1.
Absolute dating
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Absolute dating is the process of determining an age on a specified chronology in archaeology and geology. Some scientists prefer the terms chronometric or calendar dating, as use of the word implies a unwarranted certainty of accuracy. Absolute dating provides an age or range in contrast with relative dating which places events in order without any measure of the age between events. Techniques include tree rings in timbers, radiocarbon dating of wood or bones, radiometric dating is based on the known and constant rate of decay of radioactive isotopes into their radiogenic daughter isotopes. Particular isotopes are suitable for different applications due to the type of atoms present in the mineral or other material, one of the most widely used and well-known absolute dating techniques is carbon-14 dating, which is used to date organic remains. This is a technique since it is based on radioactive decay. Cosmic radiation entering the earth’s atmosphere produces carbon-14, and plants take in carbon-14 as they fix carbon dioxide, carbon-14 moves up the food chain as animals eat plants and as predators eat other animals. With death, the uptake of carbon-14 stops and it takes 5,730 years for half the carbon-14 to change to nitrogen, this is the half-life of carbon-14. After another 5,730 years only one-quarter of the original carbon-14 will remain, after yet another 5,730 years only one-eighth will be left. By measuring the carbon-14 in organic material, scientists can determine the date of death of the matter in an artifact or ecofact. The relatively short half-life of carbon-14,5,730 years, an additional problem with carbon-14 dates from archeological sites is known as the old wood problem. Thus dating that particular tree does not necessarily indicate when the fire burned or the structure was built, for this reason, many archaeologists prefer to use samples from short-lived plants for radiocarbon dating. The development of mass spectrometry dating, which allows a date to be obtained from a very small sample, has been very useful in this regard. Other radiometric dating techniques are available for earlier periods, one of the most widely used is potassium-argon dating. Potassium-40 is an isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated. Argon, a gas, is not commonly incorporated into such samples except when produced in situ through radioactive decay. The date measured reveals the last time that the object was heated past the closure temperature at which the trapped argon can escape the lattice, k-Ar dating was used to calibrate the geomagnetic polarity time scale
2.
Megaannum
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A year is the orbital period of the Earth moving in its orbit around the Sun. Due to the Earths axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the globe, four seasons are recognized, spring, summer, autumn. In tropical and subtropical regions several geographical sectors do not present defined seasons, but in the seasonal tropics, a calendar year is an approximation of the number of days of the Earths orbital period as counted in a given calendar. The Gregorian, or modern, calendar, presents its calendar year to be either a common year of 365 days or a year of 366 days, as do the Julian calendars. For the Gregorian calendar the average length of the year across the complete leap cycle of 400 years is 365.2425 days. The ISO standard ISO 80000-3, Annex C, supports the symbol a to represent a year of either 365 or 366 days, in English, the abbreviations y and yr are commonly used. In astronomy, the Julian year is a unit of time, it is defined as 365.25 days of exactly 86400 seconds, totalling exactly 31557600 seconds in the Julian astronomical year. The word year is used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year. Similarly, year can mean the period of any planet, for example. The term can also be used in reference to any long period or cycle, west Saxon ġēar, Anglian ġēr continues Proto-Germanic *jǣran. Cognates are German Jahr, Old High German jār, Old Norse ár and Gothic jer, all the descendants of the Proto-Indo-European noun *yeh₁rom year, season. Cognates also descended from the same Proto-Indo-European noun are Avestan yārǝ year, Greek ὥρα year, season, period of time, Old Church Slavonic jarŭ, Latin annus is from a PIE noun *h₂et-no-, which also yielded Gothic aþn year. Both *yeh₁-ro- and *h₂et-no- are based on verbal roots expressing movement, *h₁ey- and *h₂et- respectively, the Greek word for year, ἔτος, is cognate with Latin vetus old, from the PIE word *wetos- year, also preserved in this meaning in Sanskrit vat-sa- yearling and vat-sa-ras year. Derived from Latin annus are a number of English words, such as annual, annuity, anniversary, etc. per annum means each year, anno Domini means in the year of the Lord. No astronomical year has an number of days or lunar months. Financial and scientific calculations often use a 365-day calendar to simplify daily rates, in the Julian calendar, the average length of a year is 365.25 days. In a non-leap year, there are 365 days, in a year there are 366 days
3.
Quaternary
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Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy. It follows the Neogene Period and spans from 2.588 ±0.005 million years ago to the present, the Quaternary Period is divided into two epochs, the Pleistocene and the Holocene. The informal term Late Quaternary refers to the past 0. 5–1.0 million years, the Quaternary Period is typically defined by the cyclic growth and decay of continental ice sheets driven by Milankovitch cycles and the associated climate and environmental changes that occurred. The term Quaternary was proposed by Giovanni Arduino in 1759 for alluvial deposits in the Po River valley in northern Italy and it was introduced by Jules Desnoyers in 1829 for sediments of Frances Seine Basin that seemed clearly to be younger than Tertiary Period rocks. The Quaternary Period follows the Neogene Period and extends to the present, the Quaternary covers the time span of glaciations classified as the Pleistocene, and includes the present interglacial time-period, the Holocene. This places the start of the Quaternary at the onset of Northern Hemisphere glaciation approximately 2.6 million years ago, Quaternary stratigraphers usually worked with regional subdivisions. From the 1970s, the International Commission on Stratigraphy tried to make a single geologic time scale based on GSSPs, the Quaternary subdivisions were defined based on biostratigraphy instead of paleoclimate. This led to the problem that the base of the Pleistocene was at 1.805 Mya. The ICS then proposed to use of the name Quaternary altogether. The Anthropocene has been proposed as an epoch as a mark of the anthropogenic impact on the global environment starting with the Industrial Revolution. The Anthropocene is not officially designated by the ICS, however, the 2.6 million years of the Quaternary represents the time during which recognizable humans existed. Over this short period, there has been relatively little change in the distribution of the continents due to plate tectonics. The Quaternary geological record is preserved in detail than that for earlier periods. The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude, there was a major extinction of large mammals in Northern areas at the end of the Pleistocene Epoch. Many forms such as saber-toothed cats, mammoths, mastodons, glyptodonts, others, including horses, camels and American cheetahs became extinct in North America. Glaciation took place repeatedly during the Quaternary Ice Age – a term coined by Schimper in 1839 that began with the start of the Quaternary about 2.58 Mya and continues to the present-day. In 1821, a Swiss engineer, Ignaz Venetz, presented an article in which he suggested the presence of traces of the passage of a glacier at a distance from the Alps. This idea was initially disputed by another Swiss scientist, Louis Agassiz, a year later, Agassiz raised the hypothesis of a great glacial period that would have had long-reaching general effects
4.
Pleistocene
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The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the worlds most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period, the Pleistocene is the first epoch of the Quaternary Period or sixth epoch of the Cenozoic Era. In the ICS timescale, the Pleistocene is divided into four stages or ages, all of these stages were defined in southern Europe. In addition to this subdivision, various regional subdivisions are often used. Charles Lyell introduced the term pleistocene in 1839 to describe strata in Sicily that had at least 70% of their molluscan fauna still living today and this distinguished it from the older Pliocene Epoch, which Lyell had originally thought to be the youngest fossil rock layer. The Pleistocene has been dated from 2.588 million to 11,700 years before present and it covers most of the latest period of repeated glaciation, up to and including the Younger Dryas cold spell. The end of the Younger Dryas has been dated to about 9640 BC, the IUGS has yet to approve a type section, Global Boundary Stratotype Section and Point, for the upper Pleistocene/Holocene boundary. The proposed section is the North Greenland Ice Core Project ice core 75°06 N 42°18 W, the lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nanofossils, Discoaster pentaradiatus, the Pleistocene covers the recent period of repeated glaciations. The name Plio-Pleistocene has, in the past, been used to mean the last ice age. The revised definition of the Quaternary, by pushing back the date of the Pleistocene to 2.58 Ma. Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places and it is estimated that, at maximum glacial extent, 30% of the Earths surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the sheet, a few hundred kilometres in North America. The mean annual temperature at the edge of the ice was −6 °C, during interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions. The effects of glaciation were global, antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes were covered in the south by the Patagonian ice cap, there were glaciers in New Zealand and Tasmania. The current decaying glaciers of Mount Kenya, Mount Kilimanjaro, glaciers existed in the mountains of Ethiopia and to the west in the Atlas mountains. In the northern hemisphere, many glaciers fused into one, the Cordilleran ice sheet covered the North American northwest, the east was covered by the Laurentide
5.
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
6.
Pliocene
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The Pliocene Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era, the Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch.588 to 1.806 million years ago, and is now included in the Pleistocene. As with other geologic periods, the geological strata that define the start and end are well identified but the exact dates of the start. The boundaries defining the Pliocene are not set at an easily identified worldwide event, the upper boundary was set at the start of the Pleistocene glaciations. The Pliocene was named by Sir Charles Lyell, the name comes from the Greek words πλεῖον and καινός and means roughly continuation of the recent, referring to the essentially modern marine mollusc faunas. H. W. Fowler called the term a regrettable barbarism, in the official timescale of the ICS, the Pliocene is subdivided into two stages. From youngest to oldest they are, Piacenzian Zanclean The Piacenzian is sometimes referred to as the Late Pliocene, in the system of North American Land Mammal Ages include Hemphillian, and Blancan. The Blancan extends forward into the Pleistocene, South American Land Mammal Ages include Montehermosan, Chapadmalalan and Uquian. In the Paratethys area the Pliocene contains the Dacian and Romanian stages, as usual in stratigraphy, there are many other regional and local subdivisions in use. In Britain the Pliocene is divided into the stages, Gedgravian, Waltonian, Pre-Ludhamian, Ludhamian, Thurnian, Bramertonian or Antian, Pre-Pastonian or Baventian, Pastonian and Beestonian. The exact correlations between these stages and the ICS stages is still a matter of detail. The formation of an Arctic ice cap is signaled by a shift in oxygen isotope ratios and ice-rafted cobbles in the North Atlantic. Mid-latitude glaciation was probably underway before the end of the epoch, the global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas. Continents continued to drift, moving from positions possibly as far as 250 km from their present locations to positions only 70 km from their current locations, africas collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean. The border between the Miocene and the Pliocene is also the time of the Messinian salinity crisis, Sea level changes exposed the land-bridge between Alaska and Asia. Pliocene marine rocks are exposed in the Mediterranean, India. Elsewhere, they are exposed largely near shores, the change to a cooler, dry, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species worldwide. Deciduous forests proliferated, coniferous forests and tundra covered much of the north, tropical forests were limited to a tight band around the equator, and in addition to dry savannahs, deserts appeared in Asia and Africa
7.
Messinian
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The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ±0.005 Ma and 5.333 ±0.005 Ma and it follows the Tortonian and is followed by the Zanclean, the first age of the Pliocene. The Messinian overlaps the Turolian European Land Mammal Mega Zone and the Pontian Central European Paratethys stage and it also overlaps the late Huayquerian and early Montehermosan South American Land Mammal Ages, and falls inside the more extensive Hemphillian North American Land Mammal Age. During the Messinian, around 6 million years ago, the Messinian salinity crisis took place, the Messinian was introduced by Swiss stratigrapher Karl Mayer-Eymar in 1867. Its name comes from the Italian city of Messina on Sicily, the base of the Messinian is at the first appearance of the planktonic foram species Globorotalia conomiozea and is stratigraphically in the middle of magnetic chronozone C3Br. 1r. The Global Boundary Stratotype Section and Point for the Messinian is located in a section at Oued Akrech, the top of the Messinian lies with the top of magnetic chronozone Cr3. The top is also close to the level of the calcareous nanoplankton species Triquetrorhabdulus rugosus. Hilgen, F. J. S. Iaccarino, W. Krijgsman, G. Villa, the Global Boundary Stratotype Section and Point of the Messinian Stage. Catalogue systématique et descriptif des fossiles des terrains tertiaires qui se trouvent du Musée fédéral de Zürich
8.
Langhian
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The Langhian is, in the ICS geologic timescale, an age or stage in the middle Miocene epoch/series. It spans the time between 15.97 ±0.05 Ma and 13.65 ±0.05 Ma during the Middle Miocene. The Langhian was a continuing warming period defined by Lorenzo Pareto in 1865, it was established in the Langhe area north of Ceva in northern Italy. The Langhian is preceded by the Burdigalian and followed by the Serravallian stage, the base of the Langhian is defined by the first appearance of foraminifer species Praeorbulina glomerosa and is also coeval with the top of magnetic chronozone C5Cn. 1n. A GSSP for the Langhian stage was not yet established in 2009, & Smith, A. G.2004, A Geologic Time Scale 2004, Cambridge University Press. Pareto, L.1865, Note sur les subdivisions que lon pourrait établir dans les terrains tertaires de lApennin septentrional, Bulletin de la Societé Géologique de France 2, p. 210-277
9.
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
10.
Oligocene
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The Oligocene is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present. As with other geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start. The name Oligocene comes from the Ancient Greek ὀλίγος and καινός, the Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period, the Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major changes during the Oligocene included an expansion of grasslands. By contrast, the Oligocene–Miocene boundary is not set at an easily identified worldwide event, Oligocene faunal stages from youngest to oldest are, The Paleogene Period general temperature decline is interrupted by an Oligocene 7-million-year stepwise climate change. A deeper 8.2 °C,400, 000-year temperature depression leads the 2 °C, the stepwise climate change began 32.5 Ma and lasted through to 25.5 Ma, as depicted in the PaleoTemps chart. The Oligocene climate change was a increase in ice volume. The 7-million-year depression abruptly terminated within 1–2 million years of the La Garita Caldera eruption at 28–26 Ma, a deep 400, 000-year glaciated Oligocene Miocene boundary event is recorded at McMurdo Sound and King George Island. During this epoch, the continued to drift toward their present positions. Antarctica became more isolated and finally developed an ice cap, a brief marine incursion marks the early Oligocene in Europe. Marine fossils from the Oligocene are rare in North America, there appears to have been a land bridge in the early Oligocene between North America and Europe, since the faunas of the two regions are very similar. Sometime during the Oligocene, South America was finally detached from Antarctica and it also allowed the Antarctic Circumpolar Current to flow, rapidly cooling the Antarctic continent. Angiosperms continued their expansion throughout the world as tropical and sub-tropical forests were replaced by deciduous forests. Open plains and deserts became more common and grasses expanded from their habitat in the Eocene moving out into open tracts. However, even at the end of the period, grass was not quite enough for modern savannas. In North America, subtropical species dominated with cashews and lychee trees present, and temperate trees such as roses, beeches, the legumes spread, while sedges, bulrushes, and ferns continued their ascent. Even more open landscapes allowed animals to grow to larger sizes than they had earlier in the Paleocene epoch 30 million years earlier, marine faunas became fairly modern, as did terrestrial vertebrate fauna on the northern continents
11.
Charles Lyell
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Sir Charles Lyell, 1st Baronet, FRS was a British lawyer and the foremost geologist of his day. Principles of Geology also challenged theories popularized by Georges Cuvier, which were the most accepted and circulated ideas about geology in England at the time and he also coined the currently-used names for geological eras, Paleozoic, Mesozoic and Cenozoic. He incorrectly conjectured that icebergs may be the emphasis behind the transport of glacial erratics, Lyell was one of the first to believe that the world is older than 300 million years, on the basis of its geological anomalies. He was a friend of Charles Darwin, and contributed significantly to Darwins thinking on the processes involved in evolution. He helped to arrange the publication in 1858 of papers by Darwin and Alfred Russel Wallace on natural selection. He later published evidence from geology of the man had existed on Earth. Lyell was born 14 November 1797 in Scotland about 15 miles north of Dundee in Kinnordy and he was the eldest of ten children. Lyells father, also named Charles Lyell, was a lawyer and botanist of minor repute, the house/place of his birth is located in the north-west of the Central Lowlands in the valley of the Highland Boundary Fault. Round the house, in the valley, is farmland. His familys second home was in a different geological and ecological area, he spent much of his childhood at Bartley Lodge in the New Forest. Lyell entered Exeter College, Oxford, in 1816, and attended William Bucklands lectures and he graduated BA second class in classics, December 1819, and M. A.1821. After graduation he took up law as a profession, entering Lincolns Inn in 1820 and he completed a circuit through rural England, where he could observe geological phenomena. In 1821 he attended Robert Jamesons lectures in Edinburgh, and visited Gideon Mantell at Lewes, in 1823 he was elected joint secretary of the Geological Society. As his eyesight began to deteriorate, he turned to geology as a full-time profession and his first paper, On a recent formation of freshwater limestone in Forfarshire, was presented in 1822. In 1832, Lyell married Mary Horner in Bonn, daughter of Leonard Horner, the new couple spent their honeymoon in Switzerland and Italy on a geological tour of the area. During the 1840s, Lyell travelled to the United States and Canada, after the Great Chicago Fire, Lyell was one of the first to donate books to help found the Chicago Public Library. In 1866, he was elected a member of the Royal Swedish Academy of Sciences. Lyells wife died in 1873, and two years later Lyell himself died as he was revising the twelfth edition of Principles and he is buried in Westminster Abbey
12.
Invertebrate
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Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata, familiar examples of invertebrates include insects, crabs, lobsters and their kin, snails, clams, octopuses and their kin, starfish, sea-urchins and their kin, jellyfish, and worms. The majority of species are invertebrates, one estimate puts the figure at 97%. Many invertebrate taxa have a number and variety of species than the entire subphylum of Vertebrata. Some of the invertebrates, such as the Tunicata and Cephalochordata are more closely related to the vertebrates than to other invertebrates. This makes the term invertebrate paraphyletic and hence almost meaningless for taxonomic purposes, the word invertebrate comes from the form of the Latin word vertebra, which means a joint in general, and sometimes specifically a joint from the spinal column of a vertebrate. In turn the jointed aspect of vertebra derived from the concept of turning, coupled with the prefix in-, meaning not or without. The term invertebrates is not always precise among non-biologists since it does not accurately describe a taxon in the way that Arthropoda. Each of these describes an valid taxon, phylum, subphylum or family. Invertebrata is a term of convenience, not a taxon, it has very little circumscriptional significance except within the Chordata, the Vertebrata as a subphylum comprises such a small proportion of the Metazoa that to speak of the kingdom Animalia in terms of Vertebrata and Invertebrata has limited practicality. That would at least circumscribe the Chordata, however, even the notochord would be a less fundamental criterion than aspects of embryological development and symmetry or perhaps bauplan. The following text reflects earlier scientific understanding of the term and of animals which have constituted it. According to this understanding, invertebrates do not possess a skeleton of bone and they include hugely varied body plans. Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms, others have hard exoskeletons, outer shells like those of insects and crustaceans. The most familiar invertebrates include the Protozoa, Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Echinodermata, Mollusca, Arthropoda include insects, crustaceans and arachnids. By far the largest number of described species are insects. The following table lists the number of described extant species for major invertebrate groups as estimated in the IUCN Red List of Threatened Species,2014.3. The IUCN estimates that 66,178 extant vertebrate species have been described, the trait that is common to all invertebrates is the absence of a vertebral column, this creates a distinction between invertebrates and vertebrates
13.
Ice age
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An ice age is a period of long-term reduction in the temperature of Earths surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Within a long-term ice age, individual pulses of cold climate are termed glacial periods, in the terminology of glaciology, ice age implies the presence of extensive ice sheets in both northern and southern hemispheres. In 1742 Pierre Martel, an engineer and geographer living in Geneva, two years later he published an account of his journey. He reported that the inhabitants of that valley attributed the dispersal of erratic boulders to the glaciers, later similar explanations were reported from other regions of the Alps. In 1815 the carpenter and chamois hunter Jean-Pierre Perraudin explained erratic boulders in the Val de Bagnes in the Swiss canton of Valais as being due to glaciers previously extending further. An unknown woodcutter from Meiringen in the Bernese Oberland advocated a similar idea in a discussion with the Swiss-German geologist Jean de Charpentier in 1834, comparable explanations are also known from the Val de Ferret in the Valais and the Seeland in western Switzerland and in Goethes scientific work. Such explanations could also be found in parts of the world. When the Bavarian naturalist Ernst von Bibra visited the Chilean Andes in 1849–1850, meanwhile, European scholars had begun to wonder what had caused the dispersal of erratic material. From the middle of the 18th century, some discussed ice as a means of transport, the Swedish mining expert Daniel Tilas was, in 1742, the first person to suggest drifting sea ice in order to explain the presence of erratic boulders in the Scandinavian and Baltic regions. In 1795, the Scottish philosopher and gentleman naturalist, James Hutton, two decades later, in 1818, the Swedish botanist Göran Wahlenberg published his theory of a glaciation of the Scandinavian peninsula. He regarded glaciation as a regional phenomenon, only a few years later, the Danish-Norwegian geologist Jens Esmark argued a sequence of worldwide ice ages. In a paper published in 1824, Esmark proposed changes in climate as the cause of those glaciations and he attempted to show that they originated from changes in Earths orbit. During the following years, Esmarks ideas were discussed and taken over in parts by Swedish, Scottish, at the University of Edinburgh Robert Jameson seemed to be relatively open to Esmarks ideas, as reviewed by Norwegian professor of glaciology Bjørn G. Andersen. Jamesons remarks about ancient glaciers in Scotland were most probably prompted by Esmark, in Germany, Albrecht Reinhard Bernhardi, a geologist and professor of forestry at an academy in Dreissigacker, since incorporated in the southern Thuringian city of Meiningen, adopted Esmarks theory. In a paper published in 1832, Bernhardi speculated about former polar ice caps reaching as far as the zones of the globe. When he read his paper before the Schweizerische Naturforschende Gesellschaft, most scientists remained sceptical, finally, Venetz convinced his friend Jean de Charpentier. De Charpentier transformed Venetzs idea into a theory with a limited to the Alps. In fact, both men shared the same volcanistic, or in de Charpentiers case rather plutonistic assumptions, about the Earths history, in 1834, de Charpentier presented his paper before the Schweizerische Naturforschende Gesellschaft
14.
Ape
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The simians are the monkeys, cladistically including the apes, the New World monkeys or platyrrhines, and the catarrhine clade consisting of the Old World monkeys and apes. The simian line and the line diverged about 60 million years ago. Forty million years ago, simians from Africa colonized South America, the remaining simians split 25 million years ago into apes and Old World monkeys. Under modern classification, the tarsiers and simians are grouped under the suborder Haplorhini while the strepsirrhines are placed in suborder Strepsirrhini, in anthropoidea, evidences indicate that the Old and the New World primates went through parallel evolution. Primatology, paleoanthropology, and other related fields are split on their usage of the synonymous infraorder names, Simiiformes and Anthropoidea. According to Robert Hoffstetter, the term Simiiformes has priority over Anthropoidea because of the taxonomic term Simii by van der Hoeven, from which it is constructed, dates to 1833. In contrast, Anthropoidea by Mivart dates to 1864, while Simiiformes by Haeckel dates to 1866, Hoffstetter also argued that Simiiformes is also constructed like a proper infraorder name, whereas Anthropoidea ends in -oidea, which is reserved for superfamilies. He also noted that Anthropoidea is too easily confused with anthropoïdes, the simians are split into three distinct groups. The New World monkeys in parvorder Platyrrhini split from the rest of the line about 40 mya. This group split about 25 mya between the Old World monkeys and the apes
15.
Old World
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The Old World consists of Africa, Europe, and Asia, regarded collectively as the part of the world known to Europeans before contact with the Americas. It is used in the context of, and contrast with and these regions were connected via the Silk Road trade route, and they have a pronounced Iron Age period following the Bronze Age. The concept of the three continents in the Old World, viz. Asia, Africa, and Europe, goes back to classical antiquity and their boundaries as defined by Ptolemy and other geographers of antiquity were drawn along the Nile and Don rivers. This definition remained influential throughout the Middle Ages and the Early Modern period, the Old world has areas of North Africa, Eurasia, parts of Papua New Guinea and Solomon Islands. The mainland of Afro-Eurasia has been referred to as the World Island, the term may have been coined by Sir Halford John Mackinder in The Geographical Pivot of History. The equivalent of the Old World had names in some of its ancient cultures, including Midgard in Germanic cosmology, synoptic table of the principal old world prehistoric cultures Afro-Eurasia
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Human evolution
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Human evolution from its first separation from the last common ancestor of humans and chimpanzees is characterized by a number of morphological, developmental, physiological, and behavioral changes. The most significant of these adaptations are bipedalism, increased size, lengthened ontogeny. The relationship between these changes is the subject of ongoing debate, other significant morphological changes included the evolution of a power and precision grip, a change first occurring in H. erectus. Bipedalism is the adaptation of the hominin and is considered the main cause behind a suite of skeletal changes shared by all bipedal hominins. The earliest hominin, of presumably primitive bipedalism, is considered to be either Sahelanthropus or Orrorin, Ardipithecus, a full biped, arose somewhat later. The early bipeds eventually evolved into the australopithecines and still later into the genus Homo, There are several theories of the adaptation value of bipedalism. A new study provides support for the hypothesis that walking on two legs, or bipedalism, evolved because it used less energy than quadrupedal knuckle-walking, however, recent studies suggest that bipedality without the ability to use fire would not have allowed global dispersal. This change in gait saw a lengthening of the legs proportionately when compared to the length of the arms, another change is the shape of the big toe. Recent studies suggest that Australopithecines still lived part of the time in trees as a result of maintaining a big toe. This was progressively lost in Habilines, anatomically, the evolution of bipedalism has been accompanied by a large number of skeletal changes, not just to the legs and pelvis, but also to the vertebral column, feet and ankles, and skull. The femur evolved into a more angular position to move the center of gravity toward the geometric center of the body. The knee and ankle joints became increasingly robust to support increased weight. To support the weight on each vertebra in the upright position, the human vertebral column became S-shaped. In the feet the big toe moved into alignment with the toes to help in forward locomotion. The arms and forearms shortened relative to the making it easier to run. The foramen magnum migrated under the skull and more anterior, during human birth, because of the variation in size of the pelvic region, the fetal head must be in a transverse position during entry into the birth canal and rotate about 90 degrees upon exit. The human species developed a much larger brain than that of other primates—typically 1,330 cm3 in modern humans. This pattern of brain increase happened through the pattern of human postnatal brain growth differs from that of other apes
17.
Chimpanzee
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Chimpanzees are one of the two species of the genus Pan, the other being the bonobo. Together with gorillas, they are the only exclusively African species of ape that are currently extant. Native to sub-Saharan Africa, both chimpanzees and bonobos are found in the Congo jungle. In addition, P. troglodytes is divided into four subspecies, based on genome sequencing, the two extant Pan species diverged around one million years ago. The most obvious differences are that chimpanzees are somewhat larger, more aggressive and male-dominated, while the bonobos are more gracile, peaceful and their hair is typically black or brown. Males and females differ in size and appearance, both chimps and bonobos are some of the most social great apes, with social bonds occurring among individuals in large communities. Fruit is the most important component of a diet, however, they will also eat vegetation, bark, honey, insects. They can live over 30 years in both the wild and captivity, Chimpanzees and bonobos are equally humanitys closest living relatives. As such, they are among the largest-brained, and most intelligent of primates, they use a variety of sophisticated tools and construct elaborate sleeping nests each night from branches and they have both been extensively studied for their learning abilities. There may even be distinctive cultures within populations, field studies of Pan troglodytes were pioneered by primatologist Jane Goodall. Both Pan species are considered to be endangered as human activities have caused declines in the populations. Threats to wild populations include poaching, habitat destruction. Several conservation and rehabilitation organisations are dedicated to the survival of Pan species in the wild, the first use of the name chimpanze is recorded in The London Magazine in 1738, glossed as meaning mockman in a language of the Angolans. The spelling chimpanzee is found in a 1758 supplement to Chambers Cyclopædia, the colloquialism chimp was most likely coined some time in the late 1870s. The common chimpanzee was named Simia troglodytes by Johann Friedrich Blumenbach in 1776, the species name troglodytes is a reference to the Troglodytae, an African people described by Greco-Roman geographers. Blumenbach first used it in his De generis humani varietate nativa liber in 1776, the genus name Pan was first introduced by Lorenz Oken in 1816. An alternative Theranthropus was suggested by Brookes 1828 and Chimpansee by Voigt 1831, troglodytes was not available, as it had been given as the name of a genus of wren in 1809. The International Commission on Zoological Nomenclature adopted Pan as the official name of the genus in 1895
18.
Grassland
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Grasslands are areas where the vegetation is dominated by grasses, however sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica, grasslands are found in most ecoregions of the Earth. For example, there are five terrestrial ecoregion classifications of the grasslands, savannas, and shrublands biome. Grassland vegetation can vary in height from short, as in chalk grassland, to quite tall, as in the case of North American tallgrass prairie, South American grasslands. Woody plants, shrubs or trees, may occur on some grasslands – forming savannas, scrubby grassland or semi-wooded grassland, as flowering plants and trees, grasses grow in great concentrations in climates where annual rainfall ranges between 500 and 900 mm. The root systems of perennial grasses and forbs form complex mats that hold the soil in place, graminoids are among the most versatile life forms. Existing forest biomes declined, and grasslands became much more widespread, following the Pleistocene ice ages, grasslands expanded in range in the hotter, drier climates, and began to become the dominant land feature worldwide. Grasslands often occur in areas with annual precipitation between 600 mm and 1,500 mm and average annual temperatures ranges from −5 and 20 °C. However, some occur in colder and hotter climatic conditions. Grassland can exist in habitats that are disturbed by grazing or fire. Grasslands dominated by unsown wild-plant communities can be called natural or semi-natural habitats. The majority of grasslands in temperate climates are semi-natural and these grasslands contain many species of wild plants – grasses, sedges, rushes and herbs –25 or more species per square metre is not unusual. Chalk downlands in England can support over 40 species per square metre, in many parts of the world, few examples have escaped agricultural improvement. For example, original North American prairie grasslands or lowland wildflower meadows in the UK are now rare and their associated wild flora equally threatened. Some of the worlds largest expanses of grassland are found in African savanna, grasslands may occur naturally or as the result of human activity. Grasslands created and maintained by human activity are called anthropogenic grasslands, hunting peoples around the world often set regular fires to maintain and extend grasslands, and prevent fire-intolerant trees and shrubs from taking hold. The tallgrass prairies in the U. S. Midwest may have been extended eastward into Illinois, Indiana, much grassland in northwest Europe developed after the Neolithic Period, when people gradually cleared the forest to create areas for raising their livestock. Grassland types by Schimper, meadow steppe savannah Grassland types by Ellenberg & Mueller-Dombois, terrestrial herbaceous communities A. Savannas and related grasslands B
19.
Kelp forest
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Kelp forests are underwater areas with a high density of kelp. They are recognized as one of the most productive and dynamic ecosystems on Earth, smaller areas of anchored kelp are called kelp beds. Kelp forests occur worldwide throughout temperate and polar coastal oceans, in 2007, kelp forests were also discovered in tropical waters near Ecuador. Physically formed by brown macroalgae, kelp forests provide a unique, over the last century, they have been the focus of extensive research, particularly in trophic ecology, and continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patterns and provide ecosystem services. However, the influence of humans has often contributed to kelp forest degradation, of particular concern are the effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the overgrazing of kelp and other algae. This can rapidly result in transitions to barren landscapes where relatively few species persist, the term kelp refers to marine algae belonging to the order Laminariales. Though not considered a taxonomically diverse order, kelps are highly diverse structurally and functionally, the most widely recognized species are the giant kelps, although numerous other genera such as Laminaria, Ecklonia, Lessonia, Alaria, and Eisenia are described. Many marine mammals and birds are found, including seals, sea lions, whales, sea otters, gulls, terns, snowy egrets, great blue herons. Frequently considered an ecosystem engineer, kelp provides a physical substrate, in algae, the body of an individual organism is known as a thallus rather than as a plant. The stipe is analogous to a plant stalk, extending vertically from the holdfast, the fronds are leaf- or blade-like attachments extending from the stipe, sometimes along its full length, and are the sites of nutrient uptake and photosynthetic activity. In addition, many species have pneumatocysts, or gas-filled bladders. These structures provide the necessary buoyancy for kelp to maintain a position in the water column. The environmental factors necessary for kelp to survive include hard substrate, high nutrients, water flow and turbulence facilitate nutrient assimilation across kelp fronds throughout the water column. Water clarity affects the depth to which sufficient light can be transmitted, in ideal conditions, giant kelp can grow as much as 30-60 cm vertically per day. Some species, such as Nereocystis, are annuals, while others such as Eisenia are perennials, in perennial kelp forests, maximum growth rates occur during upwelling months and die-backs correspond to reduced nutrient availability, shorter photoperiods, and increased storm frequency. Kelps are primarily associated with temperate and arctic waters worldwide, the region with the greatest diversity of kelps is the northeastern Pacific, from north of San Francisco, California, to the Aleutian Islands, Alaska. Although kelp forests are unknown in tropical waters, a few species of Laminaria have been known to occur exclusively in tropical deep waters
20.
Whale
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Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. They are a grouping within the infraorder Cetacea, usually excluding dolphins. Whales, dolphins and porpoises belong to the order Cetartiodactyla with even-toed ungulates and their closest living relatives are the hippopotamuses, the two parvorders of whales, baleen whales and toothed whales, are thought to have split apart around 34 million years ago. The whales comprise eight extant families, Balaenopteridae, Balaenidae, Cetotheriidae, Eschrichtiidae, Monodontidae, Physeteridae, Kogiidae, Whales are creatures of the open ocean, they feed, mate, give birth, suckle and raise their young at sea. So extreme is their adaptation to life underwater that they are unable to survive on land. Whales range in size from the 2.6 metres and 135 kilograms dwarf sperm whale to the 29.9 metres and 190 metric tons blue whale, the sperm whale is the largest toothed predator on earth. Several species exhibit sexual dimorphism, in that the females are larger than males, baleen whales have no teeth, instead they have plates of baleen, a fringe-like structure used to expel water while retaining the krill and plankton which they feed on. They use their throat pleats to expand the mouth to take in huge gulps of water, balaenids have heads that can make up 40% of their body mass to take in water. Toothed whales, on the hand, have conical teeth designed for catching fish or squid. Some species, such as whales, are well adapted for diving to great depths to catch squid. Whales have evolved from land-living mammals, as such they must breathe air regularly, though they can remain submerged for long periods. They have blowholes located on top of their heads, through air is taken in. They are warm-blooded, and have a layer of fat, or blubber, under the skin, with streamlined fusiform bodies and two limbs that are modified into flippers, whales can travel at up to 20 knots, though they are not as flexible or agile as seals. Whales produce a variety of vocalizations, notably the extended songs of the humpback whale. Although whales are widespread, most species prefer the waters of the Northern and Southern Hemispheres. Species such as humpbacks and blue whales are capable of travelling thousands of miles without feeding, males typically mate with multiple females every year, but females only mate every two to three years. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them, mothers of some species fast and nurse their young for one to two years. Once relentlessly hunted for their products, whales are now protected by international law, the North Atlantic right whales nearly became extinct in the twentieth century, with a population low of 450, and the North Pacific gray whale population is ranked Critically Endangered by the IUCN
21.
Pinniped
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Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae, there are 33 extant species of pinnipeds, and more than 50 extinct species have been described from fossils. While seals were historically thought to have descended from two lines, molecular evidence supports them as a monophyletic lineage. Pinnipeds belong to the order Carnivora and their closest living relatives are bears and musteloids, Seals range in size from the 1 m and 45 kg Baikal seal to the 5 m and 3,200 kg southern elephant seal, which is also the largest carnivoran. They have streamlined bodies and four limbs that are modified into flippers, though not as fast in the water as dolphins, seals are more flexible and agile. Otariids use their front limbs primarily to themselves through the water, while phocids. Otariids and walruses have hind limbs that can be pulled under the body, by comparison, terrestrial locomotion by phocids is more cumbersome. Otariids have visible ears, while phocids and walruses lack these. Pinnipeds have well-developed senses—their eyesight and hearing are adapted for both air and water, and they have a tactile system in their whiskers or vibrissae. Some species are adapted for diving to great depths. They have a layer of fat, or blubber, under the skin to keep warm in the cold water, although pinnipeds are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres. They spend most of their lives in the water, but come ashore to mate, give birth, molt or escape predators, like sharks. They feed largely on fish and marine invertebrates, but a few, like the seal, feed on large vertebrates, such as penguins. Walruses are specialized for feeding on bottom-dwelling mollusks, male pinnipeds typically mate with more than one female, although the degree of polygyny varies with the species. The males of land-breeding species tend to mate with a number of females than those of ice- or water-breeding species. Male pinniped strategies for reproductive success vary between defending females, defending territories that attract females and performing ritual displays or lek mating, pups are typically born in the spring and summer months and females bear almost all the responsibility for raising them. Mothers of some species fast and nurse their young for a short period of time while others take foraging trips at sea between nursing bouts. Walruses are known to nurse their young while at sea, Seals produce a number of vocalizations, notably the barks of California sea lions, the gong-like calls of walruses and the complex songs of Weddell seals
22.
Geology of the Himalaya
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The geology of the Himalaya is a record of the most dramatic and visible creations of modern plate tectonic forces. This immense mountain range was formed by forces and sculpted by weathering. The Himalaya-Tibet region supplies fresh water for more than one-fifth of the world population and this last feature earned the Himalaya its name, originating from the Sanskrit for the abode of the snow. Numerous granitic intrusions dated at around 500 Ma are also attributed to this event, in the Early Carboniferous, an early stage of rifting developed between the Indian continent and the Cimmerian Superterranes. During the Early Permian, this developed into the Neotethys ocean. From that time on, the Cimmerian Superterranes drifted away from Gondwana towards the north, nowadays, Iran, Afghanistan and Tibet are partly made up of these terranes. In the Norian, a major rifting episode split Gondwana in two parts, the Indian continent became part of East Gondwana, together with Australia and Antarctica. However, the separation of East and West Gondwana, together with the formation of oceanic crust, occurred later, the Indian plate then broke off from Australia and Antarctica in the Early Cretaceous with the opening of the South Indian Ocean. The change of the speed between the Indian and Asian plates from very fast to fast at about 55 Ma is circumstantial support for collision then. The first mechanism also calls upon the subduction of the Indian continental crust below Tibet, second is the extrusion or escape tectonics mechanism which sees the Indian plate as an indenter that squeezed the Indochina block out of its way. The ongoing active collision of the Indian and Eurasian continental plates challenges one hypothesis for plate motion which relies on subduction, one of the most striking aspects of the Himalayan orogen is the lateral continuity of its major tectonic elements. The Himalaya is classically divided into four units that can be followed for more than 2400 km along the belt. The sub-Himalaya, It forms the foothills of the Himalayan Range and is composed of Miocene to Pleistocene molassic sediments derived from the erosion of the Himalaya. These molasse deposits, known as the Muree and Siwaliks Formations, are folded and imbricated. The Lesser Himalaya is mainly formed by Upper Proterozoic to lower Cambrian detrital sediments from the passive Indian margin intercalated with some granites and these sediments are thrust over the Subhimalaya along the Main Boundary Thrust. The Lesser Himalaya often appears in tectonic windows within the High Himalaya Crystalline Sequence, the Central Himalayan Domain, or High Himalaya, forms the backbone of the Himalayan orogen and encompasses the areas with the highest topographic relief. It is commonly separated into four zones, although most of the metasediments forming the HHCS are of late Proterozoic to early Cambrian age, much younger metasediments can also be found in several areas. It is now accepted that the metasediments of the HHCS represent the metamorphic equivalents of the sedimentary series forming the base of the overlying Tethys Himalaya
23.
Monsoon
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Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is sometimes used for locally heavy but short-term rains. The major monsoon systems of the world consist of the West African and Asia-Australian monsoons, the inclusion of the North and South American monsoons with incomplete wind reversal has been debated. The south-west monsoon winds are called Nairutya Maarut in India, the English monsoon came from Portuguese monção, ultimately from Arabic mawsim and/or Hindi mausam, perhaps partly via early modern Dutch monsun. Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after the collision of the Indian sub-continent and Asia around 50 million years ago. Because of studies of records from the Arabian Sea and that of the wind-blown dust in the Loess Plateau of China, testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program. The monsoon has varied significantly in strength since this time, largely linked to climate change. A study of marine plankton suggested that the Indian Monsoon strengthened around 5 million years ago, then, during ice periods, the sea level fell and the Indonesian Seaway closed. When this happened, cold waters in the Pacific were impeded from flowing into the Indian Ocean and it is believed that the resulting increase in sea surface temperatures in the Indian Ocean increased the intensity of monsoons. Five episodes during the Quaternary at 2.22 Ma,1.83 Ma,0.68 Ma,0.45 Ma and 0.04 Ma were identified which showed a weakening of Leeuwin Current. The weakening of the LC would have an effect on the sea surface temperature field in the Indian Ocean, thus these five intervals could probably be those of considerable lowering of SST in the Indian Ocean and would have influenced Indian monsoon intensity. The impact of monsoon on the weather is different from place to place. In some places there is just a likelihood of having a more or less rain. In other places, quasi semi-deserts are turned into green grasslands where all sorts of plants. The Indian Monsoon turns large parts of India from a kind of semi-desert into green lands, see photos only taken 3 months apart in the Western Ghats. In places like this it is crucial for farmers to have the right timing for putting the seeds on the fields, Monsoons are large-scale sea breezes which occur when the temperature on land is significantly warmer or cooler than the temperature of the ocean. These temperature imbalances happen because oceans and land absorb heat in different ways, in contrast, dirt, sand, and rocks have lower heat capacities, and they can only transmit heat into the earth by conduction and not by convection. Therefore, bodies of water stay at an even temperature
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Glacial period
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A glacial period is an interval of time within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the hand, are periods of warmer climate between glacial periods. The last glacial period ended about 15,000 years ago, the Holocene epoch is the current interglacial. A time when there are no glaciers on Earth is considered a greenhouse climate state, within the Quaternary glaciation, there have been a number of glacials and interglacials. The last glacial period was the most recent glacial period within the current ice age, occurring in the Pleistocene epoch, the glacial advance reached its maximum extent about 18,000 BP. In Europe, the ice sheet reached northern Germany, since orbital variations are predictable, computer models that relate orbital variations to climate can predict future climate possibilities. Work by Berger and Loutre suggests that the current warm climate may last another 50,000 years
25.
Timeline of human evolution
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The timeline of human evolution outlines the major events in the development of the human species, Homo sapiens, and the evolution of our ancestors. It includes brief explanations of some of the species, genera, and this timeline is based on studies from anthropology, paleontology, developmental biology, morphology, and from anatomical and genetic data. It does not address the origin of life, which discussion is provided by abiogenesis, a caution, Other than Mr Haeckels historic and emblematic tree, this article provides no phylogenetics analysis to help portray the complex, nonlinear facts of human evolution. One of several lines of descent, or taxonomic ranking
26.
Hominini
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Members of the human clade, that is, the Hominina, including Homo and those species of the australopithecines that arose after the split from the chimpanzees, are called homininans. Not all homininans are directly related to the emergence of early Homo and this is a modern cladogram, For each clade, the cladogram above shows approximately when newer extant clades emerged. Some texts refer to Homonini as the Hominina branch, the subtribe Hominina is the human branch, that is, it contains only the genus Homo. Researchers proposed the taxon Hominini on the basis that the least similar species of a trichotomy should be separated from the other two. The common chimpanzee and the bonobo of the genus Pan are the closest living relatives to humans. All the extinct genera listed to the right are ancestral to, or offshoots of, however, both Orrorin and Sahelanthropus existed around the time of the split, and so may be ancestral to both Pan and Homo. In the proposal of Mann and Weiss, the tribe Hominini includes Pan as well as Homo, Homo and all bipedal apes are referred to the subtribe Hominina, while Pan is assigned to the subtribe Panina. Wood discusses the different views of this taxonomy, the assumption of late hybridization was in particular based on the similarity of the X chromosome in humans and chimpanzees, suggesting a divergence as late as some 4 million years ago. Sahelanthropus tchadensis is an extinct species that lived seven million years ago. Human Timeline – Smithsonian, National Museum of Natural History
27.
Ouranopithecus
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Based on O. macedoniensiss dental and facial anatomy, it has been suggested that the Ouranopithecus were actually dryopithecines. However, Ouranopithecines are probably closely related to the Ponginae. It is true that O. macedoniensis shares derived features with some early hominins and it has been suggested that it may be a synonym of Graecopithecus freybergi, although this is widely disputed in the literature. Media related to Ouranopithecus at Wikimedia Commons Human Timeline – Smithsonian, National Museum of Natural History
28.
Sahelanthropus
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Sahelanthropus tchadensis is an extinct homininae species that is dated to about 7 million years ago, during the Miocene epoch, possibly very close to the time of the chimpanzee–human divergence. Few specimens are known, other than the partial skull nicknamed Toumaï, existing fossils include a relatively small cranium named Toumaï, five pieces of jaw, and some teeth, making up a head that has a mixture of derived and primitive features. The braincase, being only 320 cm³ to 380 cm³ in volume, is similar to that of extant chimpanzees and is less than the approximate human volume of 1350 cm³. The teeth, brow ridges, and facial structure differ markedly from those found in Homo sapiens, cranial features show a flatter face, u-shaped dental arcade, small canines, an anterior foramen magnum, and heavy brow ridges. No postcranial remains have been recovered, the only known skull suffered a large amount of distortion during the time of fossilisation and discovery, as the cranium is dorsoventrally flattened, and the right side is depressed. Sahelanthropus tchadensis may have walked on two legs, upon examination of the foramen magnum in the primary study, the lead author speculated that a bipedal gait would not be unreasonable based on basicranial morphology similar to more recent hominins. Further, according to recent information, what might be a femur of a hominid was also discovered near the cranium—but which has not been published nor accounted for. All known material of Sahelanthropus was found between July 2001 and March 2002 at three sites, TM247, TM266, which yielded most of the material, including a cranium and a femur, and TM292. The discoverers claimed that S. tchadensis is the oldest known human ancestor after the split of the line from that of chimpanzees. The bones were found far from most previous hominin fossil finds, however, an Australopithecus bahrelghazali mandible was found in Chad by Mamelbaye Tomalta, Najia and Alain Beauvilain, Michel Brunet and Aladji H. E. With the sexual dimorphism known to have existed in early hominins, Sahelanthropus may represent a common ancestor of humans and chimpanzees, though no consensus has been reached yet by the scientific community. The original placement of species as a human ancestor but not a chimpanzee ancestor would complicate the picture of human phylogeny. Another possibility is that Toumaï is related to humans and chimpanzees, but is the ancestor of neither. Brigitte Senut and Martin Pickford, the discoverers of Orrorin tugenensis, even if this claim is upheld the find would lose none of its significance, because at present, very few chimpanzee or gorilla ancestors have been found anywhere in Africa. Thus if S. tchadensis is a relative of the chimpanzees or gorillas. And S. tchadensis does indicate that the last common ancestor of humans and chimpanzees is unlikely to closely resemble extant chimpanzees, indeed, some researchers consider suggestions that Sahelanthropus is too early to be a human ancestor to have evaporated. Sediment isotope analysis of atoms in the fossil yielded an age of about 7 million years. In fact, Toumaï may have been reburied in the recent past, taphonomic analysis reveals the likelihood of one, perhaps two, burial
29.
Orrorin
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Orrorin tugenensis is a postulated early species of Homininae, estimated at 6.1 to 5.7 million years and discovered in 2000. It is not confirmed how Orrorin is related to modern humans and its discovery was an argument against the hypothesis that australopithecines are human ancestors, as much as it still remains the most prevalent hypothesis of human evolution as of 2012. The name of genus Orrorin means original man in Tugen, and the name of the only classified species, O. tugenensis, derives from Tugen Hills in Kenya, as of 2007,20 fossils of the species have been found. Orrorin had small teeth relative to its body size and its dentition differs from that found in Australopithecus in that its cheek teeth are smaller and less elongated mesiodistally and from Ardipithecus in that its enamel is thicker. The dentition differs from both species in the presence of a mesial groove on the upper canines. The canines are ape-like but reduced, like those found in Miocene apes, Orrorin had small post-canines and was microdont, like modern humans, whereas robust australopithecines were megadont. In the femur, the head is spherical and rotated anteriorly, the neck is elongated and oval in section, while these suggest that Orrorin was bipedal, the rest of the postcranium indicates it climbed trees. After the fossils were found in 2000, they were held at the Kipsaraman village community museum, since then, according to the Community Museums of Kenya chairman Eustace Kitonga, the fossils are stored at a secret bank vault in Nairobi. The main similarity is that the Orrorin femur is morphologically closer to that of H. sapiens than is Lucys, there is, however, some debate over this point. Other fossils found in the Lukeino Formation show that Orrorin lived in a dry evergreen forest environment, the team that found these fossils in 2000 was led by Brigitte Senut and Martin Pickford from the Muséum national dhistoire naturelle. This date is markedly different from those using the molecular clock approach. Life timeline List of human evolution fossils Martin Pickford Orrorin tugenensis - The Smithsonian Institutions Human Origins Program Human Timeline – Smithsonian, National Museum of Natural History
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Ardipithecus
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Ardipithecus is a genus of an extinct hominine that lived during Late Miocene and Early Pliocene in Afar Depression, Ethiopia. Two fossil species are described in the literature, A. ramidus, which lived about 4.4 million years ago during the early Pliocene, behavioral analysis showed that Ardipithecus could be very similar to chimpanzees, indicating that the early human ancestors were very chimpanzee-like in behaviour. A. ramidus was named in September 1994, the first fossil found was dated to 4.4 million years ago on the basis of its stratigraphic position between two volcanic strata, the basal Gaala Tuff Complex and the Daam Aatu Basaltic Tuff. The name Ardipithecus ramidus stems mostly from the Afar language, in which Ardi means ground/floor, the pithecus portion of the name is from the Greek word for ape. Like most hominids, but unlike all previously recognized hominins, it had a grasping hallux or big toe adapted for locomotion in the trees and it is not confirmed how much other features of its skeleton reflect adaptation to bipedalism on the ground as well. Like later hominins, Ardipithecus had reduced canine teeth, more fragments were recovered in 1994, amounting to 45% of the total skeleton. This fossil was described as a species of Australopithecus, but White. Between 1999 and 2003, a team led by Sileshi Semaw discovered bones. The fossils were dated to between 4.35 and 4.45 million years old, Ardipithecus ramidus had a small brain, measuring between 300 and 350 cm3. Like common chimpanzees, A. ramidus was much more prognathic than modern humans, the size of the upper canine tooth in A. ramidus males was not distinctly different from that of females. The features of the canine in A. ramidus contrast with the sexual dimorphism observed in common chimpanzees. The less pronounced nature of the canine teeth in A. ramidus has been used to infer aspects of the social behavior of the species. In particular, it has used to suggest that the last common ancestor of hominids. This is markedly different from social patterns in common chimpanzees, among which intermale, researchers in a 2009 study said that this condition compromises the living chimpanzee as a behavioral model for the ancestral hominid condition. A. ramidus existed more recently than the most recent common ancestor of humans and chimpanzees, nevertheless, it is in some ways unlike chimpanzees, suggesting that the common ancestor differs from the modern chimpanzee. After the chimpanzee and human lineages diverged, both underwent substantial evolutionary change, chimp feet are specialized for grasping trees, A. ramidus feet are better suited for walking. The canine teeth of A. ramidus are smaller, and equal in size between males and females, which suggests reduced male-to-male conflict, increased pair-bonding, and increased parental investment. Thus, fundamental reproductive and social behavioral changes probably occurred in long before they had enlarged brains and began to use stone tools
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Australopithecus
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Australopithecus is an extinct genus of hominins. During that time, a number of australopithecine species emerged, including Australopithecus afarensis, A. africanus, A. anamensis, A. bahrelghazali, A. deyiremeda, A. garhi, and A. sediba. For some hominid species of time, such as A. robustus and A. boisei. If so, they would be considered robust australopiths, while the others would be gracile australopiths, however, if these species do constitute their own genus, they may be given their own name, Paranthropus. Australopithecus species played a significant part in human evolution, the genus Homo being derived from Australopithecus at some time after three years ago. Among other things, they were the first hominids to show the presence of a gene that causes increased length and ability of neurons in the brain, the duplicated SRGAP2 gene. One of the species eventually became the Homo genus in Africa around two million years ago, and eventually modern humans, H. sapiens sapiens. Gracile australopiths shared several traits with modern apes and humans, and were widespread throughout Eastern and Northern Africa around 3.5 million years ago, the earliest evidence of fundamentally bipedal hominids can be observed at the site of Laetoli in Tanzania. This site contains hominid footprints that are similar to those of modern humans and have been dated to as old as 3.6 million years. The footprints have generally classified as australopith because that is the only form of prehuman known to have existed in that region at that time. Australopithecus anamensis, A. afarensis, and A. africanus are among the most famous of the extinct hominins, a. africanus was once considered to be ancestral to the genus Homo. However, fossils assigned to the genus Homo have been found that are older than A. africanus, thus, the genus Homo either split off from the genus Australopithecus at an earlier date, or both developed from a yet possibly unknown common ancestor independently. According to the Chimpanzee Genome Project, the human and chimpanzee lineages diverged from a common ancestor about five to six years ago. Sahelanthropus tchadensis, commonly called Toumai, is seven million years old. One theory suggests that the human and chimpanzee lineages diverged somewhat at first, the brains of most species of Australopithecus were roughly 35% of the size of a modern human brain. Most species of Australopithecus were diminutive and gracile, usually standing 1.2 to 1.4 m tall, in several variations is a considerable degree of sexual dimorphism, males being larger than females. According to one scholar, A. Furthermore, thermoregulatory models suggest that Australopithecus species were fully covered, more like chimpanzees and bonobos. Modern humans do not appear to display the same degree of sexual dimorphism as Australopithecus did, in modern populations, males are on average a mere 15% larger than females, while in Australopithecus, males could be up to 50% larger than females
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Homo habilis
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Homo habilis is a species of the tribe Hominini, during the Gelasian and early Calabrian stages of the Pleistocene period, which lived between roughly 2.1 and 1.5 million years ago. LD 350-1 is a fossil jawbone fragment discovered in 2013 which has dated to 2.8 million years ago. There has been debate regarding its placement in the genus Homo rather than the genus Australopithecus. The small size and rather primitive attributes have led experts to propose excluding H. habilis from the genus Homo. These were later classified as milk teeth, and therefore considered difficult to link to taxa unlike permanent teeth, however, in 1959, Mary Leakey recovered the cranium of a young adult which had a small brain, large face, tiny canines and massive chewing teeth. H. habilis was short and had long arms compared to modern humans, however. H. habilis had a capacity slightly less than half of the size of modern humans. Despite the ape-like morphology of the bodies, H. habilis remains are accompanied by primitive stone tools. Homo habilis has often thought to be the ancestor of the more gracile and sophisticated Homo ergaster. New findings in 2007 seemed to confirm the view that H. habilis and H. erectus coexisted, an alternative explanation would be that any ancestral relationship from H. habilis to H. erectus would have to have been cladogenetic rather than anagenetic. Its brain size has been shown to range from 550 cm3 to 687 cm3, a virtual reconstruction published in 2015 estimated the endocranial volume at between 729 and 824 ml, larger than any previously published value. H. habilis brain capacity of around 640 cm³ was on average 50% larger than australopithecines and these hominins were smaller than modern humans, on average standing no more than 1.3 m tall. A fragment of fossilized jawbone, dated to around 2.8 million years ago, was discovered in the Ledi-Geraru research area in Afar Regional State in 2013. The fossil is considered the earliest evidence of the Homo genus known to date, the individual in question lived just after a major climate shift in the region, when forests and waterways were rapidly replaced by arid savannah. One set of remains, discovered by Donald Johanson and Tim White in Olduvai Gorge in 1986, included the important upper and lower limbs, specifically the humerus. Their finding stimulated some debate at the time, locomotor affinities of OH62 have been assessed primarily on the basis of its forelimb to hind limb proportions, which are known to be associated with locomotor behavior among living primates. Initial analyses concentrated on comparisons to the Australopithecus afarensis A. L. 288-1, in most dimensions—measured or estimated—the OH62 upper limb remains equaled or exceeded those of A. L. 288-1, while its lower limb remains appeared to be smaller. In this sense, it was more ‘‘primitive than A. L. 288-1, KNM ER1813 is a relatively complete cranium which dates to 1.9 million years old, discovered at Koobi Fora, Kenya by Kamoya Kimeu in 1973
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Homo erectus
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Homo erectus is an extinct species of hominid that lived throughout most of the Pleistocene geological epoch. Its earliest fossil evidence dates to 1.9 million years ago and extends to 70,000 years ago, or, possibly, as recently as 35,000 years ago. It is generally thought that H. erectus originated in Africa and spread from there, migrating throughout Eurasia as far as Georgia, India, Sri Lanka, China, a new debate appeared in 2013, with the documentation of the Dmanisi skulls.58 million years ago. From there it migrated, in part, by 2, the fossil record shows that its development from about 1.8 mya to one mya was widely distributed, in Africa, the Transcaucasus, Indonesia, and in Vietnam, China, and India. The second hypothesis is that H. erectus evolved in Eurasia and they occupied the Dmanisi site from 1.85 million to 1.77 million years ago, which was about the same time or slightly before their earliest evidence in Africa. There are several proposed explanations of the dispersal of H. erectus georgicus—including whether or not Africa is the source), the Dutch anatomist Eugène Dubois was fascinated by Darwins theory of evolution especially as it applied to humankind. In 1886, he set out for Asia—which then was the region accepted as the cradle of evolution despite Darwins theory of African origin. In 1891, his team discovered a human fossil on the island of Java, the Java fossil from Indonesia aroused much public interest. It was dubbed by the press as Java Man, but few scientists accepted Dubois argument that his fossil was the transitional form—the so-called missing link—between apes. Java Man is now classified as Homo erectus, most of the spectacular discoveries of H. erectus next took place at the Zhoukoudian Project, now known as the Peking Man Site, in Zhoukoudian, China. This site was first discovered by Johan Gunnar Andersson in 1921 and was first excavated in 1921, canadian anatomist Davidson Blacks initial description of a lower molar as belonging to a previously unknown species prompted widely publicized interest. Extensive excavations followed, which altogether uncovered 200 human fossils from more than 40 individuals including five nearly complete skullcaps, german anatomist Franz Weidenreich provided much of the detailed description of this material in several monographs published in the journal Palaeontologica Sinica. Throughout much of the 20th century, anthropologists debated the role of H. erectus in human evolution, early in the century, due in part to the discoveries at Java and Zhoukoudian, it was widely accepted that modern humans first evolved in Asia. From the 1950s forward, numerous finds in East Africa confirmed the hypothesis of an African genesis and it is now generally accepted that H. erectus descended from either, 1) the earliest hominin genera, or 2) the earliest Homo-species. East Africa provided sympatric coexistence for H. erectus and H, in the 1950s, archaeologists John T. Robinson and Robert Broom named Telanthropus capensis, Robinson had discovered a jaw fragment in 1949 in Swartkrans, South Africa. Later, Simonetta proposed to re-designate it to Homo erectus, in 1961, Yves Coppens discovered a skull of Tchadanthropus uxoris, then the earliest fossil human discovered in north Africa. It was reported that the fossil had been so eroded by sand that it mimicked the appearance of an australopith. Although at first considered to be a specimen of H. habilis, T. uxoris is no longer considered a valid taxon, and has been subsumed into H. erectus
. PMID 16553316.
