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Extinction
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the Endling, last individual of the species, although the Functional extinction, capacity to breed and recover may have been lost before this point. Because a species' potential Range (biology), range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxon, Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the Fossil, fossil record) after a period of apparent absence. More than 99% of all species that ever Life, lived on Earth, amounting to over five billion species, are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryote globally, and possibly many times more if microorganisms, like bacteria, are included. Notable extinct a ...
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Holocene Extinction
The Holocene extinction, or Anthropocene extinction, is the ongoing extinction event during the Holocene epoch. The extinctions span numerous families of bacteria, fungi, plants, and animals, including mammals, birds, reptiles, amphibians, fish, invertebrates, and affecting not just terrestrial species but also large sectors of marine life. With widespread degradation of biodiversity hotspots, such as coral reefs and rainforests, as well as other areas, the vast majority of these extinctions are thought to be undocumented, as the species are undiscovered at the time of their extinction, which goes unrecorded. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates, and is increasing. During the past 100–200 years, biodiversity loss and species extinction have accelerated, to the point that most conservation biologists now believe that humankind has either entered a period of mass extinction, or is on the cu ...
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Extinction Event
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity. The "Big Five" mass extinctions In a landmark paper published in 1982, Jack Sepkoski and David M. Raup identified five particular geological intervals with excessive diversity loss. They were originally identified as outliers on a general trend of decreasing extinction rates during the Phanerozoic, but as more stringent statistical tests have been applied ...
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Thylacine
The thylacine ( , or , also ) (''Thylacinus cynocephalus'') is an extinct carnivorous marsupial that was native to the Australian mainland and the islands of Tasmania and New Guinea. The last known live animal was captured in 1930 in Tasmania. It is commonly known as the Tasmanian tiger (because of its striped lower back) or the Tasmanian wolf (because of its canid-like characteristics). Various Aboriginal Tasmanian names have been recorded, such as ''coorinna'', ''kanunnah'', ''cab-berr-one-nen-er'', ''loarinna'', ''laoonana'', ''can-nen-ner'' and ''lagunta'', while ''kaparunina'' is used in Palawa kani. The thylacine was relatively shy and nocturnal, with the general appearance of a medium-to-large-size canid, except for its stiff tail and abdominal pouch similar to that of a kangaroo. Because of convergent evolution, it displayed an anatomy and adaptations similar to the tiger (''Panthera tigris'') and wolf (''Canis lupus'') of the Northern Hemisphere, such as dark ...
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Golden Toad
The golden toad (''Incilius periglenes'') is an extinct species of true toad that was once abundant in a small, high-altitude region of about in an area north of the city of Monteverde, Costa Rica. It was endemic to elfin cloud forest. Also called the Monte Verde toad, Alajuela toad and orange toad, it is commonly considered the "poster child" for the amphibian decline crisis. This toad was first described in 1966 by herpetologist Jay Savage. The last sighting of a single male golden toad was on 15 May 1989, and it has since been classified as extinct by the International Union for Conservation of Nature (IUCN). Description The golden toad was one of about 500 species in the family Bufonidae—the "true toads". Males were orange and sometimes slightly mottled on the belly, while females showed a greater variety of colors, including black, yellow, red, green, and white; both sexes had smooth skin. While males had brilliant orange that attracted females to mate, females were ...
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Thylacinus Cynocephalus (Gould)
The thylacine ( , or , also ) (''Thylacinus cynocephalus'') is an extinct carnivorous marsupial that was native to the Mainland Australia, Australian mainland and the islands of Tasmania and New Guinea. The last known live animal was captured in 1930 in Tasmania. It is commonly known as the Tasmanian tiger (because of its striped lower back) or the Tasmanian wolf (because of its canid-like characteristics). Various Aboriginal Tasmanians, Aboriginal Tasmanian names have been recorded, such as ''coorinna'', ''kanunnah'', ''cab-berr-one-nen-er'', ''loarinna'', ''laoonana'', ''can-nen-ner'' and ''lagunta'', while ''kaparunina'' is used in Palawa kani. The thylacine was relatively shy and nocturnal, with the general appearance of a medium-to-large-size canid, except for its stiff tail and Pouch (marsupial), abdominal pouch similar to that of a kangaroo. Because of convergent evolution, it displayed an anatomy and adaptations similar to the tiger (''Panthera tigris'') and wolf ('' ...
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Dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya; their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds. Dinosaurs are varied from taxonomic, morphological and ecological standpoints. Birds, at over 10,700 living species, ar ...
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Functional Extinction
Functional extinction is the extinction of a species or other taxon such that: #It disappears from the fossil record, or historic reports of its existence cease; #The reduced population no longer plays a significant role in ecosystem function; or #The population is no longer viable. There are no individuals able to reproduce, or the small population of breeding individuals will not be able to sustain itself due to inbreeding depression and genetic drift, which leads to a loss of fitness. In plant populations, self-incompatibility mechanisms may cause related plant specimens to be incompatible, which may lead to functional extinction if an entire population becomes self-incompatible. This does not occur in larger populations. In polygynous populations, where only a few males leave offspring, there is a much smaller reproducing population than if all viable males were considered. Furthermore, the successful males act as a genetic bottleneck, leading to more rapid genetic drift or ...
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Life
Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energy transformation, and reproduction. Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. Biology is the science that studies life. The gene is the unit of heredity, whereas the cell is the structural and functional unit of life. There are two kinds of cells, prokaryotic and eukaryotic, both of which consist of cytoplasm enclosed within a membrane and contain many biomolecules such as proteins and nucleic acids. Cells reproduce through a process of cell division, in which the parent cell divides into two or more daughter cells and passes its genes onto a new generation, sometimes producing genetic variation. Organisms, or the individual entities of life, are generally thought to ...
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Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules. The theory of evolut ...
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Endling
An endling is the last known individual of a species or subspecies. Once the endling dies, the species becomes extinct. The word was coined in correspondence in the scientific journal ''Nature''. Alternative names put forth for the last individual of its kind include ender and terminarch. The word relict may also be used, but usually refers to a population, rather than an individual, that is the last of a species. Usage The 4 April 1996 issue of ''Nature'' published a correspondence in which commentators suggested that a new word, ''endling'', be adopted to denote the last individual of a species. The 23 May issue of ''Nature'' published several counter-suggestions, including ''ender'', ''terminarch'', and ''relict''. The word ''endling'' appeared on the walls of the National Museum of Australia in ''Tangled Destinies'', a 2001 exhibition by Matt Kirchman and Scott Guerin, about the relationship between Australian peoples and their land. In the exhibition, the definition, ...
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Dodo
The dodo (''Raphus cucullatus'') is an extinct flightless bird that was endemic to the island of Mauritius, which is east of Madagascar in the Indian Ocean. The dodo's closest genetic relative was the also-extinct Rodrigues solitaire. The two formed the subfamily Raphinae, a clade of extinct flightless birds that were a part of the family which includes pigeons and doves. The closest living relative of the dodo is the Nicobar pigeon. A white dodo was once thought to have existed on the nearby island of Réunion, but it is now believed that this assumption was merely confusion based on the also-extinct Réunion ibis and paintings of white dodos. Subfossil remains show the dodo was about tall and may have weighed in the wild. The dodo's appearance in life is evidenced only by drawings, paintings, and written accounts from the 17th century. Since these portraits vary considerably, and since only some of the illustrations are known to have been drawn from live specim ...
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Species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. However, only about 14% of these had been described by 2011. All species (except viruses) are given a two-part name, a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specific name or the specific epithet (in botanical nomenclature, also s ...
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