Adaptation
Adaptations are the most important features of all organisms. An adaptation is a trait or characteristic that makes an animal survive or reproduce better in its environment. These traits can be morphological, physiological, or behavioral. Adaptations include almost all kinds of traits, such as what makes an organism blend into its surroundings, find food, mate with the correct species, and be able to survive.
An example of a morphological adaptation that increases the chance of survival is the coloration of an animal. Most animals that live in the arctic snow are white. Being white helps them blend in with the snow and hide from predators. An example of a physiological adaptation that increases the likelihood of survival is the kangaroo rat's metabolism. Kangaroo rats livein the desert of the North American Southwest. It is extremely hot and dry there, and very little water is available. The kangaroo rat never needs to drink water because its metabolism has changed and adapted to conserve water; it gets all the water it needs from seeds it eats. Humans are the opposite; we must drink water daily because our metabolism uses lots of water. An example of a behavioral adaptation that increases reproduction is the croaking and calling of male frogs, which gets female frogs to come to the males for mating. Those frogs that call end up mating with more females and have more offspring than frogs that do not call.
The different fur colors of the rural jackrabbit (left) and the arctic hare (right) allow them to blend into their environments, which helps them to evade predators, therefore increasing their chance of survival.Natural selection is the mechanism that produces adaptations. It is the difference in survival or reproduction between individuals with different traits. If an arctic hare, which lives in the snow, were gray rather than solid white, it would not survive as well as pure white hares. And if it does not live very long before it is killed by a predator such as a fox, then it will not produce as many offspring as a pure white hare, either. Natural selection increases the number of individuals in a population that actually has the adaptation; natural selection also maintains adaptations once animals have them.
All traits that are adaptations must have a genetic basis to them. That is to say, the trait must be produced in some way by genes, coded for by DNA. Genes enable an animal to pass on to its offspring the survival or reproductive advantage given by the adaptation.
There is one exception to the rule that adaptations need a genetic basis—traits that are learned within an organism's lifetime. Something that is learned does not have a genetic basis; it was not inherited from the parents. An example of a learned adaptation is that some male songbirds learn the songs of their neighbors. Neighborhoods of birds sing similar songs, and females prefer males that know more songs. A male that has learned more songs will reproduce more; learning songs is an adaptation. But learned traits are not completely free from genetics; there is a genetic basis to the ability to learn, even if the actual learning does not have a genetic basis.
Biological Evolution; Morphological Evolution in Whales; Morphology; Natural Selection.
Bibliography
Campbell, Neil A., Jane B. Reece, and Lawrence G. Mitchell. Biology, 5th ed. Menlo Park, CA: Addison Wesley Longman, Inc., 1999.
Rose, Michael R., and George V. Lauder, eds. Adaptation. San Francisco, CA: Academic Press, 1996.
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