Adaptations

In biology, adaptation is the ongoing evolutionary process by which organisms come to fit their environment more closely, thereby improving their evolutionary fitness. An adaptive trait is a phenotypic feature with a real functional role in the individual organism carrying it, one that has been maintained and shaped over generations by natural selection. The chapter groups adaptive traits into three categories. Structural adaptations involve physical, bodily features — for example mammals growing a thicker coat of fur in preparation for winter, or camels obtaining part of their water requirement directly from food to offset water lost through excretion. Behavioural adaptations are instinctive or learned actions that improve survival, most notably migration (moving to find better resources or escape a threat) and courtship (behavioural patterns aimed at securing a mate); nocturnal animals remaining inactive or underground during the day is a further example of a behavioural adaptation, and the scientific study of animal behaviour under natural conditions is called ethology. Physiological adaptations are internal, functional adjustments that let an organism live successfully within its particular niche — a lion's sharp canines and meat-adapted digestive system are one example, and hibernation and aestivation, in which metabolic rate is deliberately slowed so an animal can survive long periods without eating or drinking, are the two best-known physiological adaptations of this kind. Because aquatic and terrestrial habitats present very different physical challenges, organisms in each show their own distinct suites of adaptation — aquatic animals typically show fins and a streamlined body for locomotion, myotome-arranged muscles, gill respiration, air bladders for buoyancy, a mucus-secreting, scale-protected integument, a lateral-line system for sensing water movement, and excretory structures tuned to maintain wat …