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altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born. The word is derived from the Latin root ''alere'' meaning "to nurse, to rear, or to nourish" and refers to the need for young to be fed and taken care of for a long duration. Species whose young are immediately or quickly mobile are known as precocial.
==Scope==
In bird and mammal biology, altricial species are those species whose newly hatched/born young are relatively immobile, lack hair or down, are not able to obtain food on their own, and must be cared for by adults; closed eyes are common, though not ubiquitous. Altricial young are born helpless and require care for a specific amount of time. Among birds, these include herons, hawks, woodpeckers, owls, and most passerines. Among mammals, marsupials and most rodents are altricial. Cats, dogs, and humans are some of the best-known altricial organisms.
At the opposite end of the spectrum are precocial animals in which the young have open eyes, have hair or down, have large brains, and are immediately mobile and somewhat able to flee from, or defend themselves against, predators. For example, with ground-nesting birds such as ducks or turkeys, the young are ready to leave the nest in one or two days. Among mammals, most ungulates are precocial, being able to walk almost immediately after birth. Beyond the precocial are the superprecocial animals, such as the megapode birds, which hatch with full flight feathers.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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