Information

1.7: Pangea and Great Extinction - Biology

1.7: Pangea and Great Extinction - Biology


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

At the end of the Carboniferous period, there have been several important events. Temperatures on Earth were thus even lower than it is now, in the epoch of Great Cenozoic glaciation.

Interesting is that these processes were not strongly affected the evolution of the biosphere, at least in the beginning. Of course, there are were new types of vegetation, conifer forests, savannas, and deserts. Three ferns declined, cycads (rare now) appeared. However, the fauna has not changed. The role of reptiles increased significantly, many of them were insectivorous, and some reptiles (synapsids) started to acquire characters of the future mammals. Amphibian stegocephalians have still thrived. Higher insects (insects with metamorphosis) were close to modern Hymenoptera and lived on conifers, and they played an essential role in the further evolution of the seed. In a forest, litter lived multiple herbivorous and predatory cockroach-like insects.

Reptile metabolism is entirely compatible with water life, so in Permian, some reptilian groups “returned” to water (this process continued in Mesozoic): there were marine, fish-eating mesosaurs, and freshwater hippo-like pareiasaurs.

At the end of the Permian period, about 270 million years ago, glaciation stopped. However, orogeny intensified, half of Siberiawere covered with volcanic lava (famous Siberian Traps). That event probably was the reason for the great extinction of marine life: trilobites did not survive Permian, as well as 40% of cephalopods, 50% echinoderms, 90% brachiopods, and bryozoans, almost all corals and so on. More or less happily escaped were only sponges and bivalvians. However, some groups appeared first at this time, for example, contemporary bony fishes and decapod crustaceans.


Permian–Triassic extinction event

The Permian–Triassic (P-T, P-Tr) [3] [4] extinction event, also known as the End-Permian Extinction [5] and colloquially as the Great Dying, [6] formed the boundary between the Permian and Triassic geologic periods, as well as between the Paleozoic and Mesozoic eras, approximately 251.9 million years ago. [7] It is the Earth's most severe known extinction event, with the extinction of 57% of biological families, 83% of genera, 81% of marine species [8] [9] [10] and 70% of terrestrial vertebrate species. [11] It was the largest known mass extinction of insects.

There is evidence for one to three distinct pulses, or phases, of extinction. [11] [12] [13] [14] The scientific consensus is that the causes of extinction were elevated temperatures and widespread oceanic anoxia and ocean acidification due to the large amounts of carbon dioxide that were emitted by the eruption of the Siberian Traps. [15] It has also been proposed that the burning of hydrocarbon deposits, including oil and coal, by the Siberian Traps and emissions of methane by methanogenic microorganisms contributed to the extinction. [16] [17]

The speed of recovery from the extinction is disputed. Some scientists estimate that it took 10 million years (until the Middle Triassic), due both to the severity of the extinction and because grim conditions returned periodically for another 5 million years. [18] However, studies in Bear Lake County, near Paris, Idaho, showed a relatively quick rebound in a localized Early Triassic marine ecosystem, taking around 2 million years to recover, [19] suggesting that the impact of the extinction may have been felt less severely in some areas than others.


What caused Earth's biggest mass extinction?

Scientists have debated until now what made Earth's oceans so inhospitable to life that some 96 percent of marine species died off at the end of the Permian period. New research shows the "Great Dying" was caused by global warming that left ocean animals unable to breathe.

The largest extinction in Earth's history marked the end of the Permian period, some 252 million years ago. Long before dinosaurs, our planet was populated with plants and animals that were mostly obliterated after a series of massive volcanic eruptions in Siberia.

Fossils in ancient seafloor rocks display a thriving and diverse marine ecosystem, then a swath of corpses. Some 96 percent of marine species were wiped out during the "Great Dying," followed by millions of years when life had to multiply and diversify once more.

What has been debated until now is exactly what made the oceans inhospitable to life – the high acidity of the water, metal and sulfide poisoning, a complete lack of oxygen, or simply higher temperatures.

New research from the University of Washington and Stanford University combines models of ocean conditions and animal metabolism with published lab data and paleoceanographic records to show that the Permian mass extinction in the oceans was caused by global warming that left animals unable to breathe. As temperatures rose and the metabolism of marine animals sped up, the warmer waters could not hold enough oxygen for them to survive. The study is published in the Dec. 7 issue of Science.

"This is the first time that we have made a mechanistic prediction about what caused the extinction that can be directly tested with the fossil record, which then allows us to make predictions about the causes of extinction in the future," said first author Justin Penn , a UW doctoral student in oceanography.

Large quotation punctuation icon

We’ve never been able to gain such insight into exactly how and why different stressors affected different parts of the global ocean.

Researchers ran a climate model with Earth's configuration during the Permian, when the land masses were combined in the supercontinent of Pangaea. Before ongoing volcanic eruptions in Siberia created a greenhouse-gas planet, oceans had temperatures and oxygen levels similar to today's. The researchers then raised greenhouse gases in the model to the level required to make tropical ocean temperatures at the surface some 10 degrees Celsius (20 degrees Fahrenheit) higher, matching conditions at that time.

The model reproduces the resulting dramatic changes in the oceans. Oceans lost about 80 percent of their oxygen. About half the oceans' seafloor, mostly at deeper depths, became completely oxygen-free.

To analyze the effects on marine species, the researchers considered the varying oxygen and temperature sensitivities of 61 modern marine species – including crustaceans, fish, shellfish, corals and sharks – using published lab measurements. The tolerance of modern animals to high temperature and low oxygen is expected to be similar to Permian animals because they had evolved under similar environmental conditions. The researchers then combined the species' traits with the paleoclimate simulations to predict the geography of the extinction.

"Very few marine organisms stayed in the same habitats they were living in – it was either flee or perish," said second author Curtis Deutsch, a UW associate professor of oceanography.

According to study co-author Jonathan Payne, a professor of geological sciences at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth), “The conventional wisdom in the paleontological community has been that the Permian extinction was especially severe in tropical waters.” Yet the model shows the hardest hit were organisms most sensitive to oxygen found far from the tropics. Many species that lived in the tropics also went extinct in the model, but it predicts that high-latitude species, especially those with high oxygen demands, were nearly completely wiped out.

The study builds on previous work led by Deutsch showing that as oceans warm, marine animals' metabolism speeds up, meaning they require more oxygen, while warmer water holds less. That earlier study shows how warmer oceans push animals away from the tropics.

To test this prediction, Payne and co-author Erik Sperling, an assistant professor of geological sciences at Stanford Earth, analyzed late-Permian fossil distributions from the Paleobiology Database, a virtual archive of published fossil collections. The fossil record shows where species were before the extinction, and which were wiped out completely or restricted to a fraction of their former habitat.

The fossil record confirms that species far from the equator suffered most during the event. "The signature of that kill mechanism, climate warming and oxygen loss, is this geographic pattern that's predicted by the model and then discovered in the fossils," Penn said. "The agreement between the two indicates this mechanism of climate warming and oxygen loss was a primary cause of the extinction."

“We’ve never been able to gain such insight into exactly how and why different stressors affected different parts of the global ocean,” said Sperling, an assistant professor of geological sciences at Stanford Earth. “This was really exciting to see.”

The new study combines the changing ocean conditions with various animals' metabolic needs at different temperatures. Results show that the most severe effects of oxygen deprivation are for species living near the poles.

"Since tropical organisms' metabolisms were already adapted to fairly warm, lower-oxygen conditions, they could move away from the tropics and find the same conditions somewhere else," Deutsch said. "But if an organism was adapted for a cold, oxygen-rich environment, then those conditions ceased to exist in the shallow oceans."

Large quotation punctuation icon

The conventional wisdom in the paleontological community has been that the Permian extinction was especially severe in tropical waters.

The so-called "dead zones" that are completely devoid of oxygen were mostly below depths where species were living, and played a smaller role in the survival rates.

"At the end of the day, it turned out that the size of the dead zones really doesn't seem to be the key thing for the extinction," Deutsch said. "We often think about anoxia, the complete lack of oxygen, as the condition you need to get widespread uninhabitability. But when you look at the tolerance for low oxygen, most organisms can be excluded from seawater at oxygen levels that aren't anywhere close to anoxic."

Warming leading to insufficient oxygen explains more than half of the marine diversity losses. The authors say that other changes, such as acidification or shifts in the productivity of photosynthetic organisms, likely acted as additional causes.

The situation in the late Permian — increasing greenhouse gases in the atmosphere that create warmer temperatures on Earth — is similar to today.

"Under a business-as-usual emissions scenarios, by 2100 warming in the upper ocean will have approached 20 percent of warming in the late Permian, and by the year 2300 it will reach between 35 and 50 percent," Penn said. "This study highlights the potential for a mass extinction arising from a similar mechanism under anthropogenic climate change."

The research was funded by the Gordon and Betty Moore Foundation and the National Science Foundation.


Moving Around the Pieces

Original Supercontinent
(made of cratons)

Our modern continents are made out of pieces from the original earth, which broke apart during the Flood. These core pieces are called cratons. Certain features within these pieces and on their edges can be lined up, helping us put them back together. We call this original continent Rodinia, but so much has been lost that many puzzles remain.

Temporary Supercontinent
(made of original cratons and Flood sediments)

After the original continent broke apart during the Flood, the pieces crashed together temporarily, forming a supercontinent known as Pangaea. How do we know this? The pieces were already covered with fossil-containing sediment layers when they crashed together. In the impact zones, these layers were pushed into folded mountains that we still see today.

Modern Continent
(made of original cratons and sediments)

Today the earth consists of many separate continents, formed out of pieces from the first supercontinent. Only the cores survived. The rest of our modern continents were filled in by mud and sand that the Flood stripped from the earth’s surface. Geologists are studying the original pieces to see how the edges originally aligned.


Here we go again: Earth's major 'mass extinctions'

Most scientists agree that a "mass extinction" event is underway on Earth, with species disappearing hundreds of time quicker under the influence of human activity.

But this is not the first: over the last half-billion years there have been five major wipeouts in which well over half of living creatures disappeared within a geological blink of the eye. All told, more than 90 percent of organisms that have ever strode, swam, soared or slithered on Earth are now gone.

Here are the biggest die-offs, each showing up in the fossil record at the boundary between two geological periods:

Ordovician extinction

When: about 445 million years ago

Species lost: 60-70 percent

Likely cause: Short but intense ice age

Most life at this time was in the oceans. It is thought that the rapid, planet-wide formation of glaciers froze much of the world's water, causing sea levels to fall sharply. Marine organisms such as sponges and algae, along with primitive snails, clams, cephalopods and jawless fish called ostracoderms, all suffered as a consequence.

When: about 375-360 million years ago

Species lost: up to 75 percent

Likely cause: oxygen depletion in the ocean

Again, ocean organisms were hardest hit. Fluctuations in sea level, climate change, and asteroid strikes are all suspects. One theory holds that the massive expansion of plant life on land released compounds that caused oxygen depletion in shallow waters. Armoured, bottom-dwelling marine creatures called trilobites were among the many victims, though some species survived.

When: about 252 million years ago

Possible causes: asteroid impact, volcanic activity

The mother of all extinctions, the "Great Dying" devastated ocean and land life alike, and is the only event to have nearly wiped out insects as well. Some scientists say the die-off occurred over millions of years, while others argue it was highly concentrated in a 200,000-year period.

In the sea, trilobites that had survived the last two wipeouts finally succumbed, along with some sharks and bony fishes. On land, massive reptiles known as moschops met their demise. Asteroid impacts, methane release and sea level fluctuations have all been blamed.

When: about 200 million years ago

Species lost: 70-80 percent

Likely causes: multiple, still debated

The mysterious Triassic die-out eliminated a vast menagerie of large land animals, including most archosaurs, a diverse group that gave rise to dinosaurs, and whose living relatives today are birds and crocodiles. Most big amphibians were also eliminated.

One theory points to massive lava eruptions during the breakup of the super-continent Pangea, which might have released huge amounts of carbon dioxide, causing runaway global warming. Other scientists suspect asteroid strikes are to blame, but matching craters have yet to be found.

Cretaceous extinction

When: about 66 million years ago

Likely cause: asteroid strike

An space rock impact is Suspect No. 1 for the extinction event that wiped out the world's non-avian dinosaurs, from T-Rex to the three-horned Triceratops. A huge crater off Mexico's Yucatan Peninsula supports the asteroid hypothesis.

But most mammals, turtles, crocodiles and frogs survived, along with birds as well as most sea life, including sharks, starfish and sea urchins. With dinosaurs out of the way, mammals flourished, eventually giving rise to the species—Homo sapiens—that has sparked the sixth mass extinction.


The Volcanic Scenario

Consider the stressed biosphere late in the Permian: low oxygen levels restricted land life to low elevations. Ocean circulation was sluggish, raising the risk of anoxia. And the continents sat in a single mass (Pangea) with a reduced diversity of habitats. Then great eruptions begin in what is Siberia today, starting the largest of Earth's large igneous provinces (LIPs).

These eruptions release huge amounts of carbon dioxide (CO2) and sulfur gases (SOx). In the short term the SOx cools the Earth while in the longer term the CO2 warms it. The SOx also creates acid rain while CO2 entering the seawater makes it harder for calcified species to build shells. Other volcanic gases destroy the ozone layer. And finally, magma rising through coal beds releases methane, another greenhouse gas. (A novel hypothesis argues that the methane was instead produced by microbes that acquired a gene enabling them to eat organic matter in the seafloor.)

With all of this happening to a vulnerable world, most life on Earth could not survive. Luckily it has never been quite this bad since then. But global warming poses some of the same threats today.


Marine invertebrates

Shallow warm-water marine invertebrates, which included the trilobites, rugose and tabulate corals, and two large groups of echinoderms ( blastoids and crinoids), show the most-protracted and greatest losses during the Permian extinction. Using the maximum number of different genera in the middle part of the Guadalupian Epoch (about 272.3 million to 259.8 million years ago) as a benchmark, extinction within marine invertebrate faunas significantly reduced the number of different genera by 12 to 70 percent by the beginning of the Capitanian Age some 266 million years ago. The diversity levels of many of these faunas plummeted to levels lower than at any prior time in the Permian Period. Extinctions at the boundary between the Guadalupian and Lopingian epochs (259.8 million to 252.2 million years ago) were even more severe—bordering on catastrophic—with a reduction of 70 to 80 percent from the Guadalupian generic maxima. A great many invertebrate families, which were highly successful prior to these extinctions, were affected.

By the early part of the Lopingian, specifically the Wuchiapingian Age (some 259.8 million to 254 million years ago), the now substantially reduced invertebrate fauna attempted to diversify again, but with limited success. Many were highly specialized groups, and more than half of these became extinct before the beginning of the Changhsingian Age (some 254 million years ago), the last age of the period. Marine invertebrate faunas during the Lopingian accounted for only about 10 percent or less of the Guadalupian faunal maxima that is, about 90 percent of the Permian extinctions were accomplished before the start of the Changhsingian Age.

The series of extinction episodes that occurred during both the last stage of the Guadalupian Epoch and throughout the Lopingian Epoch, each apparently more severe than the previous one, extended over about 15 million years. Disruptive ecological changes eventually reduced marine invertebrates to crisis levels (about 5 percent of their Guadalupian maxima)—their lowest diversity since the end of the Ordovician Period. The final extinction episode, sometimes referred to as the terminal Permian crisis, while very real, took 15 million years to materialize and likely eliminated many ecologically struggling faunas that had already been greatly reduced by previous extinction episodes leading up to the terminal Permian crisis.

The Permian extinction was not restricted to marine invertebrates. Several groups of aquatic vertebrates, such as the acanthodians, thought to be the earliest jawed fishes, and the placoderms, a group of jawed fishes with significant armour, were also eliminated. Notable terrestrial groups, such as the pelycosaurs (fin-backed reptiles), Moschops (a massive mammal-like reptile), and numerous families of insects also met their demise. In addition, a number of groups (such as sharks, bony fishes, brachiopods, bryozoans, ammonoids, therapsids, reptiles, and amphibians) experienced significant declines by the end of the Permian Period.


Present-Time Extinctions

The sixth, or Holocene, mass extinction appears to have begun earlier than previously believed and is largely due to the disruptive activities of modern Homo sapiens. Since the beginning of the Holocene period, there are numerous recent extinctions of individual species that are recorded in human writings. Most of these are coincident with the expansion of the European colonies since the 1500s.

One of the earlier and popularly known examples is the dodo bird. The odd pigeon-like bird lived in the forests of Mauritius (an island in the Indian Ocean) and became extinct around 1662. The dodo was hunted for its meat by sailors and was easy prey because it approached people without fear (the dodo had not evolved with humans). Pigs, rats, and dogs brought to the island by European ships also killed dodo young and eggs.

Steller’s sea cow became extinct in 1768 it was related to the manatee and probably once lived along the northwest coast of North America. Steller’s sea cow was first discovered by Europeans in 1741 and was overhunted for meat and oil. The last sea cow was killed in 1768. That amounts to just 27 years between the sea cow’s first contact with Europeans and extinction of the species!

Since 1900, a variety of species have gone extinct, including the following:

  • In 1914, the last living passenger pigeon died in a zoo in Cincinnati, Ohio. This species had once darkened the skies of North America during its migrations, but it was overhunted and suffered from habitat loss that resulted from the clearing of forests for farmland.
  • The Carolina parakeet, once common in the eastern United States, died out in 1918. It suffered habitat loss and was hunted to prevent it from eating orchard fruit. (The parakeet ate orchard fruit because its native foods were destroyed to make way for farmland.)
  • The Japanese sea lion, which inhabited a broad area around Japan and the coast of Korea, became extinct in the 1950s due to fishermen.
  • The Caribbean monk seal was distributed throughout the Caribbean Sea but was driven to extinction via hunting by 1952.

These are only a few of the recorded extinctions in the past 500 years. The International Union for Conservation of Nature (IUCN) keeps a list of extinct and endangered species called the Red List . The list is not complete, but it describes 380 extinct species of vertebrates after 1500 AD, 86 of which were driven extinct by overhunting or overfishing.


Proof Of A Single Landmass

Map of Pangea. Image credit: Tinkivinki/Shutterstock.com

While the creation and later separation of Pangea is of course, speculative, as humans did not exist at this time, there is a great deal of evidence to back these theories. Scientists' deeper understanding of plate tectonics have helped to specify movements and patterns in the Earth’s crust in a way in which previous theories of ‘Continental Drift’ could not. The formation and evidence of mountain ranges, rift valleys, and volcanic activity around plate borders and fault lines has greatly contributed to scientists’ understanding of tectonic plate movement and drift. These natural phenomena and geographical features indicate the deeper movements below the Earth’s crust, which can be tracked and traced to piece together a historical picture of how the continents have moved, in which ways the crust has broken and reformed, and the drifts and shifts that have occurred over time. Further, there is evidence which backs the idea that all continents were once one megacontinent, ie Pangea. This is seen primarily in fossil records of both flora and fauna found all over the globe. A variety of fossils have been found of similar or identical animal species across a variety of continents which are now great distances apart. This suggests that, like the Pangea theory outlines, these land masses once touched, allowing for free movement of species between now-continents. These fossils are often grouped along country or continent edges which were once joined with other continents. For example, the Eastern coast of Brazil and Western edge of Africa share fossils of the same type of reptile, indicating that these two land masses were once one, and the creatures lived in an area which later split in two.


The biggest mass extinction and Pangea integration

Their study shows that Pangea integration resulted in environmental deterioration which further caused that extinction. Their work, entitled “Mass extinction and Pangea integration during the Paleozoic-Mesozoic transition”, was published in SCIENCE CHINA Earth Sciences.2013, Vol 56(7).

The Pangea was integrated at about the beginning of Permian, and reached its acme during Late Permian to Early Triassic. Formation of the Pangea means that the scattered continents of the world gathered into one integrated continent with an area of nearly 200 million km2. Average thickness of such a giant continental lithosphere should be remarkably greater than that of each scattered continent. Equilibrium principle implies that the thicker the lithosphere, the higher its portion over the equilibrium level, hence the average altitude of the Pangea should be much higher than the separated modern continents. Correspondingly, all oceans gathered to form the Panthalassa, which should be much deeper than modern oceans. The acme of Pangea and Panthalassa was thus a period of high continent and deep ocean, which should inevitably induce great regression and influence the earth’s surface system, especially climate.

The Tunguss Trap of Siberia, the Emeishan Basalt erupted during the Pangea integration. Such global-scale volcanism should be evoked by mantle plume and related with integration of the Pangea. Volcanic activities would result in a series of extinction effects, including emission of large volume of CO2, CH4, NO2 and cyanides which would have caused green house effects, pollution by poisonous gases, damage of the ozone layer in the stratosphere, and enhancement the ultra-violet radiation.

Increase of CO2 concentration and other green house gases would have led to global warming, oxygen depletion and carbon cycle anomaly physical and chemical anomalies in ocean (acidification, euxinia, low sulfate concentration, isotopic anomaly of organic nitrogen) and great regression would have caused marine extinction due to unadaptable environments, selective death and hypercapnia continental aridity, disappearance of monsoon system and wild fire would have devastated the land vegetation, esp. the tropical rain forest.

The great global changes and mass extinction were the results of interaction among earth’s spheres. Deteriorated relations among lithosphere, atmosphere, hydrosphere, and biosphere (including internal factors of organism evolution itself) accumulated until they exceeded the threshold, and exploded at the Permian-Triassic transition time. Interaction among bio- and geospheres is an important theme. However, the processes from inner geospheres to earth’s surface system and further to organism evolution necessitate retardation in time and yields many uncertainties in causation. Most of the processes are now at a hypothetic stage and need more scientific examinations.



Comments:

  1. Spence

    Gloomy pictures are like that :)

  2. Yankel

    They are wrong. We need to discuss. Write to me in PM, speak.

  3. Toran

    I agree with told all above. We can communicate on this theme.

  4. Stephen

    Instead of criticism, it is better to write your options.

  5. Raidon

    I protest against this.

  6. Gacage

    Completely I share your opinion. In it something is and it is good idea. It is ready to support you.



Write a message