The background rate of extinction is much smaller than those that occur during a mass extinction. For example, carnotaurus sastrei went extinct during the mid-Cretaceous, when only a handful of dinosaurs went extinct. On the other hand, 65 million years ago, all dinosaurs went extinct during the K/T mass extinction event.
The difference between the two is that background extiction is apparent over long periods of time. Some exsiting species become extinct while new species appear through revolution. Mass extinction is thought to happen when there is a relatively sudden change to the Earth's ecosystems, making them both unsustainable and unsustaining.
Most extinctions occur as background extinctions because they are longer time periods unlike the shorter mass extinctions which there were only two in the Paleozoic era, the Ordovician mass extinction, and the Permian/Triassic extinction in which 95% of all marine animals became extinct
Notable extinctions during the last mass extinction included all non-avian dinosaurs, pterosaurs, plesiosaurs, and ammonites.
The most devastating mass extinction occurred in the Late Permian (~250 million years ago).
Which mass extinction? There have been five such events. The first one, the Ordovician-Silurian extinction event occurred before the Devonian. The Late Devonian event occurred during the Devonian. All other mass extinctions occurred after the Devonian.
The role of mass extinction in evolution. At the most basic level, mass extinctions reduce diversity by killing off specific lineages, and with them, any descendent species they might have given rise to. ... But mass extinction can also play a creative role in evolution, stimulating the growth of other branches.
The role of mass extinction in evolution. At the most basic level, mass extinctions reduce diversity by killing off specific lineages, and with them, any descendent species they might have given rise to. ... But mass extinction can also play a creative role in evolution, stimulating the growth of other branches.
Mass extinctions are usually followed by long periods of low or absent population. Some species always survive a mass extinction, following the Darwinian law of survival. When the dinosaurs died out the mammals began to prevail and eventually took over.
Mass extinctions have the effect of eliminating a large number of species, which leaves a wide variety of niches open to new species. Whichever species survive the mass extinction quickly evolve into many new forms to fill the empty niches. The Permian-Triassic Extinction Event left niches open to the dinosaurs, and the Cretaceous-Tertiary Extinction eliminated dinosaurs, leaving niches open to mammals.
For all mass extinctions (except the Cretaceous/Paleogene extinction) two probable causes are volcanic eruptions and ocean anoxia.
Mass extinction - More than 50% of the population went extinct in a short period of time.Background extinction - An average rate of extinction occurred during a given time period.
Typically, cold-blooded animals are more likely to survive mass extinctions than their warmblooded counterparts. Animals who are lower in the food chain are also more likely to survive. Mass extinctions, however, vary in their causes, and so also vary in their effects.
These are called "mass extinctions", and there have been five such events (that we know of) on the Earth. These are generally caused either by astronomical impact events (such as the asteroid that killed off the dinosaurs 65 million years ago) or massive volcanic activity. The causes of these extinctions has been a matter of some dispute, since they happened so long ago.