1.
Precambrian
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The Precambrian is the earliest period of Earths history, set before the current Phanerozoic Eon. The Precambrian is a supereon that is subdivided into three eons of the time scale. It spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 541 million years ago, the Precambrian accounts for 89% of geologic time. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earths history, the Precambrian fossil record is poorer than that of the succeeding Phanerozoic, and fossils from that time are of limited biostratigraphic use. This is because many Precambrian rocks have been metamorphosed, obscuring their origins, while others have been destroyed by erosion. A stable crust was apparently in place by 4,412 Ma, the term Precambrian is recognized by the International Commission on Stratigraphy as a general term including the Archean and Proterozoic eons. It is still used by geologists and paleontologists for general discussions not requiring the more specific eon names and it was briefly called the Cryptozoic eon. A specific date for the origin of life has not been determined, carbon found in 3.8 billion year old rocks from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have found in Western Australia. Probable fossils 100 million years older have been found in the same area, there is a fairly solid record of bacterial life throughout the remainder of the Precambrian. The oldest fossil evidence from that era of such complex life comes from the Lantian formation of the Ediacarian period, a very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota, hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic era. By the middle of the following Cambrian period, a diverse fauna is recorded in the Burgess Shale. The explosion in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life, while land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Evidence of the details of plate motions and other activity in the Precambrian has been poorly preserved. It is generally believed that small proto-continents existed prior to 4280 Ma, the supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch, one of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a Snowball Earth. The atmosphere of the early Earth is not well understood, most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and was lacking in free oxygen
2.
Cambrian
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The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago to the beginning of the Ordovician Period 485.4 mya and its subdivisions, and its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinised form of Cymru, the Welsh name for Wales, as a result, our understanding of the Cambrian biology surpasses that of some later periods. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia, the seas were relatively warm, and polar ice was absent for much of the period. The United States Federal Geographic Data Committee uses a barred capital C ⟨Є⟩ character similar to the capital letter Ukrainian Ye ⟨Є⟩ to represent the Cambrian Period, the proper Unicode character is U+A792 Ꞓ LATIN CAPITAL LETTER C WITH BAR. Despite the long recognition of its distinction from younger Ordovician Period rocks and older Supereon Precambrian rocks, the base of the Cambrian lies atop a complex assemblage of trace fossils known as the Treptichnus pedum assemblage. Pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA, the stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain. The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period, the Cambrian is divided into four epochs and ten ages. Currently only two series and five stages are named and have a GSSP, because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used. In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian, Middle Cambrian and Furongian, rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian. Trilobite zones allow biostratigraphic correlation in the Cambrian, each of the local epochs is divided into several stages. The International Commission on Stratigraphy list the Cambrian period as beginning at 541 million years ago, the lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites. The recognition of small shelly fossils before the first trilobites, and Ediacara biota substantially earlier and this formal designation allowed radiometric dates to be obtained from samples across the globe that corresponded to the base of the Cambrian. Early dates of 570 million years ago quickly gained favour, though the used to obtain this number are now considered to be unsuitable. A more precise date using modern radiometric dating yield a date of 541 ±0.3 million years ago, most continental land was clustered in the Southern Hemisphere at this time, but was drifting north. Large, high-velocity rotational movement of Gondwana appears to have occurred in the Early Cambrian, the sea levels fluctuated somewhat, suggesting there were ice ages, associated with pulses of expansion and contraction of a south polar ice cap. In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into a epicontinental sea, the Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwana covering the South Pole and cutting off polar ocean currents
3.
Ordovician
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The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 Mya. Lapworth recognized that the fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods. It received international sanction in 1960, when it was adopted as a period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian period, invertebrates, namely molluscs and arthropods, dominated the oceans. The Great Ordovician Biodiversification Event considerably increased the diversity of life, fish, the worlds first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land, about 100 times as many meteorites struck the Earth during the Ordovician compared with today. The Ordovician Period began with a major extinction called the Cambrian–Ordovician extinction event and it lasted for about 42 million years and ended with the Ordovician–Silurian extinction event, about 443.8 Mya which wiped out 60% of marine genera. The dates given are recent radiometric dates and vary slightly from those found in other sources and this second period of the Paleozoic era created abundant fossils that became major petroleum and gas reservoirs. The boundary chosen for the beginning of both the Ordovician Period and the Tremadocian stage is highly significant and it correlates well with the occurrence of widespread graptolite, conodont, and trilobite species. The base of the Tremadocian allows scientists to relate these species not only to each other and this makes it easier to place many more species in time relative to the beginning of the Ordovician Period. A number of terms have been used to subdivide the Ordovician Period. In 2008, the ICS erected an international system of subdivisions. There exist Baltoscandic, British, Siberian, North American, Australian, the Ordovician Period in Britain was traditionally broken into Early, Middle and Late epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, the Floian corresponds to the lower Arenig, the Arenig continues until the early Darriwilian, subsuming the Dapingian. The Llanvirn occupies the rest of the Darriwilian, and terminates with it at the base of the Late Ordovician. The Sandbian represents the first half of the Caradoc, the Caradoc ends in the mid-Katian, during the Ordovician, the southern continents were collected into Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole, the small continent Avalonia separated from Gondwana and began to move north towards Baltica and Laurentia, opening the Rheic Ocean between Gondwana and Avalonia
4.
Silurian
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The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway
5.
Devonian
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The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian,419.2 million years ago, to the beginning of the Carboniferous,358.9 Mya. It is named after Devon, England, where rocks from this period were first studied, the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents, by the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established, Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fish. The first ray-finned and lobe-finned bony fish appeared, while the placodermi began dominating almost every aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral, in the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician. The first ammonites, species of molluscs, appeared, trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, while the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, another common term is Age of the Fishes, referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian and Farlovian stages, in the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions, the rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. Early Devonian The Early Devonian lasted from 419.2 ±2.8 to 393.3 ±2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ±2.8 to 407.6 ±2.5, and was followed by the Emsian, which lasted until the Middle Devonian began,393. 3±2.7 million years ago. Middle Devonian The Middle Devonian comprised two subdivisions, first the Eifelian, which gave way to the Givetian 387. 7±2.7 million years ago. Late Devonian Finally, the Late Devonian started with the Frasnian,382.7 ±2.8 to 372.2 ±2.5, during which the first forests took shape on land. The first tetrapods appeared in the record in the ensuing Famennian subdivision. This lasted until the end of the Devonian,358. 9±2.5 million years ago, the Devonian was a relatively warm period, and probably lacked any glaciers
6.
Carboniferous
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The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period,298.9 Mya. The name Carboniferous means coal-bearing and derives from the Latin words carbō and ferō, and was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the system names to be employed. The Carboniferous is often treated in North America as two periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial life was established by the Carboniferous period. Amphibians were the dominant land vertebrates, of one branch would eventually evolve into amniotes. Arthropods were also common, and many were much larger than those of today. Vast swaths of forest covered the land, which would eventually be laid down, the atmospheric content of oxygen also reached their highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. A major marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred in the middle of the period, the later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea. In the United States the Carboniferous is usually broken into Mississippian and Pennsylvanian subperiods, the Silesian is roughly contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, and the Westphalian as the Coal Measures and Pennant Sandstone. There was also a drop in south polar temperatures, southern Gondwanaland was glaciated throughout the period and these conditions apparently had little effect in the deep tropics, where lush swamps, later to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major extinction, one that hit crinoids. This sea level drop and the unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation, the Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America, in the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, the Late Carboniferous Pangaea was shaped like an O. There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, which was inside the O in the Carboniferous Pangaea, other minor oceans were shrinking and eventually closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean
7.
Permian
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The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era, the following Triassic Period belongs to the Mesozoic Era, the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the groups of the mammals, turtles, lepidosaurs. The world at the time was dominated by two known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior, amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors. The Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earths history, in which nearly 90% of marine species and it would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian-Triassic extinction event was protracted, on land, the term Permian was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil, the region now lies in the Perm Krai of Russia. This could have in part caused the 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 Earths major landmasses were collected into a supercontinent known as Pangaea. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, a new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold, deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian, the climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an Ice Age, glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continents interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles, Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. By the close of the Permian, trilobites and a host of other groups became extinct. Terrestrial life in the Permian included diverse plants, fungi, arthropods, the period saw a massive desert covering the interior of Pangaea
8.
Triassic
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The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period 252.17 million years ago, to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era, both the start and end of the period are marked by major extinction events. Therapsids and archosaurs were the terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic, the vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south. The global climate during the Triassic was mostly hot and dry, however, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another mass extinction, the Triassic-Jurassic extinction event. The Triassic is usually separated into Early, Middle, and Late Triassic Epochs, from the east, along the equator, the Tethys sea penetrated Pangaea, causing the Paleo-Tethys Ocean to be closed. Later in the mid-Triassic a similar sea penetrated along the equator from the west, the remaining shores were surrounded by the world-ocean known as Panthalassa. All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates, thus, the supercontinent Pangaea was rifting during the Triassic—especially late in that period—but had not yet separated. In North America, for example, marine deposits are limited to a few exposures in the west, thus Triassic stratigraphy is mostly based on organisms that lived in lagoons and hypersaline environments, such as Estheria crustaceans. At the beginning of the Mesozoic Era, Africa was joined with Earths other continents in Pangaea, Africa shared the supercontinents relatively uniform fauna which was dominated by theropods, prosauropods and primitive ornithischians by the close of the Triassic period. Late Triassic fossils are found throughout Africa, but are common in the south than north. The time boundary separating the Permian and Triassic marks the advent of an event with global impact. At Paleorrota geopark, located in Rio Grande do Sul, Brazil, in these formations, one of the earliest dinosaurs, Staurikosaurus, as well as the mammal ancestors Brasilitherium and Brasilodon have been discovered. The Triassic continental interior climate was hot and dry, so that typical deposits are red bed sandstones and evaporites. Pangaeas large size limited the effect of the global ocean, its continental climate was highly seasonal, with very hot summers. The strong contrast between the Pangea supercontinent and the global ocean triggered intense cross-equatorial monsoons, the best studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event. On land, the vascular plants included the lycophytes, the dominant cycadophytes, ginkgophyta, ferns, horsetails
9.
Jurassic
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The Jurassic is a geologic period and system that spans 56.3 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles, the start of the period is marked by the major Triassic–Jurassic extinction event. The Jurassic is named after the Jura Mountains within the European Alps, by the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, on land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs, other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to a mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, the chronostratigraphic term Jurassic is directly linked to the Jura Mountains. The name Jura is derived from the Celtic root jor, which was Latinised into juria, the Jurassic period is divided into the Early Jurassic, Middle, and Late Jurassic epochs. The Jurassic System, in stratigraphy, is divided into the Lower Jurassic, Middle, the separation of the term Jurassic into three sections goes back to Leopold von Buch. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period, the Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation, as in the Triassic, there was apparently no land over either pole, and no extensive ice caps existed. In contrast, the North American Jurassic record is the poorest of the Mesozoic, the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, India, South America, Japan, Australasia. As the Jurassic proceeded, larger and more groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are well represented nor well studied in Africa. Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania, the Late Jurassic life of Tendaguru is very similar to that found in western North Americas Morrison Formation. During the Jurassic period, the primary living in the sea were fish
10.
Cretaceous
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The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls
11.
Paleogene
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The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon and this period consists of the Paleocene, Eocene and Oligocene epochs. The terms Paleogene System and lower Tertiary System are applied to the rocks deposited during the Paleogene Period. By dividing the Tertiary Period into two periods instead of directly into five epochs, the periods are more comparable to the duration of periods of the preceding Mesozoic and Paleozoic Eras. The trend was caused by the formation of the Antarctic Circumpolar Current. During the Paleogene, the continued to drift closer to their current positions. India was in the process of colliding with Asia, subsequently forming the Himalayas, the Atlantic Ocean continued to widen by a few centimeters each year. Africa was moving north to meet with Europe and form the Mediterranean, inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting towards Southeast Asia, mammals began a rapid diversification during this period. Some of these mammals would evolve into forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial. Those that took to the oceans became modern cetaceans, while those that took to the trees became primates, the group to which humans belong. Birds, which were well established by the end of the Cretaceous. In comparison to birds and mammals, most other branches of life remained unchanged during this period. As the Earth cooled, tropical plants became less numerous and were now restricted to equatorial regions, deciduous plants, which could survive through the seasonal climates the world was now experiencing, became more common. The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration and these rock formations represent the current cutting edge of deep-water oil discovery. Lower Tertiary explorations to date include, Kaskida Oil Field Tiber Oil Field Jack 2 Paleogene Microfossils, 180+ images of Foraminifera
12.
Neogene
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The Neogene is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene, some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary. During this period, mammals and birds continued to evolve into modern forms. Early hominids, the ancestors of humans, appeared in Africa near the end of the period, some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the ocean currents from the Pacific to the Atlantic ocean. The global climate cooled considerably over the course of the Neogene, the terms Neogene System and upper Tertiary System describe the rocks deposited during the Neogene Period. The continents in the Neogene were very close to their current positions, the Isthmus of Panama formed, connecting North and South America. The Indian subcontinent continued to collide with Asia, forming the Himalayas, sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America. The global climate became seasonal and continued an overall drying and cooling trend which began at the start of the Paleogene. The ice caps on both poles began to grow and thicken, and by the end of the period the first of a series of glaciations of the current Ice Age began, marine and continental flora and fauna have a modern appearance. The reptile group Choristodera became extinct in the part of the period. Mammals and birds continued to be the dominant terrestrial vertebrates, the first hominids, the ancestors of humans, appeared in Africa and spread into Eurasia. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones, grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses, antelope, and bison. The Neogene traditionally ended at the end of the Pliocene Epoch, just before the definition of the beginning of the Quaternary Period. However, there was a movement amongst geologists to also include ongoing geological time in the Neogene, by dividing the Cenozoic Era into three periods instead of seven epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras. The International Commission on Stratigraphy once proposed that the Quaternary be considered a sub-era of the Neogene, with a date of 2.58 Ma. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs, thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. Digital Atlas of Neogene Life for the Southeastern United States — by San Jose State University via Web Archive
13.
Great Barrier Reef
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The reef is located in the Coral Sea, off the coast of Queensland, Australia. The Great Barrier Reef can be seen from space and is the worlds biggest single structure made by living organisms. This reef structure is composed of and built by billions of tiny organisms and it supports a wide diversity of life and was selected as a World Heritage Site in 1981. CNN labelled it one of the seven wonders of the world. The Queensland National Trust named it a icon of Queensland. A large part of the reef is protected by the Great Barrier Reef Marine Park, other environmental pressures on the reef and its ecosystem include runoff, climate change accompanied by mass coral bleaching, and cyclic population outbreaks of the crown-of-thorns starfish. According to a study published in October 2012 by the Proceedings of the National Academy of Sciences, the Great Barrier Reef has long been known to and used by the Aboriginal Australian and Torres Strait Islander peoples, and is an important part of local groups cultures and spirituality. The reef is a popular destination for tourists, especially in the Whitsunday Islands. Tourism is an important economic activity for the region, generating over AUD$3 billion per year, in November 2014, Google launched Google Underwater Street View in 3D of the Great Barrier Reef. A March 2016 report stated that coral bleaching was more widespread than previously thought, in October 2016, Outside published an obituary for the reef, the article was criticized for being premature and hindering efforts to bolster the resilience of the reef. The Great Barrier Reef is a feature of the East Australian Cordillera division. It includes the smaller Murray Islands and it reaches from Torres Strait in the north to the unnamed passage between Lady Elliot Island and Fraser Island in the south. Lady Elliot Island is located 1,915 km southeast of Bramble Cay as the crow flies, the Plate tectonic theory indicates Australia has moved northwards at a rate of 7 cm per year, starting during the Cenozoic. Eastern Australia experienced a period of uplift, which moved the drainage divide in Queensland 400 km inland. Also during this time, Queensland experienced volcanic eruptions leading to central and shield volcanoes, some of these became high islands. The Great Barrier Reefs development history is complex, after Queensland drifted into tropical waters, it was influenced by reef growth. 10 million years ago, the sea level lowered, which further enabled sedimentation. The reefs substrate may have needed to build up from the sediment until its edge was too far away for suspended sediments to inhibit coral growth
14.
Australia
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Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the worlds sixth-largest country by total area, the neighbouring countries are Papua New Guinea, Indonesia and East Timor to the north, the Solomon Islands and Vanuatu to the north-east, and New Zealand to the south-east. Australias capital is Canberra, and its largest urban area is Sydney, for about 50,000 years before the first British settlement in the late 18th century, Australia was inhabited by indigenous Australians, who spoke languages classifiable into roughly 250 groups. The population grew steadily in subsequent decades, and by the 1850s most of the continent had been explored, on 1 January 1901, the six colonies federated, forming the Commonwealth of Australia. Australia has since maintained a liberal democratic political system that functions as a federal parliamentary constitutional monarchy comprising six states. The population of 24 million is highly urbanised and heavily concentrated on the eastern seaboard, Australia has the worlds 13th-largest economy and ninth-highest per capita income. With the second-highest human development index globally, the country highly in quality of life, health, education, economic freedom. The name Australia is derived from the Latin Terra Australis a name used for putative lands in the southern hemisphere since ancient times, the Dutch adjectival form Australische was used in a Dutch book in Batavia in 1638, to refer to the newly discovered lands to the south. On 12 December 1817, Macquarie recommended to the Colonial Office that it be formally adopted, in 1824, the Admiralty agreed that the continent should be known officially as Australia. The first official published use of the term Australia came with the 1830 publication of The Australia Directory and these first inhabitants may have been ancestors of modern Indigenous Australians. The Torres Strait Islanders, ethnically Melanesian, were originally horticulturists, the northern coasts and waters of Australia were visited sporadically by fishermen from Maritime Southeast Asia. The first recorded European sighting of the Australian mainland, and the first recorded European landfall on the Australian continent, are attributed to the Dutch. The first ship and crew to chart the Australian coast and meet with Aboriginal people was the Duyfken captained by Dutch navigator, Willem Janszoon. He sighted the coast of Cape York Peninsula in early 1606, the Dutch charted the whole of the western and northern coastlines and named the island continent New Holland during the 17th century, but made no attempt at settlement. William Dampier, an English explorer and privateer, landed on the north-west coast of New Holland in 1688, in 1770, James Cook sailed along and mapped the east coast, which he named New South Wales and claimed for Great Britain. The first settlement led to the foundation of Sydney, and the exploration, a British settlement was established in Van Diemens Land, now known as Tasmania, in 1803, and it became a separate colony in 1825. The United Kingdom formally claimed the part of Western Australia in 1828. Separate colonies were carved from parts of New South Wales, South Australia in 1836, Victoria in 1851, the Northern Territory was founded in 1911 when it was excised from South Australia
15.
Taxonomy (biology)
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Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
16.
Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
17.
Cnidaria
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Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic environments, they are predominantly marine species. Their distinguishing feature is cnidocytes, specialized cells that use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are one cell thick. They have two basic forms, swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single orifice and body cavity that are used for digestion and respiration, many cnidarian species produce colonies that are single organisms composed of medusa-like or polyp-like zooids, or both. Cnidarians activities are coordinated by a nerve net and simple receptors. Several free-swimming species of Cubozoa and Scyphozoa possess balance-sensing statocysts, not all cnidarians reproduce sexually, with many species having complex life cycles of asexual polyp stages and sexual medusae. Some, however, omit either the polyp or the medusa stage, Cnidarians were formerly grouped with ctenophores in the phylum Coelenterata, but increasing awareness of their differences caused them to be placed in separate phyla. Staurozoa have recently been recognised as a class in their own rather than a sub-group of Scyphozoa. Most cnidarians prey on organisms ranging in size from plankton to animals several times larger than themselves, but many obtain much of their nutrition from dinoflagellates, many are preyed on by other animals including starfish, sea slugs, fish and turtles. Many scleractinian corals—which form the foundation for coral reefs—possess polyps that are filled with zooxanthellae. While reef-forming corals are almost entirely restricted to warm and shallow waters, other cnidarians can be found at great depths, in polar regions. Recent phylogenetic analyses support monophyly of cnidarians, as well as the position of cnidarians as the group of bilaterians. Cnidarians form a phylum that are more complex than sponges, about as complex as ctenophores, and less complex than bilaterians. Cnidarians are distinguished from all other animals by having cnidocytes that fire like harpoons and are used mainly to capture prey, in some species, cnidocytes can also be used as anchors. Hence, cnidarians and ctenophores have traditionally been labelled diploblastic, along with sponges, however, both cnidarians and ctenophores have a type of muscle that, in more complex animals, arises from the middle cell layer. As a result, some recent text books classify ctenophores as triploblastic, adult cnidarians appear as either swimming medusae or sessile polyps, and many hydrozoan species are known to alternate between the two forms. Both are radially symmetrical, like a wheel and a tube respectively, since these animals have no heads, their ends are described as oral and aboral
18.
Anthozoa
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Anthozoa is a class within the phylum Cnidaria. Unlike other cnidarians, anthozoans do not have a stage in their development. Instead, they release sperm and eggs that form a planula, some anthozoans can also reproduce asexually through budding. More than 6,100 species have been described, the name comes from the Greek words άνθος and ζώα, hence ανθόζωα = flower animals, a reference to the floral appearance of their perennial polyp stage. Like those of cnidarians, the individual polyps have a cylindrical body crowned by a ring of tentacles surrounding the mouth. The mouth leads into a tubular pharynx which descends for some distance into the body opening into the gastrovascular cavity that fills the interior of the body. Unlike other cnidarians, however, the cavity is subdivided by a number of radiating partitions, the gonads are also located within the cavity walls. All cnidarian species can feed by catching prey with nematocysts, sea anemones are capable of catching fish, anemones and certain species of coral live in isolation, however, most corals form colonies of genetically identical polyps. These closely resemble anemones in structure, although they are much smaller. Stony coral are found in most seas, the extant orders are shown to the right. Hexacorallia includes coral reef builders, the corals, sea anemones. Genetic studies of ribosomal DNA has shown Ceriantharia to be a monophyletic group, sea whips and sea fans, known as gorgonians, are part of Alcyonacea and historically were divided into separate orders. Ceriantharia comprises the related tube-dwelling anemones, tube-dwelling anemones or cerianthids look very similar to sea anemones, but belong to an entirely different subclass of anthozoans. They are solitary, living buried in soft sediments, tube anemones live and can withdraw into tubes, which are made of a fibrous material, which is made from secreted mucus and threads of nematocyst-like organelles, known as ptychocysts. A number of orders of corals have been classified as their calcium skeleton forms a prolific fossil record. Data related to Anthozoa at Wikispecies
19.
Christian Gottfried Ehrenberg
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Christian Gottfried Ehrenberg, German naturalist, zoologist, comparative anatomist, geologist, and microscopist, was one of the most famous and productive scientists of his time. The son of a judge, Christian Gottfried Ehrenberg was born in Delitzsch and he first studied theology at the University of Leipzig, then medicine and natural sciences in Berlin and became a friend of the famous explorer Alexander von Humboldt. In 1818, he completed his dissertation on fungi, Sylvae mycologicae Berolinenses. In 1820–1825, on an expedition to the Middle East with his friend Wilhelm Hemprich, he collected thousands of specimens of plants. He investigated parts of Egypt, the Libyan Desert, the Nile valley and the coasts of the Red Sea. Subsequently parts of Syria, Arabia and Abyssinia were examined, some results of these travels and of the important collections that had been made were reported on by Humboldt in 1826. While in Sudan he designed the mansion of the governor of Dongola. After his return, Ehrenberg published several papers on insects and corals and two volumes Symbolae physicae, in many particulars of the mammals, birds, insects. Other observations were communicated to scientific societies, Ehrenberg was appointed professor of medicine at Berlin University in 1827. In 1829 he accompanied Humboldt through eastern Russia to the Chinese frontier, after his return he began to concentrate his studies on microscopic organisms, which until then had not been systematically studied. He was particularly interested in a group of protists called diatoms, but he also studied. Until Ehrenberg took up the study it was not known that considerable masses of rock were composed of forms of animals or plants. He also demonstrated that the phosphorescence of the sea was due to organisms and he was a member of the Royal Swedish Academy of Sciences from 1836 and a foreign member of the Royal Society of London from 1837. In 1839, he won the Wollaston Medal, the highest award granted by the Geological Society of London, Ehrenberg was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1849. He continued until late in life to investigate the microscopic organisms of the deep sea and he died in Berlin on 27 June 1876. After his death in 1876, his collections of organisms were deposited in the Museum für Naturkunde at the University of Berlin. The Ehrenberg Collection includes 40,000 microscope preparations,5,000 raw samples,3,000 pencil and ink drawings and his collection of scorpions, and other arachnids from the Middle East, is also held in the Berlin Museum. He was also the first winner of the Leeuwenhoek Medal in 1877, in his hometown, Delitzsch, the highest A-Level school, the Ehrenberg-Gymnasium is named after him
20.
Octocorallia
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Octocorallia is a subclass of Anthozoa comprising around 3,000 species of water-based organisms formed of colonial polyps with 8-fold symmetry. It includes the coral, soft corals, sea pens. These organisms have an internal skeleton secreted by mesoglea and polyps with eight tentacles, as with all Cnidarians these organisms have a complex life cycle including a motile phase when they are considered plankton and later characteristic sessile phase. Octocorals resemble the stony corals in general appearance and in the size of their polyps, also unlike the stony corals, each polyp has only eight tentacles, each of which is feather-like in shape, with numerous side-branches, or pinnules. Octocorals are colonial organisms, with numerous tiny polyps embedded in a matrix that forms the visible structure of the colony. The matrix is composed of mesogleal tissue, lined by a continuous epidermis, the channels interconnect the gastrovascular cavities of the polyps, allowing water and nutrients to flow freely between all the members of the colony. The skeletal material, called coenenchyme, is composed of living tissue secreted by numerous wandering amoebocytes, although it is generally soft, in many species it is reinforced with calcarous or horny material. The polyp is largely embedded within the skeleton, with only the uppermost surface, including the tentacles and mouth. The mouth is slit-like, with a single ciliated groove, or siphonoglyph and it opens into a tubular pharynx that projects down into a gastrovascular cavity that occupies the hollow interior. The gonads are located near the base of each mesentery, octocorallia is considered to be monophyletic, meaning that all contained species are descended from a common ancestor, but the relationships between subdivisions are not well known. The current phylogeny is shown below, where Calcaxonia and Holaxonia are groups of gorgonians and the four remaining divisions of Alcyonacea are merely distinguished for convenience
21.
Alcyonacea
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The Alcyonacea, or soft corals, are an order of corals which do not produce calcium carbonate skeletons. Soft corals contain minute, spiny skeletal elements called sclerites, useful in species identification, sclerites give these corals some degree of support and give their flesh a spiky, grainy texture that deters predators. Unlike stony corals, most soft corals thrive in waters with less intense light. Almost all utilize symbiotic photosynthesizing zooxanthella as an energy source. However, most will readily eat any free floating food, such as zooplankton and they are integral members of the reef ecosystem and provide habitat for fish, snails, algae and a diversity of other marine species. Many soft corals are easily collected in the wild for the aquarium hobby. Nevertheless, home-grown specimens tend to be adaptable to aquarium life. Soft corals grow quickly in captivity and are divided into new individuals. The most common examples of this are various species of Actinodiscus, the World Register of Marine Species lists the following suborders and families
22.
Helioporacea
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Coenothecalia is an order of the subclass Octocorallia that forms massive lobed crystalline calcareous skeletons in colonial corals. These corals first appeared in the Cretaceous period, the blue coral, the only species in the family Helioporidae, is most common in shallow water of the tropical Pacific and Indo-Pacific reefs. It has no spicules, and is the only known to produce a massive skeleton formed of fibrocrystalline aragonite fused into lamellae. They form large colonies that can exceed a meter in diameter and they are composed of vertical branches, or folia. The surface of blue coral and similar species appears smooth and the color in life is a distinctive grey-brown with white tips, the entire skeleton, however, has an unusual blue color and therefore the species is commonly exploited for decorative uses. The blue color of the skeleton is caused by iron salts, blue coral can be used in tropical aquaria, and the crystalline calcareous fibres in the skeletons can be used for jewelry. Individual polyps have eight tentacles and, in the gastrovascular cavity, eight septa. Cilia on six septa draw water into the cavity, cilia on the other two septa expel water. The skeleton consists of spicules that form a cup around each polyp. This order also includes the family Lithotelestidae
23.
Pennatulacea
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Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 16 families within the order, they are thought to have a distribution in tropical. Sea pens are grouped with the octocorals, together with sea whips or gorgonians, although named after their feather-like appearance reminiscent of antique quill pens, only sea pen species belonging to the suborder Subselliflorae live up to the comparison. Those belonging to the larger suborder Sessiliflorae lack feathery structures. The latter suborder includes what are known as sea pansies. The earliest accepted fossils are known from the Cambrian-aged Burgess Shale, similar fossils from the Ediacaran may represent the dawn of sea pens. Precisely what these early fossils are, however, is not decided, as octocorals, sea pens are colonial animals with multiple polyps, each with eight tentacles. The other polyps branch out from this central stalk, forming water intake structures, feeding structures with nematocysts, the entire colony is fortified by calcium carbonate in the form of spicules and a central axial rod. Using their root-like peduncles to anchor themselves in sandy or muddy substrate, sea pens are sometimes brightly coloured, the orange sea pen is a notable example. Rarely found above depths of 10 metres, sea pens prefer deeper waters where turbulence is less likely to uproot them, some species may inhabit depths of 2,000 metres or more. While generally sessile animals, sea pens are able to relocate and they position themselves favourably in the path of currents, ensuring a steady flow of plankton, the sea pens chief source of food. Their primary predators are nudibranchs and sea stars, some of which feed exclusively on sea pens, when touched, sea pens emit a bright greenish light, this is known as bioluminescence. They may also force water out of themselves as a defensive act, like other anthozoans, sea pens reproduce by co-ordinating a release of sperm and eggs into the water column, this may occur seasonally or throughout the year. Fertilized eggs develop into larvae called planulae which drift freely for about a week before settling on the substrate, mature sea pens provide shelter for other animals, such as juvenile fish. Analysis of rachis growth rings indicates sea pens may live for 100 years or more, some sea pens exhibit glide reflection symmetry, which is rare among non-extinct animals. Sea pens are sometimes sold in the aquarium trade, however, they are generally hard to care for because they need a very deep substrate and have special food requirements
24.
Hexacorallia
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Hexacorallia is a subclass of Anthozoa comprising approximately 4,300 species of aquatic organisms formed of polyps, generally with 6-fold symmetry. It includes all of the corals, most of which are colonial and reef-forming, as well as all sea anemones, tube anemones. The hexacorallia are distinguished from another subclass of Anthozoa, Octocorallia, in having six or fewer axes of symmetry in their body structure and these organisms are formed of individual soft polyps which in some species live in colonies and can secrete a calcite skeleton. As with all Cnidarians, these organisms have a life cycle including a motile planktonic phase. The subclass includes important coral reef builders the stony corals, sea anemones and related tube-dwelling anemones, antipatharia contains the black corals and Corallimorpharia are similar to anemones. The extant orders are shown below, The anemone-like Relicanthus daphneae was classified as incerti ordinis within this class in May 2014, a number of extinct orders of corals have been classified as their calcium skeleton forms a prolific fossil record
25.
Actiniaria
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Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria. They are named for the anemone, a terrestrial flower, sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. Anthozoa often have large polyps that allow for digestion of larger prey, as cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra. Many sea anemones form symbiotic relationships with single-celled dinoflagellates, zooxanthellae or with green algae, zoochlorellae, that live within their cells. A sea anemone is a sessile polyp attached at the bottom to the surface beneath it by a foot, called a basal disc. Most are from 1.8 to 3 cm in diameter and they can have from a few tens to a few hundred tentacles. A few species are pelagic and are not attached to the bottom, instead, they have a gas chamber within the pedal disc, allowing them to float upside down in the water. The mouth, also the anus of the sea anemone, is in the middle of the oral disc surrounded by tentacles armed with many cnidocytes, cnidocytes contain stinging nematocysts, capsule-like organelles capable of everting suddenly, giving the phylum Cnidaria its name. Each nematocyst contains a small venom vesicle filled with actinotoxins, a filament. This gives the anemone its characteristic sticky feeling, the sea anemone eats small fish and shrimp. The venom is a mix of toxins, including neurotoxins, that paralyzes the prey so the anemone can move it to the mouth for digestion inside the gastrovascular cavity, actinotoxins are highly toxic to prey species of fish and crustaceans. However, Amphiprioninae, small banded fish in various colors, are not affected by their host anemones sting, several other species have similar adaptions and are also unaffected. Most sea anemones are harmless to humans, but a few highly toxic species have caused injuries and are potentially lethal. A gastrovascular cavity functions as a stomach and possesses an opening to the outside. Waste and undigested matter is excreted through this opening, which can be described as an incomplete gut, the mouth is typically slit-like in shape, and bears a groove at one or both ends. The groove, termed a siphonophore, is ciliated, and helps to circulate water through the gastrovascular cavity, some anemones feed on small particles, which are caught with the aid of a mucus secretion and moving currents that are set up by the tentacles. Most sea anemones are predacious, immobilizing their prey with the aid of their nematocysts, the mouth opens into a flattened pharynx. This consists of an in-folding of the wall, and is therefore lined by the animals epidermis
26.
Antipatharia
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Black corals are a group of deep water, tree-like corals. They normally occur in the tropics and they are also found in rather dark water areas such as New Zealands Milford Sound where they can be viewed from an underwater observatory or via SCUBA diving. There are about 280 known species of Antipatharians in 42 genera, though black corals living tissue is brilliantly colored, it takes its name from the distinctive black or dark brown color of its skeleton. Also unique to black coral are the spines that cover the surface of the skeleton. In the Hawaiian language, black coral is called ‘ēkaha kū moana and is the state gem of Hawaii. Black coral is listed in Appendix II of the Convention on International Trade in Endangered Species, in March 2009, scientists released the results of their research on deep-sea corals throughout the world. They discovered specimens of Leiopathes to be among the oldest continuously living organisms on the planet and they show that the radial growth rates are as low as 4 to 35 micrometers per year and that individual colony longevities are on the order of thousands of years. Whip coral host as many as six other species, whip coral gobies and barnacles permanently inhabit the skeleton. The goby and shrimp quickly hide on the opposite side skeletons when a threat approaches, the goby and damselfish lay their eggs on the skeleton. The damselfish bites off the polyps to expose the nesting site, http, //www. marinespecies. org/aphia. php. p=taxdetails&id=22549 Antipathidae entry at Animal Diversity Web Antipathidae. Research Expedition Aimed at Halting Loss of Black Coral
27.
Corallimorpharia
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Corallimorpharia is an order of marine cnidarians closely related to stony or reef building corals. They are mostly tropical, with a column topped with a wide oral disc. The tentacles are short or very short, arranged in rows radiating from the mouth. Many species occur together in large groups, in many respects, they resemble the stony corals, except for the absence of a stony skeleton. Many species are also common invertebrates kept in marine aquaria, data related to Discosomatidae at Wikispecies
28.
Scleractinia
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Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that live on the seabed and build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by a disc with a mouth. Although some species are solitary, most are colonial, the founding polyp settles on the seabed and starts to secrete calcium carbonate to protect its soft body. Solitary corals can be as much as 25 cm across but in colonial species the polyps are only a few millimetres in diameter. These polyps reproduce by budding but remain attached to other, forming a multi-polyp colony with a common skeleton. The shape and appearance of each coral colony depends not only on the species, but also on its location, depth, many shallow-water corals contain symbiont unicellular organisms known as zooxanthellae within their tissues. These give their colour to the coral which thus may vary in hue depending on species of symbiont it contains. Stony corals are related to sea anemones, and like them are armed with stinging cells known as cnidocytes. Corals reproduce both sexually and asexually, most species release gametes into the sea where fertilisation takes place, and the planula larvae drift as part of the plankton, but a few species brood their eggs. Asexual reproduction is mostly by fragmentation, when part of a colony becomes detached, stony corals occur in all the worlds oceans. Hermatypic corals are colonial and form part of reef structures. Other corals may be solitary or colonial and do not form reefs, stony corals first appeared in the Middle Triassic, but their relationship to the tabulate and rugose corals of the Paleozoic is currently unresolved. Much of the framework of coral reefs is formed by scleractinians. Stony corals numbers are expected to decline due to the effects of global warming, scleractinian corals may be solitary or colonial. Colonies can reach considerable size, consisting of a number of individual polyps. Stony corals are members of the class Anthozoa and like other members of the group, the individual animals are known as polyps and have a cylindrical body crowned by an oral disc surrounded by a ring of tentacles. The base of the polyp secretes the stony material from which the skeleton is formed. The body wall of the consists of mesoglea sandwiched between two layers of epidermis
29.
Zoantharia
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Zoanthids are an order of cnidarians commonly found in coral reefs, the deep sea and many other marine environments around the world. These animals come in a variety of different colonizing formations and in numerous colors and they can be found as individual polyps, attached by a fleshy stolon or a mat that can be created from small pieces of sediment, sand and rock. The term zoanthid refers to all animals within this order Zoantharia, and should not be confused with Zoanthus and they are among the most commonly collected coral in reef aquaria, easily propagating and being very durable in many water conditions. The name of the order is controversial, non-specialists often use the term Zoanthidea whereas most taxonomists use Zoantharia. The term Zoantharia in turn is used instead of Hexacorallia. However, major taxonomic papers published since 1899 by specialists use Zoantharia, the main characteristic of the order is that their tentacles are organized in two distinct rows. While the most well-known zoanthids are the zooxanthellate genera found in tropical and sub-tropical waters, many species and genera exist. Many zoanthids are often found growing on marine invertebrates. Often in zooxanthellate genera such as Zoanthus and Palythoa there are a number of different morphs of the same or similar species. Zoanthidae include many species popular in the world, among hobbyists. They are relatively easy to keep alive and healthy, and will spread to cover rocks in their bright circles of color. They are known by some as carpet coral, button polyps, some zoanthids contain the highly toxic substance palytoxin. Palytoxin is one of the most toxic substances in the world. However, even in small quantities, the toxin can be fatal should it be ingested or enter the blood stream, if delivered immediately, it has been suggested that vasodilators can be injected into the ventricle of the heart to act as an antidote. A2010 study found toxic zoanthids in three Washington D. C. area aquarium stores, reports are varied and conflicting on the potential dangers of handling the animal in the aquarist hobby. Other sources state that palytoxin can be absorbed through skin. According to a report an aquarist was poisoned through skin injuries on fingers by a species of Parazoanthus and his zoanthid was found to contain 2-3 milligram of palytoxin per gram. For comparison, the intravenous LD50 dose of palytoxin for a man is less than 8 microgram
30.
Ceriantharia
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Tube-dwelling anemones or ceriantharians look very similar to sea anemones but belong to an entirely different subclass of anthozoans. They are solitary, living buried in soft sediments, Tube anemones live inside and can withdraw into tubes, which are composed of a fibrous material made from secreted mucus and threads of nematocyst-like organelles known as ptychocysts. Ceriantharians have a crown of tentacles that are composed of two whorls of distinctly different sized tentacles, the outer whorl consists of large tentacles that extend outwards. These tentacles taper to points and are used in food capture. The smaller inner tentacles are held more erect than the larger lateral tentacles and are used for manipulation and ingestion. Integrated Principles of Zoology, New York, McGraw-Hill, ISBN 978-0-07-297004-3 Photos of Tube Anemones
31.
Penicillaria
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Pennisetum /ˌpɛnᵻˈsiːtəm/ is a widespread genus of plants in the grass family, native to tropical and warm temperate regions of the world. They are known commonly as fountaingrasses, Pennisetum is closely related to the genus Cenchrus, and the boundary between them is unclear. Cenchrus was derived from Pennisetum and the two are grouped in a monophyletic clade, some species now in Pennisetum were once members of Cenchrus, and some have been moved back. A main morphological character used to them is the degree of fusion of the bristles in the inflorescence. Authors recently proposed to transfer Pennisetum into Cenchrus, along with the related genus Odontelytrum, as currently envisioned, Pennisetum is a genus of 80 to 140 species. The various species are native to Africa, Asia, Australia and they are annual or perennial grasses. Some are petite while others can produce stems up to 8 meters tall, the inflorescence is a very dense, narrow panicle containing fascicles of spikelets interspersed with bristles. There are three kinds of bristle, and some species have all three, while others do not, some bristles are coated in hairs, sometimes long, showy, plumelike hairs that inspired the genus name, the Latin penna and seta. The genus includes pearl millet, an important food crop, napier grass is used for grazing livestock in Africa. African fountaingrass is used as an ornamental plant, many Pennisetum grasses are noxious weeds, including kikuyu grass and feathertop grass. The herbage and seeds of grasses are food for herbivores, such as the chestnut-breasted mannikin, the caterpillar of the butterfly Melanitis phedima. The genus is a host of the pathogenic fungus Cochliobolus sativus. Br
32.
Marine invertebrates
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Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evolved a shell or a hard exoskeleton, as on land and in the air, marine invertebrates have a large variety of body plans, and have been categorised into over 30 phyla. They make up most of the life in the oceans. The earliest animals were marine invertebrates, that is, vertebrates came later, animals are multicellular eukaryotes, and are distinguished from plants, algae, and fungi by lacking cell walls. Marine invertebrates are animals that inhabit a marine environment apart from the members of the chordate phylum. Some have evolved a shell or a hard exoskeleton, many were flat and had a quilted appearance, and seemed so strange that there was a proposal to classify them as a separate kingdom, Vendozoa. Others, however, have interpreted as early molluscs, echinoderms. However, there seems little doubt that Kimberella was at least a triploblastic bilaterian animal, in other words, the small shelly fauna are a very mixed collection of fossils found between the Late Ediacaran and Middle Cambrian periods. The earliest, Cloudina, shows signs of successful defense against predation, in the 1970s there was already a debate about whether the emergence of the modern phyla was explosive or gradual but hidden by the shortage of Precambrian animal fossils. A re-analysis of fossils from the Burgess Shale lagerstätte increased interest in the issue when it revealed animals, such as Opabinia, which did not fit into any known phylum. Nevertheless, there is much debate about whether the Cambrian explosion was really explosive and, if so, how and why it happened. Invertebrates are grouped into different phyla, informally phyla can be thought of as a way of grouping organisms according to their body plan. A body plan refers to a blueprint which describes the shape or morphology of an organism, such as its symmetry, segmentation, the idea of body plans originated with vertebrates, which were grouped into one phylum. But the vertebrate body plan is one of many. The history of the discovery of body plans can be seen as a movement from a worldview centred on vertebrates, for comparison, the number of phyla recognised by modern zoologists has risen to 35. Arthropods total about 1,113,000 described extant species, molluscs about 85,000, sponges are animals of the phylum Porifera. They are multicellular organisms that have full of pores and channels allowing water to circulate through them
33.
Class (biology)
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In biological classification, class is, a taxonomic rank. Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, as for the other well-known ranks, there is the option of an immediately lower rank, indicated by the prefix sub-, subclass. A taxonomic unit, a taxon, in that rank, in that case the plural is classes The composition of each class is determined by a taxonomist. Often there is no agreement, with different taxonomists taking different positions. There are no rules that a taxonomist needs to follow in describing a class. For example, dogs are assigned to the phylum Chordata, in the class Mammalia. In botany, classes are now rarely discussed, for some clades, a number of alternative classifications are used. In the first edition of his Systema Naturae, carl Linnaeus divided all three of his kingdoms of Nature into classes. The class was considered the highest level of the hierarchy until George Cuviers embranchements. Cladistics List of animal classes Phylogenetics Systematics Taxonomy
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Phylum
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In biology, a phylum is a taxonomic rank below kingdom and above class. Traditionally, in botany the term division was used instead of phylum, although from 1993 the International Code of Nomenclature for algae, fungi, depending on definitions, the kingdom Animalia contains approximately 35 phyla, Plantae contains about 12, and Fungi contains around 7. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta, the definitions of zoological phyla have changed from their origins in the six Linnaean classes and the four embranchements of Georges Cuvier. Haeckel introduced the term phylum, based on the Greek word phylon, in plant taxonomy, Eichler classified plants into five groups, named divisions. Informally, phyla can be thought of as grouping organisms based on general specialization of body plan, the most important objective measure in the above definitions is the certain degree—how unrelated do organisms need to be to be members of different phyla. The minimal requirement is that all organisms in a phylum should be more closely related to one another than to any other group. So phyla can be merged or split if it becomes apparent that they are related to one another or not, a definition of a phylum based on body plan has been proposed by paleontologists Graham Budd and Sören Jensen. By Budd and Jensens definition, a phylum is defined by a set of shared by all its living representatives. This approach brings some small problems—for instance, ancestral characters common to most members of a phylum may have been lost by some members, also, this definition is based on an arbitrary point of time, the present. However, as it is based, it is easy to apply to the fossil record. A greater problem is that it relies on a decision about which groups of organisms should be considered as phyla. However, proving that a fossil belongs to the group of a phylum is difficult. Furthermore, organisms in the group of a phylum can possess the body plan of the phylum without all the characteristics necessary to fall within it. This weakens the idea that each of the phyla represents a body plan. A classification using this definition may be affected by the chance survival of rare groups. Representatives of many modern phyla did not appear until long after the Cambrian, the kingdom Plantae is defined in various ways by different biologists. All definitions include the living embryophytes, to which may be added the two green algae divisions, Chlorophyta and Charophyta, to form the clade Viridiplantae. The table below follows the influential Cavalier-Smith system in equating Plantae with Archaeplastida, a group containing Viridiplantae, the definition and classification of plants at the division level also varies from source to source, and has changed progressively in recent years
35.
Colony (biology)
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In contrast, a solitary organism is one in which all individuals live independently and have all of the functions needed to survive and reproduce. Colonies, in the context of development, may be composed of two or more unitary organisms or be modular organisms, unitary organisms have determinate development from zygote to adult form and individuals or groups of individuals are visually distinct. In the latter case, modules may have specific functions within the colony as a whole, some organisms are primarily independent and form facultative colonies in response to environmental conditions while others must live in a colony to survive. Unicellular and multicellular organisms may aggregate to form colonies. Eusocial insects like ants and honey bees are multicellular animals that live in colonies with an organized social structure. Colonies of some social insects may be deemed superorganisms, animals such as humans and rodents form breeding or nesting colonies, potentially for more successful mating and to better protect offspring. The Bracken Cave is the home to a colony of around 20 million Mexican Free-tailed Bats making it the largest known concentration of mammals. Modular organisms are those in which a genet asexually reproduces to form genetically identical clones called ramets, a clonal colony is when the ramets of a genet live in close proximity or are physically connected. Ramets may have all of the functions needed to survive on their own or be interdependent on other ramets, for example, some sea anemones go through the process of pedal laceration in which a genetically identical individual is asexually produced from tissue broken off from the anemones pedal disc. In plants, clonal colonies are created through the propagation of genetically identical trees by stolons or rhizomes, colonial organisms are clonal colonies composed of many physically connected, interdependent individuals. Colonial organisms can be unicellular, as in the alga Volvox, or multicellular, the former type may have been the first step toward multicellular organisms. Individuals within a colonial organism may be called ramets, modules. Structural and functional variation, when present, designates ramet responsibilities such as feeding, reproduction, to that end, being physically connected allows the colonial organism to distribute nutrients and energy obtained by feeding zooids throughout the colony. A microbial colony is defined as a cluster of microorganisms growing on the surface of or within a solid medium. Because the colony is clonal, with all organisms in it descending from an ancestor, they are genetically identical. Obtaining such genetically identical organisms can be useful, this is done by spreading organisms on a culture plate, a biofilm is a colony of microorganisms often comprising several species, with properties and capabilities greater than the aggregate of capabilities of the individual organisms. Individuals in social colonies and modular organisms receive benefit to such a lifestyle, for instance, it may be easier to seek out food, defend a nesting site, or increase competitive ability against other species. Modular organisms ability to reproduce asexually in addition to sexually allows them unique benefits that social colonies do not have, the energy required for sexual reproduction varies based on the frequency and length of reproductive activity, number and size of offspring, and parental care
36.
Polyp
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A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the vase-shaped body, the oral end contains the mouth, and is surrounded by a circlet of tentacles. In class Scyphozoa, the stage is dominant, and the polyp stage may or may not be present. Once strobilation is complete, the polyp may die, or regenerate itself to repeat the process again later, with Cubozoans, the planula settles onto a suitable surface, and develops into a polyp. The cubozoan polyp then eventually metamorphoses directly into a Medusa, the body of the polyp may be roughly compared in a structure to a sac, the wall of which is composed of two layers of cells. The outer layer is known technically as the ectoderm, the layer as the endoderm. Between ectoderm and endoderm is a layer of structureless gelatinous substance termed mesogloea. The mesogloea may be a thin layer, or may reach a fair thickness. The tentacles are organs which serve both for the sense and for the capture of food. Polyps extend their tentacles, particularly at night, containing coiled stinging nettle-like cells or nematocysts which pierce and poison, Polyp prey includes copepods and fish larvae. Longitudinal muscular fibrils formed from the cells of the ectoderm allow tentacles to contract when conveying the food to the mouth, similarly, circularly disposed muscular fibrils formed from the endoderm permit tentacles to be protract or thrust out once they are contracted. These muscle fibres belong to the two systems, thus allows the whole body to retract or protrude outwards. As a rule there is no opening to the body except the mouth, but in some cases excretory pores are known to occur in the foot. Thus it is seen that a polyp is an animal of very simple structure, the external form of the polyp varies greatly in different cases. The column may be long and slender, or may be so short in the direction that the body becomes disk-like. The tentacles may number many hundreds or may be very few and they may be long and filamentous, or short and reduced to mere knobs or warts. They may be simple and unbranched, or they may be feathery in pattern, the mouth may be level with the surface of the peristome, or may be projecting and trumpet-shaped. As regards internal structure, polyps exhibit two well-marked types of organization, each characteristic of one of the two classes, Hydrozoa and Anthozoa, in the class Hydrozoa, the polyps are indeed often very simple, like the common little fresh water species of the genus Hydra
37.
Coral reef
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Coral reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals. Coral reefs are built by colonies of tiny animals found in waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups, the polyps belong to a group of animals known as Cnidaria, which also includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons which support, most reefs grow best in warm, shallow, clear, sunny and agitated waters. Often called rainforests of the sea, shallow coral reefs form some of the most diverse ecosystems on Earth, paradoxically, coral reefs flourish even though they are surrounded by ocean waters that provide few nutrients. They are most commonly found at depths in tropical waters. Coral reefs deliver ecosystem services to tourism, fisheries and shoreline protection, the annual global economic value of coral reefs is estimated between US$29. 8-375 billion. However, coral reefs are fragile ecosystems, partly because they are sensitive to water temperature. Most of the coral reefs we can see today were formed after the last glacial period when melting ice caused the sea level to rise and this means that most modern coral reefs are less than 10,000 years old. As communities established themselves on the shelves, the reefs grew upwards, Reefs that rose too slowly could become drowned reefs. They are covered by so much water there was insufficient light. Coral reefs are found in the sea away from continental shelves, around oceanic islands. The vast majority of islands are volcanic in origin. The few exceptions have tectonic origins where plate movements have lifted the deep ocean floor on the surface. In 1842 in his first monograph, The Structure and Distribution of Coral Reefs, Charles Darwin set out his theory of the formation of atoll reefs and he theorized uplift and subsidence of the Earths crust under the oceans formed the atolls. Darwin’s theory sets out a sequence of three stages in atoll formation and it starts with a fringing reef forming around an extinct volcanic island as the island and ocean floor subsides. As the subsidence continues, the reef becomes a barrier reef. Darwin predicted that underneath each lagoon would be a bed rock base, where the level of the underlying earth allows, the corals grow around the coast to form what he called fringing reefs, and can eventually grow out from the shore to become a barrier reef
38.
Ocean
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An ocean is a body of saline water that composes much of a planets hydrosphere. On Earth, an ocean is one of the major divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, the word sea is often used interchangeably with ocean in American English but, strictly speaking, a sea is a body of saline water partly or fully enclosed by land. The ocean contains 97% of Earths water, and oceanographers have stated that less than 5% of the World Ocean has been explored, the total volume is approximately 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters. As the world ocean is the component of Earths hydrosphere, it is integral to all known life, forms part of the carbon cycle. The world ocean is the habitat of 230,000 known species, but because much of it is unexplored, the origin of Earths oceans remains unknown, oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds, the only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many planets and natural satellites, notably. The Solar Systems giant planets are thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of water within a circumstellar habitable zone. Ocean planets are a type of planet with a surface completely covered with liquid. The concept of Ōkeanós has an Indo-European connection, Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases, though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a body of water with relatively free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions – listed below in descending order of area and volume – are defined in part by the continents, various archipelagos, Oceans are fringed by smaller, adjoining bodies of water such as seas, gulfs, bays, bights, and straits. The Mid-Oceanic Ridge of the World are connected and form the Ocean Ridge, the continuous mountain range is 65,000 km long, and the total length of the oceanic ridge system is 80,000 km long
39.
Calcium carbonate
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Calcium carbonate is a chemical compound with the formula CaCO3. It is a substance found in rocks as the minerals calcite and aragonite and is the main component of pearls and the shells of marine organisms, snails. Calcium carbonate is the ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It is medicinally used as a supplement or as an antacid. Calcium carbonate shares the properties of other carbonates. CaCO3 + CO2 + H2O → Ca2 This reaction is important in the erosion of rock, forming caverns. An unusual form of calcium carbonate is the hexahydrate, ikaite, ikaite is stable only below 6 °C. The vast majority of calcium used in industry is extracted by mining or quarrying. Pure calcium carbonate, can be produced from a quarried source. Alternatively, calcium carbonate is prepared from calcium oxide, other forms can be prepared, the denser, orthorhombic λ-CaCO3 and μ-CaCO3, occurring as the mineral vaterite. The aragonite form can be prepared by precipitation at temperatures above 85 °C, calcite contains calcium atoms coordinated by 6 oxygen atoms, in aragonite they are coordinated by 9 oxygen atoms. The vaterite structure is not fully understood, magnesium carbonate MgCO3 has the calcite structure, whereas strontium and barium carbonate adopt the aragonite structure, reflecting their larger ionic radii. Calcite, aragonite and vaterite are pure calcium carbonate minerals, industrially important source rocks which are predominantly calcium carbonate include limestone, chalk, marble and travertine. Eggshells, snail shells and most seashells are predominantly calcium carbonate, oyster shells have enjoyed recent recognition as a source of dietary calcium, but are also a practical industrial source. While not practical as a source, dark green vegetables such as broccoli. Beyond Earth, strong evidence suggests the presence of Calcium carbonate on Mars, signs of Calcium Carbonate have been detected at more than one location. This provides some evidence for the past presence of liquid water, Carbonate is found frequently in geologic settings and constitute an enormous carbon reservoir. Calcium carbonate occurs as aragonite, calcite and dolomite, the carbonate minerals form the rock types, limestone, chalk, marble, travertine, tufa, and others
40.
Cloning
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In biology, cloning is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments, cells, the term also refers to the production of multiple copies of a product such as digital media or software. The term clone, invented by J. B. S. Haldane, is derived from the Ancient Greek word κλών klōn, twig, referring to the process whereby a new plant can be created from a twig. In horticulture, the spelling clon was used until the twentieth century, since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively. In botany, the term lusus was traditionally used, Cloning is a natural form of reproduction that has allowed life forms to spread for more than 50 thousand years. It is the method used by plants, fungi, and bacteria. Examples of these organisms include blueberry plants, hazel trees, the Pando trees, the Kentucky coffeetree, Myricas, molecular cloning refers to the process of making multiple molecules. Cloning is commonly used to amplify DNA fragments containing whole genes and it is used in a wide array of biological experiments and practical applications ranging from genetic fingerprinting to large scale protein production. In practice, localization of the gene to a chromosome or genomic region does not necessarily enable one to isolate or amplify the relevant genomic sequence, initially, the DNA of interest needs to be isolated to provide a DNA segment of suitable size. Subsequently, a procedure is used where the amplified fragment is inserted into a vector. The vector is linearised using restriction enzymes, and incubated with the fragment of interest under appropriate conditions with an enzyme called DNA ligase, following ligation the vector with the insert of interest is transfected into cells. A number of techniques are available, such as chemical sensitivation of cells, electroporation, optical injection. Finally, the cells are cultured. Modern cloning vectors include selectable antibiotic resistance markers, which allow only cells in which the vector has been transfected, additionally, the cloning vectors may contain colour selection markers, which provide blue/white screening on X-gal medium. Nevertheless, these selection steps do not absolutely guarantee that the DNA insert is present in the cells obtained, further investigation of the resulting colonies must be required to confirm that cloning was successful. This may be accomplished by means of PCR, restriction fragment analysis and/or DNA sequencing, Cloning a cell means to derive a population of cells from a single cell. In the case of organisms such as bacteria and yeast. However, in the case of cell cultures from multi-cellular organisms, a useful tissue culture technique used to clone distinct lineages of cell lines involves the use of cloning rings
41.
Tentacle
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In zoology, a tentacle is a flexible, mobile, elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs, anatomically, the tentacles of animals work mainly like muscular hydrostats. Most forms of tentacles are used for grasping and feeding, many are sensory organs, variously receptive to touch, vision, or to the smell or taste of particular foods or threats. Examples of such tentacles are the eye stalks of various kinds of snails, some kinds of tentacles have both sensory and manipulatory functions. The word tentillum literally means little tentacle, however, irrespective of size, it usually refers to a side branch of a larger tentacle. In some cases such tentilla are specialised for particular functions, for example, in the Cnidaria tentilla usually bear cnidocytes, many molluscs have tentacles of one form or another. Both pairs are fully retractable muscular hydrostats, but they are not used for manipulation or prey capture, some marine snails such as abalone and top snails, Trochidae, have numerous small tentacles around the edge of the mantle. These are known as pallial tentacles, among cephalopods, squid have spectacular tentacles. They take the form of highly mobile muscular hydrostats with various appendages such as suction disks, up to the early twentieth century tentacles were interchangeably called arms. The modern convention however, is to speak of appendages as tentacles when they have relatively thin peduncles or stalks with clubs at their tips, in contrast the convention refers to the relatively shorter appendages as arms. By this definition the eight appendages of octopuses, though quite long, in terms of this article however, both types of organs count as tentacles because in relevant ways they are structurally and functionally similar. The tentacles of the giant squid and colossal squid have powerful suckers, the teeth of the giant squid resemble bottle caps, and function like tiny, hole saws, while the tentacles of the colossal squid wield two long rows of swiveling, tri-pointed hooks. Cnidarians, such as jellyfish, sea anemones, Hydra and coral have numerous hair-like tentacles, cnidarians have huge numbers of cnidocytes on their tentacles. In medusoid form, the floats on water so that the tentacles hang down in a ring around the mouth. In polyp form, such as sea anemone and coral, the body is below with the tentacles pointed upwards, many species of the jellyfish-like ctenophores have two tentacles, while some have none. Their tentacles have adhesive structures called colloblasts or lasso cells, the colloblasts burst open when prey comes in contact with the tentacle, releasing sticky threads that secure the food. The tentacles of the Lions mane jellyfish may be up to 120 feet long and they are hollow and are arranged in 8 groups of between 70 and 150. The longer tentacles are equipped with cnidocytes whose venom paralyses and kills prey, the smaller tentacles guide food into the mouth
42.
Exoskeleton
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An exoskeleton is the external skeleton that supports and protects an animals body, in contrast to the internal skeleton of, for example, a human. In usage, some of the kinds of exoskeletons are known as shells. Examples of animals with exoskeletons include insects such as grasshoppers and cockroaches, the shells of certain sponges and the various groups of shelled molluscs, including those of snails, clams, tusk shells, chitons and nautilus, are also exoskeletons. Some animals, such as the tortoise, have both an endoskeleton and an exoskeleton, exoskeletons have a role in defense from pests and predators, support, and in providing an attachment framework for musculature. Exoskeletons contain chitin, the addition of calcium carbonate makes them harder and stronger, ingrowths of the arthropod exoskeleton known as apodemes serve as attachment sites for muscles. These structures are composed of chitin, and are six times as strong. Similar to tendons, apodemes can stretch to store energy for jumping. Many different species produce exoskeletons, which are composed of a range of materials, bone, cartilage, or dentine is used in the Ostracoderm fish and turtles. Chitin forms the exoskeleton in arthropods including insects, arachnids such as spiders, crustaceans such as crabs and lobsters, calcium carbonates constitute the shells of molluscs, brachiopods, and some tube-building polychaete worms. Silica forms the exoskeleton in the microscopic diatoms and radiolaria, one species of mollusc, the scaly-foot gastropod, even makes use of the iron sulfides greigite and pyrite. Some organisms, such as some foraminifera, agglutinate exoskeletons by sticking grains of sand, contrary to a common misconception, echinoderms do not possess an exoskeleton, as their test is always contained within a layer of living tissue. Exoskeletons have evolved many times,18 lineages evolved calcified exoskeletons alone. Further, other lineages have produced tough outer coatings analogous to an exoskeleton and this coating is constructed from bone in the armadillo, and hair in the pangolin. The armor of reptiles like turtles and Ankylosaurs is constructed of bone, crocodiles have bony scutes, since exoskeletons are rigid, they present some limits to growth. Organisms with open shells can grow by adding new material to the aperture of their shell, as is the case in snails, bivalves, a true exoskeleton, like that found in arthropods, must be shed when it is outgrown. A new exoskeleton is produced beneath the old one, as the old one is shed, the new skeleton is soft and pliable. The animal will pump itself up to expand the new shell to maximal size, when the shell has set, the empty space inside the new skeleton can be filled up as the animal eats. Failure to shed the exoskeleton once outgrown can result in the animal being suffocated within its own shell and this is the mechanism behind some insect pesticides, such as Azadirachtin
43.
Asexual reproduction
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Asexual reproduction is the primary form of reproduction for single-celled organisms such as the Archaea and bacteria. Many plants and fungi reproduce asexually as well, a complete lack of sexual reproduction is relatively rare among multicellular organisms, particularly animals. It is not entirely understood why the ability to reproduce sexually is so common among them, developmental constraints may underlie why few animals have relinquished sexual reproduction completely in their life-cycles. An important form of fission is binary fission, in binary fission, the parent/adult organism is replaced by two daughter organisms, because it literally divides in two. Only prokaryotes reproduce asexually through binary fission, eukaryotes may reproduce in a functionally similar manner by mitosis, most of these are also capable of sexual reproduction. Another type of fission is multiple fission, multiple fission at the cellular level occurs in many protists, e. g. sporozoans and algae. The nucleus of the parent cell divides several times by mitosis, the cytoplasm then separates, creating multiple daughter cells. In apicomplexans, multiple fission, or schizogony, is manifested either as merogony, sporogony or gametogony, merogony results in merozoites, which are multiple daughter cells, that originate within the same cell membrane, sporogony results in sporozoites, and gametogony results in microgametes. Some cells split via budding, resulting in a mother and daughter cell, the offspring organism is smaller than the parent. Budding is also known on a level, an animal example is the hydra. The buds grow into fully matured individuals which break away from the parent organism. Internal budding is a process of reproduction, favoured by parasites such as Toxoplasma gondii. It involves a process in which two or more daughter cells are produced inside a mother cell, which is then consumed by the offspring prior to their separation. Also, budding is present in some worm like Taenia or Echinococci, vegetative propagation is a type of asexual reproduction found in plants where new individuals are formed without the production of seeds or spores by meiosis or syngamy. Examples of vegetative reproduction include the formation of miniaturized plants called plantlets on specialized leaves, other plants reproduce by forming bulbs or tubers. Some plants produce adventitious shoots and may form a colony, where all the individuals are clones. Many multicellular organisms form spores during their life cycle in a process called sporogenesis. Exceptions are animals and some protists, who undergo meiosis immediately followed by fertilization, plants and many algae on the other hand undergo sporic meiosis where meiosis leads to the formation of haploid spores rather than gametes
44.
Full moon
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A full moon is the lunar phase that occurs when the Moon is completely illuminated as seen from Earth. This occurs when Earth is located directly between the Sun and the Moon and this means that the hemisphere of the Moon that is facing Earth is almost fully illuminated by the Sun and appears round. On some occasions at the time of full moon there is also a lunar eclipse so the face appears reddish due to the rayleigh scattering of blue light in Earths atmosphere. Lunar eclipses can occur only at full moon, where the Moons orbit allows it to pass through Earths shadow, Lunar eclipses do not occur every month because the Moon usually passes above or below Earths shadow. Lunar eclipses can only when the full moon occurs near the two nodes of the orbit, either the ascending or descending node. This causes eclipses to occur about every 6 months. The time interval between similar lunar phases—the synodic month—averages about 29.53 days, therefore, in those lunar calendars in which each month begins on the new moon, the full moon falls on either the 14th or 15th of the lunar month. Because calendar months have a number of days, lunar months may be either 29 or 30 days long. A full moon is thought of as an event of a full nights duration. This is somewhat misleading because the Moon seen from Earth is continuously becoming larger and/or smaller and its absolute maximum size occurs at the moment expansion has stopped. For any given location, about half of these absolute maximum full moons will be visible, as the other half occur during the day. Many almanacs list full moons not just by date, but by their time as well. Typical monthly calendars that include phases of the Moon may be offset by one day if intended for use in a different time zone, Full moons are generally a poor time to conduct astronomical observations, because the bright reflected sunlight from the Moon overwhelms the dimmer light from stars. On 12 December 2008, the moon occurred closer to the Earth than it had been at any time for the previous 15 years. On 19 March 2011, another full moon occurred, closer to the Earth than at any time for the previous ~18 years. On 14 November 2016, a full moon occurred closer to the Earth than at any time for the previous 68 years. The true time of a full moon may differ from this approximation by up to about 14.5 hours as a result of the non-circularity of the moons orbit, see New moon for an explanation of the formula and its parameters. The age and apparent size of the full moon vary in a cycle of just under 14 synodic months, Full moons are traditionally associated with temporal insomnia, insanity and various magical phenomena such as lycanthropy
45.
Fish
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A fish is any member of a group of animals that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. They form a group to the tunicates, together forming the olfactores. Included in this definition are the living hagfish, lampreys, and cartilaginous, tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered obsolete or paraphyletic by excluding the tetrapods, because in this manner the term fish is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology. The traditional term pisces is considered a typological, but not a phylogenetic classification, the earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts, fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators, the first fish with jaws appeared in the Silurian period, after which many became formidable marine predators rather than just the prey of arthropods. Fish are abundant in most bodies of water and they can be found in nearly all aquatic environments, from high mountain streams to the abyssal and even hadal depths of the deepest oceans. With 33,100 described species, fish exhibit greater species diversity than any group of vertebrates. Fish are an important resource for humans worldwide, especially as food, commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean. They are also caught by fishers, kept as pets, raised by fishkeepers. Fish have had a role in culture through the ages, serving as deities, religious symbols, fish do not represent a monophyletic group, and therefore the evolution of fish is not studied as a single event. Early fish from the record are represented by a group of small, jawless. Jawless fish lineages are mostly extinct, an extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placodermi fossils, the diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, fish may have evolved from a creature similar to a coral-like sea squirt, whose larvae resemble primitive fish in important ways. The first ancestors of fish may have kept the form into adulthood. Fish are a group, that is, any clade containing all fish also contains the tetrapods
46.
Plankton
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Plankton are the diverse collection of organisms that live in the water column of large bodies of water and are unable to swim against a current. They provide a source of food to many large aquatic organisms, such as fish. These organisms include bacteria, archaea, algae, protozoa and drifting or floating animals that inhabit, for example, essentially, plankton are defined by their ecological niche rather than any phylogenetic or taxonomic classification. Though many planktonic species are microscopic in size, plankton includes organisms covering a range of sizes. The name plankton is derived from the Greek adjective πλαγκτός, meaning errant and it was coined by Victor Hensen. Plankton typically flow with ocean currents, while some forms are capable of independent movement and can swim hundreds of meters vertically in a single day, their horizontal position is primarily determined by the surrounding currents. This is in contrast to nekton organisms that can swim against the ambient flow, within the plankton, holoplankton spend their entire life cycle as plankton. By contrast, meroplankton are only planktic for part of their lives, examples of meroplankton include the larvae of sea urchins, starfish, crustaceans, marine worms, and most fish. Plankton abundance and distribution are strongly dependent on such as ambient nutrient concentrations, the physical state of the water column. The study of plankton is termed planktology and an individual is referred to as a plankter. The adjective planktonic is widely used in both the scientific and popular literature, and is an accepted term. However, from the standpoint of prescriptive grammar the less commonly used planktic is more strictly the correct adjective, when deriving English words from their Greek or Latin roots the gender specific ending is normally dropped, using only the root of the word in the derivation. Among the more important groups are the diatoms, cyanobacteria, dinoflagellates and coccolithophores, zooplankton, small protozoans or metazoans that feed on other plankton and telonemia. Some of the eggs and larvae of larger animals, such as fish, crustaceans, bacterioplankton, bacteria and archaea, which play an important role in remineralising organic material down the water column. Mycoplankton, fungi and fungus-like organisms, which also are significant in nutrient cycling and this scheme divides the plankton community into broad producer, consumer and recycler groups. However, determining the level of some plankton is not straightforward. For example, although most dinoflagellates are either photosynthetic producers or heterotrophic consumers, Plankton are also often described in terms of size. Usually the following divisions are used, However, some of terms may be used with very different boundaries
47.
Cnidocyte
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A cnidocyte is an explosive cell containing one giant secretory organelle or cnida that defines the phylum Cnidaria. Cnidae are used for capture and defense from predators. Despite being morphologically simple, lacking a skeleton and many species being sessile, cnidarians prey on fish, a cnidocyte fires a structure that contains the toxin, from a characteristic subcellular organelle called a cnidocyst. This is responsible for the stings delivered by a cnidarian, each cnidocyte contains an organelle called a cnida or cnidocyst, which comprises a bulb-shape capsule containing a coiled hollow tubule structure attached to it. The immature cnidocyte is referred to as a cnidoblast, the externally oriented side of the cell also has a hair-like trigger called a cnidocil. Cnidocil is a mechano and chemo-receptor, when the trigger is activated, the tubule shaft of the cnidocyst is ejected and in the case of the penetrant nematocyst, the forcefully ejected tubule penetrates the target organism. This discharge takes no more than a few microseconds, and is able to reach accelerations of about 40,000 g, recent research suggests the process to occur as fast as 700 nanoseconds, thus reaching an acceleration of up to 5,410,000 g. After penetration, the content of the nematocyst is injected into the target organism. Cnidae capsule stores a large concentration of ions, which are released from the capsule into the cytoplasm of the cnidocyte when the trigger is activated. This causes a large gradient of calcium across the cnidocyte plasma membrane. The resulting osmotic pressure causes an influx of water into the cell. This increase in volume in the cytoplasm forces the coiled cnidae tubule to eject rapidly. Prior to discharge the coiled cnidae tubule exists inside the cell in an inside out condition and this prevents the cnidarian from stinging itself although sloughed off cnidae can be induced to fire independently. Over 30 types of cnidae are found in different cnidarians and they can be divided into the following groups, Penetrant, The penetrant or stenotele is the largest and most complex nematocyst. When discharged, it pierces the skin or chitinous exoskeleton of the prey and injects the poisonous fluid, hypotoxin and it contains a short, thick, spineless, smooth and elastic thread tube forming a single loop and closed at the far end. When discharged, it tightly coils around the prey, a single nematocyst has been shown to suffice in paralyzing a small arthropod. The most deadly cnidocytes are found on the body of a box jellyfish, one member of this family, the sea wasp, Chironex fleckeri, is claimed to be the most venomous marine animal known, according to the Australian Institute of Marine Science. It can cause excruciating pain to humans, sometimes followed by death, other cnidarians, such as the jellyfish Cyanea capillata or the siphonophore Physalia physalis can cause extremely painful and sometimes fatal stings
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. PMID 24475157. doi:10.1371/journal.pone.0086612.
