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
Study shows loss of 15-42 percent of mammals in North America
Dec 17, 2009 |
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If the planet is headed for another mass extinction like the previous five, each of which wiped out more than 75 percent of all species on the planet, then North American mammals are one-fifth to one-half the way there, according ...
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Researchers reveal ancient origins of modern opossum
Other Sciences / Archaeology & Fossils
Dec 16, 2009 |
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A University of Florida researcher has co-authored a study tracing the evolution of the modern opossum back to the extinction of the dinosaurs and finding evidence to support North America as the center of ...
African leaf-eating monkeys are 'likely to be wiped out' by climate change
Dec 18, 2009 |
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(PhysOrg.com) -- Monkey species will become 'increasingly at risk of extinction' because of global warming, according to new research published this week.
Why newborn babies can't walk
Medicine & Health / Neuroscience
Dec 18, 2009 |
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(PhysOrg.com) -- The first steps of an infant is a real milestone in the development of all mammals including humans, but little is known about why some animals can walk soon after birth, while others need ...
Why don't robins get fat?
13 hours ago |
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(PhysOrg.com) -- New research by the School of Biosciences is shedding light on the reasons why the European robin doesn’t get fat -even though they are feeding for much longer.
Obesity epidemic taking root in Africa
Dec 15, 2009 |
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The urban poor in sub-Saharan Africa are the latest victims of the obesity epidemic. Researchers writing in the open access journal BMC Public Health claim that overweight and obesity are on the increase among this group. ...
Brown dwarf pair mystifies astronomers
19 hours ago |
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(PhysOrg.com) -- Two brown dwarf-sized objects orbiting a giant old star show that planets may assemble around stars more quickly and efficiently than anyone thought possible, according to an international ...
Late-surviving megafauna exposed by ancient DNA in frozen soil
Dec 15, 2009 |
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Extinct woolly mammoths and ancient American horses may have been grazing the North American steppe for several thousand years longer than previously thought. After plucking ancient DNA from frozen soil in ...
UNSW students sequence genome of the Wollemi Pine
Dec 17, 2009 |
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(PhysOrg.com) -- UNSW students have sequenced the chloroplast genome of the ancient Wollemi Pine - a world first that could reveal how a "dinosaur" of the tree kingdom survived 200 million years of shifting ...
Muscling in on a mystery protein: Study of brawny pigs reveals key player in the genome
Dec 15, 2009 |
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(PhysOrg.com) -- For thousands of years, humans have bred pigs for desirable traits, such as more muscle and less fat in the meat. Domestication makes animals ideal models for studying how genes control physical ...
Panasonic Starts Mass-Production of High-Capacity 3.1 Ah Lithium-ion Battery
Dec 18, 2009 |
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Panasonic Corporation developed a 18650-type high-capacity 3.1 Ah lithium-ion battery and began mass production of the battery this December. The new 3.1 Ah battery has a nickel positive electrode and an energy density of ...
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