolutionary stages of the formation of specialized adaptations are clearly traceable. The next subsection is devoted to the problem of the Formation of the entire complex of species-specific adaptations.