Extinction

"Extinct" redirects here. For other uses, see Extinct (disambiguation).

The Dodo: a flightless bird from Mauritius which became extinct in the 17th century.

Extinction is when a species of animal, plant, or other organisms are no longer living or dies. Extinction is one of the major features of evolution.

Conservation status
Risk of extinction
Extinction
Extinct Extinct in the Wild
Threatened
Critically Endangered Endangered Vulnerable Threatened
Lower risk
Conservation Dependent Near Threatened Least Concern
See also
World Conservation Union IUCN Red List

Part of a series on
Evolutionary biology
Darwin's finches by John Gould
Index Introduction Main Outline Glossary Evidence History
Processes and outcomes Population genetics Variation Diversity Mutation Natural selection Adaptation Polymorphism Genetic drift Gene flow Speciation Adaptive radiation Co-operation Coevolution Coextinction Divergence Convergence Parallel evolution Extinction
Natural history Origin of life Common descent History of life Timeline of evolution Human evolution Phylogeny Biodiversity Biogeography Classification Evolutionary taxonomy Cladistics Transitional fossil Extinction event
History of evolutionary theory Overview Renaissance Before Darwin Darwin Origin of Species Before synthesis Modern synthesis Molecular evolution Evo-devo Current research History of speciation History of paleontology (timeline)
Fields and applications Applications of evolution Biosocial criminology Ecological genetics Evolutionary aesthetics Evolutionary anthropology Evolutionary computation Evolutionary ecology Evolutionary economics Evolutionary epistemology Evolutionary ethics Evolutionary game theory Evolutionary linguistics Evolutionary medicine Evolutionary neuroscience Evolutionary physiology Evolutionary psychology Experimental evolution Phylogenetics Paleontology Selective breeding Speciation experiments Sociobiology Island biogeography Systematics Universal Darwinism
Social implications Evolution as fact and theory Social effects Creation–evolution controversy Theistic evolution Objections to evolution Level of support

All species become extinct sooner or later. The end of a species may happen for many reasons. It may be caused by habitat loss or by being overhunted, or by a major extinction event. An example of an animal that is now extinct is the Dodo, from over-hunting. Another quite different way for a species to end is by species-splitting, known as cladogenesis. The species living today probably were not living in the Cambrian period, but their ancestors were.

Notable extinct animal species include the non-avian dinosaurs, the saber-toothed cats, the dodo, the mammoths, ground sloths, the thylacine, the trilobites and the golden toad.

Endangered species are those which may become extinct. A report from Kew Gardens suggests that one fifth of plant species may be at risk of extinction. Fossil species sometimes reappear millions of years after they were thought to be extinct. These cases are called Lazarus taxa. Humans are to blame due to cutting down animals’ natural habitat such as forests.

Duration of species

The average duration of species varies according to the groups studied. A study of benthic (deep water) foraminifera showed an average of 16 million years if they lived above 200 metres, but 25my if they lived below 200 metres. On the other hand, the average survival time for mammalian species over the past 20my has been 2.33my.

It is estimated that 99.9% of all species that have ever lived are now extinct. More than half of the plants and animals that have become extinct in the last 200 years have been in Australia. There the arrival of Europeans with (accidentally or deliberately) introduced species has damaged the native biota. Especially, the introduction of eutherian mammals has caused the extinction of many marsupial forms.

Duration of higher groups

Naturally, higher categories such as genera, families, orders, classes and phyla last longer, because they are composed of more species. As far as we know, no phylum has gone completely extinct since the Cambrian, but quite a few classes went extinct in one or other of the 'big five' extinction events. Examples of higher categories of animal now extinct are: placoderm fish, trilobites, ammonites, pelycosaurs, non-avian dinosaurs, pterosaurs, ichthyosaurs and plesiosaurs.

Reasons

Darwin thought that most extinctions occurred because some organisms became more effective, and replaced their less advanced competitors. No doubt that does occur, but the view now is that environmental change is more important. Organisms become adapted to the environments they live in. The environment certainly does change, and sometimes quite dramatically. When it does, some organisms can adapt to the changes. Others cannot.

The Earth's environment can stay rather stable for long periods of time. Then the rate of extinction is usually quite low. Then changes occur, sometimes quite rapidly. In these times the rate of extinction can be much higher. The rate of extinction is therefore a useful thing to measure.

Extinction Media

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  The thylacine (Thylacinus cynocephalus) is an example of an extinct species.

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  External mold of the extinct Lepidodendron from the Upper Carboniferous of Ohio

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

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

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  The passenger pigeon, one of the hundreds of species of extinct birds, was hunted to extinction over the course of a few decades.

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  Scorched land resulting from slash-and-burn agriculture

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  The golden toad was last seen on May 15, 1989. Decline in amphibian populations is ongoing worldwide.

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  The large Haast's eagle and moa from New Zealand

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  The changing distribution of the world's land mammals in tonnes of carbon. The biomass of wild land mammals has declined by 85% since the emergence of humans.

Related pages

• List of extinction events
• Lagerstätte
• Endangered species
• Living fossil

Other websites

• Extinction at Peripatus.gen.nz
• Extinction -Citizendium