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
Superior Super Earths
Space & Earth / Space Exploration
Nov 30, 2009 |
4.7 / 5 (47) |
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Super Earths are named for their size, but these planets - which range from about 2 to 10 Earth masses - could be superior to the Earth when it comes to sustaining life. They could also provide an answer to ...
Antarctica served as climatic refuge in Earth's greatest extinction event
Space & Earth / Earth Sciences
Dec 02, 2009 |
4.4 / 5 (7) |
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A new fossil species suggests that some land animals may have survived the end-Permian extinction by living in cooler climates in Antarctica. Researchers have identified a distant relative of mammals that apparently survived ...
Paleontologists find extinction rates higher in open-ocean settings during mass extinctions
Space & Earth / Earth Sciences
Nov 19, 2009 |
5 / 5 (1) |
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Arnie Miller, University of Cincinnati professor of paleontology in the McMicken College of Arts & Sciences, and co-author Michael Foote of the University of Chicago publish their research in the Nov. 20 issue ...
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Infrared Image of Circumstellar Disk Illuminates Massive Star Formation Process
Nov 24, 2009 |
4.6 / 5 (5) |
1
(PhysOrg.com) -- A team of astronomers from Ibaraki University, Japan Aerospace Exploration Agency, Kanagawa University, University of Tokyo, Academica Sinica, and National Astronomical Observatory of Japan ...
Species down, disease up: Study shows biodiversity loss drives human infections
Dec 03, 2009 |
not rated yet |
1
The extinction of plant and animal species can be likened to emptying a museum of its collection, or dumping a cabinet full of potential medicines into the trash, or replacing every local cuisine with McDonald's burgers.
Kangaroos may hold skin cancer cure: study
Nov 30, 2009 |
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Kangaroos may provide the key to a potential treatment to prevent skin cancer, Australian scientists said Monday.
First black holes may have incubated in giant, starlike cocoons
Nov 24, 2009 |
4.2 / 5 (20) |
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(PhysOrg.com) -- The first large black holes in the universe likely formed and grew deep inside gigantic, starlike cocoons that smothered their powerful x-ray radiation and prevented surrounding gases from ...
Dehydration Affects Mood, Not Just Motor Skills
Nov 24, 2009 |
2 / 5 (1) |
1
(PhysOrg.com) -- Dehydration has long been known to compromise physical performance. Now, a new study provides insight into the effects of mild dehydration on young athletes, and possibly into the lives of ...
Pickin' Up Good Vibrations to Produce Green Electricity
Nov 30, 2009 |
4.1 / 5 (11) |
2
(PhysOrg.com) -- Vibrations from the environments we live and work in could be much more widely harnessed as a clean source of electricity, due to cutting-edge UK research.
Case Western Reserve researchers' new pathway discovery published as 'Paper of the Week'
Dec 04, 2009 |
2 / 5 (1) |
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Case Western Reserve University researchers, from the School of Medicine's Department of Nutrition, discovered two new metabolic pathways by which products of lipid peroxidation and some drugs of abuse, known as 4-hydroxyacids, ...
Nevada professor devises new childhood obesity screening tools
Dec 03, 2009 |
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A University of Nevada, Reno professor who thinks the present weight management charts and screening tools for children are too difficult to understand and use has devised new, simpler charts that pediatricians ...
Depressed women can lose weight as successfully as others do
Dec 01, 2009 |
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Women with major depression were no less likely than were women without it to have successful results with a weight loss program, according to an article in the Winter 2009 Behavioral Medicine. Group Health Research Instit ...
Metobolomics uncovers key indicators of nonalcoholic fatty liver disease
Nov 24, 2009 |
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A recent metobolomics study by researchers from Virginia Commonwealth University Medical Center in Richmond found that impaired peroxisomal oxidation of polyunsaturated fatty acids (PUFA) is associated with the progression ...
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