Adaptation

Adaptation refers to any change that makes a species or an individual better suited to its environment or way of life. All living creatures must be able to adapt to changes in their environment if they are to survive and reproduce. The process of adaptation does not always result in an obvious physical change, but may affect an individual's behavior or even its internal processes.

Adaptation could be described as the theory of evolution in action. This theory was first offered in its best and most complete form in 1859 by the English naturalist, Charles Darwin (1809–1882). Darwin's theory of evolution suggested that all living things are subject to a gradual process of change over a long period of time. Evolution is therefore the process that results in living things changing through successive generations. Darwin also described a mechanism called "natural selection," which is the means through which these hereditary changes are passed on from one generation to another.

Darwin's theory of evolution by natural selection—which is highly important to understanding the life sciences—states that individual organisms possessing certain traits or characteristics that are most suited to a particular environment have a better chance of surviving and therefore of passing these traits on to their offspring. In other words, organisms in possession of favorable traits allows these traits to be "selected" by nature (natural selection) so that these organisms survive and produce young that have the same favorable traits.

Darwin's years of travel, study, and thought led him to make three important observations or conclusions. First, he stated that all living things vary, or that each individual varies slightly from the others of its species. This could be seen in any given species in which differences could be found among any group of the same organisms (such as a flower with an extra petal or a deer with larger-than-average antlers). Second, Darwin suggested that individuals were able to pass certain characteristics on to their young, who inherited them. Modern genetics has proven this to be true. Third, Darwin noted that all life is involved in a struggle for survival. To Darwin, these three observations explained why nature allowed most organisms to produce far more offspring than could ever survive. Offspring that did survive and were able to reproduce, according to Darwin, were usually the ones who possessed certain traits better suited to their environment. These individuals had a better chance of surviving and of producing more individuals like themselves. Over many generations, it was simply nature's "selection" of the individuals with the fittest (or best adapted) characteristics that explained Darwin's theory of evolution. This accounts for the well-known phrase, "survival of the fittest."

"Survival of the fittest" could also be described as "survival of the best adapted." Among any group of individuals or organisms of the same species, there will always be variations or differences (in color, shape, behavior, and even chemical makeup). An adaptation then, is considered to be any variation that makes an organism better suited to its environment. Camouflage is one way nature has of providing protection for an individual, and an organism whose color or shape allows it to blend into its environment is more likely to survive and reproduce than one whose coloration makes it easier to be noticed. Woodpeckers are highly specialized birds and are a good example of the process of adaptation. Their main job is to find and eat insects that live in and beneath the bark of trees. Consequently, those woodpeckers with the most powerful and chisel-like beaks, strong neck muscles for hammering, sturdy skulls, grasping feet, stiff-supporting tail feathers, and long tongues proved best able to survive and pass on these traits.

Darwin first described his theory of evolution by natural selection in 1859 in his classic book, On the Origin of Species by Means of Natural Selection. The idea of adaptation is key to Darwin's theory. Darwin distinguishes between genotypic adaptation and phenotypic adaptation. The type of adaptation discussed above—in which an individual possesses a "favorable" gene for a certain characteristic which it passes on to its offspring—is called genotypic or evolutionary adaptation. This type of adaptation is genetic, permanent, and is very different from phenotypic adaptations. In contrast to genotypic adaptations, phenotypic adaptations are traits that are developed during an individual's lifetime. An example of phenotypic, or nongenetic, adaptation might be a certain type of behavior that is learned or developed by an individual. The macaque monkeys in Japan, for example, have learned to wash their food in water, and newborns soon copy this behavior. Although it is not known exactly why the first macaque washed its food, this behavior in not instinctive with them. Rather it is a case of learned behavior.

[See alsoEvolution; Evolution, Evidence of; Evolutionary Theory ]