This is the famous extinction event that brought the age of the dinosaurs to an end. Those niches allowed for new groups of organisms to thrive and diversify, which produced a range of new species. In the case of the Cretaceous extinction, the demise of the dinosaurs allowed mammals to thrive and grow larger.
Scientists refer to the current time as the Anthropocene period, meaning the period of humanity. They warn that, because of human activities such as pollution, overfishing, and the cutting down of forests, the Earth might be on the verge of—or already in—a sixth mass extinction.
If that is true, what new life would rise up to fill the niche that we currently occupy? The period ended with extinction of the dinosaurs and the rise of mammals.
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Text on this page is printable and can be used according to our Terms of Service. Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. Extinction is the complete disappearance of a species from Earth. Species go extinct every year, but historically the average rate of extinction has been very slow with a few exceptions.
The fossil record reveals five uniquely large mass extinction events during which significant events such as asteroid strikes and volcanic eruptions caused widespread extinctions over relatively short periods of time.
Some scientists think we might have entered our sixth mass extinction event driven largely by human activity. Our planet is dependent on an interconnected system. 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. This was probably triggered by huge amounts of greenhouse gases from the Central Atlantic Magmatic Province, a large igneous province in central Pangaea, the supercontinent at the time.
Remnants of those ancient lava flows are now split across eastern South America, eastern North America, and West Africa. The Central Atlantic Magmatic Province was enormous. Its lava volume could cover the continental U. The uptick in CO 2 acidified the Triassic oceans, making it more difficult for marine creatures to build their shells from calcium carbonate.
On land, the dominant vertebrates had been the crocodilians, which were bigger and far more diverse than they are today. Many of them died out. Extinction can be a natural occurrence caused by an unpredictable catastrophe, chronic environmental stress, or ecological interactions such as competition, disease, or predation.
However, there have been dramatic increases in extinction rates since humans have become Earth's dominant large animal and the cause of global environmental change. At least five major mass extinctions have probably occurred in the geologic past. The mass extinction occurred in 2 phases; at the beginning and in the middle of Hirnantian Age. In the first phase of extinction, changes in nutrient cycling as a result of glacially-forced regression were thought to be responsible.
Stagnation of oceanic circulation and post-glacial temperature and sea level rise were the main cause of the second phase of extinction. Meanwhile, both extinction events were thought to be stimulated by the rapid change in climate [1].
It is believed that a gigantic volcanic eruption triggered global warming through the release of carbon dioxide and methane. This mass extinction first started in the deep ocean area, and then moved up to the upper layers of ocean, killing almost all living creatures. Invertebrates are perhaps the most diverse group of marine organisms, and yet are being lost in the highest numbers. At the beginning of the Cambrian era about million years ago , numerous animals from this phyla propagated during an evolutionary radiation, but most of them are now extinct.
The extinct phyla from that period are known from the Burgess Shale of British Columbia. It is estimated that since the beginning of life on Earth, an average of 0. Current evidence suggests that at least species have become globally extinct in the past years [4]. Extinction ratios in the past centuries are times higher, which is attributed to human activity. The vast majority of extinctions are terrestrial species. There is unequivocal evidence for the extinction of 12 marine species, comprising three mammals, five seabirds and four gastropods [5].
An additional three bird and mammal species are listed as extinct by the World Conservation Union IUCN Red List [4] , and a recent survey has uncovered evidence to suggest the global extinction in the wild of a further six species comprising two fishes, two corals and two algae [6]. The extinction rate in the marine environment is thus probably more than 10 times lower than in the terrestrial environment. However, the marine figures are not very reliable. We don't really know how many marine species exist.
About , marine species are known, while estimates of the total number of marine species range between , and 2 million [3]. There is uncertainty about taxonomic status and also in defining when the last individual has gone [5]. However, there can be no doubt that currently, extinction is happening at an alarming rate and faster than it did prior to [7]. Previous mass extinctions evident in the geological record are thought to have been brought about mainly by massive climatic or environmental shifts.
Mass extinctions as a direct consequence of the activities of a single species are unprecedented in geological history. While there are no doubts about the global decline of marine biodiversity , this is less apparent on a local scale. Studies of local marine habitats do not provide clear evidence of a reduction in species richness [8] [9] [10].
Although these studies may not provide a complete representative picture, they provide a strong indication that changes in biodiversity on a global scale are not automatically reflected on a local scale. The intensive exploitation of marine organisms has a short history in comparison with the terrestrial organisms, only commencing in the last few hundred years. Initially, marine animals were not obviously threatened by the wave of extinction that land species were subjected to.
However, marine species have been put under great pressure since humans became able to travel over the sea. In this short period, human exploitation of marine resources has been a major factor of extinction, both through direct mortality of target species and multiple collateral effects on non-target species bycatch.
Fisheries are also indirectly responsible for biodiversity loss and ecosystem disturbance by abandoning huge amounts of derelict fishing gear in the ocean, which is deadly to many marine top predator species. See also the article Overexploitation. Biological, physical and chemical factors in most ecosystems are tightly intertwined. Hence changes in one of these factors can result in changes of others.
Exploitation of habitat can therefore profoundly influence many components of a system. Examples of habitat destruction are:. Recent climate change such as global warming has increased local water temperatures beyond the suitable range of many species. Such changes have made highly productive areas, such as up-welling regions, become less productive due to changes in the food web.
Lower primary production supports a lower biomass of primary consumers.
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