WordNet

born after a gestation period of less than the normal time; "a premature infant"
uncommonly early or before the expected time; "illness led to his premature death"; "alcohol brought him to an untimely end" (同)untimely
characterized by or characteristic of exceptionally early development or maturity (especially in mental aptitude); "a precocious child"; "a precocious achievement"
appearing or developing early; "precocious flowers appear before the leaves as in some species of magnolias"

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早熟
時期尚早の,早すぎた / 早計の,早まった / 早産の
(人が)早熟の

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/01/03 19:20:02」(JST)

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California Quail chick (Callipepla californica), a precocial chick

In biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial" where the young are born or hatched helpless. Extremely precocial species may be called "superprecocial". These three categories form a continuum, without distinct gaps between them. Precocial species are normally nidifugous, meaning that they leave the nest shortly after birth or hatching.

The span between precocial and altricial species is particularly broad in birds. Precocial birds are born with their eyes open. They are covered with downy feathers that soon grow to adult feathers after hatching.^[1] Birds of this kind can also swim and run much sooner after their birth than other birds, such as songbirds.^[1] Very precocial birds can be ready to leave the nest in a short period of time following hatching (e.g. 24 hours). Many precocial chicks are not independent in thermoregulation (the ability to regulate their own body temperatures), and they depend on the attending parent(s) to brood them with body heat for a short period of time. Precocial birds find their own food, sometimes with help or instruction from the parents. Examples of precocial birds include the domestic chicken, many species of ducks and geese, waders, rails and the hoatzin. The most extreme, superprecocial birds are certain species of the megapodes, where the newly hatched chicks dig themselves out of the nest mound without parental assistance, and are capable of flight on the same day they hatch.^[2]

Precociality is found in many other animal groups. Familiar examples of precocial mammals are most ungulates, the guinea pig, and most species of hare. This last example demonstrates that precociality is not a particularly conservative characteristic, in the evolutionary sense, since the closely related rabbit is highly altricial.

Precocial species typically have a longer gestation or incubation period than related altricial species, and smaller litters or clutches, since each offspring has to be brought to a relatively advanced (and large) state before birth or hatching.

The phenomenon of imprinting studied by Konrad Lorenz is characteristic of precocial birds.

Etymology

Look up precocial in Wiktionary, the free dictionary.

The word "precocial" is derived from the same root as precocious, implying in both cases early maturity.^[3]

Phylogeny

Precociality is thought to be ancestral in birds. Thus, altricial birds tend to be found in the most derived groups. There is some evidence for precociality in Protobirds^[4] and Troodontids.^[5]

References

Footnotes

^ ^a ^b Edward S. Brinkley (2000). Creatures of the Air and Sea. Singapore: Reader's Digest Children's Books. pp. 34, 35. ISBN 0-7944-0353-0.
^ Starck, J.M., Ricklefs, R.E. (1998). Avian Growth and Development. Evolution within the altricial precocial spectrum. New York: Oxford University Press. ISBN 0-19-510608-3.
^ Webster's New World Dictionary. David B. Guralnik, Editor in Chief. New York:Simon and Schuster, 1984.
^ Elzanowski, Andrzej; Brett-Surman, Michael K. (July 1995). "Avian Premaxilla and Tarsometatarsus from the Uppermost Cretaceous of Montana". The Auk 112 (3): 762–7. JSTOR 4088693.
^ Varricchio, David J.; Horner, John R.; Jackson, Frankie D. (September 19, 2002). "Embryos and eggs for the Cretaceous theropod dinosaur Troodon formosus". Journal of Vertebrate Paleontology 22 (3): 564–76. doi:10.1671/0272-4634(2002)022[0564:EAEFTC]2.0.CO;2. JSTOR 4524250.

Notations

Starck J.M., Ricklefs R. E. Patterns of Development: The Altricial - Precocial Spectrum. In; Avian Growth and Development. Oxford University Press, New York, NY, 1998.

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English Journal

Testosterone exposure in childhood: discerning pathology from physiology.

Cabrera SM, Rogol AD.SourceChildren's Hospital of Wisconsin, Medical College of Wisconsin, Division of Endocrinology, Department of Pediatrics , 9000 W. Wisconsin Ave PO Box 1997, MS C520, Milwaukee, WI 53201 , USA +1 414 266 6750 ; +1 414 266 6749 ; scabrera@mcw.edu.
Expert opinion on drug safety.Expert Opin Drug Saf.2013 Mar 21. [Epub ahead of print]
Introduction: Testosterone (T) drives normal male sexual development both in utero and at puberty. Aberrant T exposure manifests as virilization of a female fetus, contrasexual precocity in girls, and isosexual precocity in boys. Evidence of pathologic T exposure warrants a prompt evaluation. Areas
PMID 23517636

Genetics of slaughter precocity, carcass weight and carcass weight gain in Chianina, Marchigiana and Romagnola young bulls under protected geographical indication.

Sbarra F, Mantovani R, Quaglia A, Bittante G.SourceNational Breeders Association of Italian Beef Breeds (ANABIC), Via Visciolosa, 06132 S. Martino in Colle, (PG), Italy.
Journal of animal science.J Anim Sci.2013 Mar 21. [Epub ahead of print]
The aim of this study was i) to estimate the heritability and genetic correlation of the age at slaughter (AS), as an indicator of slaughter precocity, carcass weight (CW) and carcass weight gain (CWG=CW×AS-1) obtained from young bulls of three Italian autochthonous beef cattle breeds, i.e., Chiani
PMID 23519731

Japanese Journal

Fertility and precocity of Osmunda×intermedia offspring in culture

YATABE Yoko,YAMAMOTO Kaoru,TSUTSUMI Chie,SHINOHARA Wataru,MURAKAMI Noriaki,KATO Masahiro
Journal of plant research 124(2), 265-268, 2011-03-01
NAID 10027868213