Extinction

:For other senses of this word, see extinction (disambiguation).

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In biology and ecology, extinction is the ceasing of existence of a species or group of taxons. The moment of extinction is generally considered to be the death of the last individual of that species. Extinction is a natural phenomenon; it is estimated that 99.9% of all species that have ever lived are now extinct{{ref|999Extinct}}. Through the laws of evolution, new species are created by speciation — where new organisms arise and thrive when they are able to find and exploit an ecological niche — and species become extinct when are no longer able to survive in changing conditions or against superior competition. A typical species becomes extinct within 10 million years of its first appearance, although some species survive virtually unchanged for hundreds of millions of years.

Related Topics:
Biology - Ecology - Species - Taxon - Evolution - Speciation - Niche

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Descendants may or may not exist for extinct species. Daughter species that evolve from a parent species carry on most of the parent species' genetic information, and even though the parent species may become extinct, the daughter species lives on. In other cases, species have produced no new variants, or none that are able to survive the parent species' extinction.

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Extinction of a parent species where daughter species or subspecies are still alive is also called pseudoextinction. Many of prehistoric extinct species have evolved into new species; for example the extinct Hyracotherium (an ancient horse-like animal) was the ancestor of several extant species including the horse, the zebra and the donkey. The Hyracotherium itself is no more, but its descendants live on. It is therefore said to be pseudoextinct.

Related Topics:
Pseudoextinction - Hyracotherium - Ancestor - Extant - Horse - Zebra - Donkey

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Currently, many environmental groups and governments are concerned with the extinction of species due to human intervention, and are attempting to combat further extinctions. Humans can cause extinction of a species through overharvesting, pollution, destruction of habitat, introduction of new predators and food competitors, and other influences. According to the World Conservation Union (WCU, formerly the IUCN), 784 extinctions have been recorded since the year 1500 (the arbitrary date selected to define "modern" extinctions), with many more likely to have gone unnoticed. Most of these modern extinctions can be attributed directly or indirectly to human effects. Endangered species are species that are in danger of becoming extinct; several organizations attempt to preserve recognized endangered species through a variety of conservation programs.

Related Topics:
Overharvesting - Pollution - Habitat - Predator - Competitors - World Conservation Union - IUCN - 1500 - Endangered species - Conservation

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Species which are not extinct are termed extant.

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