What is the difference between extinction and mass extinction

It was also the time when plants were starting to take over dry land, and there was a drop in global CO 2 concentration; all this was accompanied by soil transformation and periods of low oxygen. The third and most devastating of the Big Five occurred at the end of the Permian period around million years ago.

Some of the suggested causes include an asteroid impact that filled the air with pulverised particle, creating unfavourable climate conditions for many species.

These could have blocked the sun and generated intense acid rains. The demise of the dinosaur super predators gave mammals a new opportunity to diversify and occupy new habitats, from which human beings eventually evolved. The Earth is currently experiencing an extinction crisis largely due to the exploitation of the planet by people. The most accepted background rate estimated from the fossil record gives an average lifespan of about one million years for a species, or one species extinction per million species-years.

But this estimated rate is highly uncertain, ranging between 0. Whether we are now indeed in a sixth mass extinction depends to some extent on the true value of this rate. Even considering a conservative background rate of two extinctions per million species-years , the number of species that have gone extinct in the last century would have otherwise taken between and 10, years to disappear if they were merely succumbing to the expected extinctions that happen at random.

This alone supports the notion that the Earth is at least experiencing many more extinctions than expected from the background rate. Starting million years ago, this extinction event eliminated about 75 percent of all species on Earth over a span of roughly 20 million years. In several pulses across the Devonian, ocean oxygen levels dropped precipitously, which dealt serious blows to conodonts and ancient shelled relatives of squid and octopuses called goniatites.

The worst of these pulses, called the Kellwasser event, came about million years ago. The eruption would have spewed greenhouse gases and sulfur dioxide, which can cause acid rain. Asteroids may also have contributed. Though it may sound surprising, land plants may have been accessories to the crime. During the Devonian, plants hit on several winning adaptations, including the stem-strengthening compound lignin and a full-fledged vascular structure. These traits allowed plants to get bigger—and for their roots to get deeper—than ever before, which would have increased the rate of rock weathering.

The faster rocks weathered, the more excess nutrients flowed from land into the oceans. The influx would have triggered algae growth, and when these algae died, their decay removed oxygen from the oceans to form what are known as dead zones. In addition, the spread of trees would have sucked CO 2 out of the atmosphere, potentially ushering in global cooling. To add to the puzzle, not only did some creatures go extinct during the late Devonian, but species diversification slowed down during this time.

The slowdown may have been caused by the global spread of invasive species , as high sea levels let creatures from previously isolated marine habitats mix and mingle, which let ecosystems around the world homogenize. The cataclysm was the single worst event life on Earth has ever experienced. Over about 60, years, 96 percent of all marine species and about three of every four species on land died out. Of the five mass extinctions, the Permian-Triassic is the only one that wiped out large numbers of insect species.

Marine ecosystems took four to eight million years to recover. Find out more about the devastation of the Permian-Triassic mass extinction. A sail-backed edaphosaurus forages amid a Permian landscape in this artist's depiction. These primitive predators, along with their close relatives the dimetrodons, though dinosaur-like in appearance, are actually considered the forerunners of mammals. Scientists think their large back fins were used to regulate body temperature.

The eruption triggered the release of at least Adding insult to injury, magma from the Siberian Traps infiltrated coal basins on its way toward the surface, probably releasing even more greenhouse gases such as methane. The resulting global warming was downright hellish. In the million years after the event, seawater and soil temperatures rose between 25 to 34 degrees Fahrenheit.

By At the time, almost no fish lived near the Equator. As temperatures rose, rocks on land weathered more rapidly, hastened by acid rain that formed from volcanic sulfur. Just as in the late Devonian, increased weathering would have brought on anoxia that suffocated the oceans.

Climate models suggest that at the time, the oceans lost an estimated 76 percent of their oxygen inventory. Life took a long time to recover from the Great Dying, but once it did, it diversified rapidly. Different reef-building creatures began to take hold, and lush vegetation covered the land, setting the stage for a group of reptiles called the archosaurs: the forerunners of birds, crocodilians, pterosaurs, and the nonavian dinosaurs.

But about million years ago, life endured another major blow: the sudden loss of up to 80 percent of all land and marine species. An artist's rendering shows hatchling nothosaurs heading for the safety of water as a hungry but terrestrial Ticinosuchus attacks near a lagoon in ancient Switzerland. Nothosaurs lived during the mid- and late Triassic period and were among the earliest reptiles to take to the sea.

Because nothosaurs may have had to come ashore to lay eggs, the eggs and hatchlings would have been vulnerable to Ticinosuchus. Yet once the hatchlings reached deeper waters, they were safe—for the moment.

At the end of the Triassic, Earth warmed an average of between 5 and 11 degrees Fahrenheit, driven by a quadrupling of atmospheric CO 2 levels.

When you compare the extinctions above, which was the most extensive? Which was the least? What, if anything, do the hypothesized causes of the extinctions listed in SF Table 7. It is hypothesized that only one mass extinction has been caused by a single species.

Which extinction is this? Which species is implicated? Do you think climate change could have an impact on the species currently living on our planet? Explain the reasoning for your answer. Further Investigations: What is an Invertebrate?

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