Emmitsburg, town, Frederick county, northern Maryland, U.S., situated near the Pennsylvania border 23 miles (37 km) north-northeast of Frederick. Settled in the 1780s as Poplar Fields or Silver Fancy, it was renamed about 1786 for a local landowner named Emmit (sources disagree on his given name).

gray birch, (Betula populifolia), slender ornamental tree of the family Betulaceae, found in clusters on moist sites in northeastern North America. See also birch. Rarely 12 metres (40 feet) tall, it is covered almost to the ground with flexible branches that form a narrow pyramidal crown. The

Sir John A. Pople was a British mathematician and chemist who, with Walter Kohn, received the 1998 Nobel Prize for Chemistry for work on computational methodology in quantum chemistry. Pople’s share of the prize recognized his development of computer-based methods of studying the quantum mechanics

Sir John A. Pople was a British mathematician and chemist who, with Walter Kohn, received the 1998 Nobel Prize for Chemistry for work on computational methodology in quantum chemistry. Pople’s share of the prize recognized his development of computer-based methods of studying the quantum mechanics

poplin, strong fabric produced by the rib variation of the plain weave and characterized by fine, closely spaced, crosswise ribs. It is made with heavier filling yarns and a greater number of warp yarns and is similar to broadcloth, which has even finer, more closely spaced ribs. Though originally

human cardiovascular system: The aorta and its principal branches: …femoral artery continues as the popliteal artery; from this arise the posterior and anterior tibial arteries. The posterior tibial artery is a direct continuation of the popliteal, passing down the lower leg to supply structures of the posterior portion of the leg and foot.

human cardiovascular system: Inferior vena cava and its tributaries: …to terminate usually in the popliteal vein. There is some interconnection with deep veins and with the great saphenous vein. The latter vein, the longest in the body, extends from the dorsal venous arch up the inside of the lower leg and thigh, receiving venous branches from the knee and…

Popocatépetl, volcano on the border of the states of México and Puebla, central Mexico. Popocatépetl lies along Mexico’s Cordillera Neo-Volcánica at the southern edge of the Mexican Plateau, 10 miles (16 km) south of its twin, Iztaccíhuatl, and 45 miles (72 km) southeast of Mexico City. The

Popol Vuh, Maya document, an invaluable source of knowledge of ancient Mayan mythology and culture. Written in K’iche’ (a Mayan language) by a Mayan author or authors between 1554 and 1558, it uses the Latin alphabet with Spanish orthography. It chronicles the creation of humankind, the actions of

Popolare, an Italian political party organized in 1919 and inspired by Christian Socialist principles. The formation of the party marked the entrance of Roman Catholics, alienated since the government’s seizure of papal lands in 1860–70, into Italian political life as an organized force. Led by the

Popolare, an Italian political party organized in 1919 and inspired by Christian Socialist principles. The formation of the party marked the entrance of Roman Catholics, alienated since the government’s seizure of papal lands in 1860–70, into Italian political life as an organized force. Led by the

popolo, (Italian: “people”), in the communes (city-states) of 13th-century Italy, a pressure group instituted to protect the interests of the commoners (actually, wealthy merchants and businessmen) against the nobility that up to then had exclusively controlled commune governments. It was one of a

Giulio Andreotti: …of his party’s daily newspaper, Il Popolo. He was the author of De Gasperi e il suo tempo (1956; “De Gasperi and His Time”) and other books.

Italy: Shifting power: …new party known as the People of Freedom (Popolo della Libertà; PdL)—clinched a third term as prime minister.

Rome: Piazza del Popolo: The Corso emerges onto the splendid oval Piazza del Popolo (“People’s Square”), which is monumental without being intimidating. Over a period of 300 years, it was constructed as the ceremonial entryway to Rome, and, although its elements are diverse in style and…

Rome: Piazza del Popolo: In 1561 the Porta del Popolo, the medieval gate in the city wall, was rebuilt. Ninety-four years later its inner face was redone by Bernini for the grand entrance of Queen Christina, who had abandoned the Protestant throne of Sweden for the hospitality of Catholic Rome. In 1589…

Popoloca, Middle American Indians of southern Puebla state in central Mexico (not to be confused with the Popoluca of southern Mexico). The Popoloca language is most closely related to Ixcatec and Chocho and to Mazatec, all spoken nearby in northern Oaxaca state. The territory of the Popoloca is

Oaxaca: languages, notably Zapotec, Mixtec, Mazatec, Chinantec, and Mixé. Agriculture and mining employ more than half of the workforce. The chief crops are corn (maize), wheat, coffee, sugarcane, tobacco, fibres, and tropical fruits. The mountains are veined with gold, silver, uranium, diamonds, and onyx, and mining is important. Services also…

Mixe-Zoquean: …inhabiting northwestern Chiapas; and the Popoluca (not to be confused with the Popoloca), who live in eastern Veracruz and Oaxaca, about midway between the Mixe and Zoque. The languages of these people are closely related, and their cultures share a common origin.

Guadalcanal Island: …(Kavo Range) that culminates in Mount Popomanaseu (7,644 feet [2,330 metres]), the highest point in the country. Many short, rapid streams, including the Mataniko, Lungga, and Tenaru, tumble from the wooded mountains to the coast, which in some places is lined with mangrove swamps. The economy is based mainly on…

Popondetta, town, eastern Papua New Guinea, southwestern Pacific Ocean. The town, on a tributary of the Girua River, was an Allied air base during World War II; the airfield is now used for civil aviation. In addition, Popondetta is the focus of a road network 300 miles (500 km) long, extending

Olympic Games: Atlanta, Georgia, U.S., 1996: …captured two individual gold medals: Aleksandr Popov (Russia), Danyon Loader (New Zealand), and Denis Pankratov (Russia). In women’s gymnastics the team event was won by the surprising U.S. squad, while the individual contests were dominated by Lilia Podkopayeva (Ukraine), who won two gold medals and one silver, including the title…

Aleksandr Popov was a physicist and electrical engineer acclaimed in Russia as the inventor of radio. Evidently, he built his first primitive radio receiver, a lightning detector (1895), without knowledge of the contemporary work of the Italian inventor Guglielmo Marconi. The genuineness and the

Aleksandr Popov was a physicist and electrical engineer acclaimed in Russia as the inventor of radio. Evidently, he built his first primitive radio receiver, a lightning detector (1895), without knowledge of the contemporary work of the Italian inventor Guglielmo Marconi. The genuineness and the

Alexey Dmitriyevich Popov was a Soviet stage director and prominent exponent of Socialist realism whose monumental productions were notable for their meticulous attention to naturalistic detail. Popov began his career as an actor with the Moscow Art Theatre and then moved to Kostroma to be managing

Oleg Popov was a member of the Moscow Circus who was the most popular clown in the Soviet Union in the second half of the 20th century. Popov studied at the Moscow Circus School (1944–49) and then joined the circus as an eccentric tightrope walker. In 1952 he first appeared as a clown when the

Oleg Popov was a member of the Moscow Circus who was the most popular clown in the Soviet Union in the second half of the 20th century. Popov studied at the Moscow Circus School (1944–49) and then joined the circus as an eccentric tightrope walker. In 1952 he first appeared as a clown when the

Reichstag fire: …Reichstag, and three Bulgarian communists—Simon Popov, Vassili Tanev, and Georgi Dimitrov. Dimitrov in particular won international fame for his fearless and skilled defense against Nazi prosecutors. All four of the accused communists were acquitted because of the lack of evidence.

Lyubov Sergeyevna Popova was one of the most distinctly individual artists of the Russian avant-garde, who excelled as a painter, graphic artist, theatrical set designer, textile designer, teacher, and art theorist. Popova was born into a wealthy family of Moscow factory owners, which secured her a

Gregg Popovich is an American basketball coach who led the San Antonio Spurs to National Basketball Association (NBA) championships in 1999, 2003, 2005, 2007, and 2014. Popovich, who is of Serb and Croatian descent, played basketball while attending the U.S. Air Force Academy, becoming the team’s

Pavel Popovich was a Soviet cosmonaut who piloted the Vostok 4 spacecraft, launched August 12, 1962. He and Andriyan G. Nikolayev, who was launched a day earlier in Vostok 3, became the first two men to be in space simultaneously. The two spacecraft came within 5 km (3 miles) of each other. Vostok

Old Believer: One group, the Popovtsy (priestly sects), sought to attract ordained priests and were able to set up an episcopate in the 19th century. The other, the Bezpopovtsy (priestless sects), renounced priests and all sacraments, except Baptism. Many other sects developed out of these groups, some with practices considered…

Larry Woiwode: Poppa John (1981) concerns an out-of-work television actor, and Indian Affairs (1992) is a sequel to What I’m Going to Do.

Matthäus Daniel Pöppelmann was a German architect, best known for his design of the Zwinger, a building complex in Dresden that is considered one of the most successful realizations of the Baroque aesthetic. Pöppelmann spent almost his entire professional career as a state-employed architect in

Bonn: …Bonn [founded 1786]) and the Poppelsdorf Palace, with its botanical gardens, along with the city’s beautiful avenues and parks are reminders of the electoral and archiepiscopal capital. Recreational areas include the forests of Venusberg, Kreuzberg, Kottenforst, and Ennert on the southern and western fringes of the city. Beyond the city,…

snowboarding: History of snowboarding: …about in 1965, when engineer Sherman Poppen of Muskegon, Michigan—the widely acknowledged “father of the snowboard”—invented the prototype that paved the way for the modern board. The “Snurfer” got its snappy name from Poppen’s wife, who neatly combined the two words that described the contraption’s purpose: surfing on snow. Poppen’s…

New York City: Queens: …William Englehardt Steinway (pianos) and Conrad Poppenhusen (rubber); the later development of the Newtown Creek area brought heavy industry and drew many immigrant workers into the county.

amyl nitrite, drug once commonly used in the treatment of angina pectoris, a condition characterized by chest pain precipitated by oxygen deficiency in the heart muscle. Amyl nitrite is one of the oldest vasodilators (i.e., agents that expand blood vessels). The drug is useful in treating cyanide

Karl Popper was an Austrian-born British philosopher of natural and social science who subscribed to anti-determinist metaphysics, believing that knowledge evolves from experience of the mind. Although his first book, Logik der Forschung (1934; The Logic of Scientific Discovery), was published by

Karl Popper was an Austrian-born British philosopher of natural and social science who subscribed to anti-determinist metaphysics, believing that knowledge evolves from experience of the mind. Although his first book, Logik der Forschung (1934; The Logic of Scientific Discovery), was published by

valve: On gasoline engines, poppet valves are used to control the admission and rejection of the intake and exhaust gases to the cylinders. In the Figure (right centre), the valve, which consists of a disk with a tapered edge attached to a shank, is held against the tapered seat…

cricket: Field of play, equipment, and dress: …behind the wicket; and the popping crease is a line parallel with the bowling crease and 4 feet in front of it. The bowling and return creases mark the area within which the bowler’s rear foot must be grounded in delivering the ball; the popping crease, which is 62 feet…

Mary Poppins, fictional character, the heroine of several children’s books by P.L. Travers. Poppins is an efficient, sensible English nanny with magical powers. With humour and good-hearted firmness, she instills in her young charges a sense of wonder, as well as a respect for limits. Her magical

Damasus II was the pope from July 17 to Aug. 9, 1048. His brief reign, delayed by a rival claimant to the papal throne, occurred during a period when the German emperors and factions of the Roman nobility vied for control of the papacy. He was bishop of Brixen when nominated (December 1047) by the

poppy, any of several flowering plants of the poppy family (Papaveraceae), especially species of the genus Papaver. Most poppies are found in the Northern Hemisphere, and several species of poppies are cultivated as garden ornamentals. Poppies have lobed or dissected leaves and milky sap. The buds

Papaveraceae, the poppy family of flowering plants (order Ranunculales), with 44 genera and 825 species. Most of these are herbaceous plants, but the family also includes some woody shrubs and a genus of small tropical trees. The family is outstanding for its many garden ornamentals and

mallow: …ornamental shrub from South America; poppy mallow (Callirhoe involucrata), a hairy perennial, low-growing, with poppy-like reddish flowers; and Indian mallow, also called velvetleaf (Abutilon theophrasti), a weedy plant. Chaparral mallows (Malacothamnus species), a group of shrubs and small trees, are native to California and Baja California. The Carolina mallow (Modiola…

poppy seed, tiny dried seed of the opium poppy, used as food, food flavouring, and the source of poppy-seed oil. Poppy seeds have no narcotic properties, because the fluid contained in the bud that becomes opium is present only before the seeds are fully formed. The plant, Papaver somniferum, is an

Poprad, city, eastern Slovakia. Located in the Poprad River valley between the Vysoké Tatra Mountains, the Nizké Tatry Mountains, and the Levočské Mountains, it is a centre for the valley’s agricultural area, where potatoes, barley, oats, and flax are grown and sheep are reared. Lumbering is an

Popular Party, Spanish conservative political party. The Popular Party (PP) traces its origins to the Popular Alliance, a union of seven conservative political parties formed in the 1970s by Manuel Fraga Iribarne, a prominent cabinet member under Spain’s longtime dictator Francisco Franco. In March

popular art, any dance, literature, music, theatre, or other art form intended to be received and appreciated by ordinary people in a literate, technologically advanced society dominated by urban culture. Popular art in the 20th century is usually dependent on such technologies of reproduction or

Djibouti: Political process: …a single-party system, with the Popular Assembly for Progress (Rassemblement Populaire pour le Progrès; RPP) being the sole legal party. During this time deputies to the National Assembly could be elected only from a list supplied by the RPP; abstention from voting was the only legal form of opposition.

Bulgaria: Attempts to stabilize government: …a reconstituted opposition called the Popular Bloc, a coalition that included the moderate wing of the Agrarian Union, defeated the Democratic Alliance.

Democratic Front for the Liberation of Palestine (DFLP), one of several organizations associated with the Palestine Liberation Organization (PLO); it engaged in acts of terrorism in the 1970s and ’80s and originally maintained a Marxist-Leninist orientation, believing the peasants and the working

Puerto Rico: Government: …two leading parties are the Popular Democratic Party, which supports the continuation of commonwealth status, and the New Progressive Party, which favours U.S. statehood. Together these two parties have commanded virtually all the vote in elections since the late 20th century. The Puerto Rican Independence Party, which won one-fifth of…

José Manuel Barroso: Barroso joined Portugal’s centre-right Social Democratic Party (Partido Social Democrata; PSD) in 1980. When the party’s Aníbal Cavaco Silva was elected prime minister in 1985, he appointed Barroso undersecretary of state for the home affairs ministry. Two years later Barroso moved to secretary of state for the ministry of…

Peru: The short presidencies of Martín Vizcarra (2018–20), Manuel Merino (2020), and Francisco Sagasti (2020–21) and the COVID-19 pandemic: …the blocking actions of the Popular Force party, still led by Keiko Fujimori. Significantly, about one-half of Congress was under investigation for corruption, including Fujimori, who began serving a “preventive” pretrial 18-month term in prison for corruption and money laundering related to the Petrobras scandal. The investigation of that scandal…

Latvia: Independence restored: An opposition Latvian Popular Front emerged in 1988 and won the 1990 elections. On May 4 the legislature passed a declaration to renew independence after a transition period. Soviet efforts to restore the earlier situation culminated in violent incidents in Riga in January 1991. After a failed coup…

popular front, any coalition of working-class and middle-class parties united for the defense of democratic forms against a presumed Fascist assault. In the mid-1930s European Communist concern over the gains of Fascism, combined with a Soviet policy shift, led Communist parties to join with

Oman: Periodic civil unrest: …Arab Gulf (later called the Popular Front for the Liberation of Oman; PFLO) gained control of the growing rebellion by the late 1960s with the aid of the People’s Republic of China, the Soviet Union, Marxist South Yemen (which had achieved independence from the British in late 1967), and Iraq.

Popular Front for the Liberation of Palestine (PFLP), organization providing an institutional framework for militant organizations associated with the Palestine Liberation Organization (PLO), notable for its Marxist-Leninist ideology and its hijacking of a number of aircraft between 1968 and 1974.

Palestine: Fatah and other guerrilla organizations: …Liberation of Palestine (DFLP), the Popular Front for the Liberation of Palestine–General Command (PFLP–GC, a splinter group from the PFLP), and al-Ṣāʿiqah (backed by Syria). These groups joined forces inside the PLO despite their differences in ideology and tactics (some were dedicated to openly terrorist tactics). In 1969 Yasser Arafat,…

Polisario Front, politico-military organization striving to end Moroccan control of the former Spanish territory of Western Sahara, in northwestern Africa, and win independence for that region. The Polisario Front is composed largely of the indigenous nomadic inhabitants of the Western Sahara

Oman: Periodic civil unrest: …Arab Gulf (later called the Popular Front for the Liberation of Oman; PFLO) gained control of the growing rebellion by the late 1960s with the aid of the People’s Republic of China, the Soviet Union, Marxist South Yemen (which had achieved independence from the British in late 1967), and Iraq.

Popular Movement for the Liberation of Angola, Angolan political party. The MPLA, founded in 1956, merged two nationalist organizations and was centred in the country’s capital city of Luanda. From 1962 it was led by Agostinho Neto, who eventually became Angola’s first president. It fought the

Popular Mechanics, American print and online magazine that publishes articles on home improvement, automobile maintenance, and new advancements in technology and science. Founded in 1902 by Henry H. Windsor, Popular Mechanics is one of the oldest magazines in the United States. It has been

Popular Movement for the Liberation of Angola, Angolan political party. The MPLA, founded in 1956, merged two nationalist organizations and was centred in the country’s capital city of Luanda. From 1962 it was led by Agostinho Neto, who eventually became Angola’s first president. It fought the

Democratic Republic of the Congo: Political process: The Popular Movement of the Revolution (Mouvement Populaire de la Révolution; MPR) was the sole legal political party from 1970 until 1990. It was presided over by then president Mobutu and had branches at every administrative level throughout the country. The MPR splintered into factions after…

Ukraine: Political process: The centre-right, nationalistic Popular Movement of Ukraine, or Rukh, founded in 1989, was instrumental in the campaign for Ukrainian independence but afterward lost strength. The CPU—re-formed in 1993 after a 1991 ban on the Soviet-era CPU was lifted—retains support, mainly in the industrialized and Russophone reaches of eastern…

popular music, any commercially oriented music principally intended to be received and appreciated by a wide audience, generally in literate, technologically advanced societies dominated by urban culture. Unlike traditional folk music, popular music is written by known individuals, usually

Popular Party, Spanish conservative political party. The Popular Party (PP) traces its origins to the Popular Alliance, a union of seven conservative political parties formed in the 1970s by Manuel Fraga Iribarne, a prominent cabinet member under Spain’s longtime dictator Francisco Franco. In March

Ivan Evstatiev Geshov: …became the leader of the Popular Party (1901) and in 1911–13 presided over a coalition government that promoted the policy of the Balkan Alliance and waged the war with the Turks in 1912. In 1923 he joined the “Democratic Entente” after the fall of Aleksandŭr Stamboliyski.

Panama: Transitions to democracy and sovereignty: …of the largest party, the Christian Democrats (Partido Demócrata Cristiano; PDC), led by Vice President Ricardo Arias Calderón. This left the administration without a legislative majority and allowed the remnants of Noriega’s Democratic Revolutionary Party (Partido Revolucionario Democrático; PRD) to regain some political power. As a result, accomplishments were meagre…

Italian Popular Party, former centrist Italian political party whose several factions were united by their Roman Catholicism and anticommunism. They advocated programs ranging from social reform to the defense of free enterprise. The DC usually dominated Italian politics from World War II until the

Buddhism: New Year and harvest festivals: …same interplay between Buddhism and folk tradition is observable elsewhere. At harvest time in Sri Lanka, for example, there is a “first fruits” ceremony that entails offering the Buddha a large bowl of milk and rice. Moreover, an integral part of the harvest celebrations in many Buddhist countries is the…

Popular Republican Movement, former French social reform party whose policies corresponded largely to the European Christian Democratic tradition. Founded on Nov. 26, 1944, shortly after the end of the German occupation of France during World War II, the MRP consistently won some 25 percent of the

APRA, political party founded by Víctor Raúl Haya de la Torre (1924), which dominated Peruvian politics for decades. Largely synonymous with the so-called Aprista movement, it was dedicated to Latin American unity, the nationalization of foreign-owned enterprises, and an end to the exploitation of

history of publishing: Literary and scientific magazines: …whose magazine encouraged other inventors; Popular Science Monthly, which was founded in 1872, to spread scientific knowledge and which had the philosophers William James and John Dewey among its contributors; and the ever-popular National Geographic Magazine, founded in 1888 and published ever since by the National Geographic Society, which used…

Yo La Tengo: Subsequent albums, such as Popular Songs (2009) and Fade (2013), further showcased the band’s stylistic fluency as its members grew into middle age. Schramm briefly returned to the band for the covers collection Stuff Like That There (2015). The contemplative There’s a Riot Going On (2018) was the band’s…

popular sovereignty, in U.S. history, a controversial political doctrine according to which the people of federal territories should decide for themselves whether their territories would enter the Union as free or slave states. Its enemies, especially in New England, called it “squatter

Salvador Allende: …ran as the candidate of Popular Unity, a bloc of Socialists, Communists, Radicals, and some dissident Christian Democrats, leading in a three-sided race with 36.3 percent of the vote. Because he lacked a popular majority, however, his election had to be confirmed by Congress, in which there was strong opposition…

Catalonia: The Catalonian independence movement in the 21st century: The antiausterity Popular Unity Candidacy, which won 10 seats, entered into a coalition with Junts pel Sí to give pro-independence parties a narrow parliamentary majority. Those who favoured independence interpreted the result as a victory, while those who opposed it emphasized the fact that pro-independence parties received…

Juan Guaidó: Opposition to Chávez and Maduro: …2009 he helped establish the Popular Will (Voluntad Popular) party, which pledged to “build a more secure, united and prosperous country where everyone will be entitled to all rights.” In the process, he grew close to the charismatic Leopoldo López, who would become one of the most prominent leaders of…

Optimates and Populares, (Latin: respectively, “Best Ones,” or “Aristocrats”, and “Demagogues,” or “Populists”), two principal patrician political groups during the later Roman Republic from about 133 to 27 bc. The members of both groups belonged to the wealthier classes. The Optimates were the

population, in human biology, the whole number of inhabitants occupying an area (such as a country or the world) and continually being modified by increases (births and immigrations) and losses (deaths and emigrations). As with any biological population, the size of a human population is limited by

statistics: Estimation: …a particular study form the population. Because of time, cost, and other considerations, data often cannot be collected from every element of the population. In such cases, a subset of the population, called a sample, is used to provide the data. Data from the sample are then used to develop…

environmental science: Ehrlich’s The Population Bomb (1968), together with nuclear proliferation and growing concerns over the anthropogenic release of toxins and chemicals, raised awareness about the need to study the effects of human actions on the environment. The burgeoning field of environmental science took on the task of…

evolution: Genetic drift: Such occasional reductions are called population bottlenecks. The populations may later recover their typical size, but the allelic frequencies may have been considerably altered and thereby affect the future evolution of the species. Bottlenecks are more likely in relatively large animals and plants than in smaller ones, because populations of…

census, an enumeration of people, houses, firms, or other important items in a country or region at a particular time. Used alone, the term usually refers to a population census—the type to be described in this article. However, many countries take censuses of housing, manufacturing, and

Population Council, international nonprofit nongovernmental organization (NGO) founded in 1952 to contribute to an equitable and sustainable balance between the needs of the world’s population and available resources. The Population Council is especially active in three areas: HIV/AIDS;

population density, the number of individuals of a certain species per unit area. It can be expressed by the formula D p = N i / A where Dp is population density, Ni is the number of individuals of the species in question, and A is the area expressed in square units, often square kilometers (km2)

angiosperm: Distribution and abundance: …and their almost complete worldwide distribution. The only area without angiosperms is the southern region of the Antarctic continent, although two angiosperm groups are found in the islands off that continent. Angiosperms dominate terrestrial vegetation, particularly in the tropics, although submerged and floating aquatic angiosperms do exist throughout the world.…

population ecology, study of the processes that affect the distribution and abundance of animal and plant populations. A population is a subset of individuals of one species that occupies a particular geographic area and, in sexually reproducing species, interbreeds. The geographic boundaries of a

history of technology: Population explosion: …come to grips with the population problem in the next few decades if life is to be tolerable on planet Earth in the 21st century. The problem can be tackled in two ways, both drawing on the resources of modern technology.

population ecology: Population fluctuation: As stated above, populations rarely grow smoothly up to the carrying capacity and then remain there. Instead, fluctuations in population numbers, abundance, or density from one time step to the next are the norm. Population cycles make up a special type of population…

heredity: Population genetics: Because the processes of variation and selection take place at the population level, the basic theory of the genetics of evolutionary change is contained in the general area known as population genetics.

demography, statistical study of human populations, especially with reference to size and density, distribution, and vital statistics (births, marriages, deaths, etc.). Contemporary demographic concerns include the “population explosion,” the interplay between population and economic development,

population growth, in population ecology, a change in the number of members of a certain plant or animal species in a particular location during a particular time period. Factors affecting population growth include fertility, mortality, and, in animals, migration—i.e., immigration to or emigration

Populations I and II: II, in astronomy, two broad classes of stars and stellar assemblages defined in the early 1950s by the German-born astronomer Walter Baade. The members of these stellar populations differ from each other in various ways, most notably in age, chemical composition, and location within galactic…

Populations I and II: …framework has been extended to Population III stars, hypothetical objects that would have been the very first stars to form in the universe out of the interstellar gas clouds that emerged shortly after the big bang, a state of extremely high temperature and density from which the universe is believed…