From this we see that adaptation is not just a matter of visible traits: in such parasites critical adaptations take place in the life cycle, which is often quite complex. An internal parasite (such as a liver fluke) can illustrate the distinction: such a parasite may have a very simple bodily structure, but nevertheless the organism is highly adapted to its specific environment. Julian Huxley, Evolution: The Modern Synthesis What adaptation is Īdaptation is primarily a process rather than a physical form or part of a body. The significance of an adaptation can only be understood in relation to the total biology of the species. Ford and Theodosius Dobzhansky produced evidence that natural selection was not only the 'engine' behind adaptation, but was a much stronger force than had previously been thought. A century later, experimental field studies and breeding experiments by people such as E. This illustrates the real merit of Darwin and Alfred Russel Wallace, and secondary figures such as Henry Walter Bates, for putting forward a mechanism whose significance had only been glimpsed previously. Other natural historians, such as Buffon, accepted adaptation, and some also accepted evolution, without voicing their opinions as to the mechanism. This second, subsidiary element of his theory is what is now called Lamarckism, a proto-evolutionary hypothesis of the inheritance of acquired characteristics, intended to explain adaptations by natural means. Jean-Baptiste Lamarck proposed a tendency for organisms to become more complex, moving up a ladder of progress, plus "the influence of circumstances," usually expressed as use and disuse. Charles Darwin broke with the tradition by emphasising the flaws and limitations which occurred in the animal and plant worlds. Pangloss is a parody of this optimistic idea, and David Hume also argued against design. William Paley believed that organisms were perfectly adapted to the lives they led, an argument that shadowed Gottfried Wilhelm Leibniz, who had argued that God had brought about " the best of all possible worlds." Voltaire's satire Dr. In natural theology, adaptation was interpreted as the work of a deity and as evidence for the existence of God. The second of Jean-Baptiste Lamarck's two factors (the first being a complexifying force) was an adaptive force that causes animals with a given body plan to adapt to circumstances by inheritance of acquired characteristics, creating a diversity of species and genera. Some biologists try to avoid terms which imply purpose in adaptation, not least because it suggests a deity's intentions, but others note that adaptation is necessarily purposeful. Features evolved for one purpose may be co-opted for a different one, as when the insulating feathers of dinosaurs were co-opted for bird flight.Īdaptation is a major topic in the philosophy of biology, as it concerns function and purpose ( teleology). In mimicry, species evolve to resemble other species in Müllerian mimicry this is a mutually beneficial co-evolution as each of a group of strongly defended species (such as wasps able to sting) come to advertise their defenses in the same way. Often, two or more species co-adapt and co-evolve as they develop adaptations that interlock with those of the other species, such as with flowering plants and pollinating insects. Charles Darwin proposed instead that it was explained by natural selection.Īdaptation is related to biological fitness, which governs the rate of evolution as measured by change in allele frequencies. In 18th and 19th century natural theology, adaptation was taken as evidence for the existence of a deity. Historically, adaptation has been described from the time of the ancient Greek philosophers such as Empedocles and Aristotle. Thirdly, it is a phenotypic trait or adaptive trait, with a functional role in each individual organism, that is maintained and has evolved through natural selection. Secondly, it is a state reached by the population during that process. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. In biology, adaptation has three related meanings.
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