During the Great Dying (the Permian-Triassic Extinction Event) of 252 million years ago, the only mass extinction (mass extermination) of insects occurred.
At the end of the Permian, the biggest mass extinction in history took place, collectively called the Permian–Triassic extinction event. In this extinction event, it is estimated that thirty percent (30%) of all insect species became extinct making the Permian-Triassic extinction event the only mass extinction of insects in Earth's history until today.
The Permian had great diversity in insect and other invertebrate species, including the largest insects ever to have existed. The end-Permian is the only known mass extinction of insects, with eight or nine insect orders becoming extinct and ten more greatly reduced in diversity. Palaeodictyopteroids (insects with piercing and sucking mouthparts) began to decline during the mid-Permian; these extinctions have been linked to a change in flora. The greatest decline occurred in the Late Permian and was probably not directly caused by weather-related floral transitions.
Most fossil insect groups found after the Permian–Triassic boundary differ significantly from those that lived prior to the Permian-Triassic extinction. With the exception of the Glosselytrodea, Miomoptera, and Protorthoptera, Paleozoic insect groups have not been discovered in deposits dating to after the Permian–Triassic boundary. The caloneurodeans, monurans, paleodictyopteroids, protelytropterans, and protodonates became extinct by the end of the Permian. In well-documented Late Triassic deposits, fossils overwhelmingly consist of modern fossil insect groups.
Tuesday, March 19, 2013
Friday, March 15, 2013
252 Million B.C.T. - Marine Life Was Decimated
During the Permian-Triassic extinction event that began around 252 million years ago, it is estimated that as much as 96 percent of all marine species were exterminated.
Marine invertebrates suffered the greatest losses during the Permian-Triassic extinction. In the intensively-sampled south China sections at the Permian-Triassic boundary, for instance, 286 out of 329 marine invertebrate genera disappear within the final 2 sedimentary zones containing conodonts (eel-like creatures) from the Permian.
Statistical analysis of marine losses at the end of the Permian suggests that the decrease in diversity was caused by a sharp increase in extinctions instead of a decrease in speciation. The extinction primarily affected organisms with calcium carbonate skeletons, especially those reliant on ambient CO2 levels to produce their skeletons.
Among benthic organisms, the extinction event multiplied background extinction rates, and therefore caused most damage to taxa that had a high background extinction rate (by implication, taxa with a high turnover). The extinction rate of marine organisms was catastrophic.
Surviving marine invertebrate groups include: articulate brachiopods (those with a hinge), which have suffered a slow decline in numbers since the Permian-Triassic extinction. The Ceratitida order of ammonites; and crinoids ("sea lilies"), which very nearly became extinct but later became abundant and diverse.
The groups with the highest survival rates generally had active control of circulation, elaborate gas exchange mechanisms, and light calcification; more heavily calcified organisms with simpler breathing apparatus were the worst hit. In the case of the brachiopods at least, surviving taxa were generally small, rare members of a diverse community.
The ammonoids, which had been in a long-term decline for the 30 million years since the Roadian (middle Permian), suffered a selective end-Guadalupian extinction pulse. This extinction greatly reduced disparity, and suggests that environmental factors were responsible for this extinction. Diversity and disparity fell further until the Permian-Triassic boundary. The extinction here was non-selective, consistent with a catastrophic initiator. During the Triassic, diversity rose rapidly, but disparity remained low.
Marine invertebrates suffered the greatest losses during the Permian-Triassic extinction. In the intensively-sampled south China sections at the Permian-Triassic boundary, for instance, 286 out of 329 marine invertebrate genera disappear within the final 2 sedimentary zones containing conodonts (eel-like creatures) from the Permian.
Statistical analysis of marine losses at the end of the Permian suggests that the decrease in diversity was caused by a sharp increase in extinctions instead of a decrease in speciation. The extinction primarily affected organisms with calcium carbonate skeletons, especially those reliant on ambient CO2 levels to produce their skeletons.
Among benthic organisms, the extinction event multiplied background extinction rates, and therefore caused most damage to taxa that had a high background extinction rate (by implication, taxa with a high turnover). The extinction rate of marine organisms was catastrophic.
Surviving marine invertebrate groups include: articulate brachiopods (those with a hinge), which have suffered a slow decline in numbers since the Permian-Triassic extinction. The Ceratitida order of ammonites; and crinoids ("sea lilies"), which very nearly became extinct but later became abundant and diverse.
The groups with the highest survival rates generally had active control of circulation, elaborate gas exchange mechanisms, and light calcification; more heavily calcified organisms with simpler breathing apparatus were the worst hit. In the case of the brachiopods at least, surviving taxa were generally small, rare members of a diverse community.
The ammonoids, which had been in a long-term decline for the 30 million years since the Roadian (middle Permian), suffered a selective end-Guadalupian extinction pulse. This extinction greatly reduced disparity, and suggests that environmental factors were responsible for this extinction. Diversity and disparity fell further until the Permian-Triassic boundary. The extinction here was non-selective, consistent with a catastrophic initiator. During the Triassic, diversity rose rapidly, but disparity remained low.
Wednesday, March 13, 2013
252 Million B.C.T. - The Great Dying Occurred
Around 252 Million B.C.T., the Permian-Triassic extinctinon event -- the most severe extinction event in the history of the Earth -- occurred.
The Permian–Triassic (P–Tr) extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 million years ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras. It is the Earth's most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. It is the only known mass extinction of insects. Some 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event, possibly up to 10 million years.
Researchers have variously suggested that there were from one to three distinct pulses, or phases, of extinction. There are several proposed mechanisms for the extinctions; the earlier phase was likely due to gradual environmental change, while the latter phase has been argued to be due to a catastrophic event. Suggested mechanisms for the latter include large or multiple bolide impact events, increased volcanism, coal/gas fires and explosions from the Siberian Traps, and sudden release of methane clathrate from the sea floor; gradual changes include sea-level change, anoxia, increasing aridity, and a shift in ocean circulation driven by climate change.
Pin-pointing the exact cause (or causes) of the Permian–Triassic extinction event is a difficult undertaking, mostly because the catastrophe occurred over 250 million years ago, and much of the evidence that would have pointed to the cause has either been destroyed by now or is concealed deep within the Earth under many layers of rock. The sea floor is also completely recycled every 200 million years by the ongoing process of plate tectonics and seafloor spreading, thereby leaving no useful indications beneath the ocean. With the fairly significant evidence that scientists have managed to accumulate, several mechanisms have been proposed for the extinction event, including both catastrophic and gradualistic processes (similar to those theorized for the Cretaceous–Paleogene extinction event). The former include large or multiple bolide impact events, increased volcanism, or sudden release of methane hydrates from the sea floor. The latter include sealevel change, anoxia, and increasing aridity. Any hypothesis about the cause must explain the selectivity of the event, which primarily affected organisms with calcium carbonate skeletons, the long (4– to 6-million-year) period before recovery started, and the minimal extent of biological mineralization (despite inorganic carbonates being deposited) once the recovery began.
Evidence that an impact event may have caused the Cretaceous–Paleogene extinction event has led to speculation that similar impacts may have been the cause of other extinction events, including the P–Tr extinction, and therefore to a search for evidence of impacts at the times of other extinctions and for large impact craters of the appropriate age.
Reported evidence for an impact event from the P–Tr boundary level includes rare grains of shocked quartz in Australia and Antarctica; fullerenes trapping extraterrestrial noble gases; meteorite fragments in Antarctica; and grains rich in iron, nickel and silicon, which may have been created by an impact. However, the accuracy of most of these claims has been challenged. Quartz from Graphite Peak in Antarctica, for example, once considered "shocked", has been re-examined by optical and transmission electron microscopy. The observed features were concluded to be not due to shock, but rather to plastic deformation, consistent with formation in a tectonic environment such as volcanism.
Several possible impact craters have been proposed as possible causes of the P–Tr extinction, including the Bedout structure off the northwest coast of Australia and the hypothesized Wilkes Land crater of East Antarctica. In each of these cases, the idea that an impact was responsible has not been proven, and has been widely criticized. In the case of Wilkes Land, the age of this sub-ice geophysical feature is very uncertain – it may be later than the Permian–Triassic extinction.
If impact is a major cause of the P–Tr extinction, the crater likely would no longer exist. As 70% of the Earth's surface is sea, an asteroid or comet fragment is more than twice as likely to hit ocean as it is to hit land. However, Earth has no ocean-floor crust more than 200 million years old, because the "conveyor belt" process of seafloor spreading and subduction destroys it within that time. Craters produced by very large impacts may be masked by extensive flood basalting from below after the crust is punctured or weakened. Subduction should not, however, be entirely accepted as an explanation of why no firm evidence can be found: as with the K-T event, an ejecta blanket stratum rich in siderophilic elements (e.g., iridium) would be expected to be seen in formations from the time.
One attraction of large impact theories is that theoretically they could trigger other cause-considered extinction-paralleling phenomena, such as the Siberian Traps eruptions (see below) as being either an impact site or the antipode of an impact site. The abruptness of an impact also explains why species did not rapidly evolve in adaptation to more slowly manifesting and/or less than global-in-scope phenomena.
The Permian–Triassic (P–Tr) extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 million years ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras. It is the Earth's most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. It is the only known mass extinction of insects. Some 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event, possibly up to 10 million years.
Researchers have variously suggested that there were from one to three distinct pulses, or phases, of extinction. There are several proposed mechanisms for the extinctions; the earlier phase was likely due to gradual environmental change, while the latter phase has been argued to be due to a catastrophic event. Suggested mechanisms for the latter include large or multiple bolide impact events, increased volcanism, coal/gas fires and explosions from the Siberian Traps, and sudden release of methane clathrate from the sea floor; gradual changes include sea-level change, anoxia, increasing aridity, and a shift in ocean circulation driven by climate change.
Pin-pointing the exact cause (or causes) of the Permian–Triassic extinction event is a difficult undertaking, mostly because the catastrophe occurred over 250 million years ago, and much of the evidence that would have pointed to the cause has either been destroyed by now or is concealed deep within the Earth under many layers of rock. The sea floor is also completely recycled every 200 million years by the ongoing process of plate tectonics and seafloor spreading, thereby leaving no useful indications beneath the ocean. With the fairly significant evidence that scientists have managed to accumulate, several mechanisms have been proposed for the extinction event, including both catastrophic and gradualistic processes (similar to those theorized for the Cretaceous–Paleogene extinction event). The former include large or multiple bolide impact events, increased volcanism, or sudden release of methane hydrates from the sea floor. The latter include sealevel change, anoxia, and increasing aridity. Any hypothesis about the cause must explain the selectivity of the event, which primarily affected organisms with calcium carbonate skeletons, the long (4– to 6-million-year) period before recovery started, and the minimal extent of biological mineralization (despite inorganic carbonates being deposited) once the recovery began.
Evidence that an impact event may have caused the Cretaceous–Paleogene extinction event has led to speculation that similar impacts may have been the cause of other extinction events, including the P–Tr extinction, and therefore to a search for evidence of impacts at the times of other extinctions and for large impact craters of the appropriate age.
Reported evidence for an impact event from the P–Tr boundary level includes rare grains of shocked quartz in Australia and Antarctica; fullerenes trapping extraterrestrial noble gases; meteorite fragments in Antarctica; and grains rich in iron, nickel and silicon, which may have been created by an impact. However, the accuracy of most of these claims has been challenged. Quartz from Graphite Peak in Antarctica, for example, once considered "shocked", has been re-examined by optical and transmission electron microscopy. The observed features were concluded to be not due to shock, but rather to plastic deformation, consistent with formation in a tectonic environment such as volcanism.
Several possible impact craters have been proposed as possible causes of the P–Tr extinction, including the Bedout structure off the northwest coast of Australia and the hypothesized Wilkes Land crater of East Antarctica. In each of these cases, the idea that an impact was responsible has not been proven, and has been widely criticized. In the case of Wilkes Land, the age of this sub-ice geophysical feature is very uncertain – it may be later than the Permian–Triassic extinction.
If impact is a major cause of the P–Tr extinction, the crater likely would no longer exist. As 70% of the Earth's surface is sea, an asteroid or comet fragment is more than twice as likely to hit ocean as it is to hit land. However, Earth has no ocean-floor crust more than 200 million years old, because the "conveyor belt" process of seafloor spreading and subduction destroys it within that time. Craters produced by very large impacts may be masked by extensive flood basalting from below after the crust is punctured or weakened. Subduction should not, however, be entirely accepted as an explanation of why no firm evidence can be found: as with the K-T event, an ejecta blanket stratum rich in siderophilic elements (e.g., iridium) would be expected to be seen in formations from the time.
One attraction of large impact theories is that theoretically they could trigger other cause-considered extinction-paralleling phenomena, such as the Siberian Traps eruptions (see below) as being either an impact site or the antipode of an impact site. The abruptness of an impact also explains why species did not rapidly evolve in adaptation to more slowly manifesting and/or less than global-in-scope phenomena.
Tuesday, March 12, 2013
270 Million B.C.T. - Olson's Extinction Occurred
Around 270 Million B.C.T., Olson's extinction occurred.
Olson's Extinction was a mass extinction that occurred 270 million years ago in the Early Guadalupian of the Permian period and which predated the Permian–Triassic extinction event. Everett Olson noted that there was a hiatus and a sudden change in between the Early Permian and Middle/Late Permian faunas. Since then this event has been realized across many groups, including plants, marine invertebrates, and tetrapods.
The first evidence of extinction came when Everett C. Olson noted a hiatus between Early Permian faunas dominated by pelycosaurs and therapsid dominated faunas of the Middle and Late Permian. First considered to be a preservational gap in the fossil record, the event was originally dubbed 'Olson's Gap'. To compound the difficulty in identifying the cause of the 'gap', researchers were having difficulty in resolving the uncertainty which exists regarding the duration of the overall extinction and about the timing and duration of various groups' extinctions within the greater process. Theories emerged which suggested the extinction was prolonged, spread out over several million years or that multiple extinction pulses preceded the Permian–Triassic extinction event. The impact of Olson's Extinction amplified the effects of the Permian–Triassic extinction event and the final extinction killed off only about 80% of species alive at that time while the other losses occurred during the first pulse or the interval between pulses.
During the 1990s and 2000s researchers gathered evidence on the biodiversity of plants, marine organism and tetrapods that indicated an extinction pulse preceding the Permian–Triassic extinction event had a profound impact on life on land. On land, even discounting the sparse fossil assemblages from the extinction period, the event can be confirmed by the stages of time bracketing the event since well preserved sections of the fossil record from both before and after the event have been found. The 'Gap' was finally closed in 2012 when it was confirmed that the terrestrial fossil record of the Middle Permian is well represented by fossil localities in the American southwest and European Russia and that the gap is not an artifact of a poor rock record since there is no correlation between geological and biological records of the Middle Permian.
There is no widely accepted theory for the cause of Olson's Extinction. Recent research has indicated that climate change may be a possible cause. Extreme environments were observed from the Permian of Kansas which resulted from a combination of hot climate and acidic waters particularly coincident with Olson’s Extinction . Whether this climate change was a result of Earth's natural processes or exacerbated by another event is unknown.
Fauna did not recover fully from Olson's Extinction before the impact of the Permian-Triassic extinction event. Estimates of recovery time vary, where some authors indicated recovery was prolonged, lasting 30 million years into the Triassic.
Several important events took place during Olson's Extinction, most notably the origin of therapsids, a group that includes the evolutionary ancestors of mammals.
A future extinction event, specifically due to anthropogenic changes, has been hypothesized by a number of scientific and environmental groups. Various possible causes include climate change, pollution, and habitat destruction. This is of great concern, due to the loss of biomes, the resources within them, and possible extinction of animal species. A better understanding of the process of extinction in the past may help determine the best course of action to preserve similar ecosystems today. Examining the conditions that led to the Olson's Extinction and the Permo-Triassic Extinction and the recovery of ecosystem from these events, may help contribute suitable solutions to resolving the current climate crisis.
Around 270 Million B.C.T., beetles evolved.
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek koleos, meaning "sheath"; and pteron, meaning "wing", thus "sheathed wing". The reason for the name is that most beetles have two pairs of wings, the front pair, the "elytra", being hardened and thickened into a sheath-like, or shell-like, protection for the rear pair, and for the rear part of the beetle's body. The superficial consistency of most beetles' morphology, in particular their possession of elytra, has long suggested that the Coleoptera are monophyletic, but there is growing evidence that this is unjustified, there being arguments for example, in favor of allocating the current suborder Adephaga their own order, or very likely even more than one.
The oldest known insect that resembles species of Coleoptera date back to the Lower Permian (270 million years ago), although they instead have 13-segmented antennae, elytra with more fully developed venation and more irregular longitudinal ribbing, and an abdomen and ovipositor extending beyond the apex of the elytra. Today's true beetles have features that include 11-segmented antennae, regular longitudinal ribbing on the elytra, and genitalia that are internal. At the end of the Permian, the biggest mass extinction in history took place, collectively called the Permian–Triassic extinction event: 30% of all insect species became extinct. However, it is the only mass extinction of insects in Earth's history until today.
Olson's Extinction was a mass extinction that occurred 270 million years ago in the Early Guadalupian of the Permian period and which predated the Permian–Triassic extinction event. Everett Olson noted that there was a hiatus and a sudden change in between the Early Permian and Middle/Late Permian faunas. Since then this event has been realized across many groups, including plants, marine invertebrates, and tetrapods.
The first evidence of extinction came when Everett C. Olson noted a hiatus between Early Permian faunas dominated by pelycosaurs and therapsid dominated faunas of the Middle and Late Permian. First considered to be a preservational gap in the fossil record, the event was originally dubbed 'Olson's Gap'. To compound the difficulty in identifying the cause of the 'gap', researchers were having difficulty in resolving the uncertainty which exists regarding the duration of the overall extinction and about the timing and duration of various groups' extinctions within the greater process. Theories emerged which suggested the extinction was prolonged, spread out over several million years or that multiple extinction pulses preceded the Permian–Triassic extinction event. The impact of Olson's Extinction amplified the effects of the Permian–Triassic extinction event and the final extinction killed off only about 80% of species alive at that time while the other losses occurred during the first pulse or the interval between pulses.
During the 1990s and 2000s researchers gathered evidence on the biodiversity of plants, marine organism and tetrapods that indicated an extinction pulse preceding the Permian–Triassic extinction event had a profound impact on life on land. On land, even discounting the sparse fossil assemblages from the extinction period, the event can be confirmed by the stages of time bracketing the event since well preserved sections of the fossil record from both before and after the event have been found. The 'Gap' was finally closed in 2012 when it was confirmed that the terrestrial fossil record of the Middle Permian is well represented by fossil localities in the American southwest and European Russia and that the gap is not an artifact of a poor rock record since there is no correlation between geological and biological records of the Middle Permian.
There is no widely accepted theory for the cause of Olson's Extinction. Recent research has indicated that climate change may be a possible cause. Extreme environments were observed from the Permian of Kansas which resulted from a combination of hot climate and acidic waters particularly coincident with Olson’s Extinction . Whether this climate change was a result of Earth's natural processes or exacerbated by another event is unknown.
Fauna did not recover fully from Olson's Extinction before the impact of the Permian-Triassic extinction event. Estimates of recovery time vary, where some authors indicated recovery was prolonged, lasting 30 million years into the Triassic.
Several important events took place during Olson's Extinction, most notably the origin of therapsids, a group that includes the evolutionary ancestors of mammals.
A future extinction event, specifically due to anthropogenic changes, has been hypothesized by a number of scientific and environmental groups. Various possible causes include climate change, pollution, and habitat destruction. This is of great concern, due to the loss of biomes, the resources within them, and possible extinction of animal species. A better understanding of the process of extinction in the past may help determine the best course of action to preserve similar ecosystems today. Examining the conditions that led to the Olson's Extinction and the Permo-Triassic Extinction and the recovery of ecosystem from these events, may help contribute suitable solutions to resolving the current climate crisis.
Around 270 Million B.C.T., beetles evolved.
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek koleos, meaning "sheath"; and pteron, meaning "wing", thus "sheathed wing". The reason for the name is that most beetles have two pairs of wings, the front pair, the "elytra", being hardened and thickened into a sheath-like, or shell-like, protection for the rear pair, and for the rear part of the beetle's body. The superficial consistency of most beetles' morphology, in particular their possession of elytra, has long suggested that the Coleoptera are monophyletic, but there is growing evidence that this is unjustified, there being arguments for example, in favor of allocating the current suborder Adephaga their own order, or very likely even more than one.
The oldest known insect that resembles species of Coleoptera date back to the Lower Permian (270 million years ago), although they instead have 13-segmented antennae, elytra with more fully developed venation and more irregular longitudinal ribbing, and an abdomen and ovipositor extending beyond the apex of the elytra. Today's true beetles have features that include 11-segmented antennae, regular longitudinal ribbing on the elytra, and genitalia that are internal. At the end of the Permian, the biggest mass extinction in history took place, collectively called the Permian–Triassic extinction event: 30% of all insect species became extinct. However, it is the only mass extinction of insects in Earth's history until today.
Monday, March 11, 2013
299 Million B.C.T. - Pangaea and Panthalassa
Around 299 Million B.C.T., the Earth was dominated by the supercontinent Pangaea and by the superocean Panthalassa.
Sea levels in the Permian period were generally low, and near-shore environments were limited by the collection of almost all major landmasses into a single continent -- Pangaea. This could have in part caused the widespread extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms.
During the Permian, all the Earth's major land masses were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean ("Panthalassa", the "universal sea"), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmasses create climates with extreme variations of heat and cold ("continental climate") and monsoon conditions with highly seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores. The first modern trees (conifers, ginkgos and cycads) appeared in the Permian.
Sea levels in the Permian period were generally low, and near-shore environments were limited by the collection of almost all major landmasses into a single continent -- Pangaea. This could have in part caused the widespread extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms.
During the Permian, all the Earth's major land masses were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean ("Panthalassa", the "universal sea"), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmasses create climates with extreme variations of heat and cold ("continental climate") and monsoon conditions with highly seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores. The first modern trees (conifers, ginkgos and cycads) appeared in the Permian.
Wednesday, March 6, 2013
299 Million B.C.T. - The Permian Period Began
Around 299 million years ago, the Permian Period began.
The Permian is a geologic period and system which extends from 298.9 ± 0.2 to 252.2 ± 0.5 million years ago. It is the last period of the Paleozoic Era, following the Carboniferous Period and preceding the Triassic Period of the Mesozoic Era. It was first introduced in 1841 by geologist Roderick Murchison, and is named after the ancient kingdom of Permia.
The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs. The world at the time was dominated by a single supercontinent known as Pangaea, surrounded by a global ocean called Panthalassa. The extensive rainforests of the Carboniferous had disappeared, leaving behind vast regions of arid desert within the continental interior. Reptiles, who could better cope with these dryer conditions, rose to dominance in lieu of their amphibian ancestors. The Permian Period (along with the Paleozoic Era) ended with the largest mass extinction in Earth's history, in which nearly 90% of marine species and 70% of terrestrial species died out. It would take well into the Triassic for life to recover from this catastrophe.
The Permian is a geologic period and system which extends from 298.9 ± 0.2 to 252.2 ± 0.5 million years ago. It is the last period of the Paleozoic Era, following the Carboniferous Period and preceding the Triassic Period of the Mesozoic Era. It was first introduced in 1841 by geologist Roderick Murchison, and is named after the ancient kingdom of Permia.
The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs. The world at the time was dominated by a single supercontinent known as Pangaea, surrounded by a global ocean called Panthalassa. The extensive rainforests of the Carboniferous had disappeared, leaving behind vast regions of arid desert within the continental interior. Reptiles, who could better cope with these dryer conditions, rose to dominance in lieu of their amphibian ancestors. The Permian Period (along with the Paleozoic Era) ended with the largest mass extinction in Earth's history, in which nearly 90% of marine species and 70% of terrestrial species died out. It would take well into the Triassic for life to recover from this catastrophe.
Tuesday, March 5, 2013
305 Million B.C.T. - The Carboniferous Rainforest Collapse
Around 305 million years ago, the rainforests that marked the Carboniferous Period collapsed.
The Carboniferous Rainforest Collapse (CRC) was an extinction event that occurred around 305 million years ago in the Carboniferous period. Vast coal forests (so called because the compacted remains of the dense vegetation formed coal seams) covered the equatorial region of Euramerica (Europe and America). Climate change devastated tropical rainforests, fragmenting the forests into isolated 'islands' and causing the extinction of many plant and animal species. The change was abrupt, happening during the Moscovian (315 to 307 Million B.C.T.) and Kasimovian (307 to 303 Million B.C.T.) stages of the Pennsylvanian subperiod.
In the Carboniferous, the great tropical rainforests of Euramerica supported towering lycopsids, a heterogeneous mix of vegetation, as well as a great diversity of animal life: giant dragonflies, millipedes, cockroaches, amphibians, and the first reptiles.
The rise of rainforests in the Carboniferous greatly altered the landscapes by creating low-energy, organic-rich anastomosing (merging) river systems with multiple channels and stable alluvial islands. The continuing evolution of tree-like plants increased floodplain stability by the density of floodplain forests, the production of woody debris, and an increase in complexity and diversity of root assemblages.
Collapse occurred through a series of step changes. First there was a gradual rise in the frequency of opportunistic ferns in late Moscovian times. This was followed in the earliest Kasimovian by a major, abrupt extinction of the dominant lycopsids and a change to treefern dominated ecosystems. This is confirmed by a recent study showing that the presence of braided, meandering, and branching rivers, occurrences of large woody debris, and records of log jams decrease significantly at the Moscovian-Kasimovian boundary. Rainforests were fragmented forming shrinking islands further and further apart and in latest Kasimovian time, rainforests vanished from the fossil record.
Before the collapse, terrestrial invertebrates were diverse and included annelids, molluscs, and arthropods, including giant arthropleurids. Most were detritivorous, eating 'litter' off of the forest floor. However, some had evolved herbivorous and predatory forms.
Before the extinction event, terrestrial vertebrates were predominantly amphibians and a few basal amniotes (‘reptiles’). Amphibians were tied to waterside habitats and were primarily piscivores ("fish eaters"), though a few had evolved to become insectivores.
Before the collapse, animal species distribution was very cosmopolitan: the same species existed everywhere across tropical Pangaea, but after the collapse each surviving rainforest island developed its own unique mix of species. Many amphibian species became extinct while reptiles diversified into more species after the initial crisis. These patterns are explained by the theory of island biogeography, a concept that explains how evolution progresses when populations are restricted into isolated pockets. This theory was originally developed for oceanic islands but can be applied equally to any other ecosystem that is fragmented, only existing in small patches, surrounded by another habitat. According to this theory, the initial impact of habitat fragmentation is devastating, with most life dying out quickly from lack of resources. Then, as surviving plants and animals re-establish themselves, they adapt to their restricted environment to take advantage of the new allotment of resources and diversify. After the Carboniferous Rainforest Collapse, each pocket of life evolved in its own way, resulting in a unique species mix which ecologists term endemism.
The Carboniferous Rainforest Collapse affected several large groups, labyrinthodont amphibians were particularly devastated, while the first reptiles fared better, being ecologically adapted to the drier conditions that followed. Amphibians must return to water to lay eggs; in contrast, reptiles - whose amniote eggs have a membrane ensuring gas exchange out of water and can therefore be laid on land - were better adapted to the new conditions. Reptiles acquired new niches at a faster rate than before the collapse and at a much faster rate than amphibians. They acquired new feeding strategies including herbivory and carnivory, previously only having been insectivores and piscivores.
The depletion of the plant life also contributed to the deteriorating levels of oxygen in the atmosphere, which facilitated the enormous arthropods of the time. Due to the decreasing oxygen, these sizes could no longer be accommodated, and thus between this and the loss of habitat, the giant arthropods were wiped out in this event, most notably the giant dragonflies and millipedes (Meganeura and Arthropleura).
The extinction event caused by the Carboniferous Rainforest Collapse had longterm implications for the evolution of amphibians. Under prolonged cold conditions, amphibians can survive by decreasing metabolic rates and resorting to overwintering strategies (i.e. spending most of the year inactive in burrows or under logs). However, this is only a short term strategy and not an effective way of dealing with longterm unfavorable conditions, especially desiccation. Since amphibians had a limited capacity to adapt to the drier conditions that dominated Permian environments, many amphibian families failed to occupy new ecological niches and went extinct.
There are several hypotheses about the nature and cause of the Carboniferous Rainforest Collapse, some of which include climate change. Specifically, at this time, the climate became cooler and drier. This is reflected in the rock record as the Earth entered into a short, intense ice age. Sea levels dropped by a hundred meters (300 hundred feet) and glacial ice covered most of the southern continent of Gondwana.
The cooler, drier climate conditions were not favorable to the growth of rainforests and much of the biodiversity within them. Rainforests shrank into isolated patches, these islands of rainforest were mostly confined to wet valleys further and further apart. Little of the original lycopsid rainforest biome survived this initial climate crisis, only to survive in isolated refuges.
Then a succeeding period of global warming reversed the climatic trend; the remaining rainforests, unable to survive the rapidly changing conditions, were finally wiped out. As the climate aridified through the later Paleozoic, the rainforests were eventually replaced by seasonally-dry biomes. Though the exact speed and nature of the collapse is not clear, it is thought to have occurred relatively quickly in geologic terms, only a few thousand years at most.
Major meteoroid events near the time of the CRC included the formation of the Weaubleau-Osceola structure, a serial impact which has been dated to 330-335 million years ago and would have affected the Euramerican continent.
Additionally, increased volcanism may have contributed to the CRC. After restoring the center of the Skagerrak-Centered Large Igneous Province (SCLIP)using a new reference frame, it has been shown that the Skagerrak plume rose from the core–mantle boundary (CMB) to its ~300 Ma position. The major eruption interval took place in very narrow time interval, of 297 Ma ± 4 Ma. This rift formation coincides with the Moskovian/Kasimovian boundary and the Carboniferous Rainforest Collapse.
In recent years, scientists have put forth the idea that many of Earth's largest extinction events were due to multiple causes that coincided in time. Proponents of this view suggest multiples causes because they either do not see a single cause as sufficient in strength to cause the mass extinctions or believe that a single cause is likely to produce the taxonomic pattern of the extinction. Two of Earth's largest extinction events have been hypothesized to be multi-causal in nature:
The cause of the Permo-Triassic extinction (252.28 million years ago) is unclear and some authors have indicated that it may be best explained by a "Murder on the Orient Express Scenario" where multiple causes contributed to a devastating impact on life. Possible causes supported by strong evidence include the large scale volcanism at the Siberian Traps, the releases of noxious gases, global warming, and anoxia.
Additionally, a scenario combining three major causes to the K-T (Cretaceous-Tertiary) extinction (66-65 million years ago): volcanism, marine regression, and extraterrestrial impact, together wiping out the non-avian dinosaurs 65 million years ago.
The specific cause of the CRC is not known, but certainly a multiple cause scenario is a possibility.
The plant material that was lost during CRC extinction event was transported by water to low lying areas in bogs, marshes, lakes and inland seas. It decayed and as more material covered it, it was compressed, heated and eventually became coal, a fossil fuel in the form of a combustible black or brownish-black rock. Coal is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide releases. Gross carbon dioxide emissions from coal usage are slightly more than those from petroleum and about double the amount from natural gas.
The CRC has implications for the modern world. The tropical and temperate rainforests of today have been subjected to heavy logging and agricultural clearance throughout the 20th century and the area covered by rainforests around the world is shrinking. A classic pattern of fragmentation is occurring in many rainforests including those of the Amazon, specifically a 'fishbone' pattern formed by the development of roads into the forest, and littoral rainforest growing along coastal areas of eastern Australia is now rare due to urban development. It has been suggested that a combination of anthropogenic climate change and deforestation may lead to future rain forest collapse.
Modern rainforest collapse may result in massive loss of biodiversity. This is of concern not only for the loss of a biome with many untapped resources but also because animal species extinction is known to correlate with habitat fragmentation. Biologists have estimated that large numbers of species are being driven to extinction. Some estimates say that possibly more than 50,000 species are exterminated every year. At that rate, a quarter or more of all species on Earth could be exterminated within 50 years due to the removal of habitat with destruction of the rainforests.
The application of palaeodata to the present conditions of this planet is still a science in its infancy, but presumably a better understanding of the process of habitat fragmentation and rainforest collapse in the past may help determine the best course of action to preserve similar ecosystems today. Specifically, examining the conditions that led to the Carboniferous Rainforest Collapse and the recovery of ecosystems after the extinction may help contribute suitable solutions to resolving the current crisis.
The Carboniferous Rainforest Collapse (CRC) was an extinction event that occurred around 305 million years ago in the Carboniferous period. Vast coal forests (so called because the compacted remains of the dense vegetation formed coal seams) covered the equatorial region of Euramerica (Europe and America). Climate change devastated tropical rainforests, fragmenting the forests into isolated 'islands' and causing the extinction of many plant and animal species. The change was abrupt, happening during the Moscovian (315 to 307 Million B.C.T.) and Kasimovian (307 to 303 Million B.C.T.) stages of the Pennsylvanian subperiod.
In the Carboniferous, the great tropical rainforests of Euramerica supported towering lycopsids, a heterogeneous mix of vegetation, as well as a great diversity of animal life: giant dragonflies, millipedes, cockroaches, amphibians, and the first reptiles.
The rise of rainforests in the Carboniferous greatly altered the landscapes by creating low-energy, organic-rich anastomosing (merging) river systems with multiple channels and stable alluvial islands. The continuing evolution of tree-like plants increased floodplain stability by the density of floodplain forests, the production of woody debris, and an increase in complexity and diversity of root assemblages.
Collapse occurred through a series of step changes. First there was a gradual rise in the frequency of opportunistic ferns in late Moscovian times. This was followed in the earliest Kasimovian by a major, abrupt extinction of the dominant lycopsids and a change to treefern dominated ecosystems. This is confirmed by a recent study showing that the presence of braided, meandering, and branching rivers, occurrences of large woody debris, and records of log jams decrease significantly at the Moscovian-Kasimovian boundary. Rainforests were fragmented forming shrinking islands further and further apart and in latest Kasimovian time, rainforests vanished from the fossil record.
Before the collapse, terrestrial invertebrates were diverse and included annelids, molluscs, and arthropods, including giant arthropleurids. Most were detritivorous, eating 'litter' off of the forest floor. However, some had evolved herbivorous and predatory forms.
Before the extinction event, terrestrial vertebrates were predominantly amphibians and a few basal amniotes (‘reptiles’). Amphibians were tied to waterside habitats and were primarily piscivores ("fish eaters"), though a few had evolved to become insectivores.
Before the collapse, animal species distribution was very cosmopolitan: the same species existed everywhere across tropical Pangaea, but after the collapse each surviving rainforest island developed its own unique mix of species. Many amphibian species became extinct while reptiles diversified into more species after the initial crisis. These patterns are explained by the theory of island biogeography, a concept that explains how evolution progresses when populations are restricted into isolated pockets. This theory was originally developed for oceanic islands but can be applied equally to any other ecosystem that is fragmented, only existing in small patches, surrounded by another habitat. According to this theory, the initial impact of habitat fragmentation is devastating, with most life dying out quickly from lack of resources. Then, as surviving plants and animals re-establish themselves, they adapt to their restricted environment to take advantage of the new allotment of resources and diversify. After the Carboniferous Rainforest Collapse, each pocket of life evolved in its own way, resulting in a unique species mix which ecologists term endemism.
The Carboniferous Rainforest Collapse affected several large groups, labyrinthodont amphibians were particularly devastated, while the first reptiles fared better, being ecologically adapted to the drier conditions that followed. Amphibians must return to water to lay eggs; in contrast, reptiles - whose amniote eggs have a membrane ensuring gas exchange out of water and can therefore be laid on land - were better adapted to the new conditions. Reptiles acquired new niches at a faster rate than before the collapse and at a much faster rate than amphibians. They acquired new feeding strategies including herbivory and carnivory, previously only having been insectivores and piscivores.
The depletion of the plant life also contributed to the deteriorating levels of oxygen in the atmosphere, which facilitated the enormous arthropods of the time. Due to the decreasing oxygen, these sizes could no longer be accommodated, and thus between this and the loss of habitat, the giant arthropods were wiped out in this event, most notably the giant dragonflies and millipedes (Meganeura and Arthropleura).
The extinction event caused by the Carboniferous Rainforest Collapse had longterm implications for the evolution of amphibians. Under prolonged cold conditions, amphibians can survive by decreasing metabolic rates and resorting to overwintering strategies (i.e. spending most of the year inactive in burrows or under logs). However, this is only a short term strategy and not an effective way of dealing with longterm unfavorable conditions, especially desiccation. Since amphibians had a limited capacity to adapt to the drier conditions that dominated Permian environments, many amphibian families failed to occupy new ecological niches and went extinct.
There are several hypotheses about the nature and cause of the Carboniferous Rainforest Collapse, some of which include climate change. Specifically, at this time, the climate became cooler and drier. This is reflected in the rock record as the Earth entered into a short, intense ice age. Sea levels dropped by a hundred meters (300 hundred feet) and glacial ice covered most of the southern continent of Gondwana.
The cooler, drier climate conditions were not favorable to the growth of rainforests and much of the biodiversity within them. Rainforests shrank into isolated patches, these islands of rainforest were mostly confined to wet valleys further and further apart. Little of the original lycopsid rainforest biome survived this initial climate crisis, only to survive in isolated refuges.
Then a succeeding period of global warming reversed the climatic trend; the remaining rainforests, unable to survive the rapidly changing conditions, were finally wiped out. As the climate aridified through the later Paleozoic, the rainforests were eventually replaced by seasonally-dry biomes. Though the exact speed and nature of the collapse is not clear, it is thought to have occurred relatively quickly in geologic terms, only a few thousand years at most.
Major meteoroid events near the time of the CRC included the formation of the Weaubleau-Osceola structure, a serial impact which has been dated to 330-335 million years ago and would have affected the Euramerican continent.
Additionally, increased volcanism may have contributed to the CRC. After restoring the center of the Skagerrak-Centered Large Igneous Province (SCLIP)using a new reference frame, it has been shown that the Skagerrak plume rose from the core–mantle boundary (CMB) to its ~300 Ma position. The major eruption interval took place in very narrow time interval, of 297 Ma ± 4 Ma. This rift formation coincides with the Moskovian/Kasimovian boundary and the Carboniferous Rainforest Collapse.
In recent years, scientists have put forth the idea that many of Earth's largest extinction events were due to multiple causes that coincided in time. Proponents of this view suggest multiples causes because they either do not see a single cause as sufficient in strength to cause the mass extinctions or believe that a single cause is likely to produce the taxonomic pattern of the extinction. Two of Earth's largest extinction events have been hypothesized to be multi-causal in nature:
The cause of the Permo-Triassic extinction (252.28 million years ago) is unclear and some authors have indicated that it may be best explained by a "Murder on the Orient Express Scenario" where multiple causes contributed to a devastating impact on life. Possible causes supported by strong evidence include the large scale volcanism at the Siberian Traps, the releases of noxious gases, global warming, and anoxia.
Additionally, a scenario combining three major causes to the K-T (Cretaceous-Tertiary) extinction (66-65 million years ago): volcanism, marine regression, and extraterrestrial impact, together wiping out the non-avian dinosaurs 65 million years ago.
The specific cause of the CRC is not known, but certainly a multiple cause scenario is a possibility.
The plant material that was lost during CRC extinction event was transported by water to low lying areas in bogs, marshes, lakes and inland seas. It decayed and as more material covered it, it was compressed, heated and eventually became coal, a fossil fuel in the form of a combustible black or brownish-black rock. Coal is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide releases. Gross carbon dioxide emissions from coal usage are slightly more than those from petroleum and about double the amount from natural gas.
The CRC has implications for the modern world. The tropical and temperate rainforests of today have been subjected to heavy logging and agricultural clearance throughout the 20th century and the area covered by rainforests around the world is shrinking. A classic pattern of fragmentation is occurring in many rainforests including those of the Amazon, specifically a 'fishbone' pattern formed by the development of roads into the forest, and littoral rainforest growing along coastal areas of eastern Australia is now rare due to urban development. It has been suggested that a combination of anthropogenic climate change and deforestation may lead to future rain forest collapse.
Modern rainforest collapse may result in massive loss of biodiversity. This is of concern not only for the loss of a biome with many untapped resources but also because animal species extinction is known to correlate with habitat fragmentation. Biologists have estimated that large numbers of species are being driven to extinction. Some estimates say that possibly more than 50,000 species are exterminated every year. At that rate, a quarter or more of all species on Earth could be exterminated within 50 years due to the removal of habitat with destruction of the rainforests.
The application of palaeodata to the present conditions of this planet is still a science in its infancy, but presumably a better understanding of the process of habitat fragmentation and rainforest collapse in the past may help determine the best course of action to preserve similar ecosystems today. Specifically, examining the conditions that led to the Carboniferous Rainforest Collapse and the recovery of ecosystems after the extinction may help contribute suitable solutions to resolving the current crisis.
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