In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, sleet, snow and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates", thus and mist are not precipitation but suspensions, because the water vapor does not condense sufficiently to precipitate. Two processes acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called "showers."Moisture, lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into clouds and rain. This process is active when freezing rain occurs. A stationary front is present near the area of freezing rain and serves as the foci for forcing and rising air.
Provided necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely stratus and cumulonimbus. The cloud droplets will grow large enough to form raindrops and descend toward the Earth where they will freeze on contact with exposed objects. Where warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow is possible within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. Most precipitation is caused by convection; the movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah climes.
Precipitation is a major component of the water cycle, is responsible for depositing the fresh water on the planet. 505,000 cubic kilometres of water falls as precipitation each year. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres, but over land it is only 715 millimetres. Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Precipitation may occur on other celestial bodies, e.g. when it gets cold, Mars has precipitation which most takes the form of frost, rather than rain or snow. Precipitation is a major component of the water cycle, is responsible for depositing most of the fresh water on the planet. 505,000 km3 of water falls as precipitation each year, 398,000 km3 of it over the oceans. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres. Mechanisms of producing precipitation include convective and orographic rainfall.
Convective processes involve strong vertical motions that can cause the overturning of the atmosphere in that location within an hour and cause heavy precipitation, while stratiform processes involve weaker upward motions and less intense precipitation. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Mixtures of different types of precipitation, including types in different categories, can fall simultaneously. Liquid forms of precipitation include drizzle. Rain or drizzle that freezes on contact within a subfreezing air mass is called "freezing rain" or "freezing drizzle". Frozen forms of precipitation include snow, ice needles, ice pellets and graupel; the dew point is the temperature to which a parcel must be cooled in order to become saturated, condenses to water. Water vapor begins to condense on condensation nuclei such as dust and salt in order to form clouds. An elevated portion of a frontal zone forces broad areas of lift, which form clouds decks such as altostratus or cirrostratus.
Stratus is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. It can form due to the lifting of advection fog during breezy conditions. There are four main mechanisms for cooling the air to its dew point: adiabatic cooling, conductive cooling, radiational cooling, evaporative cooling. Adiabatic cooling occurs when air expands; the air can rise due to convection, large-scale atmospheric motions, or a physical barrier such as a mountain. Conductive cooling occurs when the air comes into contact with a colder surface by being blown from one surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to the emission of infrared radiation, either by the air or by the surface underneath. Evaporative cooling occurs when moisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature, or until it reaches saturation; the main ways water vapor is added to the air are: wind convergence into areas of upward motion, precipitation or virga falling from above, daytime heating evaporating water from the surface of oceans, water bodies or wet lan
In earth science, erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust, transports it to another location. This natural process is caused by the dynamic activity of erosive agents, that is, ice, air, plants and humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind erosion, zoogenic erosion, anthropogenic erosion; the particulate breakdown of rock or soil into clastic sediment is referred to as physical or mechanical erosion. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Natural rates of erosion are controlled by the action of geological weathering geomorphic drivers, such as rainfall; the rates at which such processes act control. Physical erosion proceeds fastest on steeply sloping surfaces, rates may be sensitive to some climatically-controlled properties including amounts of water supplied, wind speed, wave fetch, or atmospheric temperature.
Feedbacks are possible between rates of erosion and the amount of eroded material, carried by, for example, a river or glacier. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, which control the arrival and emplacement of material at a new location. While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the natural rate of erosion in the region. Excessive erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses.
Water and wind erosion are the two primary causes of land degradation. Intensive agriculture, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion. However, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, the surface runoff which may result from rainfall, produces four main types of soil erosion: splash erosion, sheet erosion, rill erosion, gully erosion. Splash erosion is seen as the first and least severe stage in the soil erosion process, followed by sheet erosion rill erosion and gully erosion. In splash erosion, the impact of a falling raindrop creates a small crater in the soil, ejecting soil particles; the distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rainfall rate is greater than the rate at which water can infiltrate into the soil, surface runoff occurs.
If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope. Sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes. Where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are of the order of a few centimetres or less and along-channel slopes may be quite steep; this means that rills exhibit hydraulic physics different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when runoff water accumulates and flows in narrow channels during or after heavy rains or melting snow, removing soil to a considerable depth. Valley or stream erosion occurs with continued water flow along a linear feature; the erosion is both downward, deepening the valley, headward, extending the valley into the hillside, creating head cuts and steep banks.
In the earliest stage of stream erosion, the erosive activity is dominantly vertical, the valleys have a typical V cross-section and the stream gradient is steep. When some base level is reached, the erosive activity switches to lateral erosion, which widens the valley floor and creates a narrow floodplain; the stream gradient becomes nearly flat, lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion, by far the most erosion occurs during times of flood when more and faster-moving water is available to carry a larger sediment load. In such processes, it is not the water alone
A documentary film is a nonfictional motion picture intended to document some aspect of reality for the purposes of instruction, education, or maintaining a historical record. "Documentary" has been described as a "filmmaking practice, a cinematic tradition, mode of audience reception", continually evolving and is without clear boundaries. Documentary films were called'actuality' films and were only a minute or less in length. Over time documentaries have evolved to be longer in length and to include more categories, such as educational and even'docufiction'. Documentaries are educational and used in schools to teach various principles. Social media platforms such as YouTube, have allowed documentary films to improve the ways the films are distributed and able to educate and broaden the reach of people who receive the information. Polish writer and filmmaker Bolesław Matuszewski was among those who identified the mode of documentary film, he wrote two of the earliest texts on cinema Une nouvelle source de l'histoire and La photographie animée.
Both were published in 1898 in French and among the early written works to consider the historical and documentary value of the film. Matuszewski is among the first filmmakers to propose the creation of a Film Archive to collect and keep safe visual materials. In popular myth, the word documentary was coined by Scottish documentary filmmaker John Grierson in his review of Robert Flaherty's film Moana, published in the New York Sun on 8 February 1926, written by "The Moviegoer". Grierson's principles of documentary were that cinema's potential for observing life could be exploited in a new art form. In this regard, Grierson's definition of documentary as "creative treatment of actuality" has gained some acceptance, with this position at variance with Soviet film-maker Dziga Vertov's provocation to present "life as it is" and "life caught unawares"; the American film critic Pare Lorentz defines a documentary film as "a factual film, dramatic." Others further state that a documentary stands out from the other types of non-fiction films for providing an opinion, a specific message, along with the facts it presents.
Documentary practice is the complex process of creating documentary projects. It refers to what people do with media devices, content and production strategies in order to address the creative and conceptual problems and choices that arise as they make documentaries. Documentary filmmaking can be used as a form of advocacy, or personal expression. Early film was dominated by the novelty of showing an event, they were single-shot moments captured on film: a train entering a station, a boat docking, or factory workers leaving work. These short films were called "actuality" films. Many of the first films, such as those made by Auguste and Louis Lumière, were a minute or less in length, due to technological limitations. Films showing many people were made for commercial reasons: the people being filmed were eager to see, for payment, the film showing them. One notable film clocked in at over an hour and The Corbett-Fitzsimmons Fight. Using pioneering film-looping technology, Enoch J. Rector presented the entirety of a famous 1897 prize-fight on cinema screens across the United States.
In May 1896, Bolesław Matuszewski recorded on film few surigical operations in Warsaw and Saint Petersburg hospitals. In 1898, French surgeon Eugène-Louis Doyen invited Bolesław Matuszewski and Clément Maurice and proposed them to recorded his surigical operations, they started in Paris a series of surgical films sometime before July 1898. Until 1906, the year of his last film, Doyen recorded more than 60 operations. Doyen said that his first films taught him how to correct professional errors he had been unaware of. For scientific purposes, after 1906, Doyen combined 15 of his films into three compilations, two of which survive, the six-film series Extirpation des tumeurs encapsulées, the four-film Les Opérations sur la cavité crânienne; these and five other of Doyen's films survive. Between July 1898 and 1901, the Romanian professor Gheorghe Marinescu made several science films in his neurology clinic in Bucharest: Walking Troubles of Organic Hemiplegy, The Walking Troubles of Organic Paraplegies, A Case of Hysteric Hemiplegy Healed Through Hypnosis, The Walking Troubles of Progressive Locomotion Ataxy, Illnesses of the Muscles.
All these short films have been preserved. The professor called his works "studies with the help of the cinematograph," and published the results, along with several consecutive frames, in issues of "La Semaine Médicale" magazine from Paris, between 1899 and 1902. In 1924, Auguste Lumiere recognized the merits of Marinescu's science films: "I've seen your scientific reports about the usage of the cinematograph in studies of nervous illnesses, when I was still receiving "La Semaine Médicale," but back I had other concerns, which left me no spare time to begin biological studies. I must say I am thankful to you that you reminded them to me. Not many scientists have followed your way." Travelogue films were popular in the early part of the 20th century. They were referred to by distributors as "scenics." Scenics were among the most popu
Moldova the Republic of Moldova, is a landlocked country in Eastern Europe, bordered by Romania to the west and Ukraine to the north and south. The capital city is Chișinău. Most of the Moldovan territory was a part of the Principality of Moldavia from the 14th century until 1812, when it was ceded to the Russian Empire by the Ottoman Empire and became known as Bessarabia. In 1856, southern Bessarabia was returned to Moldavia, which three years united with Wallachia to form Romania, but Russian rule was restored over the whole of the region in 1878. During the 1917 Russian Revolution, Bessarabia became autonomous and the independent Moldavian Democratic Republic until it was integrated into Romania in 1918 following a vote of its assembly; the decision was disputed by Soviet Russia, which in 1924 allowed the establishment, within the Ukrainian SSR, of a Moldavian autonomous republic on partial Moldovan-inhabited territories to the east of the Dniester. In 1940, as a consequence of the Molotov–Ribbentrop Pact, Romania was compelled to cede Bessarabia to the Soviet Union, leading to the creation of the Moldavian Soviet Socialist Republic, which included the greater part of Bessarabia and the westernmost strip of the former MASSR.
On 27 August 1991, as the dissolution of the Soviet Union was under way, the Moldavian SSR declared independence and took the name Moldova. The Constitution of Moldova was adopted in 1994; the strip of the Moldovan territory on the east bank of the Dniester river has been under the de facto control of the breakaway government of Transnistria since 1990. Due to a decrease in industrial and agricultural output following the dissolution of the Soviet Union, the service sector has grown to dominate Moldova's economy and is over 60% of the nation's GDP, its economy is the poorest in Europe in per capita terms and has the lowest Human Development Index in the continent. Moldova is the least visited country in Europe by tourists with only 11,000 annually recorded visitors from abroad. Moldova is a parliamentary republic with a president as head of state and a prime minister as head of government, it is a member state of the United Nations, the Council of Europe, the World Trade Organization, the Organization for Security and Cooperation in Europe, the GUAM Organization for Democracy and Economic Development, the Commonwealth of Independent States and the Organization of the Black Sea Economic Cooperation and aspires to join the European Union.
The name "Moldova" is derived from the Moldova River. The origin of the name of the river remains unclear. According to a legend recounted by Moldavian chroniclers Dimitrie Cantemir and Grigore Ureche, Prince Dragoș named the river after hunting an aurochs: following the chase, the prince's exhausted hound Molda drowned in the river; the dog's name, given to the river, extended to the Principality. For a short time in the 1990s, at the founding of the Commonwealth of Independent States, the name of the current Republic of Moldova was spelled "Moldavia". After the dissolution of the Soviet Union, the country began to use Moldova; the name Republic of Moldova is designated by the United Nations. The prehistory of Moldova covers the period from the Upper Paleolithic which begins with the presence of Homo sapiens in the area of Southeastern Europe some 44,000 years ago and extends into the appearance of the first written records in Classical Antiquity in Greece. In 2010 N. K. Anisjutkin discovered Oldowan flint tools at Bayraki.
During the Neolithic stone-age era, Moldova's territory stood at the centre of the large Cucuteni–Trypillia culture that stretched east beyond the Dniester River in Ukraine and west up to and beyond the Carpathian Mountains in Romania. The people of this civilization, which lasted from 5500 to 2750 BC, practised agriculture, raised livestock and made intricately-designed pottery. In antiquity, Moldova's territory was inhabited by Dacian tribes. Between the 1st and 7th centuries AD, the south was intermittently under the Roman, Byzantine Empires. Due to its strategic location on a route between Asia and Europe, the territory of modern Moldova was invaded many times in late antiquity and the early Middle Ages, including by Goths, Avars, Magyars, Cumans and Tatars. Friar William of Rubruck, who visited the court of the Great Khan in the 1250s, listed "the Blac", or Vlachs, among the peoples who paid tribute to the Mongols, but the Vlachs' territory is uncertain. Rubruck described "Blakia" as "Assan's territory" south of the Lower Danube, showing that he identified it with the northern regions of the Second Bulgarian Empire.
The Bolohoveni, a Vlach population, is mentioned by the Hypatian Chronicle in the 13th century. The chronicle shows that this land is bordered on the principalities of Halych and Kiev. Archaeological research identified the location of 13th-century fortified settlements in this region. Alexandru V. Boldur identified Voscodavie, Voloscovti, Volcovti and their other towns and villages between the middle course of the rivers Nistru/Dniester and Nipru/Dnieper; the Bolohoveni disappeared from chronicles after their defeat in 1257 by Daniel of Galicia's troops. In the early 13th century, the Brodniks, a possible Slavic–Vlach vassal state of Halych, were present, alongside the Vlachs, in much of the region's territory. On the border between Halych and the
Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is flora. Flora and other forms of life such as fungi are collectively referred to as biota. Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess Shale fauna". Paleontologists sometimes refer to a sequence of faunal stages, a series of rocks all containing similar fossils; the study of animals of a particular region is called faunistics. Fauna comes from the name Fauna, a Roman goddess of earth and fertility, the Roman god Faunus, the related forest spirits called Fauns. All three words are cognates of the name of the Greek god Pan, panis is the Greek equivalent of fauna. Fauna is the word for a book that catalogues the animals in such a manner; the term was first used by Carl Linnaeus from Sweden in the title of his 1745 work Fauna Suecica. Cryofauna refers to the animals that live in, or close to, cold areas.
Cryptofauna are the fauna. Infauna are benthic organisms that live within the bottom substratum of a water body within the bottom-most oceanic sediments, rather than on its surface. Bacteria and microalgae may live in the interstices of bottom sediments. In general, infaunal animals become progressively smaller and less abundant with increasing water depth and distance from shore, whereas bacteria show more constancy in abundance, tending toward one million cells per milliliter of interstitial seawater. Epifauna called epibenthos, are aquatic animals that live on the bottom substratum as opposed to within it, that is, the benthic fauna that live on top of the sediment surface at the seafloor. Macrofauna are soil organisms which are retained on a 0.5 mm sieve. Studies in the deep sea define macrofauna as animals retained on a 0.3 mm sieve to account for the small size of many of the taxa. Megafauna are large animals of any particular time. For example, Australian megafauna. Meiofauna are small benthic invertebrates that live in both freshwater environments.
The term meiofauna loosely defines a group of organisms by their size, larger than microfauna but smaller than macrofauna, rather than a taxonomic grouping. One environment for meiofauna is between grains of damp sand. In practice these are metazoan animals that can pass unharmed through a 0.5 – 1 mm mesh but will be retained by a 30–45 μm mesh, but the exact dimensions will vary from researcher to researcher. Whether an organism passes through a 1 mm mesh depends upon whether it is alive or dead at the time of sorting. Mesofauna are macroscopic soil animals such as nematodes. Mesofauna are diverse. Microfauna are microscopic or small animals. Other terms include avifauna, which means "bird fauna" and piscifauna, which means "fish fauna". Linnaeus, Carolus. Fauna Suecica. 1746 "Biodiversity of Collembola and their functional role in the ecosystem"
Hîncești is a district of Moldova, with the city of Hîncești as its administrative center. As of 1 January 2011, its population was 122,000; the district has been inhabited since the Stone Age. On the territory of the present localities Rusca and Anina many cemeteries and settlements pertaining to the native Getae culture have been discovered. Localities with the earliest historical attestation are Secăreni, Leușeni, Lăpușna, Ciuciuleni, which were first attested in the period 1420–1430. During the 15th–18th centuries, the district was part of Lăpușna. Tirgul Lăpușnei was the administrative center, headed by a pârcălab. Lăpușna existed as a fair in the 14th century. A branch of the Moldovan Road passed by Lapusna, linking the economic centers of Transylvania and Poland to the North Pontic cities; the branch continued on in Dobruja, to Constantinople. Lăpușna Fair was a resting place for merchants, where they paid a small customs, besides the great customs from abroad. In 1489, Lăpușna was expressly recorded as a fair.
After the conquest of Cetatea Albă and Chilia by the Turks, Bugeac by Noha Tatars, the southern border of Moldova was moved farther north, closer to the region. Lăpușna has served as a resting place for many foreign travelers, missionaries and merchants. In 1812, after the Russo-Turkish War, the Russian Empire occupied the region of Basarabia, leading to an intense russification of the native population. In 1918, after the collapse of the Russian Empire, Bessarabia united with Romania. In this period, the district was part of the Lăpușna County. In 1940, after the Molotov-Ribbentrop Treaty, Basarabia was occupied by the USSR. In 1991, as a result of the proclamation of Independence of Moldova, the region became part of Lăpușna County, in 2003 it became an administrative unit of Moldova. Hîncești District is located in the central part of the Republic of Moldova. Neighboring districts include Nisporeni District to the northwest, Strășeni District to the northeast, Ialoveni District to the east, Cimișlia and Leova districts to the south, the border with Romania on the river Prut to the west.
The topography is predominantly hilly with heights between 100 and 350 m. The landscape of the district is divided into three areas: the forested hills of Codru, the forested and less hilly steppe, the steppe of Prut; the Codru forests are characterized by complicated terrain. From north to south, the territory is intersected by the Cogalnic River and the Galbena River; the forested steppe is characterized by gentler topography. The area is intersected by a tributary of the Prut; the Prut steppe zone is characterized by less wooded landscape. This area is crossed by the river Călmățui, which in Turkish translates as "white matter". Erosional processes differ in each area; the climate is moderate continental, variable. The average annual air temperature is 10 °C; the average temperature in January is −4 °C, the absolute minimum is −30 to −32 °C, in July the average temperature is 22 °C, with a maximum of 39 to 40 °C. Annual rainfall is 500–650 mm; the fauna are typical of Europe, include mammals such as foxes, deer, red deer, wild boar, wild cats, ermine and wolves and others.
Birds include egrets, crows, sparrows and storks. Forests occupy 18.5% of the district area, consist of oaks, maples, beeches and others. Other plants include bells, knotweeds and wormwood. Localities: 63 Administrative center: Hîncești Cities: Hîncești Villages: 24 Communes: 38 As of 1 January 2012, the district population was 121,600, of which 13.9% was urban and 88.1% was rural. There were 1455 births and 1829 deaths in 2010, for a growth rate of −374. Christians – 98.6% Orthodox Christians – 95.3% Protestant – 3.3% Baptists – 1.9% Seventh-day Adventists 0.9% Evangelicals – 0.3% Pentecostals – 0.3% Other – 0.9% No Religion – 0.5% Agriculture is the primary economic activity in the district. Products include wine, bakery products and sausages. All agricultural land is owned. There are 93,361 ha of agricultural land, including arable land and orchards. Other products include shoes, clothes and concrete building blocks; the district has 59 educational institutions, teaching 18,908 children, 350 students in the College of Construction, 600 in various professional schools.
There are 1600 teachers. The district traditionally supports right-wing parties the AEI. In the district, the PLDM had the highest percentage of votes of all of the districts of Moldova. Support for the PCRM has declined. During the last three elections support for the AEI had a 99.0% increase. The district is home to two museums, 77 works of art, 13 bands; the district has two hospitals with 540 beds, a center for family doctors that has 25 family physician offices, 14 health centers, 18 health points. There are 472 medical staff and auxiliary; the council of the Romanian Vaslui County, the county councils of the Moldovan Leova and Hîncești districts, the European Union, have set up a program to promote tourism in these regions. The main tourist attractions of the Vaslui-Hîncești-Leova area are the medieval and early modern churches and monasteries, the Manuc Bei Hunting Palace and the Manuc–Mirzaian Manor Palace in Hîncești, the region's natural riches; the district is home to the Hîncești Forest Landscape Reserve and two natural reserve
Agriculture is the science and art of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to live in cities; the history of agriculture began thousands of years ago. After gathering wild grains beginning at least 105,000 years ago, nascent farmers began to plant them around 11,500 years ago. Pigs and cattle were domesticated over 10,000 years ago. Plants were independently cultivated in at least 11 regions of the world. Industrial agriculture based on large-scale monoculture in the twentieth century came to dominate agricultural output, though about 2 billion people still depended on subsistence agriculture into the twenty-first. Modern agronomy, plant breeding, agrochemicals such as pesticides and fertilizers, technological developments have increased yields, while causing widespread ecological and environmental damage. Selective breeding and modern practices in animal husbandry have increased the output of meat, but have raised concerns about animal welfare and environmental damage.
Environmental issues include contributions to global warming, depletion of aquifers, antibiotic resistance, growth hormones in industrial meat production. Genetically modified organisms are used, although some are banned in certain countries; the major agricultural products can be broadly grouped into foods, fibers and raw materials. Food classes include cereals, fruits, meat, milk and eggs. Over one-third of the world's workers are employed in agriculture, second only to the service sector, although the number of agricultural workers in developed countries has decreased over the centuries; the word agriculture is a late Middle English adaptation of Latin agricultūra, from ager, "field", which in its turn came from Greek αγρός, cultūra, "cultivation" or "growing". While agriculture refers to human activities, certain species of ant and ambrosia beetle cultivate crops. Agriculture is defined with varying scopes, in its broadest sense using natural resources to "produce commodities which maintain life, including food, forest products, horticultural crops, their related services".
Thus defined, it includes arable farming, animal husbandry and forestry, but horticulture and forestry are in practice excluded. The development of agriculture enabled the human population to grow many times larger than could be sustained by hunting and gathering. Agriculture began independently in different parts of the globe, included a diverse range of taxa, in at least 11 separate centres of origin. Wild grains were eaten from at least 105,000 years ago. From around 11,500 years ago, the eight Neolithic founder crops and einkorn wheat, hulled barley, lentils, bitter vetch, chick peas and flax were cultivated in the Levant. Rice was domesticated in China between 11,500 and 6,200 BC with the earliest known cultivation from 5,700 BC, followed by mung and azuki beans. Sheep were domesticated in Mesopotamia between 11,000 years ago. Cattle were domesticated from the wild aurochs in the areas of modern Turkey and Pakistan some 10,500 years ago. Pig production emerged in Eurasia, including Europe, East Asia and Southwest Asia, where wild boar were first domesticated about 10,500 years ago.
In the Andes of South America, the potato was domesticated between 10,000 and 7,000 years ago, along with beans, llamas and guinea pigs. Sugarcane and some root vegetables were domesticated in New Guinea around 9,000 years ago. Sorghum was domesticated in the Sahel region of Africa by 7,000 years ago. Cotton was domesticated in Peru by 5,600 years ago, was independently domesticated in Eurasia. In Mesoamerica, wild teosinte was bred into maize by 6,000 years ago. Scholars have offered multiple hypotheses to explain the historical origins of agriculture. Studies of the transition from hunter-gatherer to agricultural societies indicate an initial period of intensification and increasing sedentism. Wild stands, harvested started to be planted, came to be domesticated. In Eurasia, the Sumerians started to live in villages from about 8,000 BC, relying on the Tigris and Euphrates rivers and a canal system for irrigation. Ploughs appear in pictographs around 3,000 BC. Farmers grew wheat, vegetables such as lentils and onions, fruits including dates and figs.
Ancient Egyptian agriculture relied on its seasonal flooding. Farming started in the predynastic period at the end of the Paleolithic, after 10,000 BC. Staple food crops were grains such as wheat and barley, alongside industrial crops such as flax and papyrus. In India, wheat and jujube were domesticated by 9,000 BC, soon followed by sheep and goats. Cattle and goats were domesticated in Mehrgarh culture by 8,000–6,000 BC. Cotton was cultivated by the 5th-4th millennium BC. Archeological evidence indicates an animal-drawn plough from 2,500 BC in the Indus Valley Civilisation. In China, from the 5th century BC there was a nationwide granary system and widespread silk farming. Water-powered grain mills were in use followed by irrigation. By the late 2nd century, heavy ploughs had been developed with iron mouldboards; these spread westwards across Eurasia. Asian rice was domesticated 8,200–13,500 years ago – depending on the molecular clock estimate, used – on the Pearl River in southern China with a single genetic origin from the wild rice Oryza rufipogon