Phoenix is the capital and most populous city of Arizona, with 1,626,000 people. It is the fifth most populous city in the United States, the most populous American state capital, the only state capital with a population of more than one million residents. Phoenix is the anchor of the Phoenix metropolitan area known as the Valley of the Sun, which in turn is part of the Salt River Valley; the metropolitan area is the 11th largest by population in the United States, with 4.73 million people as of 2017. Phoenix is the seat of Maricopa County and the largest city in the state at 517.9 square miles, more than twice the size of Tucson and one of the largest cities in the United States. Phoenix was settled in 1867 as an agricultural community near the confluence of the Salt and Gila Rivers and was incorporated as a city in 1881, it became the capital of Arizona Territory in 1889. It has a hot desert climate. Despite this, its canal system led to a thriving farming community with the original settler's crops remaining important parts of the Phoenix economy for decades, such as alfalfa, cotton and hay.
Cotton, citrus and copper were known locally as the "Five C's" anchoring Phoenix's economy. These remained the driving forces of the city until after World War II, when high-tech companies began to move into the valley and air conditioning made Phoenix's hot summers more bearable; the city averaged a four percent annual population growth rate over a 40-year period from the mid-1960s to the mid-2000s. This growth rate slowed during the Great Recession of 2007–09, has rebounded slowly. Phoenix is the cultural center of the state of Arizona; the Hohokam people occupied the Phoenix area for 2,000 years. They created 135 miles of irrigation canals, making the desert land arable, paths of these canals were used for the Arizona Canal, Central Arizona Project Canal, the Hayden-Rhodes Aqueduct, they carried out extensive trade with the nearby Ancient Puebloans and Sinagua, as well as with the more distant Mesoamerican civilizations. It is believed that periods of drought and severe floods between 1300 and 1450 led to the Hohokam civilization's abandonment of the area.
After the departure of the Hohokam, groups of Akimel O'odham, Tohono O'odham, Maricopa tribes began to use the area, as well as segments of the Yavapai and Apache. The O'odham were offshoots of the Sobaipuri tribe, who in turn were thought to be the descendants of the Hohokam; the Akimel O'odham were the major group in the area and lived in small villages, with well-defined irrigation systems that spread over the entire Gila River Valley, from Florence in the east to the Estrellas in the west. Their crops included corn and squash for food, while cotton and tobacco were cultivated, they banded together with the Maricopa for protection against incursions by the Yuma and Apache tribes. The Maricopa are part of the larger Yuma people; the Tohono O'odham lived in the region, as well, but their main concentration was to the south and stretched all the way to the Mexican border. The O'odham lived in small settlements as seasonal farmers who took advantage of the rains, rather than the large-scale irrigation of the Akimel.
They grew crops such as sweet corn, tapery beans, lentils, sugar cane, melons, as well as taking advantage of native plants such as saguaro fruits, cholla buds, mesquite tree beans, mesquite candy. They hunted local game such as deer and javelina for meat; the Mexican–American War ended in 1848, Mexico ceded its northern zone to the United States, residents of that region became U. S. citizens. The Phoenix area became part of the New Mexico Territory. In 1863, the mining town of Wickenburg was the first to be established in Maricopa County, to the northwest of Phoenix. Maricopa County had not yet been incorporated; the Army created Fort McDowell on the Verde River in 1865 to forestall Indian uprisings. The fort established a camp on the south side of the Salt River by 1866, the first settlement in the valley after the decline of the Hohokam. Other nearby settlements merged to become the city of Tempe; the history of the city of Phoenix begins with Jack Swilling, a Confederate veteran of the Civil War.
He saw a potential for farming. He formed a small community that same year about four miles east of the city. Lord Darrell Duppa was one of the original settlers in Swilling's party, he suggested the name "Phoenix", as it described a city born from the ruins of a former civilization; the Board of Supervisors in Yavapai County recognized the new town on May 4, 1868, the first post office was established the following month with Swilling as the postmaster. On February 12, 1871, the territorial legislature created Maricopa County by dividing Yavapai County; the first election for county office was held in 1871. He ran unopposed; the town grew during the 1870s, President Ulysses S. Grant issued a land patent for the site of Phoenix on April 10, 1874. By 1875, the town had a telegraph office
A circadian rhythm is any biological process that displays an endogenous, entrainable oscillation of about 24 hours. These 24-hour rhythms are driven by a circadian clock, they have been observed in plants, animals and cyanobacteria; the term circadian comes from the Latin circa, meaning "around", diēm, meaning "day". The formal study of biological temporal rhythms, such as daily, weekly and annual rhythms, is called chronobiology. Processes with 24-hour oscillations are more called diurnal rhythms. Although circadian rhythms are endogenous, they are adjusted to the local environment by external cues called zeitgebers, which include light and redox cycles. In medical science, an abnormal circadian rhythm in humans is known as circadian rhythm disorder. In 2017, the Nobel Prize in Physiology or Medicine was awarded to Jeffrey C. Hall, Michael Rosbash and Michael W. Young "for their discoveries of molecular mechanisms controlling the circadian rhythm" in fruit flies; the earliest recorded account of a circadian process dates from the 4th century BC, when Androsthenes, a ship captain serving under Alexander the Great, described diurnal leaf movements of the tamarind tree.
The observation of a circadian or diurnal process in humans is mentioned in Chinese medical texts dated to around the 13th century, including the Noon and Midnight Manual and the Mnemonic Rhyme to Aid in the Selection of Acu-points According to the Diurnal Cycle, the Day of the Month and the Season of the Year. The first recorded observation of an endogenous circadian oscillation was by the French scientist Jean-Jacques d'Ortous de Mairan in 1729, he noted that 24-hour patterns in the movement of the leaves of the plant Mimosa pudica continued when the plants were kept in constant darkness, in the first experiment to attempt to distinguish an endogenous clock from responses to daily stimuli. In 1896, Patrick and Gilbert observed that during a prolonged period of sleep deprivation, sleepiness increases and decreases with a period of 24 hours. In 1918, J. S. Szymanski showed that animals are capable of maintaining 24-hour activity patterns in the absence of external cues such as light and changes in temperature.
In the early 20th century, circadian rhythms were noticed in the rhythmic feeding times of bees. Extensive experiments were done by Auguste Forel, Ingeborg Beling, Oskar Wahl to see whether this rhythm was due to an endogenous clock; the existence of circadian rhythm was independently discovered in the fruit fly Drosophila melanogaster in 1935 by two German zoologists, Hans Kalmus and Erwin Bünning. In 1954, an important experiment was reported by Colin Pittendrigh who showed that eclosion in D. pseudoobscura was a circadian behaviour. He demonstrated that while temperature played a vital role in eclosion rhythm, the period of eclosion was delayed but not stopped when temperature was decreased, it was an indication. The term circadian was coined by Franz Halberg in 1959. According to Halberg's original definition: The term "circadian" dies. Herein, "circadian" might be applied to all "24-hour" rhythms, whether or not their periods, individually or on the average, are different from 24 hours, longer or shorter, by a few minutes or hours.
In 1977, the International Committee on Nomenclature of the International Society for Chronobiology formally adopted the definition, which states: Circadian: relating to biologic variations or rhythms with a frequency of 1 cycle in 24 ± 4 h. Note: term describes rhythms with an about 24-h cycle length, whether they are frequency-synchronized with or are desynchronized or free-running from the local environmental time scale, with periods of yet different from 24-h. Ron Konopka and Seymour Benzer identified the first clock mutant in Drosophila in 1971 and called it "period" gene, the first discovered genetic determinant of behavioral rhythmicity. Per gene was isolated in 1984 by two teams of researchers. Konopka, Jeffrey Hall, Michael Roshbash and their team showed that per locus is the centre of the circadian rhythm, that loss of per stops circadian activity. At the same time, Michael W. Young's team reported similar effects of per, that the gene covers 7.1-kilobase interval on the X chromosome and encodes a 4.5-kb poly+ RNA.
They went on to discover the key genes and neurones in Drosophila circadian system, for which Hall and Young received the Nobel Prize in Physiology or Medicine 2017. Joseph Takahashi discovered the first mammalian circadian clock mutation using mice in 1994. However, recent studies show that deletion of clock does not lead to a behavioral phenotype, which questions its importance in rhythm generation. To be called circadian, a biological rhythm must meet these three general criteria: The rhythm has an endogenous free-running period that lasts 24 hours; the rhythm persists with a period of about 24 hours. The period of the rhythm in constant conditions is called the free-running period and is denoted by the Greek letter τ; the rationale for this criterion is to distinguish circadian rhythms from simple responses to daily external cues. A rhythm cannot be said to be endogenous unless it ha
An equator of a rotating spheroid is its zeroth circle of latitude. It is the imaginary line on the spheroid, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the plane perpendicular to its axis of rotation and midway between its geographical poles. On Earth, the Equator is 21.3 % over land. Indonesia is the country straddling the greatest length of the equatorial line across both land and sea; the name is derived from medieval Latin word aequator, in the phrase circulus aequator diei et noctis, meaning ‘circle equalizing day and night’, from the Latin word aequare meaning ‘make equal’. The latitude of the Earth's equator is, by definition, 0° of arc; the Equator is one of the five notable circles of latitude on Earth. The Equator is the only line of latitude, a great circle — that is, one whose plane passes through the center of the globe; the plane of Earth's equator, when projected outwards to the celestial sphere, defines the celestial equator.
In the cycle of Earth's seasons, the equatorial plane runs through the Sun twice per year: on the equinoxes in March and September. To a person on Earth, the Sun appears to travel above the Equator at these times. Light rays from the Sun's center are perpendicular to Earth's surface at the point of solar noon on the Equator. Locations on the Equator experience the shortest sunrises and sunsets because the Sun's daily path is nearly perpendicular to the horizon for most of the year; the length of daylight is constant throughout the year. Earth bulges at the Equator. Sites near the Equator, such as the Guiana Space Centre in Kourou, French Guiana, are good locations for spaceports as they have a faster rotational speed than other latitudes. Since Earth rotates eastward, spacecraft must be launched eastward to take advantage of this Earth-boost of speed; the precise location of the Equator is not fixed. This effect must be accounted for in detailed geophysical measurements; the International Association of Geodesy and the International Astronomical Union have chosen to use an equatorial radius of 6,378.1366 kilometres.
This equatorial radius is in the 2003 and 2010 IERS Conventions. It is the equatorial radius used for the IERS 2003 ellipsoid. If it were circular, the length of the Equator would be 2π times the radius, namely 40,075.0142 kilometres. The GRS 80 as approved and adopted by the IUGG at its Canberra, Australia meeting of 1979 has an equatorial radius of 6,378.137 kilometres. The WGS 84, a standard for use in cartography and satellite navigation including GPS has an equatorial radius of 6,378.137 kilometres. For both GRS 80 and WGS 84, this results in a length for the Equator of 40,075.0167 km. The geographical mile is defined as one arc-minute of the Equator, so it has different values depending on which radius is assumed. For example, by WSG-84, the distance is 1,855.3248 metres, while by IAU-2000, it is 1,855.3257 metres. This is a difference of less than one millimetre over the total distance; the earth is modeled as a sphere flattened 0.336% along its axis. This makes the Equator 0.16% longer than a meridian.
The IUGG standard meridian is, to the nearest millimetre, 40,007.862917 kilometres, one arc-minute of, 1,852.216 metres, explaining the SI standardization of the nautical mile as 1,852 metres, more than 3 metres less than the geographical mile. The sea-level surface of the Earth is irregular, so the actual length of the Equator is not so easy to determine. Aviation Week and Space Technology on 9 October 1961 reported that measurements using the Transit IV-A satellite had shown the equatorial "diameter" from longitude 11° West to 169° East to be 1,000 feet greater than its "diameter" ninety degrees away; the Equator passes through the land of 11 countries. Starting at the Prime Meridian and heading eastwards, the Equator passes through: Despite its name, no part of Equatorial Guinea lies on the Equator. However, its island of Annobón is 155 km south of the Equator, the rest of the country lies to the north. Seasons result from the tilt of the Earth's axis compared to the plane of its revolution around the Sun.
Throughout the year the northern and southern hemispheres are alternately turned either toward or away from the sun depending on Earth's position in its orbit. The hemisphere turned toward the sun receives more sunlight and is in summer, while the other hemisphere receives less sun and is in winter. At the equinoxes, the Earth's axis
A jet aircraft is an aircraft propelled by jet engines. Whereas the engines in propeller-powered aircraft achieve their maximum efficiency at much lower speeds and altitudes, jet engines and aircraft achieve maximum efficiency at speeds close to or well above the speed of sound. Jet aircraft cruise at faster than about Mach 0.8 at altitudes around 10,000–15,000 metres or more. Frank Whittle, an English inventor and RAF officer, developed the concept of the jet engine in 1928, Hans von Ohain in Germany developed the concept independently in the early 1930s, he wrote in February 1936 to Ernst Heinkel, who led the construction of the world's first turbojet aircraft and jet plane Heinkel He 178. However, it can be argued that the English engineer A. A. Griffith, who published a paper in July 1926 on compressors and turbines deserves credit. After the first instance of powered flight, a large number of jet powerplants were suggested. René Lorin, Harris proposed systems for creating a jet efflux. In 1910 the Romanian inventor Henri Coandă filed a patent on a jet propulsion system which used piston-engine exhaust gases to add heat to an otherwise pure air stream compressed by rotating fan blades in a duct.
It was installed in his Coandă-1910 but this craft never flew. Rocket-powered jet aircraft were pioneered in Germany; the first aircraft to fly under rocket power was the Lippisch Ente, in 1928. The Ente had been flown as a glider; the next year, in 1929, the Opel RAK.1 became the first purpose-built rocket plane to fly. The turbojet was invented in the 1930s, independently by Frank Whittle and Hans von Ohain; the first turbojet aircraft to fly was the Heinkel He 178 V1 first prototype of the German Air Force, the Luftwaffe, on August 27, 1939 in Rostock. The first flight of a jet-engined aircraft to come to public attention was the Italian Caproni Campini N.1 motorjet prototype that flew on August 27, 1940. It was the first jet aircraft recognised by the Fédération Aéronautique Internationale. Campini had proposed the motorjet in 1932; the British experimental Gloster E.28/39 first took to the air on May 15, 1941, powered by Sir Frank Whittle's turbojet. The United States produced the Bell XP-59A using two examples of a version of the Whittle engine built by General Electric, which flew on October 1, 1942.
The Meteor was the first production jet as it entered production a few months before the Me 262, which itself had been in development since before the start of the war as Projekt 1065. The first operational jet fighter was the Messerschmitt Me 262, manufactured by Germany during World War II, which entered service on 19 April 1944 with Erprobungskommando 262 at Lechfeld just south of Augsburg, it was the fastest conventional aircraft of World War II – although there were faster aircraft propelled by unconventional means, such as the rocket-powered Messerschmitt Me 163 Komet. The Messerschmitt Me 262 had first flown on April 18, 1941, with initial plans drawn up by Dr Waldemar Voigt's design team in April 1939, but mass production did not start until early 1944 with the first squadrons operational that year, too late for a decisive effect on the outcome of the war. Around this time, mid 1944, the United Kingdom's Gloster Meteor was being committed to defence of the UK against the V-1 flying bomb – itself a pulsejet-powered aircraft and direct ancestor of the cruise missile– and ground-attack operations over Europe in the last months of the war.
In 1944 Germany introduced into service the Arado Ar 234 jet reconnaissance and bomber, though chiefly used in the former role, with the Heinkel He 162 Spatz single-jet light fighter premiering as 1944 ended. USSR tested its own Bereznyak-Isayev BI-1 in 1942, but the project was scrapped by Joseph Stalin in 1945; the Imperial Japanese Navy developed jet aircraft in 1945, including the Nakajima J9Y Kikka, a modified, smaller version of the Me 262 that had folding wings. By the end of 1945, the US had introduced their first jet fighter, the Lockheed P-80 Shooting Star into service and the UK its second fighter design, the de Havilland Vampire; the US introduced the North American B-45 Tornado, their first jet bomber, into service in 1948. Although capable of carrying nuclear weapons it was used for reconnaissance over Korea. On November 8, 1950, during the Korean War, United States Air Force Lt. Russell J. Brown, flying in an F-80, intercepted two North Korean MiG-15s near the Yalu River and shot them down in the first jet-to-jet dogfight in history.
The UK put the English Electric Canberra into service in 1951 as a light bomber. It was designed to fly faster than any interceptor. BOAC operated the first commercial jet service, from London to Johannesburg, in 1952 with the de Havilland Comet jetliner; this innovative aircraft travelled far faster and higher than the propeller aircraft, was much quieter and had stylish blended wings containing hidden jet engines. However, due to a design defect, use of aluminium alloys, the aircraft suffered catastrophic metal fatigue which led to several crashes; the series of crashes gave time for the Boeing 707 to enter service in 1958 and this came to dominate the market for civilian airliners. The underslung engines were found to be advantageous in the event of a propellant leak, so the 707 looked rather different from the Comet: the 707 has a shape, the same as that of contemporary aircraft, with marked commonality still evident today for example with the 737 and A340. Turbofan aircraft began ente
Physiology is the scientific study of the functions and mechanisms which work within a living system. As a sub-discipline of biology, the focus of physiology is on how organisms, organ systems, organs and biomolecules carry out the chemical and physical functions that exist in a living system. Central to an understanding of physiological functioning is the investigation of the fundamental biophysical and biochemical phenomena, the coordinated homeostatic control mechanisms, the continuous communication between cells; the physiologic state is the condition occurring from normal body function, while the pathological state is centered on the abnormalities that occur in animal diseases, including humans. According to the type of investigated organisms, the field can be divided into, animal physiology, plant physiology, cellular physiology and microbial physiology; the Nobel Prize in Physiology or Medicine is awarded to those who make significant achievements in this discipline by the Royal Swedish Academy of Sciences.
Human physiology seeks to understand the mechanisms that work to keep the human body alive and functioning, through scientific enquiry into the nature of mechanical and biochemical functions of humans, their organs, the cells of which they are composed. The principal level of focus of physiology is at the level of systems within systems; the endocrine and nervous systems play major roles in the reception and transmission of signals that integrate function in animals. Homeostasis is a major aspect with regard to such interactions within plants as well as animals; the biological basis of the study of physiology, integration refers to the overlap of many functions of the systems of the human body, as well as its accompanied form. It is achieved through communication that occurs in a variety of both electrical and chemical. Changes in physiology can impact the mental functions of individuals. Examples of this would be toxic levels of substances. Change in behavior as a result of these substances is used to assess the health of individuals.
Much of the foundation of knowledge in human physiology was provided by animal experimentation. Due to the frequent connection between form and function and anatomy are intrinsically linked and are studied in tandem as part of a medical curriculum. Plant physiology is a subdiscipline of botany concerned with the functioning of plants. Related fields include plant morphology, plant ecology, cell biology, genetics and molecular biology. Fundamental processes of plant physiology include photosynthesis, plant nutrition, nastic movements, photomorphogenesis, circadian rhythms, seed germination and stomata function and transpiration. Absorption of water by roots, production of food in the leaves, growth of shoots towards light are examples of plant physiology. Although there are differences between animal and microbial cells, the basic physiological functions of cells can be divided into the processes of cell division, cell signaling, cell growth, cell metabolism. Microorganisms can be found everywhere on Earth.
Types of microorganisms include archaea, eukaryotes, protists and micro-plants. Microbes are important in human culture and health in many ways, serving to ferment foods, treat sewage, produce fuel and other bioactive compounds, they are essential tools in biology as model organisms and have been put to use in biological warfare and bioterrorism. They are a vital component of fertile soils. In the human body microorganisms make up the human microbiota including the essential gut flora, they are the pathogens responsible for many infectious diseases and as such are the target of hygiene measures. Most microorganisms can reproduce and bacteria are able to exchange genes through conjugation and transduction between divergent species; the study of human physiology as a medical field originates in classical Greece, at the time of Hippocrates. Outside of Western tradition, early forms of physiology or anatomy can be reconstructed as having been present at around the same time in China and elsewhere.
Hippocrates incorporated his belief system called the theory of humours, which consisted of four basic substance: earth, water and fire. Each substance is known for having a corresponding humour: black bile, phlegm and yellow bile, respectively. Hippocrates noted some emotional connections to the four humours, which Claudius Galenus would expand on; the critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece. Like Hippocrates, Aristotle took to the humoral theory of disease, which consisted of four primary qualities in life: hot, cold and dry. Claudius Galenus, known as Galen of Pergamum, was the first to use experiments to probe the functions of the body. Unlike Hippocrates, Galen argued that humoral imbalances can be located in specific organs, including the entire body, his modification of this theory better equipped doctors to make more precise diagnoses. Galen played off of Hippocrates idea that emotions were tied to the humours, added the notion of temperaments: sanguine corresponds with blood.
Galen saw the human body consisting of three connected systems: the brain and nerves, which are responsible for thoughts and sensations.
The suprachiasmatic nucleus or nuclei is a tiny region of the brain in the hypothalamus, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms; the neuronal and hormonal activities it generates regulate many different body functions in a 24-hour cycle, using around 20,000 neurons. The SCN interacts with many other regions of the brain, it contains several cell types and several different neurotransmitters. The SCN is situated in the anterior part of the hypothalamus dorsal, or superior to the optic chiasm bilateral to the third ventricle. Different organisms such as bacteria, plants and animals, show genetically-based near-24-hour rhythms. Although all of these clocks appear to be based on a similar type of genetic feedback loop, the specific genes involved are thought to have evolved independently in each kingdom. Many aspects of mammalian behavior and physiology show circadian rhythmicity, including sleep, physical activity, hormone levels, body temperature, immune function, digestive activity.
The SCN coordinates these rhythms across the entire body, rhythmicity is lost if the SCN is destroyed. For example, total time of sleep is maintained in rats with SCN damage, but the length and timing of sleep episodes becomes erratic; the SCN maintains control across the body by synchronizing "slave oscillators," which exhibit their own near-24-hour rhythms and control circadian phenomena in local tissue. The SCN receives input from specialized photosensitive ganglion cells in the retina via the retinohypothalamic tract. Neurons in the ventrolateral SCN have the ability for light-induced gene expression. Melanopsin-containing ganglion cells in the retina have a direct connection to the ventrolateral SCN via the retinohypothalamic tract; when the retina receives light, the vlSCN relays this information throughout the SCN allowing entrainment, synchronization, of the person's or animal's daily rhythms to the 24-hour cycle in nature. The importance of entraining organisms, including humans, to exogenous cues such as the light/dark cycle, is reflected by several circadian rhythm sleep disorders, where this process does not function normally.
Neurons in the dorsomedial SCN are believed to have an endogenous 24-hour rhythm that can persist under constant darkness. A GABAergic mechanism couples the ventral and dorsal regions of the SCN; the SCN sends information to other hypothalamic nuclei and the pineal gland to modulate body temperature and production of hormones such as cortisol and melatonin. Information about the direct neuronal regulation of metabolic processes and circadian rhythm-controlled behaviors is not well known among either endothermic or ectothermic vertebrates, although extensive research has been done on the SCN in model animals such as the mammalian mouse and ectothermic reptiles, in particular, lizards; the SCN is known to be involved not only in photoreception through innervation from the retinohypothalamic tract but in thermoregulation of vertebrates capable of homeothermy, as well as regulating locomotion and other behavioral outputs of the circadian clock within ectothermic vertebrates. The behavioral differences between both classes of vertebrates, when compared to the respective structures and properties of the SCN and various other nuclei proximate to the hypothalamus, provide insight into how these behaviors are the consequence of differing circadian regulation.
Many neuroethological studies must be done to ascertain the direct and indirect roles of the SCN on circadian-regulated behaviors of vertebrates. In general, external temperature does not influence endothermic animal behavior or circadian rhythm because of the ability of these animals to keep their internal body temperature constant through homeostatic thermoregulation. Furthermore, when individual neurons of the SCN from a mouse were treated with heat pulses, a similar resetting of oscillators was observed, but when an intact SCN was treated with the same heat pulse treatment the SCN was resistant to temperature change by exhibiting an unaltered circadian oscillating phase. In ectothermic animals the ruin lizard Podacris sicula, temperature has been shown to affect the circadian oscillators within the SCN; this reflects a potential evolutionary relationship among endothermic and ectothermic vertebrates, in how ectotherms rely on environmental temperature to affect their circadian rhythms and behavior and endotherms have an evolved SCN to ignore external temperature and use photoreception as a means for entraining the circadian oscillators within their SCN.
In addition, the differences of the SCN between endothermic and ectothermic vertebrates suggest that the neuronal organization of the temperature-resistant SCN in endotherms is responsible for driving thermoregulatory behaviors in those animals differently from those of ectotherms, since they rely on external temperature for engaging in certain behaviors. Significant research has been conducted on the genes responsible for controlling circadian rhythm, in particular within the SCN. Knowledge of the gene expression of Clock and Period2, two of the many genes responsible for regulating circadian rhythm within the individual cells of the SCN, has allowed for a greater understanding of how genetic expression influences th
New York City
The City of New York called either New York City or New York, is the most populous city in the United States. With an estimated 2017 population of 8,622,698 distributed over a land area of about 302.6 square miles, New York is the most densely populated major city in the United States. Located at the southern tip of the state of New York, the city is the center of the New York metropolitan area, the largest metropolitan area in the world by urban landmass and one of the world's most populous megacities, with an estimated 20,320,876 people in its 2017 Metropolitan Statistical Area and 23,876,155 residents in its Combined Statistical Area. A global power city, New York City has been described as the cultural and media capital of the world, exerts a significant impact upon commerce, research, education, tourism, art and sports; the city's fast pace has inspired the term New York minute. Home to the headquarters of the United Nations, New York is an important center for international diplomacy.
Situated on one of the world's largest natural harbors, New York City consists of five boroughs, each of, a separate county of the State of New York. The five boroughs – Brooklyn, Manhattan, The Bronx, Staten Island – were consolidated into a single city in 1898; the city and its metropolitan area constitute the premier gateway for legal immigration to the United States. As many as 800 languages are spoken in New York, making it the most linguistically diverse city in the world. New York City is home to more than 3.2 million residents born outside the United States, the largest foreign-born population of any city in the world. In 2017, the New York metropolitan area produced a gross metropolitan product of US$1.73 trillion. If greater New York City were a sovereign state, it would have the 12th highest GDP in the world. New York is home to the highest number of billionaires of any city in the world. New York City traces its origins to a trading post founded by colonists from the Dutch Republic in 1624 on Lower Manhattan.
The city and its surroundings came under English control in 1664 and were renamed New York after King Charles II of England granted the lands to his brother, the Duke of York. New York served as the capital of the United States from 1785 until 1790, it has been the country's largest city since 1790. The Statue of Liberty greeted millions of immigrants as they came to the U. S. by ship in the late 19th and early 20th centuries and is an international symbol of the U. S. and its ideals of liberty and peace. In the 21st century, New York has emerged as a global node of creativity and entrepreneurship, social tolerance, environmental sustainability, as a symbol of freedom and cultural diversity. Many districts and landmarks in New York City are well known, with the city having three of the world's ten most visited tourist attractions in 2013 and receiving a record 62.8 million tourists in 2017. Several sources have ranked New York the most photographed city in the world. Times Square, iconic as the world's "heart" and its "Crossroads", is the brightly illuminated hub of the Broadway Theater District, one of the world's busiest pedestrian intersections, a major center of the world's entertainment industry.
The names of many of the city's landmarks and parks are known around the world. Manhattan's real estate market is among the most expensive in the world. New York is home to the largest ethnic Chinese population outside of Asia, with multiple signature Chinatowns developing across the city. Providing continuous 24/7 service, the New York City Subway is the largest single-operator rapid transit system worldwide, with 472 rail stations. Over 120 colleges and universities are located in New York City, including Columbia University, New York University, Rockefeller University, which have been ranked among the top universities in the world. Anchored by Wall Street in the Financial District of Lower Manhattan, New York has been called both the most economically powerful city and the leading financial center of the world, the city is home to the world's two largest stock exchanges by total market capitalization, the New York Stock Exchange and NASDAQ. In 1664, the city was named in honor of the Duke of York.
James's older brother, King Charles II, had appointed the Duke proprietor of the former territory of New Netherland, including the city of New Amsterdam, which England had seized from the Dutch. During the Wisconsinan glaciation, 75,000 to 11,000 years ago, the New York City region was situated at the edge of a large ice sheet over 1,000 feet in depth; the erosive forward movement of the ice contributed to the separation of what is now Long Island and Staten Island. That action left bedrock at a shallow depth, providing a solid foundation for most of Manhattan's skyscrapers. In the precolonial era, the area of present-day New York City was inhabited by Algonquian Native Americans, including the Lenape, whose homeland, known as Lenapehoking, included Staten Island; the first documented visit into New York Harbor by a European was in 1524 by Giovanni da Verrazzano, a Florentine explorer in the service of the French crown. He named it Nouvelle Angoulême. A Spanish expedition led by captain Estêvão Gomes, a Portuguese sailing for Emperor Charles V, arrived in New York Harbor in January 1525 and charted the mouth of the Hudson River, which he named Río de San Antonio.
The Padrón Rea