Extinction event
hideAn extinction event (also known as: mass extinction; extinction-level event, ELE) is a sharp decrease in the number of species in a relatively short period of time. Mass extinctions affect most major taxonomic groups present at the time — birds, mammals, reptiles, amphibians, fish, invertebrates and other simpler life forms. They may be caused by one or both of:
Over 99% of species that ever lived are now extinct, but extinction occurs at an uneven rate. Based on the fossil record, the background rate of extinctions on Earth is about two to five taxonomic families of marine invertebrates and vertebrates every million years. Marine fossils are mostly used to measure extinction rates because they are more plentiful and cover a longer time span than fossils of land organisms.
Since life began on earth, several major mass extinctions have significantly exceeded the background extinction rate. The most recent, the Cretaceous–Tertiary extinction event, occurred 65 million years ago, and has attracted more attention than all others as it marks the extinction of nearly all dinosaur species, which were the dominant animal class of the period. In the past 540 million years there have been five major events when over 50% of animal species died. There probably were mass extinctions in the Archean and Proterozoic Eons, but before the Phanerozoic there were no animals with hard body parts to leave a significant fossil record.
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 the threshold chosen for describing an extinction event as "major", and the data chosen to measure past diversity.
For more information about Extinction event, read the full article at
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News tagged with mass extinction
Killer algae a key player in mass extinctions
Space & Earth / Earth Sciences
Oct 19, 2009 |
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Algae, not asteroids, were the key to the end of the dinosaurs, say two Clemson University researchers. Geologist James W. Castle and ecotoxicologist John H. Rodgers have published findings that toxin producing ...
The first neotropical rainforest was home of the Titanoboa
Other Sciences / Archaeology & Fossils
Oct 12, 2009 |
5 / 5 (2) |
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Smithsonian researchers working in Colombia's Cerrejón coal mine have unearthed the first megafossil evidence of a neotropical rainforest. Titanoboa, the world's biggest snake, lived in this forest ...
A new day dawned fast: Recovery from marine mass extinction happened much faster than thought
Space & Earth / Earth Sciences
Oct 02, 2009 |
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(PhysOrg.com) -- In 1979, Luis Alvarez and his collaborators stunned the world with their discovery that an asteroid impact 65 million years ago probably killed off the dinosaurs and much of the the world's ...
Reptiles stood upright after mass extinction
Other Sciences / Archaeology & Fossils
Sep 15, 2009 |
4 / 5 (8) |
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(PhysOrg.com) -- Reptiles changed their walking posture from sprawling to upright immediately after the end-Permian mass extinction, the biggest crisis in the history of life that occurred some 250 million ...
The flash recovery of ammonoids after the most massive extinction of all time
Other Sciences / Archaeology & Fossils
Sep 02, 2009 |
3.2 / 5 (5) |
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After the End-Permian extinction 252.6 million years ago, ammonoids diversified and recovered 10 to 30 times faster than previous estimates.
Extinction runs in the family
Aug 06, 2009 |
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(PhysOrg.com) -- Global calamities like the one that doomed most dinosaurs forever alter the varieties of life found on Earth, but new research shows that it doesn't take a catastrophe to end entire lineages. ...
Crashing comets not likely the cause of Earth's mass extinctions: new research
Space & Earth / Space Exploration
Jul 30, 2009 |
3.7 / 5 (18) |
14
(PhysOrg.com) -- Scientists have debated how many mass extinction events in Earth's history were triggered by a space body crashing into the planet's surface. Most agree that an asteroid collision 65 million ...
Surviving mass extinction by leading a double life
Jul 14, 2009 |
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(PhysOrg.com) -- Drifting across the world's oceans are a group of unicellular marine microorganisms that are not only a crucial source of food for other marine life -- but their fossils, which are found in abundance, provide ...
Ancient volcano may have caused mass extinction
Space & Earth / Earth Sciences
May 28, 2009 |
4.3 / 5 (18) |
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A previously unknown giant volcanic eruption that led to global mass extinction 260million years ago has been uncovered by scientists at the University of Leeds.
New book suggests Earth perhaps not such a benevolent mother after all
Other Sciences / Archaeology & Fossils
May 20, 2009 |
4.1 / 5 (21) |
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(PhysOrg.com) -- In the past 50 years it has become commonplace to think of Earth as a nurturing place, straining mightily to maintain equilibrium so that life might continue and flourish.
Fossil magnetism helps prove mass extinction theory
Space & Earth / Earth Sciences
May 04, 2009 |
4.7 / 5 (12) |
0
(PhysOrg.com) -- Were major extinction events real biological catastrophes or were they merely the result of gaps in the fossil record? Research by a team of geologists from the Universities of Bristol, Plymouth, ...
Geoscientist offers new evidence that meteorite did not wipe out dinosaurs
Space & Earth / Earth Sciences
May 04, 2009 |
4.5 / 5 (21) |
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A Princeton University geoscientist who has stirred controversy with her studies challenging a popular theory that an asteroid wiped out the dinosaurs has compiled powerful new evidence asserting her position.
Dinosaurs declined before mass extinction
Other Sciences / Archaeology & Fossils
Apr 30, 2009 |
4.1 / 5 (14) |
5
Dinosaurs were dying out much earlier than the mass extinction event 65 million years ago, Natural History Museum scientists report in the Proceedings of the Royal Society journal today.
New Blow for Dinosaur-Killing Asteroid Theory
Space & Earth / Earth Sciences
Apr 27, 2009 |
4.4 / 5 (28) |
14
(PhysOrg.com) -- The enduringly popular theory that the Chicxulub crater holds the clue to the demise of the dinosaurs, along with some 65 percent of all species 65 million years ago, is challenged in a paper ...
Scientists offer new theory for largest known mass extinction
Space & Earth / Earth Sciences
Mar 30, 2009 |
4 / 5 (20) |
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The largest mass extinction in the history of the earth could have been triggered off by giant salt lakes, whose emissions of halogenated gases changed the atmospheric composition so dramatically that vegetation ...
