Adaptation

An adaptation is a feature of an organism that increases its chance of survival and reproduction in its environment. Organisms that are well adapted are more likely to pass on their alleles, so they are said to have high fitness.Adaptations are produced over many generations by natural selection. Individuals that happen to have alleles giving a useful feature survive and reproduce more, so the feature becomes more common in the population. Adaptations are inherited, which means they are passed on to offspring.A common mistake is to say that organisms develop features because they need them. A giraffe's long neck did not grow longer because it needed to reach high leaves. Giraffes that happened to have alleles for longer necks could reach more food, survived and reproduced more, and passed on these alleles.Adaptations must be distinguished from acclimatisation. Acclimatisation is a change within one organism's lifetime in response to its environment, such as a person producing more red blood cells after living at high altitude. It is not caused by a change in alleles and is not passed on, so it is not an adaptation.Adaptations are grouped into three types:
• anatomical: structural features of the body
• physiological: processes inside the body
• behavioural: the way an organism actsMost organisms show all three types together. The following lessons look at each type in turn.