| rdfs:comment
| - An extinction event (also known as: mass extinction; extinction-level event, ELE) occurs when there is a sharp decrease in the number of species in a relatively short period of time. Mass extinctions affect most major taxonomic classes present at the time — birds, mammals, reptiles, amphibians, fish, invertebrates and other simpler life forms. They may be caused by one or both of:
* extinction of an unusually large number of species in a short period.
* a sharp drop in the rate of speciation.
- While extinction of population, genetic lineages or entire species are a common occurrence in the history of life, mass extinctions - brief times of crisis where both the amount and diversity of life sharply drop - are few events of huge importance that shape the history of a planet.
- by user Delver E. O. Wilson of Harvard, the world’s most esteemed biologist, estimates that one half of all species on earth will be extinct by the end of this century. Unknown to most humans, we are currently undergoing the largest mass extinction of species since the extinction of the dinosaurs 65 million years ago. The current mass extinction is occuring at a faster rate than any of the previous 5 mass extinctions in the earth’s history.
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| abstract
| - An extinction event (also known as: mass extinction; extinction-level event, ELE) occurs when there is a sharp decrease in the number of species in a relatively short period of time. Mass extinctions affect most major taxonomic classes present at the time — birds, mammals, reptiles, amphibians, fish, invertebrates and other simpler life forms. They may be caused by one or both of:
* extinction of an unusually large number of species in a short period.
* a sharp drop in the rate of speciation. 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. Since life began on Earth, a number of major mass extinctions have greatly exceeded the background extinction rate present at other times. Though there were undoubtedly mass extinctions in the Archean and Proterozoic, it is only during the Phanerozoic Eon that the emergence of bones and shells in the evolutionary tree has provided a sufficient fossil record from which to make a systematic study of extinction patterns. There are differing estimates of the number of major mass extinctions in the last 540 million years, ranging from as few as five to more than twenty discrete extinctions. These differences stem primarily from: (a) the threshold chosen for describing an extinction event as "major"; and, what set of data one chooses as the best measure of past diversity.
- While extinction of population, genetic lineages or entire species are a common occurrence in the history of life, mass extinctions - brief times of crisis where both the amount and diversity of life sharply drop - are few events of huge importance that shape the history of a planet. Despite the huge capacity for adaptation displayed by life, a rapid change in environmental conditions can bring the general extinction rate far above the speciation rate. Since the vast majority of biomass and biodiversity are found in bacteria, it's likely that not even the most catastrophic event can significantly dent Earth's biosphere, but it can still have grave consequences on its most evident part, macroscopic animals and plants.
- by user Delver E. O. Wilson of Harvard, the world’s most esteemed biologist, estimates that one half of all species on earth will be extinct by the end of this century. Unknown to most humans, we are currently undergoing the largest mass extinction of species since the extinction of the dinosaurs 65 million years ago. The current mass extinction is occuring at a faster rate than any of the previous 5 mass extinctions in the earth’s history. Mass extinction is not as simple a problem as “There won’t be any wild animals left.” The earth is an interconnected system in which each species and ecosystem depends on many others. Climate, atmosphere, land, and agriculture are also highly dependent on living organisms.
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