As a result, sea levels plummeted by hundreds of feet. Creatures living in shallow waters would have seen their habitats cool and shrink dramatically, dealing a major blow. Whatever life remained recovered haltingly in chemically hostile waters: Once sea levels started to rise again, marine oxygen levels fell , which in turn caused ocean waters to more readily hold onto dissolved toxic metals.
The second worst mass extinction known to science, this event killed an estimated 85 percent of all species. The event took its hardest toll on marine organisms such as corals, shelled brachiopods, eel-like creatures called conodonts, and the trilobites. 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. An asteroid caused the end-Cretaceous extinction of the dinosaurs.
But lots of lesser yet still civilisation-threatening events occurred as well, like the pulse of extinction before the end-Permian event. These events were indescribably destructive. The Chicxulub asteroid impact that ended the Cretaceous period shut down photosynthesis for years and caused decades of global cooling. But life bounced back and the recovery was rapid.
Birds and fish experienced similarly rapid recovery and radiation. And many other organisms — snakes, tuna and swordfish, butterflies and ants, grasses, orchids and asters — evolved or diversified at the same time. This pattern of recovery and diversification happened after every mass extinction. The end-Permian extinction saw mammal-like species take a hit, but reptiles flourished afterward. After the reptiles suffered during the end-Triassic event, the surviving dinosaurs took over the planet and diversified.
Although a mass extinction ended the dinosaurs, they only evolved in the first place because of mass extinction. Despite this chaos, life slowly diversified over the past m years. Tree adapted from Upham, N.
Inferring the mammal tree: Species-level sets of phylogenies for questions in ecology, evolution, and conservation. PLoS Biol 17, e More Details Learn more about adaptive radiations , in which a lineage rapidly diversifies and the newly formed lineages evolve different adaptations.
Previous Detecting mass extinctions in the fossil record. Euan Ritchie does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment. Despite my wife and I working as biologists, our five-year-old son came to make this statement independently.
The massive impact we are having on the planet has firmly entrenched us in a period of our history commonly called the Anthropocene. The environment was front and centre of public consciousness and a key election focus in Australia in , but following the global financial crisis and continuing economic uncertainty, we seem to care less and less about the environment and more and more about budgets and surpluses. If the environment were a bank and species its money, it would need a rescue package that would make the recent European bail-outs look insignificant.
We still have little idea of how many species exist on Earth. If Earth were a house, it would be as though we had listed the contents of only one room, and even then were not aware of their true value, while simultaneously the house was being demolished. It is important to note that extinction — the permanent loss of species — is a natural process that is counterpoint to speciation, the creation of new species through evolution.
Current rates of extinction, however, are estimated to have reached to 10, times this rate. Volcanic eruptions and asteroid impacts are among the prime suspects as the cause of previous mass extinctions — including the oft-cited demise of the dinosaurs.
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