Iran called Persia, the Islamic Republic of Iran, is a country in Western Asia. With over 81 million inhabitants, Iran is the world's 18th most populous country. Comprising a land area of 1,648,195 km2, it is the second largest country in the Middle East and the 17th largest in the world. Iran is bordered to the northwest by Armenia and the Republic of Azerbaijan, to the north by the Caspian Sea, to the northeast by Turkmenistan, to the east by Afghanistan and Pakistan, to the south by the Persian Gulf and the Gulf of Oman, to the west by Turkey and Iraq; the country's central location in Eurasia and Western Asia, its proximity to the Strait of Hormuz, give it geostrategic importance. Tehran is the country's capital and largest city, as well as its leading economic and cultural center. Iran is home to one of the world's oldest civilizations, beginning with the formation of the Elamite kingdoms in the fourth millennium BCE, it was first unified by the Iranian Medes in the seventh century BCE, reaching its greatest territorial size in the sixth century BCE, when Cyrus the Great founded the Achaemenid Empire, which stretched from Eastern Europe to the Indus Valley, becoming one of the largest empires in history.
The Iranian realm fell to Alexander the Great in the fourth century BCE and was divided into several Hellenistic states. An Iranian rebellion culminated in the establishment of the Parthian Empire, succeeded in the third century CE by the Sasanian Empire, a leading world power for the next four centuries. Arab Muslims conquered the empire in the seventh century CE; the Islamization of Iran led to the decline of Zoroastrianism, by the country's dominant religion, Iran's major contributions to art and science spread within the Muslim rule during the Islamic Golden Age. After two centuries, a period of various native Muslim dynasties began, which were conquered by the Seljuq Turks and the Ilkhanate Mongols; the rise of the Safavids in the 15th century led to the reestablishment of a unified Iranian state and national identity, with the country's conversion to Shia Islam marking a turning point in Iranian and Muslim history. Under Nader Shah, Iran was one of the most powerful states in the 18th century, though by the 19th century, a series of conflicts with the Russian Empire led to significant territorial losses.
The Iranian Constitutional Revolution in the early 20th century led to the establishment of a constitutional monarchy and the country's first legislature. A 1953 coup instigated by the United Kingdom and the United States resulted in greater autocracy and growing Western political influence. Subsequent widespread dissatisfaction and unrest against the monarchy led to the 1979 Revolution and the establishment of an Islamic republic, a political system that includes elements of a parliamentary democracy vetted and supervised by a theocracy governed by an autocratic "Supreme Leader". During the 1980s, the country was engaged in a war with Iraq, which lasted for eight years and resulted in a high number of casualties and economic losses for both sides; the sovereign state of Iran is a founding member of the UN, ECO, NAM, OIC, OPEC. It is a major regional and middle power, its large reserves of fossil fuels – which include the world's largest natural gas supply and the fourth largest proven oil reserves – exert considerable influence in international energy security and the world economy.
The country's rich cultural legacy is reflected in part by its 22 UNESCO World Heritage sites, the third largest number in Asia and 11th largest in the world. Iran is a multicultural country comprising numerous ethnic and linguistic groups, the largest being Persians, Azeris and Lurs. Organizations including Amnesty International and Human Rights Watch have criticized Iran's women's rights record; the term Iran derives directly from Middle Persian Ērān, first attested in a third-century inscription at Rustam Relief, with the accompanying Parthian inscription using the term Aryān, in reference to the Iranians. The Middle Iranian ērān and aryān are oblique plural forms of gentilic nouns ēr- and ary-, both deriving from Proto-Iranian *arya-, recognized as a derivative of Proto-Indo-European *ar-yo-, meaning "one who assembles". In the Iranian languages, the gentilic is attested as a self-identifier, included in ancient inscriptions and the literature of the Avesta, remains in other Iranian ethnic names Alan and Iron.
Iran has been referred to as Persia by the West, due to the writings of Greek historians who referred to all of Iran as Persís, meaning "land of the Persians", while Persis itself was one of the provinces of ancient Iran, today defined as Fars. As the most extensive interaction the Ancient Greeks had with any outsider was with the Persians, the term persisted long after the Greco-Persian Wars. In 1935, Reza Shah requested the international community to refer to the country by its native name, effective March 22 that year; as The New York Times explained at the time, "At the suggestion of the Persian Legation in Berlin, the Tehran government, on the Persian New Year, March 21, 1935, substituted Iran for Persia as the official name of the country." Opposition to the name change led to the reversal of the decision, Professor Ehsan Yarshater, editor of Encyclopædia Iranica, propagated a move to use Persia and Iran interchangeably. Today, both Iran and Persia are used in cultural contexts, while Iran remains irreplaceab
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago. Reverse genetic engineering and the fossil record both demonstrate that birds are modern feathered dinosaurs, having evolved from earlier theropods during the late Jurassic Period; as such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event 66 million years ago. Dinosaurs can therefore be divided into birds; this article deals with non-avian dinosaurs. Dinosaurs are a varied group of animals from taxonomic and ecological standpoints. Birds, at over 10,000 living species, are the most diverse group of vertebrates besides perciform fish. Using fossil evidence, paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs.
Dinosaurs are represented on every continent by fossil remains. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded. Most research conducted since the 1970s, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction; some were herbivorous, others carnivorous. Evidence suggests that egg-laying and nest-building are additional traits shared by all dinosaurs and non-avian alike. While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, some were able to shift between these stances. Elaborate display structures such as horns or crests are common to all dinosaur groups, some extinct groups developed skeletal modifications such as bony armor and spines. While the dinosaurs' modern-day surviving avian lineage are small due to the constraints of flight, many prehistoric dinosaurs were large-bodied—the largest sauropod dinosaurs are estimated to have reached lengths of 39.7 meters and heights of 18 meters and were the largest land animals of all time.
Still, the idea that non-avian dinosaurs were uniformly gigantic is a misconception based in part on preservation bias, as large, sturdy bones are more to last until they are fossilized. Many dinosaurs were quite small: Xixianykus, for example, was only about 50 cm long. Since the first dinosaur fossils were recognized in the early 19th century, mounted fossil dinosaur skeletons have been major attractions at museums around the world, dinosaurs have become an enduring part of world culture; the large sizes of some dinosaur groups, as well as their monstrous and fantastic nature, have ensured dinosaurs' regular appearance in best-selling books and films, such as Jurassic Park. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, new discoveries are covered by the media; the taxon'Dinosauria' was formally named in 1841 by paleontologist Sir Richard Owen, who used it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were being recognized in England and around the world.
The term is derived from Ancient Greek δεινός, meaning'terrible, potent or fearfully great', σαῦρος, meaning'lizard or reptile'. Though the taxonomic name has been interpreted as a reference to dinosaurs' teeth and other fearsome characteristics, Owen intended it to evoke their size and majesty. Other prehistoric animals, including pterosaurs, ichthyosaurs and Dimetrodon, while popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs. Pterosaurs are distantly related to dinosaurs; the other groups mentioned are, like dinosaurs and pterosaurs, members of Sauropsida, except Dimetrodon. Under phylogenetic nomenclature, dinosaurs are defined as the group consisting of the most recent common ancestor of Triceratops and Neornithes, all its descendants, it has been suggested that Dinosauria be defined with respect to the MRCA of Megalosaurus and Iguanodon, because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions result in the same set of animals being defined as dinosaurs: "Dinosauria = Ornithischia + Saurischia", encompassing ankylosaurians, ceratopsians, ornithopods and sauropodomorphs.
Birds are now recognized as being the sole surviving lineage of theropod dinosaurs. In traditional taxonomy, birds were considered a separate class that had evolved from dinosaurs, a distinct superorder. However, a majority of contemporary paleontologists concerned with dinosaurs reject the traditional style of classification in favor of phylogenetic taxonomy. Birds are thus considered to be dinosaurs and dinosaurs are, not extinct. Birds are classified as belonging to the subgroup M
A qanat or kariz is a sloping underground channel to transport water from an aquifer or water well to surface for irrigation and drinking, acting as an underground aqueduct. This is an old system of water supply from a deep well with a series of vertical access shafts; the qanats still create a reliable supply of water for human settlements and irrigation in hot and semi-arid climates, but the value of this system is directly related to the quality and regularity of the water flow. Traditionally qanats are built by a group of muqannīs, with hand labor; the profession paid well and was handed down from father to son. According to most sources, the qanat technology was developed in ancient Iran by the Persian people sometime in the early 1st millennium BC, spread from there westward and eastward. However, some other sources suggest a Southeast Arabian origin. Common variants of qanat in English include kanat, kunut, konait, ghundat. Qanāh is an Arabic word that means "channel". In Persian, the words for "qanat" are kārīz, is derived from earlier word kāhrēz.
The word qanāt is used in Persian. Other names for qanat include kahan, kahriz/kəhriz. Alternative terms for qanats in Asia and North Africa are kakuriz, chin-avulz, mayun. Traditionally it is recognized that the qanat technology was invented in ancient Iran sometime in the early 1st millennium BC, spread from there westward and eastward. Accordingly some sources state qanats were invented in Iran before 1000 BC and as far back as 3000 BC; the qanats of Gonabad have been estimated to be nearly 2700 years old. In 2002, archaeologist Walid Yasin Al Tikriti provided a counterpoint that the qanat did not originate in Persia; as evidence, he noted seven Iron Age aflaj discovered in the Al Ain area of the UAE which were dated back to the first millennium BCE based on sherds, pottery and architecture. Tikriti pointed to excavations in Sharjah, by the French archaeological team working there, as well as a German team working in Oman of possible Iron age aflaj, he concludes that the technology originated in South East Arabia and was taken to Persia by the Sasanian conquest of the Oman peninsular.
In 2013, Boualem Remini and Bachir Achour, stated that the origin of the qanat technology is uncertain, yet confirmed the technology was in use in northwest Iran c.1000 BCE. In 2016, Rémy Boucharlat in his paper Qanāt and Falaj: Polycentric and Multi-Period Innovations Iran and the United Arab Emirates as Case Studies, asserted that the attribution of the technology to Iranians in the early first millennium BCE is a position that cannot longer be maintained. Whereas Boucharlat contends archeological evidence indicates a polycentric innovation as opposed to a radial diffusion. "In arid and semi-arid regions, owing to high evaporation, transportation routes were in the form of ganats, which lead groundwater to consumption areas along underground tunnels. In the long run, the qanat system is not only economical but sustainable for irrigation and agricultural purposes... The ground water flow was known to depend on grain size of sediments, therefore, the tunnels in qanats are filled in with coarser material than the surrounding hose geological formations.
The qanats are constructed along the valleys where Quartenary sediments are deposited." The original ancient engineered design of the Qanat and its multiple aligned bore-holes are thought to have controlled desert endorheic basin flooding without destroying the salt mirror playa or causing erosion of the flat evaporation fields. The Qanat water was needed to extract salt, rather than for simple domestic irrigation. Additionally considerable quantities of subsoil brines existing in such basin water tables would ensure brine supplies, as is demonstrated by the new potash plants in the Tarim basin using the ancient Qanat technology; the surface crust of an inland Sabkha endorheic basin is made up of layers of salts that have re-crystallized and settled or precipitated during the evaporation process of controlled Qanat system flood waters. Leached salts dissolve in a desert endorheic basin, over a short intensely hot period, the process of re-crystallizing the salts can produce purer and more concentrated, layered playa cakes.
The dissolved salts leached out of the underlying layers in such vast desert basin flats, are intermittently precipitated back onto the basin surface, predominantly sodium chloride crystals, one after the other. It is thought that the many Qanat systems in the Taklamakan desert basin were built to produce and trade salt along the Silk Road; the position of the Silk Road skirting these endorheic basins may well have resulted due to efficient and pure salt leaching technique still producing salt cake crust in similar deserts. Qanats are constructed as a series of well-like vertical shafts, connected by sloping tunnels. Qanats efficiently deliver large amounts of subterranean water to the surface without need for pumping; the water drains by gravity from an upland aquifer, with the destination lower than the source. Qanats allow water to be transported over long distances in hot dry climates without much water loss to evaporation; the qanat should not be confused with the spring-flow tunnel typical to the mountainous area around Jerusalem.
Although both are excavated tunnels designed to extract water by gravity flow, there are crucial differences. Firstly, the origin of the qanat was a well, turned into an artificial spring. In con
Yazd also known as Yezd, is the capital of Yazd Province, Iran. The city is located 270 km southeast of Esfahan. At the 2011 census, the population was 529,673, it is 15th largest city in Iran. Since 2017, the historical city of Yazd is recognized as a World Heritage Site by UNESCO; because of generations of adaptations to its desert surroundings, Yazd has a unique Persian architecture. It is nicknamed the "City of Windcatchers" from its many examples, it is very well known for its Zoroastrian fire temples, ab anbars, yakhchals, Persian handicrafts, handwoven cloth, silk weaving, Persian Cotton Candy, its time-honored confectioneries. Yazd is known as City of Bicycles, because of its old history of bike riders, the highest amount of bicycle per capita in Iran, it is reported that bicycle culture is entered and developed from Yazd, in contacting with the European visitors and tourists in the last century. The name is derived from a Sassanid ruler of Persia; the city was a Zoroastrian center during Sassanid times.
The word yazd means God. After the Arab conquest of Iran, many Zoroastrians migrated to Yazd from neighboring provinces. By paying a levy, Yazd was allowed to remain Zoroastrian after its conquest, Islam only became the dominant religion in the city; because of its remote desert location and the difficulty of access, Yazd remained immune to large battles and the destruction and ravages of war. For instance, it was a haven for those fleeing from destruction in other parts of Persian Empire during the Mongol invasion. In 1272 it was visited by Marco Polo. In the book The Travels of Marco Polo, he described Yazd in the following way: It is a good and noble city, has a great amount of trade, they weave there quantities of a certain silk tissue known as Yasdi, which merchants carry into many quarters to dispose of. When you leave this city to travel further, you ride for seven days over great plains, finding harbour to receive you at three places only. There are many fine woods producing dates upon the way, such as one can ride through.
There are wild asses, handsome creatures. At the end of those seven marches over the plain, you come to a fine kingdom, called Kerman. Yazd served as the capital of the Muzaffarid Dynasty in the fourteenth century, was unsuccessfully besieged in 1350–1351 by the Injuids under Shaikh Abu Ishaq; the Friday mosque, arguably the city's greatest architectural landmark, as well as other important buildings, date to this period. During the Qajar dynasty it was ruled by the Bakhtiari Khans. Under the rule of the Safavid, some people migrated from Yazd and settled in an area, today on the Iran-Afghanistan border; the settlement, named Yazdi, was located in what is now Farah City in the province of the same name in Afghanistan. Today, people from this area speak with an accent similar to that of the people of Yazd. One of the notable things about Yazd is its family-centered culture. According to official statistics from Iran's National Organization for Civil Registration, Yazd is among the three cities with the lowest divorce rates in Iran.
The majority of the people of Yazd are Persians, they speak Persian with Yazdi accent different from Persian accent of Tehran. The majority of people in Yazd are Muslims. There is a sizable population of Zoroastrians in the city. In 2013, Sepanta Niknam was elected to the city council of Yazd and became the first Zoroastrian councillor in Iran. There was once a large Jewish-Yazdi community, after the creation of Israel, many have moved there for varying reasons. Former president of Israel Moshe Katsav is an example; the Pir-e-Naraki sanctuary is one the important pilgrimage destinations for Zoroastrians where an annual congregation is held and frequent visits are made during the year. The story of the last Persian prince to come to Yazd before the arrival of Islam adds to its importance; such a transformation has occurred several times. Several other city traditions are the Muslim parades and gatherings, which are processions called azadari held to commemorate the events experienced by the main Islamic martyrs and other important figures.
These huge public gatherings created a series of spaces which, since most are near important urban monuments, are used at other times as hubs from which visitors can tour the main spots in the city. According to the Iranian Census of 2011 the population of Yazd is 486,152 people from 168,528 families, which includes 297,546 men and 285,136 women. Yazd is an important centre of Persian architecture; because of its climate, it has one of the largest networks of qanats in the world, Yazdi qanat makers are considered the most skilled in Iran. To deal with the hot summers, many old buildings in Yazd have magnificent wind towers and large underground areas; the city is home to prime examples of yakhchals, which were used to store ice retrieved from glaciers in the nearby mountains. Yazd is one of the largest cities built entirely out of adobe. Yazd's heritage as a center of Zoroastrianism is important. There is a Tower of Silence on the outskirts, the city has an ateshkadeh which holds a fire, kept alight continuously since 470 AD.
Zoroastrians make up a significant minority of the population, around 2
2003 Bam earthquake
The 2003 Bam earthquake struck the Kerman province of southeastern Iran at 01:56 UTC on December 26. The shock had a moment magnitude of 6.6 and a maximum Mercalli intensity of IX. The earthquake was destructive in Bam, with the death toll amounting to at least 26,271 people and injuring up to 30,000; the effects of the earthquake were exacerbated by the use of mud brick as the standard construction medium. Following the earthquake the U. S. offered direct humanitarian assistance to Iran and in return the state promised to comply with an agreement with the International Atomic Energy Agency which supports greater monitoring of its nuclear interests. In total a reported 44 countries sent in personnel to assist in relief operations and 60 countries offered assistance. Following the earthquake, the Iranian government considered moving the capital of Tehran in fear of an earthquake occurring there; the earthquake had a psychological impact on many of the victims for years afterwards. A new institutional framework in Iran was established to address problems of urban planning and to reconstruct the city of Bam in compliance with strict seismic regulations.
This process marked a turning point, as government ministers and international organizations collaborated under this framework with local engineers and local people to organize the systematic rebuilding of the city. Before the earthquake, Bam had a population of 97,000, it is one of the most popular tourism areas of Iran, one of its most popular attractions being its 2000-year-old mud-brick Bam Citadel. During the Safavid dynasty Bam was a large trading hub due to its location on the Silk Road, it declined in significance after the Afghans invaded in 1722, serving as an army camp until its abandonment in 1932. The city became a tourist attraction in 1953. There is little earthquake education in Iran although the International Institute of Earthquake Engineering and Seismology established a Public Education Department in 1990 to improve "the safety and preparedness culture against the earthquake among all groups of the society". In October 2003, Bahram Akasheh, professor of geophysics at Tehran University, called the effects of public ignorance about earthquakes "poisonous".
Iran suffers from frequent earthquakes, with minor quakes occurring daily. This earthquake occurred as a result of stresses generated by movement of one tectonic plate, the Arabian plate, moving northward against another, the Eurasian plate, at 3 centimetres per year; the Earth's crust deforms in response to the plate motion in a broad zone spanning the width of Iran and extending north into Turkmenistan. Earthquakes occur as the result of reverse faulting and strike-slip faulting in the zone of deformation; the preliminary analysis of the pattern of seismic-waves radiating from December 26, 2003 earthquake was consistent with the earthquake having been caused by right-lateral strike-slip motion on a north-south oriented fault. The earthquake occurred in a region within which major north-south, right-lateral, strike-slip faults had been mapped, the epicenter is near the mapped, north-south oriented Bam Fault. However, field investigations will be necessary to find if the earthquake occurred on the Bam Fault or on another.
The Bam earthquake is 100 kilometres south of the destructive earthquakes of June 11, 1981 and July 28, 1981. These earthquakes were caused by a combination of reverse-motion and strike-slip motion on the north-south oriented Gowk fault; the rupture length of the earthquake was estimated to be around 24 kilometers. More than half of the quake was produced from its southern segment of 13 kilometres, where the slip reached a maximum of up to 270 centimetres resulting in a large stress drop of at least 6 MPa. Optical remote sensing data shows that the Bam fault is not a single fault but consists of a 4–5 km wide fault system with the main branch running between the cities of Bam and Baravat; the fault ruptured by the Bam earthquake is believed to stretch the along northwest branch of this fault system from Bam southward. Based on these results, scientists suggest that the Bam earthquake ruptured a hidden fault and that in this process an unusually strong asperity was involved, causing the widespread devastation of the tremor.
The quake occurred at 01:56 UTC on December 26, 2003. Its epicenter was 10 kilometres southwest of the ancient city of Bam. Maximum intensities were at Bam and Baravat, with the most damage concentrated within the 16 kilometres radius around the city. At least 26,271 people were 30,000 injured. In terms of human loss the quake was the worst to occur in Iranian history; the BBC reported. Eleven-thousand students were killed and 1/5 of the 5,400 local teaching staff were also; this caused a significant problem for the local education system. Up to ninety percent of buildings and infrastructure in the Bam area were either damaged or destroyed, with 70% of houses being destroyed, plus 70–90% of Bam's residential areas; this left an estimated 100,000 homeless. Not a single house was standing in Baravat. An important regional center during the 16th and 17th centuries, Bam contained many buildings that were not constructed to survive such ruptures. Many houses in Bam were homemade, its owners did not use skilled labor or proper building materials to resist earthquakes in the construction.
These were oft
Phoenix dactylifera known as date or date palm, is a flowering plant species in the palm family, cultivated for its edible sweet fruit. Although its exact place of origin is uncertain because of long cultivation, it originated from the Fertile Crescent region straddling between Egypt and Mesopotamia; the species is cultivated across Northern Africa, the Middle East, The Horn of Africa and South Asia, is naturalized in many tropical and subtropical regions worldwide. P. dactylifera is the type species of genus Phoenix, which contains 12–19 species of wild date palms, is the major source of commercial production. Date trees reach about 21–23 metres in height, growing singly or forming a clump with several stems from a single root system. Date fruits are oval-cylindrical, 3–7 cm long, about an inch in diameter, ranging from bright red to bright yellow in color, depending on variety, they are sweet, containing about 75 percent of sugar when dried. Dates have been the Indus Valley for thousands of years.
There is archaeological evidence of date cultivation in Arabia from the 6th millennium BCE. The total annual world production of dates amounts to 8.5 million metric tons, countries of the Middle East and North Africa being the largest producers. The species name dactylifera "date-bearing" comes from the Greek words daktylos, which means "date", fero, which means "I bear"; the fruit is known as a date. The fruit's English name, as well as the Latin both come from the Greek word for "finger", dáktulos, because of the fruit's elongated shape. Fossil records show. Dates have been the Indus Valley for thousands of years. There is archaeological evidence of date cultivation in eastern Arabia between 5530 and 5320 calBC, they are believed to have originated around what is now Iraq, have been cultivated since ancient times from Mesopotamia to prehistoric Egypt. The Ancient Egyptians used the fruits to make date wine, ate them at harvest. There is archeological evidence of date cultivation in Mehrgarh around 7000 BCE, a Neolithic civilization in what is now western Pakistan.
Evidence of cultivation is continually found throughout civilizations in the Indus Valley, including the Harappan period 2600 to 1900 BCE. In Ancient Rome the palm fronds used in triumphal processions to symbolize victory were most those of Phoenix dactylifera; the date palm was a popular garden plant in Roman peristyle gardens, though it would not bear fruit in the more temperate climate of Italy. It is recognizable in frescoes from Pompeii and elsewhere in Italy, including a garden scene from the House of the Wedding of Alexander. In times, traders spread dates around South West Asia, northern Africa, Spain. Dates were introduced into Mexico and California by the Spaniards in 1765, around Mission San Ignacio. A date palm cultivar what used to be called Judean date palm, is renowned for its long-lived orthodox seed, which sprouted after accidental storage for 2000 years; the upper survival time limit of properly stored. A genomic study from New York University Abu Dhabi Center for Genomics and Systems Biology showed that domesticated date palm varieties from North Africa, including well-known varieties such as Medjool and Deglet Noor, are a hybrid between Middle East date palms and the Cretan wild palm P. theophrasti.
Date palms appear in the archaeological record in North Africa about 2,800 years ago, suggesting that the hybrid was spread by the Minoans or Phoenicians. Date trees reach about 21–23 metres in height, growing singly or forming a clump with several stems from a single root system; the leaves are 4–6 metres long, with spines on the petiole, pinnate, with about 150 leaflets. The leaflets are 2 cm wide; the full span of the crown ranges from 6–10 m. The date palm is dioecious, having separate female plants, they can be grown from seed, but only 50% of seedlings will be female and hence fruit bearing, dates from seedling plants are smaller and of poorer quality. Most commercial plantations thus use cuttings of cropping cultivars. Plants grown from cuttings will fruit 2–3 years earlier than seedling plants. Dates are wind pollinated, but in both traditional oasis horticulture and in the modern commercial orchards they are pollinated manually. Natural pollination occurs with about an equal number of female plants.
However, with assistance, one male can pollinate up to 100 females. Since the males are of value only as pollinators, this allows the growers to use their resources for many more fruit-producing female plants; some growers do not maintain any male plants, as male flowers become available at local markets at pollination time. Manual pollination is done by use of a wind machine. In some areas such as Iraq the pollinator climbs the tree using a special climbing tool that wraps around the tree trunk and the climber's back to keep him attached to the trunk while climbing. Date fruits are oval-cylindrical, 3–7 cm long, 2–3 cm diameter, when ripe, range from bright red to bright yellow in colour, depending on variety. Dates contain a single stone about 2 -- 6 -- 8 mm thick. Three main cultivar groups of date exist: soft, semi-dry, dry; the type of fruit depends on the gluc
A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, petrified wood, coal, DNA remnants; the totality of fossils is known as the fossil record. Paleontology is the study of fossils: their age, method of formation, evolutionary significance. Specimens are considered to be fossils if they are over 10,000 years old; the oldest fossils are around 3.48 billion years old to 4.1 billion years old. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils; the development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolute ages of rocks and the fossils they host. There are many processes that lead to fossilization, including permineralization and molds, authigenic mineralization and recrystallization, adpression and bioimmuration.
Fossils vary in size from one-micrometre bacteria to dinosaurs and trees, many meters long and weighing many tons. A fossil preserves only a portion of the deceased organism that portion, mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates. Fossils may consist of the marks left behind by the organism while it was alive, such as animal tracks or feces; these types of fossil are called trace ichnofossils, as opposed to body fossils. Some fossils are called chemofossils or biosignatures; the process of fossilization varies according to external conditions. Permineralization is a process of fossilization; the empty spaces within an organism become filled with mineral-rich groundwater. Minerals precipitate from the groundwater; this process can occur in small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce detailed fossils. For permineralization to occur, the organism must become covered by sediment soon after death, otherwise decay commences.
The degree to which the remains are decayed when covered determines the details of the fossil. Some fossils consist only of skeletal teeth; this is a form of diagenesis. In some cases, the original remains of the organism dissolve or are otherwise destroyed; the remaining organism-shaped hole in the rock is called an external mold. If this hole is filled with other minerals, it is a cast. An endocast, or internal mold, is formed when sediments or minerals fill the internal cavity of an organism, such as the inside of a bivalve or snail or the hollow of a skull; this is a special form of mold formation. If the chemistry is right, the organism can act as a nucleus for the precipitation of minerals such as siderite, resulting in a nodule forming around it. If this happens before significant decay to the organic tissue fine three-dimensional morphological detail can be preserved. Nodules from the Carboniferous Mazon Creek fossil beds of Illinois, USA, are among the best documented examples of such mineralization.
Replacement occurs. In some cases mineral replacement of the original shell occurs so and at such fine scales that microstructural features are preserved despite the total loss of original material. A shell is said to be recrystallized when the original skeletal compounds are still present but in a different crystal form, as from aragonite to calcite. Compression fossils, such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues. In this case the fossil consists of original material, albeit in a geochemically altered state; this chemical change is an expression of diagenesis. What remains is a carbonaceous film known as a phytoleim, in which case the fossil is known as a compression. However, the phytoleim is lost and all that remains is an impression of the organism in the rock—an impression fossil. In many cases, however and impressions occur together. For instance, when the rock is broken open, the phytoleim will be attached to one part, whereas the counterpart will just be an impression.
For this reason, one term covers the two modes of preservation: adpression. Because of their antiquity, an unexpected exception to the alteration of an organism's tissues by chemical reduction of the complex organic molecules during fossilization has been the discovery of soft tissue in dinosaur fossils, including blood vessels, the isolation of proteins and evidence for DNA fragments. In 2014, Mary Schweitzer and her colleagues reported the presence of iron particles associated with soft tissues recovered from dinosaur fossils. Based on various experiments that studied the interaction of iron in haemoglobin with blood vessel tissue they proposed that solution hypoxia coupled with iron chelation enhances the stability and preservation of soft tissue and provides the basis for an explanation for the unforeseen preservation of fossil soft tissues. However, a older study based on eight taxa ranging in time from the Devonian to the Jurassic found that reasonably well-preserved fibrils that represent collagen were preser