Extinction

Conservation status
Extinct (EX)
  • Extinct in the Wild (EW)
  • Threatened
    Lower Risk

    Other categories

    Related topics

    IUCN Red List category abbreviations (version 3.1, 2001)
    NatureServe category abbreviations

    In biology, extinction is the termination of an organism or of a group of organisms (taxon), normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence.

    More than 99 percent of all species, amounting to over five billion species,[1] that ever lived on Earth are estimated to have died out.[2][3][4] Estimates on the number of Earth's current species range from 10 million to 14 million,[5] of which about 1.2 million have been documented and over 86 percent have not yet been described.[6] More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described.[7]

    Through evolution, species arise through the process of speciation—where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche—and species become extinct when they are no longer able to survive in changing conditions or against superior competition. The relationship between animals and their ecological niches has been firmly established.[8] A typical species becomes extinct within 10 million years of its first appearance,[4] although some species, called living fossils, survive with virtually no morphological change for hundreds of millions of years.

    Mass extinctions are relatively rare events; however, isolated extinctions are quite common. Only recently have extinctions been recorded and scientists have become alarmed at the current high rate of extinctions.[9][10][11][12] Most species that become extinct are never scientifically documented. Some scientists estimate that up to half of presently existing plant and animal species may become extinct by 2100.[13]

    A dagger symbol (†) placed next to the name of a species or other taxon is often done to indicate its status as extinct.

    Definition

    External mold of the extinct Lepidodendron from the Upper Carboniferous of Ohio[14]

    A species is extinct when the last existing member dies. Extinction therefore becomes a certainty when there are no surviving individuals that can reproduce and create a new generation. A species may become functionally extinct when only a handful of individuals survive, which cannot reproduce due to poor health, age, sparse distribution over a large range, a lack of individuals of both sexes (in sexually reproducing species), or other reasons.

    Pinpointing the extinction (or pseudoextinction) of a species requires a clear definition of that species. If it is to be declared extinct, the species in question must be uniquely distinguishable from any ancestor or daughter species, and from any other closely related species. Extinction of a species (or replacement by a daughter species) plays a key role in the punctuated equilibrium hypothesis of Stephen Jay Gould and Niles Eldredge.[15]

    Skeleton of various extinct dinosaurs; some other dinosaur lineages still flourish in the form of birds

    In ecology, extinction is often used informally to refer to local extinction, in which a species ceases to exist in the chosen area of study, but may still exist elsewhere. This phenomenon is also known as extirpation. Local extinctions may be followed by a replacement of the species taken from other locations; wolf reintroduction is an example of this. Species which are not extinct are termed extant. Those that are extant but threatened by extinction are referred to as threatened or endangered species.

    The dodo of Mauritius, shown here in a 1626 illustration by Roelant Savery, is an often-cited example of modern extinction[16]

    Currently an important aspect of extinction is human attempts to preserve critically endangered species. These are reflected by the creation of the conservation status "extinct in the wild" (EW). Species listed under this status by the International Union for Conservation of Nature (IUCN) are not known to have any living specimens in the wild, and are maintained only in zoos or other artificial environments. Some of these species are functionally extinct, as they are no longer part of their natural habitat and it is unlikely the species will ever be restored to the wild.[17] When possible, modern zoological institutions try to maintain a viable population for species preservation and possible future reintroduction to the wild, through use of carefully planned breeding programs.

    The extinction of one species' wild population can have knock-on effects, causing further extinctions. These are also called "chains of extinction".[18] This is especially common with extinction of keystone species.

    A new study suggests that it could take up to 5 to 7 million years for mammal diversity to be restored to its state prior to the arrival of humans.[19]

    Pseudoextinction

    Extinction of a parent species where daughter species or subspecies are still extant is called pseudoextinction or phyletic extinction. Effectively, the old taxon vanishes, transformed (anagenesis) into a successor,[20] or split into more than one (cladogenesis).[21]

    Pseudoextinction is difficult to demonstrate unless one has a strong chain of evidence linking a living species to members of a pre-existing species. For example, it is sometimes claimed that the extinct Hyracotherium, which was an early horse that shares a common ancestor with the modern horse, is pseudoextinct, rather than extinct, because there are several extant species of Equus, including zebra and donkey. However, as fossil species typically leave no genetic material behind, one cannot say whether Hyracotherium evolved into more modern horse species or merely evolved from a common ancestor with modern horses. Pseudoextinction is much easier to demonstrate for larger taxonomic groups.

    Lazarus taxa

    The coelacanth, a fish related to lungfish and tetrapods, was considered to have been extinct since the end of the Cretaceous Period until 1938 when a specimen was found, off the Chalumna River (now Tyolomnqa) on the east coast of South Africa.[22] Museum curator Marjorie Courtenay-Latimer discovered the fish among the catch of a local angler, Captain Hendrick Goosen, on December 23, 1938.[22] A local chemistry professor, JLB Smith, confirmed the fish's importance with a famous cable: "MOST IMPORTANT PRESERVE SKELETON AND GILLS = FISH DESCRIBED".[22]

    Far more recent possible or presumed extinctions of species which may turn out still to exist include the thylacine, or Tasmanian tiger (Thylacinus cynocephalus), the last known example of which died in Hobart Zoo in Tasmania in 1936; the Japanese wolf (Canis lupus hodophilax), last sighted over 100 years ago; the ivory-billed woodpecker (Campephilus principalis), last sighted for certain in 1944; and the slender-billed curlew (Numenius tenuirostris), not seen since 2007.[23]

    Other Languages
    Afrikaans: Uitsterwing
    العربية: انقراض
    asturianu: Estinción
    azərbaycanca: Nəsil kəsilməsi
    বাংলা: বিলুপ্তি
    Bân-lâm-gú: Bia̍t-choa̍t
    башҡортса: Юҡҡа сығыу
    беларуская: Выміранне
    български: Измиране
    bosanski: Izumiranje
    català: Extinció
    čeština: Vymírání
    Cymraeg: Difodiant
    dansk: Udryddelse
    Deutsch: Aussterben
    español: Extinción
    Esperanto: Formorto
    فارسی: انقراض
    galego: Extinción
    ગુજરાતી: વિલુપ્ત જાતિ
    客家語/Hak-kâ-ngî: Chhie̍t-chúng
    한국어: 절멸
    हिन्दी: विलुप्ति
    hrvatski: Izumiranje
    Bahasa Indonesia: Kepunahan
    íslenska: Útdauði
    italiano: Estinzione
    Basa Jawa: Spesies cures
    ქართული: ამოწყდომა
    қазақша: Қырылу
    kernowek: Difeudhans
    Kreyòl ayisyen: Ekstenksyon
    kurdî: Nemabûyî
    Latina: Exstinctio
    latviešu: Izmiršana
    lietuvių: Išnykimas
    magyar: Kihalás
    مصرى: انقراض
    Bahasa Melayu: Kepupusan
    မြန်မာဘာသာ: မျိုးသုဉ်းခြင်း
    Nederlands: Uitsterven
    日本語: 絶滅
    norsk: Utryddelse
    norsk nynorsk: Utdøydde artar
    ਪੰਜਾਬੀ: ਲੋਪ
    polski: Wymieranie
    português: Extinção
    română: Extincție
    Runa Simi: Rikch'aq wañuy
    русский: Вымирание
    Scots: Extinction
    Simple English: Extinction
    slovenščina: Izumrtje
    Soomaaliga: Dabar Go'
    српски / srpski: Изумирање
    srpskohrvatski / српскохрватски: Izumiranje
    suomi: Sukupuutto
    svenska: Utdöd
    Tagalog: Ekstinsiyon
    татарча/tatarça: Юкка чыгу
    Türkçe: Soy tükenmesi
    українська: Вимирання
    اردو: معدومیت
    Tiếng Việt: Tuyệt chủng
    粵語: 絕種
    中文: 绝灭