extinction


extinction
/ik stingk"sheuhn/, n.
1. the act of extinguishing.
2. the fact or condition of being extinguished or extinct.
3. suppression; abolition; annihilation: the extinction of an army.
4. Biol. the act or process of becoming extinct; a coming to an end or dying out: the extinction of a species.
5. Psychol. the reduction or loss of a conditioned response as a result of the absence or withdrawal of reinforcement.
6. Astron. the diminution in the intensity of starlight caused by absorption as it passes through the earth's atmosphere or through interstellar dust.
7. Crystall., Optics. the darkness that results from rotation of a thin section to an angle (extinction angle) at which plane-polarized light is absorbed by the polarizer.
[1375-1425; late ME extinccio(u)n < L ex(s)tinction- (s. of ex(s)tinctio). See EXTINCT, -ION]

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      in biology, the dying out or termination of a race or species. Extinction occurs when a species can no longer reproduce at replacement levels. Most extinctions are thought to have resulted from environmental changes that affected the species in either of two ways. The doomed species might not have been able to adapt to the changed environment and thus perished without descendants; or it may have adapted but, in the process, may have evolved into a distinctly new species. The effect of humans on the environment, through hunting, collecting, and habitat destruction, has become a significant factor in plant and animal extinctions.

      Although extinction is an ongoing feature of the Earth's flora and fauna (the vast majority of species ever to have lived are extinct), the fossil record reveals the occurrence of a number of mass extinctions, each involving the demise of vast numbers of species. One such mass extinction occurred at the end of the Cretaceous period, some 66,000,000 years ago, when the dinosaurs (dinosaur) and much of the marine life of the day perished. Evidence points to the impact of an asteroid hitting the Earth as the cause of the Cretaceous extinctions. It is suspected that catastrophic events—such as an asteroid impact—may have triggered other mass extinctions as well. In fact, mass extinctions appear to have taken place approximately every 26,000,000 years, which has led some paleontologists to propose that a cyclical cosmic event causes these periodic die-offs.

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Universalium. 2010.

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  • extinction — [ ɛkstɛ̃ksjɔ̃ ] n. f. • 1374; lat. exstinctio, de exstinguere « éteindre » 1 ♦ Action d éteindre. L extinction d un feu, d un incendie. Extinction des feux, des lumières : moment où toutes les lumières doivent être éteintes. Clairon qui sonne l… …   Encyclopédie Universelle

  • extinction — Extinction. s. f. Action par laquelle on esteint. Extinction d un embrasement. on adjugea cette ferme, cette terre à l extinction de la chandelle. On dit aussi, l Extinction de la chaleur naturelle. On dit aussi fig. L extinction d un crime. l… …   Dictionnaire de l'Académie française

  • Extinction — Ex*tinc tion, n. [L. extinctio, exstinction: cf. F. extinction.] 1. The act of extinguishing or making extinct; a putting an end to; the act of putting out or destroying light, fire, life, activity, influence, etc. [1913 Webster] 2. State of… …   The Collaborative International Dictionary of English

  • Extinction — (v. lat.), so v.w. Exstinction …   Pierer's Universal-Lexikon

  • extinction — index aberemurder, abolition, ademption, cancellation, catastrophe, death, demise (death), destruction …   Law dictionary

  • extinction — EXTINCTION: Ne s emploie qu avec paupérisme …   Dictionnaire des idées reçues

  • extinction — early 15c., from L. extinctionem/exstinctionem (nom. extinctio/exstinctio), noun of action from pp. stem of extinguere/exstinguere (see EXTINGUISH (Cf. extinguish)). Originally of fires, lights; figurative use, of wiping out a material thing (a… …   Etymology dictionary

  • extinction — see under extinguish at ABOLISH …   New Dictionary of Synonyms

  • extinction — [n] dying out annihilation, death, destruction, elimination, end of life, no life, obsolescence, thing of the past*; concept 252 …   New thesaurus

  • extinction — ► NOUN ▪ the state or process of being or becoming extinct …   English terms dictionary

  • extinction — [ek stiŋk′shən, ikstiŋk′shən] n. [ME extinccioun < L exstinctio < exstinctus: see EXTINCT] 1. a putting out or being put out, as of a fire 2. a destroying or being destroyed; annihilation; abolition 3. the fact or state of being or becoming …   English World dictionary


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