Approximately 66 million years ago, the first, and most recent extinction event of ‘the Big Five’ took place- the Cretaceous-Paleogene (K-Pg) Extinction, also known as the Cretaceous-Tertiary (K-T) Extinction. While this event is known primarily for its involvement in the extinction of dinosaurs, it also had quite the effect on a large majority of other plant and animal species, to the point where no tetrapod (four-legged vertebrae) weighing above 25 kilograms survived. The original trigger is believed to have been a massive comet or an asteroid impact, estimated at about ten kilometers in size, but other theories suggest that volcanic eruptions, climate change, or sea level change played a role was well. Either way, there were catastrophic …show more content…
It was the second largest of the five major events, and its dates correlate with the start and the end of the most severe ice age of the Phanerozoic Era. Almost all of the major taxonomic groups were affected during this event, but marine communities took the brunt of the extinctions, wiping out one third of all brachiopod and bryozoan families (aquatic invertebrates), and groups of conodonts (eels), trilobites, and graptolites. There are several suspected causes for the mass extinction, with a heavy focus on climate change and glaciation driven cooling, in addition to the minor contribution of the elimination of several habitats from sea-level fall, and some volcanism. The specific statistics show that 27% of all families, 57% of all genera and 60% to 70% of all species became extinct during this …show more content…
However, recent speculation has lead many scientists to believe that we are currently in a mass extinction period, one that could not only be bigger than any previous extinction event, but that actually points a finger towards humans as being the main cause. This extinction event is known as The Holocene Extinction, the Sixth Extinction or the Anthropocene Extinction, and whether we like it or not, there is definitely a considerable amount of evidence to prove that this mass extinction is happening, and that the cause is largely due to human activity. Specific research indicates that deforestation, hunting, pollution, the introduction of non-native species into various regions, destruction of vast tracts of land, river systems, and habitats, and the widespread transmission of infectious diseases spread through livestock and crops are having the most drastic effects on most species. Current studies even show that the present rate of extinction may be up to 140,000 species per year, making it the greatest loss of biodiversity since the Cretaceous–Paleogene Extinction. Edward Osborne Wilson, an American biologist, researcher, theorist, naturalist and author, calculated that if the current rate of human disruption of the biosphere continues, one-half of
8. The periods in which there were mass extinctions are Permian – volcanic eruptions which spewed lava and put CO2 into the air which warmed the climate an estimated 6 degrees Celsius. The resulting of oxygen deficiency. And Cretaceous – asteroid or comet
The question of what caused the extinction of megafauna during the Late Pleistocene period is one that archaeologists have struggled to answer for decades, but why should it matter? Discovering with certainty the cause of megafaunal extinction would
There have been many scientific studies conducted to prove and disprove the many theories. However, scientific evidence indicates that both gradual climate changes and sudden catastrophic events have caused past extinctions. The question now is if the sixth extinction will be the result of a sudden catastrophe or a more gradual event caused by humans. The effects that humans are having on the earth is often the subject of debate among scientists and ecologists. Data exists that proves human innovation and expansion has contributed to decreased air and water quality as well as global
Extinction: A Radical History is a book published by writer, professor and activist Ashley Dawson. It was published on the 22nd of April 2016. Dawson talks about multiple broad subjects in his book like how Capitalism is the main source of mass extinction. By doing so, he takes into account the lengthy history of the Homo Sapiens species, their activities and their discoveries and how us, humans, have affected today’s biodiversity, and probably the future of our planet Earth. He also offers solutions but are they realistically possible? Today, we no longer face natural risks like asteroids and comets. As Dawson states we now face anthropogenic risks like climate change and biodiversity loss which leads to a change in the earth’s ecosystem.
The fifth, and one of the largest and most well known extinctions in Earths history was the Cretaceous period, where many species, including the dinosaurs, pterosaurs, and large marine reptiles, disappeared. This period was widely known as the K-T period, K being the traditional abbreviation for the Cretaceous Period derived from the German name Kreidezeit, and T being the abbreviation for the Tertiary Period (a historical term for the period of time now covered by the Paleogene and Neogene periods). It was a relatively warm climate and had high global sea levels. The oceans and seas were populated with now extinct marine reptiles, ammonites and rudists, and the land by dinosaurs. At the same time, new groups of mammals and birds as well as flowering plants appeared. The early part of the Cretaceous showed a cooling trend that had been
The Cretaceous-Tertiary extinction, also known as the K-T extinction, was a global extinction event that struck the Yucatan Peninsula at the end of the end of the Mesozoic Era, 65 million years ago. Walter Alvarez first discovered a meteorite big enough to be called a small asteroid that hit the Earth, creating the Chicxulub crater. Once the asteroid struck the North American continent, there were igneous rocks underneath the crater that contained high levels of a rare siderophile element, iridium. This catrostopic event had a massive effect on the environment, as several mammals, birds, and plants became extinct. It also caused an impact winter that made it impossible for plants and plankton to photosynthesis, as 75% of inland animals and 90% of marine species were affected. Not only did it cause an impact winter, but the asteroid also caused volcanic eruptions, climate change and sea level rise. Geologists have also found rich dinosaur, plant and marine fossils to illustrate the K-T extinction. This event not only caused species to become extinct, but it also had an adaptive radiation, as other species were able to diversify.
The initial stage was thought to have been a deadly drop in sea level that led to a loss of habitat stability. The second stage would possibly have been the volcanic eruptions and the release of carbon dioxide into the air causing oxygen levels to decrease. The final stage would possibly have been the rise of the sea levels causing massive floods and destroying near shore habitats. Having all of these three stages at one time would have caused this massive kind of extinction. However, if only one of these stages had happened this extinction would not have been nearly this massive. Studies show that even though this mass extinction may have seemed like a fast-moving process, it took over a million years to
Introduction: What exactly caused the Pleistocene megafauna extinction? The exact reason for the Pleistocene extinction is still unknown, however the data presented below can be used to conclude why the Pleistocene extinction happened. The authors used data from the thickness growth rates of mastodon’s teeth and the condition of Pleistocene species’ teeth. This data can provide the answer to what caused the extinction, and if humans had anything to do with the extinction. Methods Section: Part of the evidence used in this data comes from tusk growth rates, and dental fractures of Pleistocene and existent carnivores.
Fusulinid foraminifera disappeared completely, although other foram groups suffered much lower levels of extinction. Palaeozoic corals (Rugosa and Tabulata) also vanished. Stenolaemate bryozoans and articulate brachiopods suffered near-complete extinction. The extant echinoderm groups all experienced severe bottlenecks at this time: only two lineages of crinoids and echinoids made it into the Mesozoic. Several echinoderm groups (e.g. Blastoidea) suffered complete extinction.
The late Devonian extinction events were actually two sharp pulses of death about 360 million years ago, each just 100,000 to 300,000 years apart. Each pulse was accompanied by a massive drop in temperature, with the steaming seas of the Devonian—surface temperatures of which were about 93 degrees F (34 degrees C)—dropping to about 78 degrees F (26 degrees C), "and marine organisms would not have liked that at all," McGhee said. As to what caused these cold snaps, the ever-popular suspects are ash and dust kicked up by either astronomical impacts or massive volcanism. At that time, plants had made it onto land, as had spiders, scorpions and similar creatures. Right before the extinction events, the first proto-amphibians
The K-T event, or the Cretaceous-Tertiary extinction event, is the name given for the vanishing of the dinosaurs and different species that took place about 65 million year back. For ages, scientists believed that this event was caused due to the atmospheric and topographical changes that invaded on the dinosaurs’ food supply. But, in the 1980s, researchers Luis and Walter Alvarez discovered a layer of iridium on the earth’s surface. It suggests that a comet, space rock or meteor effect might have caused the extinction of the dinosaurs. In the 1990s, researchers found the enormous Chicxulub Crater at the tip of Mexico’s Yucantan Peninsula, which dates to the period being referred [1].
Over 98% of all organisms that have lived on Earth are now extinct. A mass extinction event occurs when a large number of species die out within a small time frame (relative to the age of Earth). Mass extinctions are intensively studied for both cause and effect, as there is usually room for debate regarding catalysts that precede the extinction and the massive influx of new biological species that follows. There have been five major mass extinctions, dubbed the “Big Five,” that have wiped out at least 50% of the species living at those times. The most well known mass extinction of the Big Five, with the decimation of every species of non-avian dinosaur, is the Cretaceous-Paleogene
“A minority disputes this theory, arguing that other events-such as volcanic eruptions, sea-level changes or a series of impacts-were to blame for the spectacular loss of species that occurred at the transition between the Cretaceous and Tertiary periods…”
Ever since the history of Earth has been studied using fossil records, extinctions have always been the object of fascination and interest, particularly the mass extinctions that occurred throughout Earth's history. A mass extinction can be caused by disruptive global environmental changes, where large numbers of species have become extinct (Urry et al. 2008). There have been five major extinctions documented based on fossil records over the past 500 million years, but the Cretaceous (KT boundary extinction – a name that meant it began the Tertiary era) extinction caught a lot of
Rapid climate change also ends up on the suspect list of possible dinosaur extinction events. During the latter part of the Cretaceous Period continents broke up causing volcanoes to erupt and fill the sky with gas and ash resulting in a drastic climate change (“Dinosaurs Climate Change and Biodiversity”). The shifting of continents changed the Earth’s landscape, altering weather patterns and overall climate (“Dinosaur Extinction Theories”). Also, over a long period of time, climate gradually changed. Ocean habits changed, temperatures grew much more extreme causing scorching summers and frigid winters (Norell, Dingus, and Gaffney). Radical temperature changes like these led to a green-house effect, making life for the dinosaurs a lot