In biology and ecology, extinction is the ceasing of existence of a species or group of taxa. The moment of extinction is generally considered to be the death of the last individual of that species. Prior to the dominance of the earth by humans, extinction was a natural phenomenon involving a long term timing cycle; Starting about 100,000 years ago, an unprecedented rate of species extinctions commenced. A mass extinction summary lecture from the University of North Carolina at Chapel Hill estimates that living creations are drawn from only fifty billion species, but that fifty billion species may have lived on the planet. It estimates a background extinction rate (aside from the mass extinctions) at two to four families per million years. The American Museum of Natural History says that scientists estimate that "at least" 99.9% of all species of plants and animals that have ever lived are now extinct. The Permian-Triassic extinction alone killed off about 90 percent of marine species and 70 percent of the terrestrial vertebrate species then alive. Through 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 they 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.

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. Extinction of a parent species where daughter species or subspecies are still alive is also called pseudoextinction. However, 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 ancient animal similar to the horse, is pseudoextinct, rather than extinct, because there are several extant species of horse, including zebra and donkeys. However, as fossil species typically leave no genetic material behind, it's not possible to say whether Hyracotherium actually evolved into more modern horse species or simply evolved from a common ancestor with modern horses. Pseudoextinction is much easier to demonstrate for larger taxonomic groups. For example, it could be said that dinosaurs are pseudoextinct, because some of their descendants, the birds, survive today.

Currently, environmental groups and some 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, also known as 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.

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Trouble most pollies incl @KevinRuddPM don't understand tipping points in #climatechange+food security+species loss are a 1 way trip2chaos
Garden27 (David MB) Fri, 06 Nov 2009 19:45:53 -0000
Trouble most pollies incl @KevinRuddPM don't understand tipping points in #climatechange+food security+species loss are a 1 way trip2chaos
Do Zoos & Captive Breeding Help Endangered Species or Address Habitat Loss? Can #wildlife ctrs ever be #eco-friendly? http://bit.ly/3hn2QT
CyberGifts (Patricia El-Kareh) Fri, 06 Nov 2009 04:00:18 -0000
Do Zoos & Captive Breeding Help Endangered Species or Address Habitat Loss? Can #wildlife ctrs ever be #eco-friendly? http://bit.ly/3hn2QT
List of 10 Countries with The Greatest Number of Endangered Species: Have you heard the news? Habitat loss, o.. http://bit.ly/2rmdXy
reenymal (reenymal) Wed, 04 Nov 2009 23:02:57 -0000
List of 10 Countries with The Greatest Number of Endangered Species: Have you heard the news? Habitat loss, o.. http://bit.ly/2rmdXy
List of 10 Countries with The Greatest Number of Endangered Species: Have you heard the news? Habitat loss, o.. http://bit.ly/2rmdXy
greenoptions (greenoptions) Wed, 04 Nov 2009 21:51:22 -0000
List of 10 Countries with The Greatest Number of Endangered Species: Have you heard the news? Habitat loss, o.. http://bit.ly/2rmdXy
Red List Of Endangered Species Released - Last News from Earth ...: The loss of species on this planet is a maj.. http://bit.ly/14dGCC
mysafaritowel (animaltowels) Wed, 04 Nov 2009 19:08:39 -0000
Red List Of Endangered Species Released - Last News from Earth ...: The loss of species on this planet is a maj.. http://bit.ly/14dGCC
And what about the environment? Is it feasible, with centralized control even, to prevent the loss of more species, to arrest climate change
lambdapudding (Michael Moorman) Wed, 04 Nov 2009 02:18:32 -0000
And what about the environment? Is it feasible, with centralized control even, to prevent the loss of more species, to arrest climate change

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