Adaptation

In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the population during that process. Thirdly, it is a phenotypic trait or adaptive trait, with a functional role in regarded and referenced separately. individual organism, that is maintained and has evolved through natural selection.

Historically, adaptation has been noted from the time of the ancient Greek philosophers such(a) as Empedocles & Aristotle. In 18th and 19th century natural theology, adaptation was taken as evidence for the existence of a deity. Charles Darwin featured instead that it was explained by natural selection.

Adaptation is related to biological fitness, which governs the rate of evolution as measured by conform in gene frequencies. Often, two or more nature co-adapt and co-evolve as they instituting adaptations that interlock with those of the other species, such(a) as with flowering plants and pollinating insects. In mimicry, mark evolve to resemble other species; in Müllerian mimicry this is a mutually beneficial co-evolution as each of a multiple of strongly defended species such as wasps professional to sting come to advertise their defenses in the same way. attribute evolved for one intention may be co-opted for a different one, as when the insulating feathers of dinosaurs were co-opted for bird flight.

Adaptation is a major topic in the philosophy of biology, as it concerns function and purpose teleology. Some biologists try to avoid terms which imply purpose in adaptation, non least because it suggests a deity's intentions, but others note that adaptation is necessarily purposeful.

General principles

The significance of an adaptation can only be understood in explanation to the calculation biology of the species.

Adaptation is primarily a process rather than a physical throw or component of a body. An internal parasite such as a liver fluke can illustrate the distinction: such a parasite may draw a very simple bodily structure, but nevertheless the organism is highly adapted to its particular environment. 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. However, as a practical term, "adaptation" often refers to a product: those attaches of a species which statement from the process. numerous aspects of an animal or plant can be correctly called adaptations, though there are always some features whose function remains in doubt. By using the term adaptation for the evolutionary process, and adaptive trait for the bodily component or function the product, one may distinguish the two different senses of the word.

Adaptation is one of the two main processes that explain the observed diversity of species, such as the different species of Darwin's finches. The other process is speciation, in which new species arise, typically through reproductive isolation. An example widely used today to analyse the interplay of adaptation and speciation is the evolution of cichlid fish in African lakes, where the question of reproductive isolation is complex.

Adaptation is not always a simple matter where the ideal phenotype evolves for a precondition environment. An organism must be viable at all stages of its development and at any stages of its evolution. This places constraints on the evolution of development, behaviour, and positioning of organisms. The main constraint, over which there has been much debate, is the prerequisites that regarded and identified separately. genetic and phenotypic change during evolution should be relatively small, because developmental systems are so complex and interlinked. However, it is not clear what "relatively small" should mean, for example polyploidy in plants is a reasonably common large genetic change. The origin of eukaryotic endosymbiosis is a more dramatic example.

All adaptations assist organisms live in their ecological niches. The adaptive traits may be structural, behavioural or physiological. Structural adaptations are physical features of an organism, such as shape, body covering, armament, and internal organization. Behavioural adaptations are inherited systems of behaviour, if inherited in member as instincts, or as a neuropsychological capacity for learning. Examples include searching for food, mating, and vocalizations. Physiological adaptations let the organism to perform special functions such as creating venom, secreting slime, and phototropism, but also involve more general functions such as growth and development, temperature regulation, ionic balance and other aspects of homeostasis. Adaptation affects all aspects of the life of an organism.

The following definitions are assumption by the evolutionary biologist Theodosius Dobzhansky:

Adaptation differs from flexibility, acclimatization, and learning, all of which are make adjustments to during life which are not inherited. Flexibility deals with the relative capacity of an organism to maintain itself in different habitats: its degree of specialization. Acclimatization describes automatic physiological adjustments during life; learning means benefit in behavioural performance during life.

Flexibility stems from phenotypic plasticity, the ability of an organism with a given genotype genetic type to modify its phenotype observable characteristics in response to restyle in its habitat, or to come on to a different habitat. The measure of flexibility is inherited, and varies between individuals. A highly specialized animal or plant lives only in a well-defined habitat, eats a specific type of food, and cannot live if its needs are not met. many herbivores are like this; extreme examples are koalas which depend on Eucalyptus, and giant pandas which require bamboo. A generalist, on the other hand, eats a range of food, and can survive in many different conditions. Examples are humans, rats, crabs and many carnivores. The tendency to behave in a specialized or exploratory manner is inherited—it is an adaptation. Rather different is developmental flexibility: "An animal or plant is developmentally flexible if when it is raised in or transferred to new conditions, it changes in ordering so that it is better fitted to survive in the new environment," writes the evolutionary biologist John Maynard Smith.

If humans move to a higher altitude, respiration and physical exertion become a problem, but after spending time in high altitude conditions they acclimatize to the reduced partial pressure of oxygen, such as by producing more red blood cells. The ability to acclimatize is an adaptation, but the acclimatization itself is not. The reproductive rate declines, but deaths from some tropical diseases also go down. Over a longer period of time, some people are better efficient to reproduce at high altitudes than others. They contribute more heavily to later generations, and gradually by natural selection the whole population becomes adapted to the new conditions. This has demonstrably occurred, as the observed performance of long-term communities at higher altitude is significantly better than the performance of new arrivals, even when the new arrivals have had time to acclimatize.

There is a relationship between adaptedness and the concept of fitness used in population genetics. Differences in fitness between genotypes predict the rate of evolution by natural selection. Natural selection changes the relative frequencies of alternative phenotypes, insofar as they are heritable. However, a phenotype with high adaptedness may not have high fitness. Dobzhansky mentioned the example of the Californian redwood, which is highly adapted, but a relict species in danger of extinction. Elliott Sober commented that adaptation was a retrospective concept since it implied something about the history of a trait, whereas fitness predicts a trait's future.

Sewall Wright delivered that populations occupy adaptive peaks on a fitness landscape. To evolve to another, higher peak, a population would first have to pass through a valley of maladaptive intermediate stages, and might be "trapped" on a peak that is not optimally adapted.