12/10/2023 0 Comments Molecular chaperone definition![]() Effectively, there are two possibilities for doing such comparisons. Since the mechanisms of inheritance in ancestral organisms cannot be precisely determined, Vermeij (1996) has recommended to make a difference between functional benefit or adaptation and the mechanism of transmission of the trait in question. At the organismal level, inheritance occurs by means of transmission of nuclear genes, although maternal effects, repeated infection, etc. Vermeij's concept of adaptation assumes that adaptive traits have to be heritable, as well as that there must be a selective factor, which discriminates among heritable alternatives, favoring those with greater reproduction or survival. As was previously pointed out, the term adaptation refers to both the beneficial trait and the process that generates and maintains it. Yet, since its advantage is context dependent, it implies that under different environmental conditions an alternative trait will be adaptive. His definition implicates the superiority of one trait over the alternative ones. Vermeij (1996) advocated a comparative concept of adaptation, defining adaptation as a “heritable attribute of an entity that confers advantages in survival and reproduction of that entity in a given environment” ( Vermeij, 1996). In other words, exaptations are traits currently showing beneficial effects for which they were not selected. They also contrasted the concept of adaptation with the term “exaptations“, which refers to aptations that are nonadaptations. Тhus, aptation is a trait that confers fitness advantage irrespective of its origin. As proponents of the historical concept of adaptation, they introduced the term “aptation“ to modify the nonhistorical definition of adaptation. On the nonhistorical definition, however, a trait is an adaptation just in the case if it provides the current fitness benefits. According to the historical definition of adaptation, an existing trait is an adaptation for a current function only if it was improved by natural selection for that function. Gould & Vrba (1982) called attention to the presence of another two distinct concepts of adaptation, one designated as historical and one as nonhistorical. Notably, in all of these definitions, natural selection is the principal mechanism that simultaneously generates both adaptation and adaptation(s) ( Amudson, 1996). The generic state reflects the functional efficiency of a given trait in an environment adapted to it, whereas an adaptation is a modified part of an organism that fulfills a biological function for that organism. Thus, if it is viewed as a process, adaptation signifies how an entity fits to the other one. However, irrespective of being a process, a generic state, or an individual trait, adaptation is a relational concept. In this context, adaptation is a process, which creates the generic state of adaptedness, as well as specific traits that - because arising by adaptive modifications - are referred as adaptations. Amudson pointed out that “Natural selection, the mechanism universally regarded as the primary causal influence on phenotypic evolutionary change, is first and foremost an explanation of adaptation“( Amudson, 1996). Conceptual approaches to study adaptationĮvolutionary biologists are well conscious that the term adaptation refers to both a process and its product however, there still exists the controversy about the perception of that biological phenomenon.
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