an arctic hare
in 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.
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.
SEE ALSO Biological Evolution; Morphological Evolution in Whales;Morphology; Natural Selection.
