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Andorra | Economy | Economy
Tourism, the mainstay of Andorra's economy, accounts for roughly 80% of GDP. An estimated 8 million tourists visit annually, attracted by Andorra's duty-free status and by its summer and winter resorts.
One of the main sources of income in Andorra is from ski resorts, which total over of ski grounds. The sport brings in over 7 million visitors annually and an estimated 340 million euros per year, sustaining 2,000 direct and 10,000 indirect jobs at present since 2007.
The banking sector, with its tax haven status, also contributes substantially to the economy with revenues raised exclusively through import tariffs (the financial and insurance sector accounts for approximately 19% of GDP). However, during the European sovereign-debt crisis of the 21st century, the tourist industry suffered a decline, partly caused by a drop in the prices of goods in Spain, undercutting duty-free shopping and increasing unemployment. On 1 January 2012, a business tax of 10% was introduced, followed by a sales tax of 2% a year later, which raised just over 14 million euros in its first quarter.
Agricultural production is limited; only 1.7% of the land is arable, and most food has to be imported. Some tobacco is grown locally. The principal livestock activity is domestic sheep raising. Manufacturing output consists mainly of cigarettes, cigars, and furniture. Andorra's natural resources include hydroelectric power, mineral water, timber, iron ore, and lead.
Andorra is not a member of the European Union, but enjoys a special relationship with it, such as being treated as an EU member for trade in manufactured goods (no tariffs) and as a non-EU member for agricultural products. Andorra lacked a currency of its own and used both the French franc and the Spanish peseta in banking transactions until 31 December 1999, when both currencies were replaced by the EU's single currency, the euro. Coins and notes of both the franc and the peseta remained legal tender in Andorra until 31 December 2002. Andorra negotiated to issue its own euro coins, beginning in 2014.
Andorra has historically had one of the world's lowest unemployment rates. In 2023 it stood at 1.5%.
On 31 May 2013, it was announced that Andorra intended to legislate for the introduction of an income tax by the end of June, against a background of increasing dissatisfaction with the existence of tax havens among EU members. The announcement was made following a meeting in Paris between the Prime Minister Antoni Martí and the French President and Prince of Andorra François Hollande. Hollande welcomed the move as part of a process of Andorra "bringing its taxation in line with international standards".
By the mid-2010s, the financial system comprised five banking groups, one specialised credit entity, eight investment undertaking management entities, three asset management companies, and 29 insurance companies, 14 of which are branches of foreign insurance companies authorised to operate in the principality. The last mergers between banks took place in 2022, bringing the Andorran financial sector to currently have 3 active banking groups. |
Andorra | Demographics | Demographics
thumb|The town of Encamp, as seen from the Vall dels Cortals |
Andorra | Population | Population
The population of Andorra is estimated at (). The Andorrans are a Romance ethnic group of originally Catalan descent. The population has grown from 5,000 in 1900.
Two-thirds of residents lack Andorran nationality and do not have the right to vote in communal elections. Moreover, they are not allowed to be elected as prime minister or to own more than 33% of the capital stock of a privately held company.
The largest national groups in Andorra are Spanish (34.3%), Andorrans (32.1%), Portuguese (10%), and French (5.6%). The remaining 18% of the population includes British, Dutch, Germans, Italians and other Europeans, as well as Argentinians, Chileans, Indians, Moroccans and Uruguayans. |
Andorra | Languages | Languages
The historic and official language is Catalan, a Romance language. The Andorran government encourages the use of Catalan. It funds a Commission for Catalan Toponymy in Andorra (Catalan: ), and provides free Catalan classes to assist immigrants. Andorran television and radio stations use Catalan.
Because of immigration, historical links, and close geographic proximity, Spanish, Portuguese and French are commonly spoken. Most Andorran residents can speak one or more of these, in addition to Catalan. English is less commonly spoken among the general population, though it is understood to varying degrees in the major tourist resorts. Andorra is one of only four European countries (together with France, Monaco, and Turkey) that have never signed the Council of Europe Framework Convention on National Minorities. |
Andorra | Religion | Religion
Few official statistics are available on religion; estimates of the Catholic population in 2020 range from 89.5% to 99.21%. The patron saint is Our Lady of Meritxell. There are also members of various Protestant denominations and small numbers of Hindus, and Bahá'ís. In 2022 there were approximately 2000 Muslims and roughly 100 Jews. |
Andorra | Largest cities | Largest cities |
Andorra | Education | Education
The Qualified Education Law (llei qualificada d'educació) of Andorra was passed in 1993. It guarantees free, public education from age four until the end of compulsory schooling. |
Andorra | Schools | Schools
Children between the ages of 6 and 16 are required by law to have full-time education. Education up to secondary level is provided free of charge by the government.
There are three systems of school, Andorran, French and Spanish, which use Catalan, French and Spanish languages respectively, as the main language of instruction. Parents may choose which system their children attend. All schools are built and maintained by Andorran authorities, but teachers in the French and Spanish schools are paid for the most part by France and Spain. 39% of Andorran children attend Andorran schools, 33% attend French schools, and 28% Spanish schools. |
Andorra | University of Andorra | University of Andorra
The Universitat d'Andorra (UdA) is the state public university and is the only university in Andorra. It was established in 1997. The university provides first-level degrees in nursing, computer science, business administration, and educational sciences, in addition to higher professional education courses. The only two graduate schools in Andorra are the Nursing School and the School of Computer Science, the latter having a PhD programme. |
Andorra | Virtual Studies Centre | Virtual Studies Centre
The geographical complexity of the country as well as the small number of students prevents the University of Andorra from developing a full academic programme, and it serves principally as a centre for virtual studies, connected to Spanish and French universities. The Virtual Studies Centre (Centre d'Estudis Virtuals) at the university runs approximately 20 different academic degrees at both undergraduate and postgraduate levels in fields including tourism, law, Catalan philology, humanities, psychology, political sciences, audiovisual communication, telecommunications engineering, and East Asia studies. The centre also runs various postgraduate programmes and continuing-education courses for professionals. |
Andorra | Transport | Transport
left|thumb|Andorra–La Seu d'Urgell Airport, located away from Andorra, in Montferrer i Castellbò (Catalonia, Eastern Spain)
Until the 20th century, Andorra had very limited transport links to the outside world, and development of the country was affected by its physical isolation. Even now, the nearest major airports at Toulouse and Barcelona are both three hours' drive from Andorra.
Andorra has a road network of , of which is unpaved. The two main roads out of Andorra la Vella are the CG-1 to the Spanish border near Sant Julià de Lòria, and the CG-2 to the French border via the Envalira Tunnel near El Pas de la Casa. Bus services cover all metropolitan areas and many rural communities, with services on most major routes running half-hourly or more frequently during peak travel times. There are frequent long-distance bus services from Andorra to Barcelona and Toulouse, plus a daily tour from the former city. Bus services mostly are run by private companies, but some local ones are operated by the government.
thumb|A train at Latour-de-Carol (La Tor de Querol), one of the two stations serving Andorra. Andorra has no railways, although the line connecting Latour-de-Carol and Toulouse, which in turn connects to France's TGVs at Toulouse, runs within of the Andorran border
There are no airports for fixed-wing aircraft within Andorra's borders but there are, however, heliports in La Massana (Camí Heliport), Arinsal and Escaldes–Engordany with commercial helicopter services and an airport located in the neighbouring Spanish comarca of Alt Urgell, south of the Andorran–Spanish border. Since July 2015, Andorra–La Seu d'Urgell Airport has operated commercial flights to Madrid and Palma de Mallorca, and is the main hub for Andorra Airlines.
Nearby airports located in Spain and France provide access to international flights for the principality. The nearest airports are at Perpignan, France ( from Andorra) and Lleida, Spain ( from Andorra). The largest nearby airports are at Toulouse, France ( from Andorra and Barcelona, Spain ( from Andorra). There are hourly bus services from both Barcelona and Toulouse airports to Andorra.
The nearest railway station is Andorre-L'Hospitalet station east of Andorra which is on the -gauge line from Latour-de-Carol () southeast of Andorra, to Toulouse and on to Paris by the French high-speed trains. This line is operated by the SNCF. Latour-de-Carol has a scenic trainline to Villefranche-de-Conflent, as well as the SNCF's -gauge line connecting to Perpignan, and the Renfe's -gauge line to Barcelona. There are also direct Intercités de nuit trains between L'Hospitalet-près-l'Andorre and Paris on certain dates. |
Andorra | Media and telecommunications | Media and telecommunications
thumb|RTVA, the public service television and radio broadcaster in Andorra
thumb|Andorra Telecom, the national telecom company in Andorra
In Andorra, mobile and fixed telephone and internet services are operated exclusively by the Andorran national telecommunications company, SOM, also known as Andorra Telecom (STA). The same company also manages the technical infrastructure for national broadcasting of digital television and radio. In 2010 Andorra became the first country to provide a direct optical fiber link to all homes (FTTH) and businesses.
The first commercial radio station to broadcast was Radio Andorra, which was active from 1939 to 1981. On 12 October 1989, the General Council established radio and television as essential public services creating and managing the entity ORTA, becoming on 13 April 2000, in the public company Ràdio i Televisió d'Andorra (RTVA). In 1990, the public radio was founded on the Radio Nacional d'Andorra. As an autochthonous television channel, there is only the national public television network Andorra Televisió, created in 1995. Additional TV and radio stations from Spain and France are available via digital terrestrial television and IPTV.
There are three national newspapers, Diari d'Andorra, El Periòdic d'Andorra, and Bondia as well as several local newspapers. The history of the Andorran press begins in the period between 1917 and 1937 with the appearance of several periodicals papers such as Les Valls d'Andorra (1917), Nova Andorra (1932) and Andorra Agrícola (1933). In 1974, the Poble Andorrà became the first regular newspaper in Andorra. There is also an amateur radio societyUnió de Radioaficionats Andorra. Ura.ad. Retrieved on 30 December 2015. and news agency ANA with independent management. |
Andorra | Culture | Culture
Andorra is home to folk dances like the contrapàs and marratxa, which survive in Sant Julià de Lòria especially. Andorran folk music has similarities to the music of its neighbours, but is especially Catalan in character, especially in the presence of dances such as the sardana. Other Andorran folk dances include contrapàs in Andorra la Vella and Saint Anne's dance in Escaldes-Engordany. Andorra's national holiday is Our Lady of Meritxell Day, 8 September.
Among the more important festivals and traditions are the Canólich Gathering in May, the Roser d'Ordino in July, the Meritxell Day (National Day of Andorra), the Andorra la Vella Fair, the Sant Jordi Day, the Santa Llúcia Fair, the Festivity from La Candelera to Canillo, the Carnival of Encamp, the sung of caramelles, the Festivity of Sant Esteve and the Festa del Poble.
Andorra participated regularly in the Eurovision Song Contest between 2004 and 2009, being the only participating country presenting songs in Catalan.
In popular folklore, the best-known Andorran legends are the legend of Charlemagne, according to which this Frankish King would have founded the country, the White Lady of Auvinyà, the Buner d'Ordino, the legend of Engolasters Lake and the legend of Our Lady of Meritxell.
Andorran gastronomy is mainly Catalan, although it has also adopted other elements of French and Italian cuisines. The cuisine of the country has similar characteristics with the neighbours of Cerdanya and Alt Urgell, with whom it has strong cultural ties. Andorra's cuisine is marked by its nature as mountain valleys. Typical dishes of the country are quince all-i-oli, duck with winter pear, roast lamb with nuts, pork civet, massegada cake, escarole with pears, duck confit and mushrooms, escudella, spinach with raisins and pine nuts, jelly marmalade, stuffed murgues (mushrooms) with pork, dandelion salad, and Andorran river trout. To drink, mulled wine and beer are also popular. Some of the dishes are very common in the mountainous regions of Catalonia, such as trinxat, embotits, cooked snails, rice with mushrooms, mountain rice and mató.
Pre-Romanesque and Romanesque art are one of the most important artistic manifestations and characteristics of the Principality. The Romanesque one allows to know the formation of the parochial communities, the relations of (social and political) power and the national culture. There are a total of forty Romanesque churches that stand out as being small austere ornamentation constructions, as well as bridges, fortresses and manor houses of the same period.
Summer solstice fire festivals in the Pyrenees was included as UNESCO Intangible cultural heritage in 2015. Also the Madriu-Perafita-Claror Valley became Andorra's first, and to date its only, UNESCO World Heritage Site in 2004, with a small extension in 2006. |
Andorra | Sports | Sports
Andorra is famous for its winter sports. Andorra has the largest territory of ski slopes in the Pyrenees (3100 hectares and about 350 km of slopes) and two ski resorts. Grandvalira is the largest and most popular resort. Other popular sports played in Andorra include football, rugby union, basketball, and roller hockey.
For roller hockey, Andorra usually plays in the CERH Euro Cup and FIRS Roller Hockey World Cup. In 2011, Andorra was the host country to the 2011 European League Final Eight.
The country is represented in association football by the Andorra national football team. The team gained its first competitive win in a European Championship qualifier on 11 October 2019, against Moldova. Football is governed in Andorra by the Andorran Football Federation – founded in 1994, it organises the national competitions of association football (Primera Divisió, Copa Constitució and Supercopa) and futsal. Andorra was admitted to UEFA and FIFA in the same year, 1996. FC Andorra, a club based in Andorra la Vella founded in 1942, compete in the Spanish football league system.
Rugby is a traditional sport in Andorra, mainly influenced by its popularity in southern France. The Andorra national rugby union team, nicknamed Els Isards, plays on the international stage in rugby union and rugby sevens. VPC Andorra XV is a rugby team based in Andorra la Vella, which actually plays in the French championship.
Basketball's popularity has increased in the country since the 1990s, when the Andorran team BC Andorra played in the top league of Spain (Liga ACB). After 18 years the club returned to the top league in 2014.
Other sports practised in Andorra include cycling, volleyball, judo, Australian Rules football, handball, swimming, gymnastics, tennis, and motorsports. In 2012, Andorra raised its first national cricket team and played a home match against the Dutch Fellowship of Fairly Odd Places Cricket Club, the first match played in the history of Andorra at an altitude of .
Andorra first participated at the Olympic Games in 1976. The country has appeared in every Winter Olympic Games since 1976. Andorra competes in the Games of the Small States of Europe, being twice the host country, in 1991 and 2005.
As one of the Catalan Countries, Andorra is home to a team of castellers, or Catalan human tower builders. The , based in the town of Santa Coloma d'Andorra, are recognised by the , the governing body of castells. |
Andorra | Tourism | Tourism
Skiing, hiking, cross-country running, and cycling are all popular sports tourism activities in Andorra. Andorra's economy is heavily built on tourism.
Andorra generally enjoys a ski season from late November to early April, depending on weather conditions. Outside of the ski season, some of the ski lift facilities continue to operate at lower capacity, facilitating access to popular view points such as the Tristaina solar viewpoint, a viewpoint–sundial located on the peak of Peyreguils at an altitude of 2,701 metres and a few metres from the geographical border between Andorra and France. This peak is part of the Tristaina cirque, along with the Costa Rodona, Tristaina, Creussans, and Cabanyó peaks. |
Andorra | See also | See also
Index of Andorra-related articles
Outline of Andorra
Bibliography of Andorra |
Andorra | Explanatory notes | Explanatory notes |
Andorra | Citations | Citations |
Andorra | General and cited bibliography | General and cited bibliography
|
Andorra | Further reading | Further reading
Berthet, Elie, The Valley of Andorra. Bristol, UK: J. W. Arrowsmith, 1886.
Butler, Michael, Frisch: Andorra.
Carrick, Noel, Let's Visit Andorra. London: Macmillan, 1988.
Deane, Shirley, The Road to Andorra. London: John Murray, 1960.
Duursma, John C., Fragmentation and the International Relations of Micro-States. Cambridge University Press, 1996.
Jenner, Paul; Christine Smith, Landscapes of the Pyrenees. London: Sunflower Books, 1990.
Johnson, Virginia W., Two Quaint Republics: Andorra and San Marino.
Leary, Lewis Gaston, Andorra the Hidden Republic. London: T. Fisher Unwin, 1912.
Mackintosh, May, Assignment in Andorra. London: Pan, 1976.
Murray, James Erskine, A Summer in the Pyrenees. London: John Macrone, 1837.
Newman, Bernard, Round About Andorra. London: George Allen; Unwin, 1928.
Piesold, Werner, Andorra.
Reichert, Thomas, Andorra: A Country Survey. Nuremberg, 1986.
Spender, Harold; H. Llewellyn Smith, Through the High Pyrenees. London: A. D. Innes, 1898.
Vila, Linda Armengol, Approach to the History of Andorra. Perpignan: Institut d'Estudis Andorrans, 1989.
Vilajoana, Ricard Fiter; M. Marti Rebols, All Andorra. Barcelona: Escudo de Oro, 1979.
Waagenaar, Sam, The Little Five. London: Andre Deutsch, 1960. |
Andorra | External links | External links
Govern d'Andorra – Official governmental site
Andorra. The World Factbook. Central Intelligence Agency.
Portals to the World from the United States Library of Congress
Andorra from UCB Libraries GovPubs
Andorra from the BBC News
Andorra – Guía, turismo y de viajes
History of Andorra: Primary Documents from EuroDocs
A New Path for Andorra – slideshow by The New York Times
Category:1278 establishments in Europe
Category:Catalan Countries
Category:Christian states
Category:Countries in Europe
Category:Diarchies
Category:Duty-free zones of Europe
Category:Iberian Peninsula countries
Category:Important Bird Areas of Andorra
Category:Landlocked countries
Category:Member states of the Council of Europe
Category:Member states of the Organisation internationale de la Francophonie
Category:Member states of the United Nations
Category:Monarchies of Europe
Category:Prince-bishoprics
Category:Principalities
Category:Pyrenees
Category:Religion and politics
Category:Spanish-speaking countries and territories
Category:Special economic zones
Category:States and territories established in 1278
Category:Microstates in Europe |
Andorra | Table of Content | short description, Etymology, History, Prehistory, Iberian and Roman Andorra, Visigoths and Carolingians: the legend of Charlemagne, Middle Ages: The Paréages and the founding of the Co-Principality, 16th to 18th centuries, 19th century: the New Reform and the Andorran Question <span class="anchor" id="New Reform of Andorra"></span>, 20th and 21st century: Modernisation of the country and constitutional Andorra, Politics, Law and criminal justice, Foreign relations, defence and security, Military, Andorra in the Council of Europe, Police Corps, GIPA, Fire brigade, Geography, Parishes, Physical geography, Environment, Important Bird Area, Climate, Economy, Demographics, Population, Languages, Religion, Largest cities, Education, Schools, University of Andorra, Virtual Studies Centre, Transport, Media and telecommunications, Culture, Sports, Tourism, See also, Explanatory notes, Citations, General and cited bibliography, Further reading, External links |
Arithmetic mean | Short description | In mathematics and statistics, the arithmetic mean ( ), arithmetic average, or just the mean or average (when the context is clear) is the sum of a collection of numbers divided by the count of numbers in the collection. The collection is often a set of results from an experiment, an observational study, or a survey. The term "arithmetic mean" is preferred in some mathematics and statistics contexts because it helps distinguish it from other types of means, such as geometric and harmonic.
In addition to mathematics and statistics, the arithmetic mean is frequently used in economics, anthropology, history, and almost every academic field to some extent. For example, per capita income is the arithmetic average income of a nation's population.
While the arithmetic mean is often used to report central tendencies, it is not a robust statistic: it is greatly influenced by outliers (values much larger or smaller than most others). For skewed distributions, such as the distribution of income for which a few people's incomes are substantially higher than most people's, the arithmetic mean may not coincide with one's notion of "middle". In that case, robust statistics, such as the median, may provide a better description of central tendency. |
Arithmetic mean | Definition | Definition
The arithmetic mean of a set of observed data is equal to the sum of the numerical values of each observation, divided by the total number of observations. Symbolically, for a data set consisting of the values , the arithmetic mean is defined by the formula:
(For an explanation of the summation operator, see summation.)
In simpler terms, the formula for the arithmetic mean is:
For example, if the monthly salaries of employees are , then the arithmetic mean is:
If the data set is a statistical population (i.e., consists of every possible observation and not just a subset of them), then the mean of that population is called the population mean and denoted by the Greek letter . If the data set is a statistical sample (a subset of the population), it is called the sample mean (which for a data set is denoted as ).
The arithmetic mean can be similarly defined for vectors in multiple dimensions, not only scalar values; this is often referred to as a centroid. More generally, because the arithmetic mean is a convex combination (meaning its coefficients sum to ), it can be defined on a convex space, not only a vector space. |
Arithmetic mean | History | History
The statistician Churchill Eisenhart, senior researcher fellow at the U. S. National Bureau of Standards, traced the history of the arithmetic mean in detail. In the modern age it started to be used as a way of combining various observations that should be identical, but were not such as estimates of the direction of magnetic north.
In 1635 the mathematician Henry Gellibrand described as “meane” the midpoint of a lowest and highest number, not quite the arithmetic mean. In 1668, a person known as “DB” was quoted in the Transactions of the Royal Society describing “taking the mean” of five values: |
Arithmetic mean | Motivating properties | Motivating properties
The arithmetic mean has several properties that make it interesting, especially as a measure of central tendency. These include:
If numbers have mean , then . Since is the distance from a given number to the mean, one way to interpret this property is by saying that the numbers to the left of the mean are balanced by the numbers to the right. The mean is the only number for which the residuals (deviations from the estimate) sum to zero. This can also be interpreted as saying that the mean is translationally invariant in the sense that for any real number , .
If it is required to use a single number as a "typical" value for a set of known numbers , then the arithmetic mean of the numbers does this best since it minimizes the sum of squared deviations from the typical value: the sum of . The sample mean is also the best single predictor because it has the lowest root mean squared error. If the arithmetic mean of a population of numbers is desired, then the estimate of it that is unbiased is the arithmetic mean of a sample drawn from the population.
The arithmetic mean is independent of scale of the units of measurement, in the sense that So, for example, calculating a mean of liters and then converting to gallons is the same as converting to gallons first and then calculating the mean. This is also called first order homogeneity. |
Arithmetic mean | Additional properties | Additional properties
The arithmetic mean of a sample is always between the largest and smallest values in that sample.
The arithmetic mean of any amount of equal-sized number groups together is the arithmetic mean of the arithmetic means of each group. |
Arithmetic mean | Contrast with median | Contrast with median
The arithmetic mean may be contrasted with the median. The median is defined such that no more than half the values are larger, and no more than half are smaller than it. If elements in the data increase arithmetically when placed in some order, then the median and arithmetic average are equal. For example, consider the data sample . The mean is , as is the median. However, when we consider a sample that cannot be arranged to increase arithmetically, such as , the median and arithmetic average can differ significantly. In this case, the arithmetic average is , while the median is . The average value can vary considerably from most values in the sample and can be larger or smaller than most.
There are applications of this phenomenon in many fields. For example, since the 1980s, the median income in the United States has increased more slowly than the arithmetic average of income. |
Arithmetic mean | Generalizations | Generalizations |
Arithmetic mean | Weighted average | Weighted average
A weighted average, or weighted mean, is an average in which some data points count more heavily than others in that they are given more weight in the calculation. For example, the arithmetic mean of and is , or equivalently . In contrast, a weighted mean in which the first number receives, for example, twice as much weight as the second (perhaps because it is assumed to appear twice as often in the general population from which these numbers were sampled) would be calculated as . Here the weights, which necessarily sum to one, are and , the former being twice the latter. The arithmetic mean (sometimes called the "unweighted average" or "equally weighted average") can be interpreted as a special case of a weighted average in which all weights are equal to the same number ( in the above example and in a situation with numbers being averaged). |
Arithmetic mean | Functions | Functions |
Arithmetic mean | Continuous probability distributions | Continuous probability distributions
thumb|300px|Comparison of two log-normal distributions with equal median, but different skewness, resulting in various means and modes
If a numerical property, and any sample of data from it, can take on any value from a continuous range instead of, for example, just integers, then the probability of a number falling into some range of possible values can be described by integrating a continuous probability distribution across this range, even when the naive probability for a sample number taking one certain value from infinitely many is zero. In this context, the analog of a weighted average, in which there are infinitely many possibilities for the precise value of the variable in each range, is called the mean of the probability distribution. The most widely encountered probability distribution is called the normal distribution; it has the property that all measures of its central tendency, including not just the mean but also the median mentioned above and the mode (the three Ms), are equal. This equality does not hold for other probability distributions, as illustrated for the log-normal distribution here. |
Arithmetic mean | Angles | Angles
Particular care is needed when using cyclic data, such as phases or angles. Taking the arithmetic mean of 1° and 359° yields a result of 180°.
This is incorrect for two reasons:
Firstly, angle measurements are only defined up to an additive constant of 360° ( or , if measuring in radians). Thus, these could easily be called 1° and -1°, or 361° and 719°, since each one of them produces a different average.
Secondly, in this situation, 0° (or 360°) is geometrically a better average value: there is lower dispersion about it (the points are both 1° from it and 179° from 180°, the putative average).
In general application, such an oversight will lead to the average value artificially moving towards the middle of the numerical range. A solution to this problem is to use the optimization formulation (that is, define the mean as the central point: the point about which one has the lowest dispersion) and redefine the difference as a modular distance (i.e., the distance on the circle: so the modular distance between 1° and 359° is 2°, not 358°). |
Arithmetic mean | Symbols and encoding | Symbols and encoding
The arithmetic mean is often denoted by a bar (vinculum or macron), as in .
Some software (text processors, web browsers) may not display the "x̄" symbol correctly. For example, the HTML symbol "x̄" combines two codes — the base letter "x" plus a code for the line above ( ̄ or ¯).
In some document formats (such as PDF), the symbol may be replaced by a "¢" (cent) symbol when copied to a text processor such as Microsoft Word. |
Arithmetic mean | See also | See also
Fréchet mean
Generalized mean
Inequality of arithmetic and geometric means
Sample mean and covariance
Standard deviation
Standard error of the mean
Summary statistics |
Arithmetic mean | Notes | Notes |
Arithmetic mean | References | References |
Arithmetic mean | Further reading | Further reading |
Arithmetic mean | External links | External links
Calculations and comparisons between arithmetic mean and geometric mean of two numbers
Calculate the arithmetic mean of a series of numbers on MeanCalculator.com compare it with median and mode
Category:Means |
Arithmetic mean | Table of Content | Short description, Definition, History, Motivating properties, Additional properties, Contrast with median, Generalizations, Weighted average, Functions, Continuous probability distributions, Angles, Symbols and encoding, See also, Notes, References, Further reading, External links |
American Football Conference | short description | The American Football Conference (AFC) is one of the two conferences of the National Football League (NFL), the highest level of professional American football in the United States. The AFC and its counterpart, the National Football Conference (NFC), each have 16 teams organized into four divisions. Both conferences were created as part of the 1970 merger between the National Football League, and the American Football League (AFL). All ten of the AFL teams, and three NFL teams, became members of the new AFC, with the remaining thirteen NFL teams forming the NFC. A series of league expansions and division realignments have occurred since the merger, thus making the current total of 16 teams in each conference. The current AFC champions are the Kansas City Chiefs, who defeated the Buffalo Bills in the 2024 season's AFC Championship Game for their fifth conference championship and went on to lose Super Bowl LIX against the Philadelphia Eagles. |
American Football Conference | Teams | Teams
Like the NFC, the conference has 16 teams organized into four divisions each with four teams: East, North, South and West.
Division Team Location StadiumRef(s) East Buffalo Bills Orchard Park, New York Highmark Stadium Miami Dolphins Miami Gardens, Florida Hard Rock Stadium New England Patriots Foxborough, Massachusetts Gillette Stadium New York Jets East Rutherford, New Jersey MetLife Stadium North Baltimore Ravens Baltimore, Maryland M&T Bank Stadium Cincinnati Bengals Cincinnati, Ohio Paycor Stadium Cleveland Browns Cleveland, Ohio Huntington Bank Field Pittsburgh Steelers Pittsburgh, Pennsylvania Acrisure Stadium South Houston Texans Houston, Texas NRG Stadium Indianapolis Colts Indianapolis, Indiana Lucas Oil Stadium Jacksonville Jaguars Jacksonville, Florida EverBank Stadium Tennessee Titans Nashville, Tennessee Nissan Stadium West Denver Broncos Denver, Colorado Empower Field at Mile High Kansas City Chiefs Kansas City, Missouri Arrowhead Stadium Las Vegas Raiders Paradise, Nevada Allegiant Stadium Los Angeles Chargers Inglewood, CaliforniaSoFi Stadium |
American Football Conference | Season structure | Season structure
AFC East AFC North AFC South AFC West 1st Bills Ravens Texans Chiefs 2nd Dolphins Steelers Colts Chargers 3rd Jets Bengals Jaguars Broncos 4th Patriots Browns Titans Raiders NFC East NFC North NFC South NFC West 1st Eagles Lions Buccaneers Rams 2nd Commanders Vikings Falcons Seahawks 3rd Cowboys Packers Panthers Cardinals 4th Giants Bears Saints 49ers
This chart of the 2024 season standings displays an application of the NFL scheduling formula. The Chiefs in 2024 (highlighted in green) finished in first place in the AFC West. Thus, in 2025, the Chiefs will play two games against each of its division rivals (highlighted in light blue), one game against each team in the AFC South and NFC East (highlighted in yellow), and one game each against the first-place finishers in the AFC East, AFC North (highlighted in orange) and NFC North (highlighted in pink).
Currently, the fourteen opponents each team faces over the 17-game regular season schedule are set using a predetermined formula:
Each AFC team plays the other teams in their respective division twice (home and away) during the regular season, in addition to eleven other games assigned to their schedule by the NFL: three games are assigned on the basis of a particular team's final divisional standing from the previous season, and the remaining eight games are split between the roster of two other NFL divisions. This assignment shifts each year and will follow a standard cycle. Using the 2023 regular season schedule as an example, each team in the AFC West plays against every team in the AFC East and NFC North. In this way, non-divisional competition will be mostly among common opponents – the exception being the three games assigned based on the team's prior-season divisional standing.
At the end of each season, the four division winners and three wild cards (non-division winners with best regular season record) in the AFC qualify for the playoffs. The AFC playoffs culminate in the AFC Championship Game, with the winner receiving the Lamar Hunt Trophy. The AFC champion then plays the NFC champion in the Super Bowl. |
American Football Conference | History | History
thumb|right|150px|Original American Football Conference logo, based on the AFL logo with blue stars
With the impending merger with the American Football League (AFL) for the 1970 NFL season, the league had careful discussion over the nature of which teams would play in the newly instituted conferences. Then-NFL President and owner of the Cleveland Browns Art Modell had suggested of a format in which three teams from the NFL would move to the AFC to create two thirteen-team conferences. But negotiations between NFL commissioner Pete Rozelle and other owners was rampant in who would move (for his part, Modell had first assumed the three most recent expansion NFL teams - Minnesota Vikings, Atlanta Falcons, New Orleans Saints would be the ones to move to the AFC), since others wanted to simply have no realignment of NFL teams. The AFL had begun play in 1960 with eight teams before adding two more expansion clubs (the Miami Dolphins in 1966 and the Cincinnati Bengals in 1968) before the merger.
Modell was hospitalized for internal bleeding around the time negotiations were still going. Moreover, Modell was struggling to service the debt he incurred from his purchase of the Browns. Furthermore, he realized there was an opportunity to establish a lucrative in-state rivalry with the newly-established Bengals, who had been founded by Paul Brown after Modell had forced him out of Cleveland after purchasing the team.
When Modell was visited in the hospital by Art Rooney (owner of the Pittsburgh Steelers) and Wellington Mara (owner of the New York Giants), Modell offered to have his franchise move to the AFC, provided two other "old guard" franchises did so as well and the three affected teams to move were adequately compensated for joining what was still looked down on in NFL circles as a "junior" or "inferior" circuit. Not wanting to lose his long-established rivalry with Cleveland, the equally cash-strapped Rooney quickly agreed to join the Browns in the AFC. The other NFL owner to ultimately agree to move was the Baltimore Colts' Carroll Rosenbloom.
Thus, in order to equalize the number of teams in each conference, three NFL teams that predated the AFL's launch (the Cleveland Browns, Pittsburgh Steelers, and the then-Baltimore Colts) joined the ten former AFL teams to form the AFC in exchange for $3 million each in indemnities, with the announcement coming on May 10, 1969. The two AFL divisions AFL East and AFL West were more or less intact, while the NFL's Century Division, in which the Browns and the Steelers had played since 1967, was moved from the NFL to become the new AFC Central. Upon the completion of the merger of the AFL and NFL in 1970, the newly minted American Football Conference had already agreed upon their divisional setup along mostly geographical lines for the 1970 season; the National Football Conference, however, could not agree upon their setup, and one was chosen from a fishbowl on January 16, 1970.
Since the merger, five expansion teams have joined the AFC and two have left, thus making the current total 16. When the Seattle Seahawks and the Tampa Bay Buccaneers joined the league in 1976, they were temporarily placed in the NFC and AFC respectively. This arrangement lasted for one season only before the two teams switched conferences. The Seahawks eventually returned to the NFC as a result of the 2002 realignment. The expansion Jacksonville Jaguars joined the AFC in 1995. There have been five teams that have relocated at least once. In 1984, the Baltimore Colts relocated to Indianapolis. In 1995, the Cleveland Browns had attempted to move to Baltimore; the resulting dispute between Cleveland and the team led to Modell establishing the Baltimore Ravens with the players and personnel from the Browns, while the Browns were placed in suspended operations before they were reinstated by the NFL. The Ravens were treated as an expansion team.
In California, the Oakland Raiders relocated to Los Angeles in 1982, back to Oakland in 1995, and then to Las Vegas in 2020, while the San Diego Chargers returned to Los Angeles in 2017 after 56 years in San Diego.
The Houston Oilers moved to Tennessee in 1997, where they were renamed the Tennessee Oilers. The team would change its name again, two years later, to the Tennessee Titans.
The NFL would again expand in 2002, adding the Houston Texans to the AFC. With the exception of the aforementioned relocations since that time, the divisional setup has remained static ever since.
Between 1995 and 2022, the AFC has sent only 9 of its 16 teams to the Super Bowl: New England Patriots (10 times), Pittsburgh Steelers (4 times), Denver Broncos (4 times), Baltimore Ravens (2 times), Indianapolis Colts (2 times), Kansas City Chiefs (3 times), Cincinnati Bengals (1 time), Las Vegas Raiders (1 time), Tennessee Titans (1 time). By contrast, the NFC has sent 13 of the 16 NFC teams during that same time frame with only the Detroit Lions, Minnesota Vikings, and Washington Commanders missing out on an appearance in the Super Bowl. 17 of the 19 AFC champions from 2001 to 2019 have started one of just three quarterbacks - Tom Brady, Peyton Manning and Ben Roethlisberger - in the Super Bowl. The AFC has started 7 quarterbacks in the last 20 Super Bowls, while the NFC has started 16. |
American Football Conference | Logo | Logo
right|thumb|2nd American Football Conference logo used from 1970 to 2009|216x216px The original AFC logo was very similar to the AFL logo, however the merged league quickly created an updated logo for the AFC that, while preserving the basic elements of the old AFL logo, used a much bolder red "A" and six similarly bold red stars surrounding it, in contrast to the six blue AFL stars. The league also created a logo for the NFC in 1970, which like the AFL and AFC logos also contained only the first letter as opposed to a full abbreviation, but with only three stars (to represent the then-three divisions of the Conference). The AFC logo basically remained unchanged from 1970 to 2009. The 2010 NFL season introduced an updated AFC logo, with the most notable revision being the removal of two stars (leaving four representing the four divisions of the AFC), and moving the stars inside the letter, similar to the NFC logo, which itself was updated at the same time to add a fourth star.
Notably, the Kansas City Chiefs (still owned by the descendants of AFL founder Lamar Hunt) continue to regularly feature the original AFL logo on their jerseys as of . |
American Football Conference | Television | Television
NBC aired the AFC's Sunday afternoon and playoff games from 1970 through the 1997 season. From 1998 to 2013, CBS was the primary broadcast rightsholder to the AFC; in those years, all interconference games in which the AFC team was the visiting team were broadcast on either NBC or CBS. Since 2014, the cross-flex policy allows select AFC games (that involve them playing an NFC team at home or intraconference games) to be moved from CBS to Fox. Since 1990, select AFC playoff games have been seen on ABC or ESPN. |
American Football Conference | See also | See also
AFC Championship Game |
American Football Conference | AFC Divisions | AFC Divisions
AFC East
AFC North
AFC South
AFC West |
American Football Conference | AFC Rivalries | AFC Rivalries
AFC East
Bills–Dolphins rivalry
Bills–Patriots rivalry
Bills–Jets rivalry
Dolphins–Patriots rivalry
Dolphins–Jets rivalry
Jets–Patriots rivalry
AFC North
Bengals–Ravens rivalry
Bengals–Browns rivalry
Bengals–Steelers rivalry
Browns–Ravens rivalry
Browns–Steelers rivalry
Ravens–Steelers rivalry
AFC South
Colts–Jaguars rivalry
Colts–Texans rivalry
Colts–Titans rivalry
Jaguars–Texans rivalry
Jaguars–Titans rivalry
Texans–Titans rivalry
AFC West
Broncos–Raiders rivalry
Broncos–Chiefs rivalry
Broncos–Chargers rivalry
Chargers–Raiders rivalry
Chargers–Chiefs rivalry
Chiefs–Raiders rivalry
Interdivisional
Bills–Chiefs rivalry
Bills–Titans rivalry
Broncos–Patriots rivalry
Broncos–Steelers rivalry
Colts–Patriots rivalry
Dolphins–Raiders rivalry
Raiders–Steelers rivalry
Patriots–Ravens rivalry
Patriots–Steelers rivalry
Steelers–Titans rivalry
Ravens–Titans rivalry |
American Football Conference | AFC Television Network | AFC Television Network
NFL on NBC (1970–1997)
NFL on CBS (1998–present) |
American Football Conference | References | References
Category:National Football League
Conference
Category:Sports organizations established in 1970 |
American Football Conference | Table of Content | short description, Teams, Season structure, History, Logo, Television, See also, AFC Divisions, AFC Rivalries, AFC Television Network, References |
Animal Farm | Short description | Animal Farm is a satirical allegorical novella, in the form of a beast fable, by George Orwell, first published in England on 17 August 1945. It tells the story of a group of anthropomorphic farm animals who rebel against their human farmer, hoping to create a society where the animals can be equal, free, and happy. Ultimately, the rebellion is betrayed, and under the dictatorship of a pig named Napoleon, the farm ends up in a far worse state than before.
According to Orwell, Animal Farm reflects events leading up to the Russian Revolution of 1917 and then on into the Stalinist era of the Soviet Union, a period when Russia lived under the Marxist–Leninist ideology of Joseph Stalin. Orwell, a democratic socialist, was a critic of Stalin and hostile to Moscow-directed Stalinism, an attitude that was critically shaped by his experiences during the Barcelona May Days conflicts between the POUM and Stalinist forces, during the Spanish Civil War. In a letter to Yvonne Davet, Orwell described Animal Farm as a satirical tale against Stalin (""), and in his essay, "Why I Write" (1946), wrote: "Animal Farm was the first book in which I tried, with full consciousness of what I was doing, to fuse political purpose and artistic purpose into one whole".
The original title of the novel was Animal Farm: A Fairy Story. American publishers dropped the subtitle when it was published in 1946, and only one of the translations, during Orwell's lifetime, the Telugu version, kept it. Other title variations include subtitles like "A Satire" and "A Contemporary Satire". Orwell suggested the title for the French translation, which abbreviates to URSA, the Latin word for "bear", a symbol of Russia. It also played on the French name of the Soviet Union, .
Orwell wrote the book between November 1943 and February 1944, when the United Kingdom was in its wartime alliance with the Soviet Union against Nazi Germany and the British intelligentsia held Stalin in high esteem, which Orwell hated. The manuscript was initially rejected by several British and American publishers, including one of Orwell's own, Victor Gollancz, which delayed its publication. It became a great commercial success when it did appear, as international relations and public opinion were transformed as the wartime alliance gave way to the Cold War.
Time magazine chose the book as one of the 100 best English-language novels (1923 to 2005); it also featured at number 31 on the Modern Library List of Best 20th-Century Novels, and number 46 on the BBC's The Big Read poll. It won a Retrospective Hugo Award in 1996, and is included in the Great Books of the Western World selection. |
Animal Farm | Plot summary | Plot summary
The animal populace of the poorly run Manor Farm near Willingdon, England, is ripened for rebellion by neglect at the hands of the irresponsible and alcoholic farmer Mr. Jones. One night, the exalted boar Old Major holds a conference, at which he calls for the overthrow of humans and teaches the animals a revolutionary song called "Beasts of England". When Old Major dies, two young pigs, Snowball and Napoleon, assume command and stage a revolt, driving Mr. Jones off the farm and renaming the property "Animal Farm". They adopt the Seven Commandments of Animalism, the most important of which is, "All animals are equal". The decree is painted in large letters on one side of the barn. Snowball teaches the animals to read and write, while Napoleon educates young puppies on the principles of Animalism. To commemorate the start of Animal Farm, Snowball raises a green flag with a white hoof and horn. Food is plentiful, and the farm runs smoothly. The pigs elevate themselves to positions of leadership and set aside special food items, ostensibly for their health. Following an unsuccessful attempt by Mr. Jones and his associates to retake the farm (later dubbed the "Battle of the Cowshed"), Snowball announces his plans to modernise the farm by building a windmill. Napoleon disputes this idea, and matters come to a head, which culminates in Napoleon's dogs chasing Snowball away and Napoleon effectively declaring himself supreme commander.
Napoleon enacts changes to the governance structure of the farm, replacing meetings with a committee of pigs who will run the farm. Through a young porker named Squealer, Napoleon claims credit for the idea of building the windmill, claiming that Snowball was only trying to win animals to his side. The animals work harder with the promise of easier lives with the windmill. When the animals find the windmill collapsed after a violent storm, Napoleon and Squealer persuade the animals that Snowball is trying to sabotage their project, and begin to purge the farm of animals accused by Napoleon of consorting with his old rival. When some animals recall the Battle of the Cowshed, Napoleon (who was nowhere to be found during the battle) gradually smears Snowball to the point of saying he is a collaborator of Mr. Jones, even dismissing the fact that Snowball was given an award of courage, while falsely representing himself as the main hero of the battle. "Beasts of England" is replaced with "Animal Farm", while an anthem glorifying Napoleon, who is presumably adopting the lifestyle of a man ("Comrade Napoleon"), is composed and sung. Napoleon then conducts a second purge, during which many animals who are alleged to be helping Snowball in plots are executed by Napoleon's dogs, which troubles the rest of the animals. Despite their hardships, the animals are easily pacified by Napoleon's retort that they are better off than they were under Mr. Jones, as well as by the sheep's continual bleating of "four legs good, two legs bad".
Mr. Frederick, a neighbouring farmer, attacks the farm, using blasting powder to blow up the restored windmill. Although the animals win the battle, they do so at great cost, as many, including Boxer the workhorse, are wounded. Although he recovers from this, Boxer eventually collapses while working on the windmill (being almost 12 years old at that point). He is taken away in a knacker's van and a donkey called Benjamin alerts the animals of this, but Squealer quickly waves off their alarm by persuading the animals that the van had been purchased from the knacker by an animal hospital and that the previous owner's signboard had not been repainted. Squealer subsequently reports Boxer's death and honours him with a festival the following day. In truth, Napoleon had engineered the sale of Boxer to the knacker, allowing him and his inner circle to acquire money to buy whisky for themselves.
Years pass, the windmill is rebuilt and another windmill is constructed, which makes the farm a good amount of income. However, the ideals that Snowball discussed, including stalls with electric lighting, heating, and running water, are forgotten, with Napoleon advocating that the happiest animals live simple lives. Snowball has been forgotten, alongside Boxer, with "the exception of the few who knew him". Many of the animals who participated in the rebellion are dead or old. Mr. Jones is also now known to be dead, having "died in an inebriates' home in another part of the country". The pigs start to resemble humans, as they walk upright, carry whips, drink alcohol, and wear clothes. The Seven Commandments are abridged to just one phrase: "All animals are equal, but some animals are more equal than others". The maxim "Four legs good, two legs bad" is similarly changed to "Four legs good, two legs better". Other changes include the Hoof and Horn flag being replaced with a plain green banner and Old Major's skull, which was previously put on display, being reburied.
Napoleon holds a dinner party for the pigs and local farmers, with whom he celebrates a new alliance. The other farm animals, who have not been invited, gather toward the window to watch. He abolishes the practice of the revolutionary traditions and restores the name "The Manor Farm". The men and pigs start playing cards, flattering and praising each other while cheating at the game. Both Napoleon and Mr. Pilkington, one of the farmers, play the ace of spades at the same time and both sides begin fighting loudly over who cheated first. When the animals outside look at the pigs and men, they can no longer distinguish between the two. |
Animal Farm | Characters | Characters |
Animal Farm | Pigs | Pigs
Old Major – An aged prize Middle White boar provides the inspiration that fuels the rebellion. He is also called Willingdon Beauty when showing. He is an allegorical combination of Karl Marx, one of the creators of communism, and Vladimir Lenin, the communist leader of the Russian Revolution and the early Soviet nation, in that he draws up the principles of the revolution. His skull being put on revered public display recalls Lenin, whose embalmed body was left in indefinite repose. By the end of the book, the skull is reburied.
Napoleon – "A large, rather fierce-looking Berkshire boar, the only Berkshire on the farm, not much of a talker, but with a reputation for getting his own way". An allegory of Joseph Stalin, Napoleon is the leader of Animal Farm.
Snowball – Napoleon's rival and original head of the farm after Jones's overthrow. His life parallels that of Leon Trotsky, although there is no reference to Snowball having been murdered (as Trotsky was); he may also combine some elements from Lenin.
Squealer – A small, white, fat large white who serves as Napoleon's second-in-command and minister of propaganda, is a collective portrait of the Soviet nomenklatura and journalists, such as of the national daily Pravda (The Truth), able to justify every twist and turn in Stalin's policy.
Minimus – A poetic pig who writes the second national anthem of Animal Farm after the singing of "Beasts of England" is banned; later he composes a poem "Comrade Napoleon". Literary theorist John Rodden compares him to the poet Vladimir Mayakovsky, who eulogized Lenin and the Soviet Union, although Mayakovsky neither wrote anthems nor praised Stalin in his poems.
The piglets – Hinted to be the children of Napoleon and are the first generation of animals subjugated to his idea of animal inequality.
The young pigs – Four pigs who complain about Napoleon's takeover of the farm but are quickly silenced and later executed, the first animals killed in Napoleon's farm purge. Probably based on the Great Purge of Grigory Zinoviev, Lev Kamenev, Nikolai Bukharin, and Alexei Rykov.
Pinkeye – A minor pig who is mentioned only once; he is the taste-tester that samples Napoleon's food to make sure it is not poisoned, in response to rumours about an assassination attempt on Napoleon. |
Animal Farm | Humans | Humans
Mr. Jones – A heavy drinker who is the original owner of Manor Farm, a farm in disrepair with farmhands who often loaf on the job. He is an allegory of Russian Tsar Nicholas II, who was forced to abdicate following the February Revolution of 1917 and was executed, along with the rest of his family, by the Bolsheviks on 17 July 1918. The animals revolt after Jones goes on a drinking binge, returns hungover the following day and neglects them completely. Jones is married, but his wife plays no active role in the book. She seems to live with her husband's drunkenness, going to bed while he stays up drinking until late into the night. In her only other appearance, she hastily throws a few things into a travel bag and flees when she sees that the animals are revolting. Towards the end of the book, Napoleon's "favourite sow" wears her old Sunday dress.
Mr. Frederick – The tough owner of Pinchfield Farm, a small but well-kept neighbouring farm, who briefly allies with Napoleon. Animal Farm shares land boundaries with Pinchfield on one side and Foxwood on another, making Animal Farm a "buffer zone" between the two bickering farmers. The animals of Animal Farm are terrified of Frederick, as rumours abound of him abusing his animals and entertaining himself with cockfighting. Napoleon allies with Frederick to sell surplus timber that Pilkington also sought, but is enraged to learn Frederick paid him in counterfeit money. Shortly after the swindling, Frederick and his men invade Animal Farm, killing many animals and destroying the windmill. The brief alliance and subsequent invasion may allude to the Molotov–Ribbentrop Pact and Operation Barbarossa.
Mr. Pilkington – The easy-going but crafty and well-to-do owner of Foxwood Farm, a large neighbouring farm overgrown with weeds. Pilkington is wealthier than Frederick and owns more land, but his farm needs care as opposed to Frederick's smaller but more efficiently run farm. Although on bad terms with Frederick, Pilkington is also concerned about the animal revolution that deposed Jones and is worried that this could also happen to him.
Mr. Whymper – A man hired by Napoleon to act as the liaison between Animal Farm and human society. At first, he acquires necessities that cannot be produced on the farm, such as dog biscuits and paraffin wax, but later he procures luxuries like alcohol for the pigs. |
Animal Farm | Equines | Equines
Boxer – A loyal, kind, dedicated, powerful, hard-working, and respectable cart-shire horse, although quite naive and gullible. Boxer does a large share of the physical labour on the farm. He is shown to believe that "Napoleon is always right." At one point, he questions Squealer's statement that Snowball was always against the welfare of the farm, causing him to be attacked by Napoleon's dogs, however Boxer's immense strength repels the attack, worrying the pigs that their authority can be challenged. Boxer has been compared to Alexey Stakhanov, a diligent and enthusiastic role model of the Stakhanovite movement. He has been described as "faithful and strong"; he believes any problem can be solved if he works harder. When Boxer is injured, Napoleon sells him to a local knacker to buy himself whisky, and Squealer gives a moving account, falsifying the circumstances of Boxer's death.
Mollie – A self-centred, self-indulgent, and vain young white mare who quickly leaves for another farm after the revolution, like those who left Russia after the fall of the Tsar. She is only once mentioned again, and has an affinity for hair ribbons and sugar cubes.
Clover – A gentle, caring mare, who shows concern, especially for Boxer, who often pushes himself too hard. Clover can read all the letters of the alphabet, but cannot "put words together".
Benjamin – A donkey, one of the oldest, wisest animals on the farm, and one of the few who can read properly. He is sceptical, temperamental and cynical: his most frequent remark is, "Life will go on as it has always gone on – that is, badly". Academic Morris Dickstein has suggested there is "a touch of Orwell himself in this creature's timeless scepticism" and indeed, friends called Orwell "Donkey George", "after his grumbling donkey Benjamin, in Animal Farm". Benjamin manages to evade the purges and survive despite the threat he potentially poses given his knowledge, his age, and his equivocal, albeit apolitical, positions. |
Animal Farm | Other animals | Other animals
Muriel – A goat who is another of the oldest, wisest animals on the farm and friends with all of the animals on the farm. Similar to Benjamin, Muriel is one of the few animals on the farm who is not a pig but can read. She survives, as does Benjamin, by eschewing politics.
The puppies – Offspring of Jessie and Bluebell, the puppies were taken away at birth by Napoleon and raised by him to serve as his powerful security force.
Moses – The Raven, "Mr. Jones's especial pet, was a spy and a tale-bearer, but he was also a clever talker". Initially following Mrs. Jones into exile, he reappears several years later and resumes his role of talking but not working. He regales Animal Farm's denizens with tales of a wondrous place beyond the clouds called "Sugarcandy Mountain, that happy country where we poor animals shall rest forever from our labours!" Orwell portrays established religion as "the black raven of priestcraft – promising pie in the sky when you die, and faithfully serving whoever happens to be in power". His preaching to the animals heartens them, and Napoleon allows Moses to reside at the farm "with an allowance of a gill of beer daily", akin to how Stalin brought back the Russian Orthodox Church during the Second World War.
The sheep – They are not given individual names or personalities. They show limited understanding of Animalism and the political atmosphere of the farm, yet nonetheless, they are the voice of blind conformity as they bleat their support of Napoleon's ideals with jingles during his speeches and meetings with Snowball. Their constant bleating of "four legs good, two legs bad" was used as a device to drown out any opposition or alternative views from Snowball, much as Stalin used hysterical crowds to drown out Trotsky. Towards the end of the book, Squealer (the propagandist) trains the sheep to alter their slogan to "four legs good, two legs better", which they dutifully do.
The hens – The hens are promised following the rebellion that they will get to keep their eggs, which are stolen from them under Mr. Jones, however, their eggs are soon taken from them under the premise of buying goods from outside the farm. The hens are among the first to rebel, albeit unsuccessfully, against Napoleon, being brutally suppressed through starvation. They represent the Ukrainian victims of the Holodomor.George Orwell's Animal Farm – Ch. VII – An Academic Collaboration of the Symbolism Relating to the 1932-33 Soviet Ukrainian Famine- Genocide (Holodomor).The Holodomor
The cows – Unnamed. The cows are enticed into the revolution by promises that their milk will not be stolen but can be used to raise their calves. Their milk is then stolen by the pigs, who learn to milk them. The milk is stirred into the pigs' mash every day, while the other animals are denied such luxuries.
The cat – Unnamed and never seen to carry out any work. The cat is absent for long periods and is forgiven because her excuses are so convincing and she "purred so affectionately that it was impossible not to believe in her good intentions". She has no interest in the politics of the farm, and the only time she is recorded as having participated in an election, she is found to have actually "voted on both sides".
The ducks – Unnamed. A brood of ducklings is said to have lost their mother. They are protected by Clover.
The roosters – One arranges to wake Boxer early, and a black one acts as a trumpeter for Napoleon since he was a young cockerel.
The geese – Unnamed. One gander commits suicide by eating nightshade berries.
The rats – Unnamed. Classed among the wild animals, unsuccessful attempts were made to civilise them and teach them the principles of Animalism.
The rabbits – Like the rats unsuccessful attempts were made to civilise them. At one point, Jones' men go rabbiting. |
Animal Farm | Genre and style | Genre and style
George Orwell's Animal Farm is an example of a political satire and an allegory that was intended to have a "wider application", according to Orwell himself, in terms of its relevance. Stylistically, the work shares many similarities with some of Orwell's other works, most notably Nineteen Eighty-Four, as both have been considered works of Swiftian satire. Furthermore, these two prominent works seem to suggest Orwell's bleak view of the future for humanity; he seems to stress the potential/current threat of dystopias similar to those in Animal Farm and Nineteen Eighty-Four. In these kinds of works, Orwell distinctly references the disarray and traumatic conditions of Europe following the Second World War. Orwell's style and writing philosophy as a whole were very concerned with the pursuit of truth in writing.
Orwell was committed to communicating straightforwardly, given the way that he felt words were commonly used in politics to deceive and confuse. For this reason, he is careful, in Animal Farm, to make sure the narrator speaks in an unbiased and uncomplicated fashion. The difference is seen in the way that the animals speak and interact, as the general moral animals seem to speak their minds clearly, while the wicked animals on the farm, such as Napoleon, twist language in such a way that it meets their insidious desires. This style reflects Orwell's proximity to the issues facing Europe at the time and his determination to comment critically on Stalin's Soviet Russia. |
Animal Farm | Background | Background |
Animal Farm | Origin and writing | Origin and writing
Just as Nineteen Eighty-Four would be inspired by Yevgeny Zamyatin's We, Animal Farm also had its influences: "In 1937, the year in which Orwell said he first thought of Animal Farm, Gollancz's Left Book Club published both The Road to Wigan Pier and a left-wing children's book, The Adventures of the Little Pig and Other Stories by F. Le Gros and Ida Clark.""Bloom's Modern Critical Views, George Orwell, Updated Edition", edited and with an introduction by, Harold Bloom; Chelsea House; 2007:168.
George Orwell wrote the manuscript between November 1943 and February 1944 after his experiences during the Spanish Civil War, which he described in Homage to Catalonia (1938). In the preface of a 1947 Ukrainian edition of Animal Farm, he explained how escaping the communist purges in Spain taught him "how easily totalitarian propaganda can control the opinion of enlightened people in democratic countries". This motivated Orwell to expose and strongly condemn what he saw as the Stalinist corruption of the original socialist ideals. Homage to Catalonia sold poorly; after seeing Arthur Koestler's best-selling Darkness at Noon about the Moscow Trials, Orwell decided that fiction would be the best way to describe totalitarianism.
Immediately before writing the book, Orwell quit the BBC. He was also upset about a booklet for propagandists the Ministry of Information had put out. The booklet included instructions on how to quell ideological fears of the Soviet Union, such as directions to claim that the Red Terror was a figment of Nazi imagination.
In the preface, Orwell described the source of the idea of setting the book on a farm:
In 1944, the manuscript was almost lost when a German V-1 flying bomb destroyed his London home. Orwell spent hours sifting through the rubble to find the pages intact. |
Animal Farm | Publication | Publication |
Animal Farm | Publishing | Publishing
Orwell initially encountered difficulty getting the manuscript published, largely due to fears that the book might upset the alliance between Britain, the United States, and the Soviet Union. Four publishers refused to publish Animal Farm, yet one had initially accepted the work but declined it after consulting the Ministry of Information. Eventually, Secker and Warburg published the first edition in 1945.
During World War II, it became clear to Orwell that anti-Soviet literature was not something which most major publishing houses would touch – including his regular publisher Gollancz. He also submitted the manuscript to Faber and Faber, where the poet T. S. Eliot (who was a director of the firm) rejected it; Eliot wrote back to Orwell praising the book's "good writing" and "fundamental integrity", but declared that they would only accept it for publication if they had some sympathy for the viewpoint "which I take to be generally Trotskyite". Eliot said he found the view "not convincing", and contended that the pigs were made out to be the best to run the farm; he posited that someone might argue "what was needed ... was not more communism but more public-spirited pigs". Orwell let André Deutsch, who was working for Nicholson & Watson in 1944, read the typescript, and Deutsch was convinced that Nicholson & Watson would want to publish it; however, they did not, and "lectured Orwell on what they perceived to be errors in Animal Farm". In his London Letter on 17 April 1944 for Partisan Review, Orwell wrote that it was "now next door to impossible to get anything overtly anti-Russian printed. Anti-Russian books do appear, but mostly from Catholic publishing firms and always from a religious or frankly reactionary angle".
The publisher Jonathan Cape, who had initially accepted Animal Farm, subsequently rejected the book after an official at the British Ministry of Information warned him off – although the civil servant who it is assumed gave the order was later found to be a Soviet spy. Writing to Leonard Moore, a partner in the literary agency of Christy & Moore, publisher Jonathan Cape explained that the decision had been taken on the advice of a senior official in the Ministry of Information. Such flagrant anti-Soviet bias was unacceptable, and the choice of pigs as the dominant class was thought to be especially offensive. It may reasonably be assumed that the "important official" was a man named Peter Smollett, who was later unmasked as a Soviet agent. Orwell was suspicious of Smollett/Smolka, and he would be one of the names Orwell included in his list of Crypto-Communists and Fellow-Travellers sent to the Information Research Department in 1949. The publisher wrote to Orwell, saying:
Frederic Warburg also faced pressures against publication, even from people in his own office and from his wife Pamela, who felt that it was not the moment for ingratitude towards Stalin and the Red Army, which had played a major part in defeating Adolf Hitler. A Russian translation was printed in the paper Posev, and in permitting a Russian translation of Animal Farm, Orwell refused in advance all royalties. A translation in Ukrainian, which was produced in Germany, was confiscated in large part by the American wartime authorities and handed over to the Soviet repatriation commission.
In October 1945, Orwell wrote to Frederic Warburg expressing interest in pursuing the possibility that the political cartoonist David Low might illustrate Animal Farm. Low had written a letter saying that he had had "a good time with Animal Farm – an excellent bit of satire – it would illustrate perfectly". Nothing came of this, and a trial issue produced by Secker & Warburg in 1956 illustrated by John Driver was abandoned. The Folio Society published an edition in 1984 illustrated by Quentin Blake and an edition illustrated by the cartoonist Ralph Steadman was published by Secker & Warburg in 1995 to celebrate the fiftieth anniversary of the first edition of Animal Farm. |
Animal Farm | Preface | Preface
Orwell originally wrote a preface complaining about British self-censorship and how the British people were suppressing criticism of the USSR, their World War II ally:
Although the first edition allowed space for the preface in the author's proof, it was not included, and the page numbers had to be renumbered at the last minute. As of June 2009, most editions of the book have not included it.
In 1972, Ian Angus found the original typescript titled "The Freedom of the Press", and Bernard Crick published it, together with his introduction, in The Times Literary Supplement on 15 September 1972 as "How the essay came to be written". Orwell's essay criticised British self-censorship by the press, specifically the suppression of unflattering descriptions of Stalin and the Soviet government. The same essay also appeared in the Italian 1976 edition of Animal Farm with another introduction by Crick, claiming to be the first edition with the preface. Other publishers were still declining to publish it. |
Animal Farm | Reception | Reception
Contemporary reviews of the work were not universally positive. Writing in the American New Republic magazine, George Soule expressed his disappointment in the book, writing that it "puzzled and saddened me. It seemed on the whole dull. The allegory turned out to be a creaking machine for saying in a clumsy way things that have been said better directly". Soule believed that the animals were not consistent enough with their real-world inspirations, and said, "It seems to me that the failure of this book (commercially it is already assured of tremendous success) arises from the fact that the satire deals not with something the author has experienced, but rather with stereotyped ideas about a country which he probably does not know very well".
The Guardian on 24 August 1945 called Animal Farm "a delightfully humorous and caustic satire on the rule of the many by the few". Tosco Fyvel, writing in Tribune on the same day, called the book "a gentle satire on a certain State and on the illusions of an age which may already be behind us". Julian Symons responded, on 7 September, "Should we not expect, in Tribune at least, acknowledgement of the fact that it is a satire not at all gentle upon a particular State – Soviet Russia? It seems to me that a reviewer should have the courage to identify Napoleon with Stalin, and Snowball with Trotsky, and express an opinion favourable or unfavourable to the author, upon a political ground. In a hundred years perhaps, Animal Farm may be simply a fairy story; today it is a political satire with a good deal of point". Animal Farm has been subject to much comment in the decades since these early remarks.
Between 1952 and 1957, the CIA, in an operation codenamed Aedinosaur, sent millions of balloons carrying copies of the novel into Poland, Hungary and Czechoslovakia, whose air forces tried to shoot the balloons down. The Information Research Department, a secret Cold War propaganda agency of the British government, translated the book into various languages such as Arabic.
Time magazine chose Animal Farm as one of the 100 best English-language novels (1923 to 2005); it also featured at number 31 on the Modern Library List of Best 20th-Century Novels. It won a Retrospective Hugo Award in 1996 and is included in the Great Books of the Western World selection.
Popular reading in schools, Animal Farm was ranked the UK's favourite book from school in a 2016 poll.
Animal Farm has also faced an array of challenges in school settings around the US. The following are examples of this controversy that has existed around Orwell's work:
The John Birch Society in Wisconsin challenged the reading of Animal Farm in 1965 because of its reference to the masses revolting.
New York State English Council's Committee on Defense Against Censorship found that in 1968, Animal Farm had been widely deemed a "problem book".
A censorship survey conducted in DeKalb County, Georgia, relating to the years 1979–1982, revealed that many schools had attempted to limit access to Animal Farm due to its "political theories".
A superintendent in Bay County, Florida, banned Animal Farm at the middle school and high school levels in 1987.
The Board quickly brought back the book, however, after receiving complaints of the ban as "unconstitutional".
Animal Farm was removed from the Stonington, Connecticut school district curriculum in 2017.
Animal Farm has also faced similar forms of resistance in other countries. The ALA also mentions the way that the book was prevented from being featured at the International Book Fair in Moscow, Russia, in 1977 and banned from schools in the United Arab Emirates for references to practices or actions that defy Arab or Islamic beliefs, such as pigs or alcohol.
In the same manner, Animal Farm has also faced relatively recent issues in China. In 2018, the Chinese government decided to censor all online posts about or referring to Animal Farm. However, the book itself, as of 2019, remains sold in stores. Amy Hawkins and Jeffrey Wasserstrom of The Atlantic stated in 2019 that the book is widely available in mainland China for several reasons: censors believe the general public is unlikely to read a highbrow book, because the elites who do read books feel connected to the ruling party anyway, and because the Communist Party sees being too aggressive in blocking cultural products as a liability. The authors stated: "It was – and remains – as easy to buy 1984 and Animal Farm in Shenzhen or Shanghai as it is in London or Los Angeles". An enhanced version of the book, launched in India in 2017, was widely praised for capturing the author's intent, by republishing the proposed preface of the First Edition and the preface he wrote for the Ukrainian edition. |
Animal Farm | Analysis | Analysis |
Animal Farm | Animalism | Animalism
Snowball, Napoleon, and Squealer adapt Old Major's ideas into "a complete system of thought", which they formally name Animalism, an allegoric reference to Communism, not to be confused with the philosophy of Animalism. Soon after, Napoleon and Squealer partake in activities associated with the humans (drinking alcohol, sleeping in beds, trading), which were explicitly prohibited by the Seven Commandments. Squealer is employed to alter the Seven Commandments to account for this humanisation, an allusion to the Soviet government's revising of history to exercise control of the people's beliefs about themselves and their society.
thumb|Squealer sprawls at the foot of the end wall of the big barn where the Seven Commandments were written (ch. viii) – preliminary artwork for a 1950 strip cartoon by Norman Pett and Donald Freeman
The original commandments are:
Whatever goes upon two legs is an enemy.
Whatever goes upon four legs, or has wings, is a friend.
No animal shall wear clothes.
No animal shall sleep in a bed.
No animal shall drink alcohol.
No animal shall kill any other animal.
All animals are equal.
These commandments are also distilled into the maxim "Four legs good, two legs bad!" which is primarily used by the sheep on the farm, often to disrupt discussions and disagreements between animals on the nature of Animalism.
Later, Napoleon and his pigs secretly revise some commandments to clear themselves of accusations of law-breaking. The changed commandments are as follows, with the changes bolded:
Eventually, these are replaced with the maxims, "All animals are equal, but some animals are more equal than others", and "Four legs good, two legs better" as the pigs become more anthropomorphic. This is an ironic twist to the original purpose of the Seven Commandments, which was supposed to keep order within Animal Farm by uniting the animals together against the humans and preventing animals from following the humans' evil habits. Through the revision of the commandments, Orwell demonstrates how simply political dogma can be turned into malleable propaganda. |
Animal Farm | Significance and allegory | Significance and allegory
thumb|left|The Hoof and Horn flag described in the book appears to be based on the hammer and sickle, the Communist symbol. By the end of the book when Napoleon takes full control, the Hoof and Horn is removed from the flag.
Orwell biographer Jeffrey Meyers has written, "virtually every detail has political significance in this allegory". Orwell himself wrote in 1946, "Of course I intended it primarily as a satire on the Russian revolution ... [and] that kind of revolution (violent conspiratorial revolution, led by unconsciously power-hungry people) can only lead to a change of masters [–] revolutions only effect a radical improvement when the masses are alert". In a preface for a 1947 Ukrainian edition, he stated, "for the past ten years I have been convinced that the destruction of the Soviet myth was essential if we wanted a revival of the socialist movement. On my return from Spain [in 1937] I thought of exposing the Soviet myth in a story that could be easily understood by almost anyone and which could be easily translated into other languages".
The revolt of the animals against Farmer Jones is Orwell's analogy with the October 1917 Bolshevik Revolution. The Battle of the Cowshed has been said to represent the allied invasion of Soviet Russia in 1918, and the defeat of the White Russians in the Russian Civil War. The pigs' rise to preeminence mirrors the rise of a Stalinist bureaucracy in the USSR, just as Napoleon's emergence as the farm's sole leader reflects Stalin's emergence. The pigs' appropriation of milk and apples for their own use, "the turning point of the story" as Orwell termed it in a letter to Dwight Macdonald, stands as an analogy for the crushing of the left-wing 1921 Kronstadt revolt against the Bolsheviks, and the difficult efforts of the animals to build the windmill suggest the various five-year plans. The puppies controlled by Napoleon parallel the nurture of the secret police in the Stalinist structure, and the pigs' treatment of the other animals on the farm recalls the internal terror faced by the populace in the 1930s. In chapter seven, when the animals confess their non-existent crimes and are killed, Orwell directly alludes to the purges, confessions and show trials of the late 1930s. These contributed to Orwell's conviction that the Bolshevik revolution had been corrupted and the Soviet system become rotten.
Peter Edgerly Firchow and Peter Davison contend that the Battle of the Windmill, specifically referencing the Battle of Stalingrad and the Battle of Moscow, represents World War II. During the battle, Orwell first wrote, "All the animals, including Napoleon" took cover. Orwell had the publisher alter this to "All the animals except Napoleon" in recognition of Stalin's decision to remain in Moscow during the German advance. Orwell requested the change after he met Józef Czapski in Paris in March 1945. Czapski, a survivor of the Katyn Massacre and an opponent of the Soviet regime, told Orwell, as Orwell wrote to Arthur Koestler, that it had been "the character [and] greatness of Stalin" that saved Russia from the German invasion.
thumb|Front row (left to right): Rykov, Skrypnyk, and Stalin – 'When Snowball comes to the crucial points in his speeches he is drowned out by the sheep (Ch. V), just as in the party Congress in 1927 [above], at Stalin's instigation 'pleas for the opposition were drowned in the continual, hysterically intolerant uproar from the floor'. (Isaac Deutscher)
Other connections that writers have suggested illustrate Orwell's telescoping of Russian history from 1917 to 1943, including the wave of rebelliousness that ran through the countryside after the Rebellion, which stands for the abortive revolutions in Hungary and Germany (Ch. IV); the conflict between Napoleon and Snowball (Ch. V), parallelling "the two rival and quasi-Messianic beliefs that seemed pitted against one another: Trotskyism, with its faith in the revolutionary vocation of the proletariat of the West; and Stalinism with its glorification of Russia's socialist destiny"; Napoleon's dealings with Whymper and the Willingdon markets (Ch. VI), paralleling the Treaty of Rapallo; and Frederick's forged bank notes, parallelling the Molotov–Ribbentrop Pact of August 1939, after which Frederick attacks Animal Farm without warning and destroys the windmill.
The book's close, with the pigs and men in a kind of rapprochement, reflected Orwell's view of the 1943 Tehran Conference that seemed to display the establishment of "the best possible relations between the USSR and the West" – but in reality were destined, as Orwell presciently predicted, to continue to unravel. The disagreement between the allies and the start of the Cold War is suggested when Napoleon and Pilkington, both suspicious, each "played an ace of spades simultaneously".
Similarly, the music in the novel, starting with "Beasts of England" and the later anthems, parallels "The Internationale" and its adoption and repudiation by the Soviet authorities as the anthem of the USSR in the 1920s and 1930s.
According to Masha Gessen, the metamorphosis of the eighth commandment ("some animals are more equal") was likely inspired by similar change of a party line which declared all Soviet people equal: the Russian nation and language suddenly became "first among equals" in official CPSU publications in 1936–1937. |
Animal Farm | Adaptations | Adaptations |
Animal Farm | Stage productions | Stage productions
thumb|A National Youth Theatre performance of Animal Farm at Soulton Hall
A theatrical version, with music by Richard Peaslee and lyrics by Adrian Mitchell, was staged at the National Theatre London on 25 April 1984, directed by Peter Hall. It toured nine cities in 1985.
A solo version, adapted and performed by Guy Masterson, premiered at the Traverse Theatre Edinburgh in January 1995 and has toured worldwide since.
In 2021, during pandemic restrictions, the National Youth Theatre toured a stage version of Animal Farm; this run included outdoor performances on a farm at Soulton Hall.
A new adaptation written and directed by Robert Icke, designed by Bunny Christie with puppetry designed and directed by Toby Olié opened at the Birmingham Repertory Theatre in January 2022 before touring the UK.
The Russian composer Alexander Raskatov has written an opera based on the book. Its premiere took place on 4 March 2023 in Amsterdam as part of Dutch National Opera's 2022/2023 season. |
Animal Farm | Films | Films
Animal Farm has been adapted to film twice. Both differ from the novel and have been accused of taking significant liberties, including sanitising some aspects.
Animal Farm (1954) is an animated film, in which Napoleon is eventually overthrown in a second revolution. In 1974, E. Howard Hunt revealed that he had been sent by the CIA's Psychological Warfare department to obtain the film rights from Orwell's widow, and the resulting 1954 animation was funded by the agency.
Animal Farm (1999) is a live-action TV version that shows Napoleon's regime collapsing in on itself, with the farm having new human owners, reflecting the collapse of Soviet communism.
Andy Serkis is directing an upcoming animated film adaptation. |
Animal Farm | Radio dramatisations | Radio dramatisations
A BBC radio version, produced by Rayner Heppenstall, was broadcast in January 1947. Orwell listened to the production at his home in Canonbury Square, London, with Hugh Gordon Porteous, amongst others. Orwell later wrote to Heppenstall that Porteous, "who had not read the book, grasped what was happening after a few minutes".
A further radio production, again using Orwell's dramatisation of the book, was broadcast in January 2013 on BBC Radio 4. Tamsin Greig narrated, and the cast included Nicky Henson as Napoleon, Toby Jones as the propagandist Squealer, and Ralph Ineson as Boxer. |
Animal Farm | Comic strip | Comic strip
thumb|A Foreign Office copy of the first instalment of Pett and Freeman's Animal Farm comic strip
In 1950, Norman Pett and his writing partner Don Freeman were secretly hired by the Information Research Department, a secret department of the Foreign Office, to adapt Animal Farm into a comic strip. This comic was not published in the United Kingdom but ran in Brazilian and Burmese newspapers. |
Animal Farm | Video game | Video game
Developers Nerial and The Dairymen released a game based on the book in December 2020, entitled Orwell's Animal Farm, for Windows, macOS, iOS and Android in coordination with the Orwell Estate. |
Animal Farm | See also | See also
Information Research Department
Authoritarian personality
History of Soviet Russia and the Soviet Union (1917–1927)
History of the Soviet Union (1927–1953)
Ideocracy
New class
Anthems in Animal Farm
Animals, an album based on Animal Farm |
Animal Farm | Books | Books
Gulliver's Travels was a favourite book of Orwell's. Swift reverses the role of horses and human beings in the fourth book. Orwell brought to Animal Farm "a dose of Swiftian misanthropy, looking ahead to a time 'when the human race had finally been overthrown."
Bunt (Revolt), published in 1924, is a book by Polish Nobel laureate Władysław Reymont with a theme similar to Animal Farm.
White Acre vs. Black Acre, published in 1856 and written by William M. Burwell, is a satirical novel that features allegories for slavery in the United States similar to Animal Farms portrayal of Soviet history.
George Orwell's own Nineteen Eighty-Four is a dystopian novel about totalitarianism. |
Animal Farm | References | References |
Animal Farm | Explanatory notes | Explanatory notes |
Animal Farm | Citations | Citations |
Animal Farm | General sources | General sources
|
Animal Farm | Further reading | Further reading
O'Neill, Terry, Readings on Animal Farm (1998), Greenhaven Press. . |
Animal Farm | External links | External links
Animal Farm Book Notes from Literapedia
Excerpts from Orwell'sd letters to his agent concerning Animal Farm
Review in the Antigonish Review
Orwell's original preface to the book
Animal Farm Revisited by John Molyneux, International Socialism, 44 (1989)
Animal Farm at the British Library
Category:1945 British novels
Category:Allegory
Category:British novellas
Category:British novels adapted for radio
Category:British novels adapted into films
Category:British novels adapted into plays
Category:British novels adapted into television shows
Category:British political novels
Category:British satirical novels
Category:Censored books
Category:Dystopian novels
Category:English novels
Category:Hugo Award for Best Novella–winning works
Category:Novels about animals
Category:Novels about cats
Category:Novels about dogs
Category:Novels about pigs
Category:Novels about propaganda
Category:Novels about revolutionaries
Category:Novels about totalitarianism
Category:Novels adapted into comics
Category:Novels by George Orwell
Category:Novels set on farms
Category:Novels set in East Sussex
Category:Cattle in literature
Category:Political literature
Category:Political satire novels
Category:Roman à clef novels
Category:Secker & Warburg books
Category:Cultural depictions of Karl Marx
Category:Cultural depictions of Vladimir Lenin
Category:Cultural depictions of Joseph Stalin
Category:Cultural depictions of Leon Trotsky
Category:Cultural depictions of Nicholas II of Russia
Category:Totalitarianism in fiction |
Animal Farm | Table of Content | Short description, Plot summary, Characters, Pigs, Humans, Equines, Other animals, Genre and style, Background, Origin and writing, Publication, Publishing, Preface, Reception, Analysis, Animalism, Significance and allegory, Adaptations, Stage productions, Films, Radio dramatisations, Comic strip, Video game, See also, Books, References, Explanatory notes, Citations, General sources, Further reading, External links |
Amphibian | Short description | thumb|250px|Many amphibians—like this Ceratophrys cranwelli—exhibit biofluorescence.
Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all tetrapods, but excluding the amniotes (tetrapods with an amniotic membrane, such as modern reptiles, birds and mammals). All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura (frogs and toads), Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems (such as riparian woodland, fossorial and even arboreal habitats). Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this.
Young amphibians generally undergo metamorphosis from an aquatic larval form with gills to an air-breathing adult form with lungs. Amphibians use their skin as a secondary respiratory interface, and some small terrestrial salamanders and frogs even lack lungs and rely entirely on their skin. They are superficially similar to reptiles like lizards, but unlike reptiles and other amniotes, require access to water bodies to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators to habitat conditions; in recent decades there has been a dramatic decline in amphibian populations for many species around the globe.
The earliest amphibians evolved in the Devonian period from tetrapodomorph sarcopterygians (lobe-finned fish with articulated limb-like fins) that evolved primitive lungs, which were helpful in adapting to dry land. They diversified and became ecologically dominant during the Carboniferous and Permian periods, but were later displaced in terrestrial environments by early reptiles and basal synapsids (predecessors of mammals). The origin of modern lissamphibians, which first appeared during the Early Triassic, around 250 million years ago, has long been contentious. The most popular hypothesis is that they likely originated from temnospondyls, the most diverse group of prehistoric amphibians, during the Permian period. Another hypothesis is that they emerged from lepospondyls.Marjanović, D. & Laurin, M. (2019) Phylogeny of Paleozoic limbed vertebrates reassessed through revision and expansion of the largest published relevant data matrix. PeerJ:6:e5565. doi: 10.7717/peerj.5565. eCollection 2019. A fourth group of lissamphibians, the Albanerpetontidae, became extinct around 2 million years ago.
The number of known amphibian species is approximately 8,000, of which nearly 90% are frogs. The smallest amphibian (and vertebrate) in the world is a frog from New Guinea (Paedophryne amauensis) with a length of just . The largest living amphibian is the South China giant salamander (Andrias sligoi), but this is dwarfed by prehistoric temnospondyls such as Mastodonsaurus which could reach up to in length. The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology. |
Amphibian | Classification | Classification
thumb|alt=World's smallest vertebrate|The world's smallest known vertebrate, Paedophryne amauensis, sitting on a U.S. dime. The dime is 17.9 mm in diameter, for scale
The word amphibian is derived from the Ancient Greek term (), which means 'both kinds of life', meaning 'of both kinds' and meaning 'life'. The term was initially used as a general adjective for animals that could live on land or in water, including seals and otters. Traditionally, the class Amphibia includes all tetrapod vertebrates that are not amniotes. Amphibia in its widest sense () was divided into three subclasses, two of which are extinct:
Subclass Lepospondyli† (A potentially polyphyletic Late Paleozoic group of small forms, likely more closely related to amniotes than Lissamphibia)
Subclass Temnospondyli† (diverse Late Paleozoic and early Mesozoic grade, some of which were large predators)
Subclass Lissamphibia (all modern amphibians, including frogs, toads, salamanders, newts and caecilians)
Salientia (frogs, toads and relatives): Early Triassic to present—7,360 current species in 53 families. Modern (crown group) salientians are described via the name Anura.
Caudata (salamanders, newts and relatives): Late Triassic to present—764 current species in 9 families. Modern (crown group) caudatans are described via the name Urodela.
Gymnophiona (caecilians and relatives): Late Triassic to present—215 current species in 10 families. The name Apoda is also sometimes used for caecilians.
Allocaudata† (Albanerpetontidae) Middle Jurassic – Early Pleistocene
These three subclasses do not include all extinct amphibians. Other extinct amphibian groups include Embolomeri (Late Paleozoic large aquatic predators), Seymouriamorpha (semiaquatic to terrestrial Permian forms related to amniotes), among others. Names such as Tetrapoda and Stegocephalia encompass the entirety of amphibian-grade tetrapods, while Reptiliomorpha or Anthracosauria are variably used to describe extinct amphibians more closely related to amniotes than to lissamphibians.thumb|alt=Triadobatrachus massinoti|Triadobatrachus massinoti, a proto-frog from the Early Triassic of Madagascar
The actual number of species in each group depends on the taxonomic classification followed. The two most common systems are the classification adopted by the website AmphibiaWeb, University of California, Berkeley, and the classification by herpetologist Darrel Frost and the American Museum of Natural History, available as the online reference database "Amphibian Species of the World". The numbers of species cited above follows Frost and the total number of known (living) amphibian species as of March 31, 2019, is exactly 8,000, of which nearly 90% are frogs.
With the phylogenetic classification, the taxon Labyrinthodontia has been discarded as it is a polyparaphyletic group without unique defining features apart from shared primitive characteristics. Classification varies according to the preferred phylogeny of the author and whether they use a stem-based or a node-based classification. Traditionally, amphibians as a class are defined as all tetrapods with a larval stage, while the group that includes the common ancestors of all living amphibians (frogs, salamanders and caecilians) and all their descendants is called Lissamphibia. The phylogeny of Paleozoic amphibians is uncertain, and Lissamphibia may possibly fall within extinct groups, like the Temnospondyli (traditionally placed in the subclass Labyrinthodontia) or the Lepospondyli, and in some analyses even in the amniotes. This means that advocates of phylogenetic nomenclature have removed a large number of basal Devonian and Carboniferous amphibian-type tetrapod groups that were formerly placed in Amphibia in Linnaean taxonomy, and included them elsewhere under cladistic taxonomy. If the common ancestor of amphibians and amniotes is included in Amphibia, it becomes a paraphyletic group.
All modern amphibians are included in the subclass Lissamphibia, which is usually considered a clade, a group of species that have evolved from a common ancestor. The three modern orders are Anura (the frogs), Caudata (or Urodela, the salamanders), and Gymnophiona (or Apoda, the caecilians). It has been suggested that salamanders arose separately from a temnospondyl-like ancestor, and even that caecilians are the sister group of the advanced reptiliomorph amphibians, and thus of amniotes. Although the fossils of several older proto-frogs with primitive characteristics are known, the oldest "true frog", with hopping adaptations is Prosalirus bitis, from the Early Jurassic Kayenta Formation of Arizona. It is anatomically very similar to modern frogs. The oldest known caecilians are Funcusvermis gilmorei (from the Late Triassic) and Eocaecilia micropodia (from the Early Jurassic), both from Arizona. The earliest salamander is Beiyanerpeton jianpingensis from the Late Jurassic of northeastern China.
Authorities disagree as to whether Salientia is a superorder that includes the order Anura, or whether Anura is a sub-order of the order Salientia. The Lissamphibia are traditionally divided into three orders, but an extinct salamander-like family, the Albanerpetontidae, is now considered part of Lissamphibia alongside the superorder Salientia. Furthermore, Salientia includes all three recent orders plus the Triassic proto-frog, Triadobatrachus. |
Amphibian | Evolutionary history | Evolutionary history
The first major groups of amphibians developed in the Devonian period, around 370 million years ago, from lobe-finned fish which were similar to the modern coelacanth and lungfish. These ancient lobe-finned fish had evolved multi-jointed leg-like fins with digits that enabled them to crawl along the sea bottom. Some fish had developed primitive lungs that help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required. Eventually, their bony fins would evolve into limbs and they would become the ancestors to all tetrapods, including modern amphibians, reptiles, birds, and mammals. Despite being able to crawl on land, many of these prehistoric tetrapodomorph fish still spent most of their time in the water. They had started to develop lungs, but still breathed predominantly with gills.
Many examples of species showing transitional features have been discovered. Ichthyostega was one of the first primitive amphibians, with nostrils and more efficient lungs. It had four sturdy limbs, a neck, a tail with fins and a skull very similar to that of the lobe-finned fish, Eusthenopteron. Amphibians evolved adaptations that allowed them to stay out of the water for longer periods. Their lungs improved and their skeletons became heavier and stronger, better able to support the weight of their bodies on land. They developed "hands" and "feet" with five or more digits; the skin became more capable of retaining body fluids and resisting desiccation. The fish's hyomandibula bone in the hyoid region behind the gills diminished in size and became the stapes of the amphibian ear, an adaptation necessary for hearing on dry land. An affinity between the amphibians and the teleost fish is the multi-folded structure of the teeth and the paired supra-occipital bones at the back of the head, neither of these features being found elsewhere in the animal kingdom.
thumb|left|upright|alt=Diplocaulus|The Permian lepospondyl Diplocaulus was largely aquatic
At the end of the Devonian period (360 million years ago), the seas, rivers and lakes were teeming with life while the land was the realm of early plants and devoid of vertebrates, though some, such as Ichthyostega, may have sometimes hauled themselves out of the water. It is thought they may have propelled themselves with their forelimbs, dragging their hindquarters in a similar manner to that used by the elephant seal. In the early Carboniferous (360 to 323 million years ago), the climate was relatively wet and warm. Extensive swamps developed with mosses, ferns, horsetails and calamites. Air-breathing arthropods evolved and invaded the land where they provided food for the carnivorous amphibians that began to adapt to the terrestrial environment. There were no other tetrapods on the land and the amphibians were at the top of the food chain, with some occupying ecological positions currently held by crocodiles. Though equipped with limbs and the ability to breathe air, most still had a long tapering body and strong tail. Others were the top land predators, sometimes reaching several metres in length, preying on the large insects of the period and the many types of fish in the water. They still needed to return to water to lay their shell-less eggs, and even most modern amphibians have a fully aquatic larval stage with gills like their fish ancestors. It was the development of the amniotic egg, which prevents the developing embryo from drying out, that enabled the reptiles to reproduce on land and which led to their dominance in the period that followed.
After the Carboniferous rainforest collapse amphibian dominance gave way to reptiles, and amphibians were further devastated by the Permian–Triassic extinction event. During the Triassic Period (252 to 201 million years ago), the reptiles continued to out-compete the amphibians, leading to a reduction in both the amphibians' size and their importance in the biosphere. According to the fossil record, Lissamphibia, which includes all modern amphibians and is the only surviving lineage, may have branched off from the extinct groups Temnospondyli and Lepospondyli at some period between the Late Carboniferous and the Early Triassic. The relative scarcity of fossil evidence precludes precise dating, but the most recent molecular study, based on multilocus sequence typing, suggests a Late Carboniferous/Early Permian origin for extant amphibians.
thumb|alt=Eryops|The temnospondyl Eryops had sturdy limbs to support its body on land
The origins and evolutionary relationships between the three main groups of amphibians is a matter of debate. A 2005 molecular phylogeny, based on rDNA analysis, suggests that salamanders and caecilians are more closely related to each other than they are to frogs. It also appears that the divergence of the three groups took place in the Paleozoic or early Mesozoic (around 250 million years ago), before the breakup of the supercontinent Pangaea and soon after their divergence from the lobe-finned fish. The briefness of this period, and the swiftness with which radiation took place, would help account for the relative scarcity of primitive amphibian fossils. There are large gaps in the fossil record, the discovery of the dissorophoid temnospondyl Gerobatrachus from the Early Permian in Texas in 2008 provided a missing link with many of the characteristics of modern frogs. Molecular analysis suggests that the frog–salamander divergence took place considerably earlier than the palaeontological evidence indicates. One study suggested that the last common ancestor of all modern amphibians lived about 315 million years ago, and that stereospondyl temnospondyls are the closest relatives to the caecilians. However, most studies support a single monophyletic origin of all modern amphibians within the dissorophoid temnospondyls.
As they evolved from lunged fish, amphibians had to make certain adaptations for living on land, including the need to develop new means of locomotion. In the water, the sideways thrusts of their tails had propelled them forward, but on land, quite different mechanisms were required. Their vertebral columns, limbs, limb girdles and musculature needed to be strong enough to raise them off the ground for locomotion and feeding. Terrestrial adults discarded their lateral line systems and adapted their sensory systems to receive stimuli via the medium of the air. They needed to develop new methods to regulate their body heat to cope with fluctuations in ambient temperature. They developed behaviours suitable for reproduction in a terrestrial environment. Their skins were exposed to harmful ultraviolet rays that had previously been absorbed by the water. The skin changed to become more protective and prevent excessive water loss. |
Amphibian | Characteristics | Characteristics
The superclass Tetrapoda is divided into four classes of vertebrate animals with four limbs. Reptiles, birds and mammals are amniotes, the eggs of which are either laid or carried by the female and are surrounded by several membranes, some of which are impervious. Lacking these membranes, amphibians require water bodies for reproduction, although some species have developed various strategies for protecting or bypassing the vulnerable aquatic larval stage. They are not found in the sea with the exception of one or two frogs that live in brackish water in mangrove swamps; the Anderson's salamander meanwhile occurs in brackish or salt water lakes. On land, amphibians are restricted to moist habitats because of the need to keep their skin damp.
Modern amphibians have a simplified anatomy compared to their ancestors due to paedomorphosis, caused by two evolutionary trends: miniaturization and an unusually large genome, which result in a slower growth and development rate compared to other vertebrates. Another reason for their size is associated with their rapid metamorphosis, which seems to have evolved only in the ancestors of Lissamphibia; in all other known lines the development was much more gradual. Because a remodeling of the feeding apparatus means they do not eat during the metamorphosis, the metamorphosis has to go faster the smaller the individual is, so it happens at an early stage when the larvae are still small. (The largest species of salamanders do not go through a metamorphosis.) Amphibians that lay eggs on land often go through the whole metamorphosis inside the egg. An anamniotic terrestrial egg is less than 1 cm in diameter due to diffusion problems, a size which puts a limit on the amount of posthatching growth.
The smallest amphibian (and vertebrate) in the world is a microhylid frog from New Guinea (Paedophryne amauensis) first discovered in 2012. It has an average length of and is part of a genus that contains four of the world's ten smallest frog species. The largest living amphibian is the Chinese giant salamander (Andrias davidianus) but this is a great deal smaller than the largest amphibian that ever existed—the extinct Prionosuchus, a crocodile-like temnospondyl dating to 270 million years ago from the middle Permian of Brazil. The largest frog is the African Goliath frog (Conraua goliath), which can reach and weigh .
Amphibians are ectothermic (cold-blooded) vertebrates that do not maintain their body temperature through internal physiological processes. Their metabolic rate is low and as a result, their food and energy requirements are limited. In the adult state, they have tear ducts and movable eyelids, and most species have ears that can detect airborne or ground vibrations. They have muscular tongues, which in many species can be protruded. Modern amphibians have fully ossified vertebrae with articular processes. Their ribs are usually short and may be fused to the vertebrae. Their skulls are mostly broad and short, and are often incompletely ossified. Their skin contains little keratin and lacks scales, apart from a few fish-like scales in certain caecilians. The skin contains many mucous glands and in some species, poison glands (a type of granular gland). The hearts of amphibians have three chambers, two atria and one ventricle. They have a urinary bladder and nitrogenous waste products are excreted primarily as urea. Most amphibians lay their eggs in water and have aquatic larvae that undergo metamorphosis to become terrestrial adults. Amphibians breathe by means of a pump action in which air is first drawn into the buccopharyngeal region through the nostrils. These are then closed and the air is forced into the lungs by contraction of the throat. They supplement this with gas exchange through the skin. |
Amphibian | Anura | Anura
thumb|alt=Red-eyed tree frog|Red-eyed tree frog (Agalychnis callidryas) with limbs and feet specialised for climbing
The order Anura (from the Ancient Greek a(n)- meaning "without" and oura meaning "tail") comprises the frogs and toads. They usually have long hind limbs that fold underneath them, shorter forelimbs, webbed toes with no claws, no tails, large eyes and glandular moist skin. Members of this order with smooth skins are commonly referred to as frogs, while those with warty skins are known as toads. The difference is not a formal one taxonomically and there are numerous exceptions to this rule. Members of the family Bufonidae are known as the "true toads". Frogs range in size from the Goliath frog (Conraua goliath) of West Africa to the Paedophryne amauensis, first described in Papua New Guinea in 2012, which is also the smallest known vertebrate. Although most species are associated with water and damp habitats, some are specialised to live in trees or in deserts. They are found worldwide except for polar areas.
Anura is divided into three suborders that are broadly accepted by the scientific community, but the relationships between some families remain unclear. Future molecular studies should provide further insights into their evolutionary relationships. The suborder Archaeobatrachia contains four families of primitive frogs. These are Ascaphidae, Bombinatoridae, Discoglossidae and Leiopelmatidae which have few derived features and are probably paraphyletic with regard to other frog lineages. The six families in the more evolutionarily advanced suborder Mesobatrachia are the fossorial Megophryidae, Pelobatidae, Pelodytidae, Scaphiopodidae and Rhinophrynidae and the obligatorily aquatic Pipidae. These have certain characteristics that are intermediate between the two other suborders. Neobatrachia is by far the largest suborder and includes the remaining families of modern frogs, including most common species. Approximately 96% of the over 5,000 extant species of frog are neobatrachians. |
Amphibian | Caudata | Caudata
thumb|left|upright|alt=Japanese giant salamander|Japanese giant salamander (Andrias japonicus), a primitive salamander
The order Caudata (from the Latin cauda meaning "tail") consists of the salamanders—elongated, low-slung animals that mostly resemble lizards in form. This is a symplesiomorphic trait and they are no more closely related to lizards than they are to mammals. Salamanders lack claws, have scale-free skins, either smooth or covered with tubercles, and tails that are usually flattened from side to side and often finned. They range in size from the Chinese giant salamander (Andrias davidianus), which has been reported to grow to a length of , to the diminutive Thorius pennatulus from Mexico which seldom exceeds in length. Salamanders have a mostly Laurasian distribution, being present in much of the Holarctic region of the northern hemisphere. The family Plethodontidae is also found in Central America and South America north of the Amazon basin; South America was apparently invaded from Central America by about the start of the Miocene, 23 million years ago. Urodela is a name sometimes used for all the extant species of salamanders. Members of several salamander families have become paedomorphic and either fail to complete their metamorphosis or retain some larval characteristics as adults. Most salamanders are under long. They may be terrestrial or aquatic and many spend part of the year in each habitat. When on land, they mostly spend the day hidden under stones or logs or in dense vegetation, emerging in the evening and night to forage for worms, insects and other invertebrates.
thumb|alt=Danube crested newt|Danube crested newt (Triturus dobrogicus), an advanced salamander
The suborder Cryptobranchoidea contains the primitive salamanders. A number of fossil cryptobranchids have been found, but there are only three living species, the Chinese giant salamander (Andrias davidianus), the Japanese giant salamander (Andrias japonicus) and the hellbender (Cryptobranchus alleganiensis) from North America. These large amphibians retain several larval characteristics in their adult state; gills slits are present and the eyes are unlidded. A unique feature is their ability to feed by suction, depressing either the left side of their lower jaw or the right. The males excavate nests, persuade females to lay their egg strings inside them, and guard them. As well as breathing with lungs, they respire through the many folds in their thin skin, which has capillaries close to the surface.
The suborder Salamandroidea contains the advanced salamanders. They differ from the cryptobranchids by having fused prearticular bones in the lower jaw, and by using internal fertilisation. In salamandrids, the male deposits a bundle of sperm, the spermatophore, and the female picks it up and inserts it into her cloaca where the sperm is stored until the eggs are laid. The largest family in this group is Plethodontidae, the lungless salamanders, which includes 60% of all salamander species. The family Salamandridae includes the true salamanders and the name "newt" is given to members of its subfamily Pleurodelinae.
The third suborder, Sirenoidea, contains the four species of sirens, which are in a single family, Sirenidae. Members of this order are eel-like aquatic salamanders with much reduced forelimbs and no hind limbs. Some of their features are primitive while others are derived. Fertilisation is likely to be external as sirenids lack the cloacal glands used by male salamandrids to produce spermatophores and the females lack spermathecae for sperm storage. Despite this, the eggs are laid singly, a behaviour not conducive for external fertilisation. |
Amphibian | Gymnophiona | Gymnophiona
thumb|alt=Siphonops paulensis|The limbless South American caecilian Siphonops paulensis
The order Gymnophiona (from the Greek gymnos meaning "naked" and ophis meaning "serpent") or Apoda comprises the caecilians. These are long, cylindrical, limbless animals with a snake- or worm-like form. The adults vary in length from 8 to 75 centimetres (3 to 30 inches) with the exception of Thomson's caecilian (Caecilia thompsoni), which can reach . A caecilian's skin has a large number of transverse folds and in some species contains tiny embedded dermal scales. It has rudimentary eyes covered in skin, which are probably limited to discerning differences in light intensity. It also has a pair of short tentacles near the eye that can be extended and which have tactile and olfactory functions. Most caecilians live underground in burrows in damp soil, in rotten wood and under plant debris, but some are aquatic. Most species lay their eggs underground and when the larvae hatch, they make their way to adjacent bodies of water. Others brood their eggs and the larvae undergo metamorphosis before the eggs hatch. A few species give birth to live young, nourishing them with glandular secretions while they are in the oviduct. Caecilians have a mostly Gondwanan distribution, being found in tropical regions of Africa, Asia and Central and South America. |
Amphibian | Anatomy and physiology | Anatomy and physiology |
Amphibian | Skin | Skin
thumb|left|upright|alt=Common reed frog|The bright colours of the common reed frog (Hyperolius viridiflavus) are typical of a toxic species
The integumentary structure contains some typical characteristics common to terrestrial vertebrates, such as the presence of highly cornified outer layers, renewed periodically through a moulting process controlled by the pituitary and thyroid glands. Local thickenings (often called warts) are common, such as those found on toads. The outside of the skin is shed periodically mostly in one piece, in contrast to mammals and birds where it is shed in flakes. Amphibians often eat the sloughed skin. Caecilians are unique among amphibians in having mineralized dermal scales embedded in the dermis between the furrows in the skin. The similarity of these to the scales of bony fish is largely superficial. Lizards and some frogs have somewhat similar osteoderms forming bony deposits in the dermis, but this is an example of convergent evolution with similar structures having arisen independently in diverse vertebrate lineages.
thumb|upright=1.35|Cross section of frog skin:
Amphibian skin is permeable to water. Gas exchange can take place through the skin (cutaneous respiration) and this allows adult amphibians to respire without rising to the surface of water and to hibernate at the bottom of ponds. To compensate for their thin and delicate skin, amphibians have evolved mucous glands, principally on their heads, backs and tails. The secretions produced by these help keep the skin moist. In addition, most species of amphibian have granular glands that secrete distasteful or poisonous substances. Some amphibian toxins can be lethal to humans while others have little effect. The main poison-producing glands, the parotoids, produce the neurotoxin bufotoxin and are located behind the ears of toads, along the backs of frogs, behind the eyes of salamanders and on the upper surface of caecilians.
The skin colour of amphibians is produced by three layers of pigment cells called chromatophores. These three cell layers consist of the melanophores (occupying the deepest layer), the guanophores (forming an intermediate layer and containing many granules, producing a blue-green colour) and the lipophores (yellow, the most superficial layer). The colour change displayed by many species is initiated by hormones secreted by the pituitary gland. Unlike bony fish, there is no direct control of the pigment cells by the nervous system, and this results in the colour change taking place more slowly than happens in fish. A vividly coloured skin usually indicates that the species is toxic and is a warning sign to predators. |
Amphibian | Skeletal system and locomotion | Skeletal system and locomotion
thumb|Skull diagram of Xenotosuchus, a temnospondyl
Amphibians have a skeletal system that is structurally homologous to other tetrapods, though with a number of variations. They all have four limbs except for the legless caecilians and a few species of salamander with reduced or no limbs. The bones are hollow and lightweight. The musculoskeletal system is strong to enable it to support the head and body. The bones are fully ossified and the vertebrae interlock with each other by means of overlapping processes. The pectoral girdle is supported by muscle, and the well-developed pelvic girdle is attached to the backbone by a pair of sacral ribs. The ilium slopes forward and the body is held closer to the ground than is the case in mammals.
thumb|alt=Frog skeleton|Skeleton of the Surinam horned frog(Ceratophrys cornuta)
In most amphibians, there are four digits on the fore foot and five on the hind foot, but no claws on either. Some salamanders have fewer digits and the amphiumas are eel-like in appearance with tiny, stubby legs. The sirens are aquatic salamanders with stumpy forelimbs and no hind limbs. The caecilians are limbless. They burrow in the manner of earthworms with zones of muscle contractions moving along the body. On the surface of the ground or in water they move by undulating their body from side to side.
In frogs, the hind legs are larger than the fore legs, especially so in those species that principally move by jumping or swimming. In the walkers and runners the hind limbs are not so large, and the burrowers mostly have short limbs and broad bodies. The feet have adaptations for the way of life, with webbing between the toes for swimming, broad adhesive toe pads for climbing, and keratinised tubercles on the hind feet for digging (frogs usually dig backwards into the soil). In most salamanders, the limbs are short and more or less the same length and project at right angles from the body. Locomotion on land is by walking and the tail often swings from side to side or is used as a prop, particularly when climbing. In their normal gait, only one leg is advanced at a time in the manner adopted by their ancestors, the lobe-finned fish. Some salamanders in the genus Aneides and certain plethodontids climb trees and have long limbs, large toepads and prehensile tails. In aquatic salamanders and in frog tadpoles, the tail has dorsal and ventral fins and is moved from side to side as a means of propulsion. Adult frogs do not have tails and caecilians have only very short ones.
thumb|left|upright=0.65|Didactic model of an amphibian heart.
Salamanders use their tails in defence and some are prepared to jettison them to save their lives in a process known as autotomy. Certain species in the Plethodontidae have a weak zone at the base of the tail and use this strategy readily. The tail often continues to twitch after separation which may distract the attacker and allow the salamander to escape. Both tails and limbs can be regenerated. Adult frogs are unable to regrow limbs but tadpoles can do so. |
Amphibian | Circulatory system | Circulatory system
thumb|Juvenile amphibian circulatory systems are single loop systems which resemble fish. Red indicates oxygenated blood, and blue represents oxygen depleted blood.
Amphibians have a juvenile stage and an adult stage, and the circulatory systems of the two are distinct. In the juvenile (or tadpole) stage, the circulation is similar to that of a fish; the two-chambered heart pumps the blood through the gills where it is oxygenated, and is spread around the body and back to the heart in a single loop. In the adult stage, amphibians (especially frogs) lose their gills and develop lungs. They have a heart that consists of a single ventricle and two atria. When the ventricle starts contracting, deoxygenated blood is pumped through the pulmonary artery to the lungs. Continued contraction then pumps oxygenated blood around the rest of the body. Mixing of the two bloodstreams is minimized by the anatomy of the chambers. |
Amphibian | Nervous and sensory systems | Nervous and sensory systems
The nervous system is basically the same as in other vertebrates, with a central brain, a spinal cord, and nerves throughout the body. The amphibian brain is relatively simple but broadly the same structurally as in reptiles, birds and mammals. Their brains are elongated, except in caecilians, and contain the usual motor and sensory areas of tetrapods. The pineal body, known to regulate sleep patterns in humans, is thought to produce the hormones involved in hibernation and aestivation in amphibians.
Tadpoles retain the lateral line system of their ancestral fishes, but this is lost in terrestrial adult amphibians. Many aquatic salamanders and some caecilians possess electroreceptors called ampullary organs (completely absent in anurans), that allow them to locate objects around them when submerged in water.A Natural History of Amphibians The ears are well developed in frogs. There is no external ear, but the large circular eardrum lies on the surface of the head just behind the eye. This vibrates and sound is transmitted through a single bone, the stapes, to the inner ear. Only high-frequency sounds like mating calls are heard in this way, but low-frequency noises can be detected through another mechanism. There is a patch of specialized haircells, called papilla amphibiorum, in the inner ear capable of detecting deeper sounds. Another feature, unique to frogs and salamanders, is the columella-operculum complex adjoining the auditory capsule which is involved in the transmission of both airborne and seismic signals. The ears of salamanders and caecilians are less highly developed than those of frogs as they do not normally communicate with each other through the medium of sound.
The eyes of tadpoles lack lids, but at metamorphosis, the cornea becomes more dome-shaped, the lens becomes flatter, and eyelids and associated glands and ducts develop. The adult eyes are an improvement on invertebrate eyes and were a first step in the development of more advanced vertebrate eyes. They allow colour vision and depth of focus. In the retinas are green rods, which are receptive to a wide range of wavelengths. |
Amphibian | Digestive and excretory systems | Digestive and excretory systems
thumb|alt=Dissected frog|Dissected frog:
Many amphibians catch their prey by flicking out an elongated tongue with a sticky tip and drawing it back into the mouth before seizing the item with their jaws. Some use inertial feeding to help them swallow the prey, repeatedly thrusting their head forward sharply causing the food to move backwards in their mouth by inertia. Most amphibians swallow their prey whole without much chewing so they possess voluminous stomachs. The short oesophagus is lined with cilia that help to move the food to the stomach and mucus produced by glands in the mouth and pharynx eases its passage. The enzyme chitinase produced in the stomach helps digest the chitinous cuticle of arthropod prey.
Amphibians possess a pancreas, liver and gall bladder. The liver is usually large with two lobes. Its size is determined by its function as a glycogen and fat storage unit, and may change with the seasons as these reserves are built or used up. Adipose tissue is another important means of storing energy and this occurs in the abdomen (in internal structures called fat bodies), under the skin and, in some salamanders, in the tail.
There are two kidneys located dorsally, near the roof of the body cavity. Their job is to filter the blood of metabolic waste and transport the urine via ureters to the urinary bladder where it is stored before being passed out periodically through the cloacal vent. Larvae and most aquatic adult amphibians excrete the nitrogen as ammonia in large quantities of dilute urine, while terrestrial species, with a greater need to conserve water, excrete the less toxic product urea. Some tree frogs with limited access to water excrete most of their metabolic waste as uric acid. |
Amphibian | Urinary bladder | Urinary bladder
Most aquatic and semi-aquatic amphibians have a membranous skin which allows them to absorb water directly through it. Some semi-aquatic animals also have similarly permeable bladder membrane. As a result, they tend to have high rates of urine production to offset this high water intake, and have urine which is low in dissolved salts. The urinary bladder assists such animals to retain salts. Some aquatic amphibian such as Xenopus do not reabsorb water, to prevent excessive water influx. For land-dwelling amphibians, dehydration results in reduced urine output.
The amphibian bladder is usually highly distensible and among some land-dwelling species of frogs and salamanders may account for between 20% and 50% of their total body weight. Urine flows from the kidneys through the ureters into the bladder and is periodically released from the bladder to the cloaca. |
Amphibian | Respiratory system | Respiratory system
thumb|left|alt=Axolotl|The axolotl (Ambystoma mexicanum) retains its larval form with gills into adulthood
The lungs in amphibians are primitive compared to those of amniotes, possessing few internal septa and large alveoli, and consequently having a comparatively slow diffusion rate for oxygen entering the blood. Ventilation is accomplished by buccal pumping. Most amphibians, however, are able to exchange gases with the water or air via their skin. To enable sufficient cutaneous respiration, the surface of their highly vascularised skin must remain moist to allow the oxygen to diffuse at a sufficiently high rate. Because oxygen concentration in the water increases at both low temperatures and high flow rates, aquatic amphibians in these situations can rely primarily on cutaneous respiration, as in the Titicaca water frog and the hellbender salamander. In air, where oxygen is more concentrated, some small species can rely solely on cutaneous gas exchange, most famously the plethodontid salamanders, which have neither lungs nor gills. Many aquatic salamanders and all tadpoles have gills in their larval stage, with some (such as the axolotl) retaining gills as aquatic adults. |
Amphibian | Reproduction | Reproduction
thumb|alt=Orange-thighed frogs in amplexus|Male orange-thighed frog (Litoria xanthomera) grasping the female during amplexus
For the purpose of reproduction, most amphibians require fresh water although some lay their eggs on land and have developed various means of keeping them moist. A few (e.g. Fejervarya raja) can inhabit brackish water, but there are no true marine amphibians. There are reports, however, of particular amphibian populations unexpectedly invading marine waters. Such was the case with the Black Sea invasion of the natural hybrid Pelophylax esculentus reported in 2010.
Several hundred frog species in adaptive radiations (e.g., Eleutherodactylus, the Pacific Platymantis, the Australo-Papuan microhylids, and many other tropical frogs), however, do not need any water for breeding in the wild. They reproduce via direct development, an ecological and evolutionary adaptation that has allowed them to be completely independent from free-standing water. Almost all of these frogs live in wet tropical rainforests and their eggs hatch directly into miniature versions of the adult, passing through the tadpole stage within the egg. Reproductive success of many amphibians is dependent not only on the quantity of rainfall, but the seasonal timing.
In the tropics, many amphibians breed continuously or at any time of year. In temperate regions, breeding is mostly seasonal, usually in the spring, and is triggered by increasing day length, rising temperatures or rainfall. Experiments have shown the importance of temperature, but the trigger event, especially in arid regions, is often a storm. In anurans, males usually arrive at the breeding sites before females and the vocal chorus they produce may stimulate ovulation in females and the endocrine activity of males that are not yet reproductively active.
In caecilians, fertilisation is internal, the male extruding an intromittent organ, the , and inserting it into the female cloaca. The paired Müllerian glands inside the male cloaca secrete a fluid which resembles that produced by mammalian prostate glands and which may transport and nourish the sperm. Fertilisation probably takes place in the oviduct.
The majority of salamanders also engage in internal fertilisation. In most of these, the male deposits a spermatophore, a small packet of sperm on top of a gelatinous cone, on the substrate either on land or in the water. The female takes up the sperm packet by grasping it with the lips of the cloaca and pushing it into the vent. The spermatozoa move to the spermatheca in the roof of the cloaca where they remain until ovulation which may be many months later. Courtship rituals and methods of transfer of the spermatophore vary between species. In some, the spermatophore may be placed directly into the female cloaca while in others, the female may be guided to the spermatophore or restrained with an embrace called amplexus. Certain primitive salamanders in the families Sirenidae, Hynobiidae and Cryptobranchidae practice external fertilisation in a similar manner to frogs, with the female laying the eggs in water and the male releasing sperm onto the egg mass.
With a few exceptions, frogs use external fertilisation. The male grasps the female tightly with his forelimbs either behind the arms or in front of the back legs, or in the case of Epipedobates tricolor, around the neck. They remain in amplexus with their cloacae positioned close together while the female lays the eggs and the male covers them with sperm. Roughened nuptial pads on the male's hands aid in retaining grip. Often the male collects and retains the egg mass, forming a sort of basket with the hind feet. An exception is the granular poison frog (Oophaga granulifera) where the male and female place their cloacae in close proximity while facing in opposite directions and then release eggs and sperm simultaneously. The tailed frog (Ascaphus truei) exhibits internal fertilisation. The "tail" is only possessed by the male and is an extension of the cloaca and used to inseminate the female. This frog lives in fast-flowing streams and internal fertilisation prevents the sperm from being washed away before fertilisation occurs. The sperm may be retained in storage tubes attached to the oviduct until the following spring.
Most frogs can be classified as either prolonged or explosive breeders. Typically, prolonged breeders congregate at a breeding site, the males usually arriving first, calling and setting up territories. Other satellite males remain quietly nearby, waiting for their opportunity to take over a territory. The females arrive sporadically, mate selection takes place and eggs are laid. The females depart and territories may change hands. More females appear and in due course, the breeding season comes to an end. Explosive breeders on the other hand are found where temporary pools appear in dry regions after rainfall. These frogs are typically fossorial species that emerge after heavy rains and congregate at a breeding site. They are attracted there by the calling of the first male to find a suitable place, perhaps a pool that forms in the same place each rainy season. The assembled frogs may call in unison and frenzied activity ensues, the males scrambling to mate with the usually smaller number of females.
right|thumb|upright=1.1|Sexual selection has been studied in the red back salamander
There is a direct competition between males to win the attention of the females in salamanders and newts, with elaborate courtship displays to keep the female's attention long enough to get her interested in choosing him to mate with. Some species store sperm through long breeding seasons, as the extra time may allow for interactions with rival sperm. |
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