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Cognates. Afroasiatic languages share a vocabulary of Proto-Afroasiatic origin to varying extents. Writing in 2004, John Huehnergard notes the great difficulty in establishing cognate sets across the family. Identifying cognates is difficult because the languages in question are often separated by thousands of years of...
Andorra Andorra, officially the Principality of Andorra, is a sovereign landlocked country on the Iberian Peninsula, in the eastern Pyrenees in Western Europe, bordered by France to the north and Spain to the south. Believed to have been created by Charlemagne, Andorra was ruled by the count of Urgell until 988, when i...
Tourism in Andorra brings approximately 8 million visitors to the country annually. Andorra is not a member state of the European Union. It has been a member of the Council of Europe and of the United Nations since 1993. Etymology. The origin of the word Andorra is unknown, although several hypotheses have been propose...
Other theories suggest that the term derives from the Navarro-Aragonese "andurrial", which means "land covered with bushes" or "scrubland". The folk etymology holds that Charlemagne had named the region as a reference to the Biblical Canaanite valley of Endor or Andor (where the Midianites had been defeated), a name be...
Other archaeological deposits include the Tombs of Segudet (Ordino) and Feixa del Moro (Sant Julià de Lòria), both dated in 4900–4300 BCE as an example of the Urn culture in Andorra. The model of small settlements began to evolve to complex urbanism during the Bronze Age. Metallurgical items of iron, ancient coins, and...
Some of the most significant remains of this era are the Castle of the Roc d'Enclar (part of the early Marca Hispanica), l'Anxiu in Les Escaldes and Roc de L'Oral in Encamp. The presence of Roman influence is recorded from the 2nd century BCE to the 5th century CE. The places with the most Roman presence are in Camp Ve...
Tradition holds that Charles the Great (Charlemagne) granted a charter to the Andorran people for a contingent of 5,000 soldiers under the command of Marc Almugaver, in return for fighting against the Moors near Porté-Puymorens (Cerdanya). Andorra remained part of the Frankish "Marca Hispanica", the buffer zone between...
Middle Ages: The Paréages and the founding of the Co-Principality. Before 1095, Andorra had no military protection, and the bishop of Urgell, who knew that the count of Urgell wanted to reclaim the Andorran valleys, asked the Lord of Caboet for help and protection. In 1095, the lord of Caboet and the bishop of Urgell s...
A second paréage was signed in 1288 after a dispute when the count of Foix ordered the construction of a castle in Roc d'Enclar. The document was ratified by the noble notary Jaume Orig of Puigcerdà, and construction of military structures in the country was prohibited. In 1364, the political organisation of the countr...
The Catalan Pyrenees were embryonic of the Catalan language at the end of the 11th century. Andorra was influenced by this language, which was adopted locally decades before it expanded to the rest of the Crown of Aragon. The local economy during the Middle Ages was based on livestock, agriculture, furs and weavers. La...
During 1617, communal councils form the sometent (popular militia or army) to deal with the rise of bandolerisme (brigandage) and the Consell de la Terra was defined and structured in terms of its composition, organisation and competences current today. Andorra continued with the same economic system that it had during...
Three centuries after its foundation, the Consell de la Terra located its headquarters and the Tribunal de Corts in Casa de la Vall in 1702. The manor house built in 1580 served as a noble fortress of the Busquets family. Inside the parliament was placed the Closet of the six keys (Armari de les sis claus), representat...
During this period, Andorra's late medieval institutions and rural culture remained largely unchanged. In 1866, the syndic Guillem d'Areny-Plandolit led the reformist group in a Council General of 24 members elected by suffrage limited to heads of families. The Council General replaced the aristocratic oligarchy that p...
Andorra participated in the cultural movement of the Catalan Renaixença. Between 1882 and 1887, the first academic schools were formed where trilingualism coexisted with the official language, Catalan. Romantic authors from France and Spain reported the awakening of the national consciousness of the country. Jacint Ver...
On 6 July 1934, adventurer and nobleman Boris Skossyreff, with his promise of freedoms and modernisation of the country and wealth through the establishment of a tax haven and foreign investments, received the support of the members of the General Council to proclaim himself the sovereign of Andorra. On 8 July 1934 Bor...
During World War II, Andorra remained neutral and was an important smuggling route between Vichy France and Francoist Spain. Many Andorrans criticised the passivity of the General Council for impeding both the entry and expulsion of foreigners and refugees, committing economic crimes, reducing the rights of citizens an...
In the capital city there was a smuggling black market of propaganda, culture and cinematic art not favourable to totalitarian regimes, promulgated in such places as the Hotel Mirador or the Casino Hotel, as a meeting place for Free French forces and a route for escorting crashed Allied pilots out of Europe. The networ...
The Andorran government necessarily involved planning, projection and forecasts for the future: with the official visit of the French co-prince Charles de Gaulle in 1967 and 1969, it was given approval for the economic boom and national demands within the framework of human rights and international openness. Andorra ex...
Its political system was modernised in 1993 after the Andorran constitutional referendum, when the constitution was drafted by the co-princes and the General Council and approved on 14 March by 74.2% of voters, with a 76% turnout. The first elections under the new constitution were held later in the year. The same year...
The current prime minister is Xavier Espot Zamora of the Democrats for Andorra (DA). Executive power is exercised by the government. Legislative power is vested in both government and parliament. The Parliament of Andorra is known as the General Council. The General Council consists of between 28 and 42 councillors. Th...
Candidates can be proposed by a minimum of one-fifth of the councillors. The Council then elects the candidate with the absolute majority of votes to be prime minister. The Syndic General then notifies the co-princes, who in turn appoint the elected candidate as the prime minister of Andorra. The General Council is als...
Law and criminal justice. The judiciary is composed of the Magistrates Court, the Criminal Law Court, the High Court of Andorra, and the Constitutional Court. The High Court of Justice is composed of five judges: one appointed by the prime minister, one each by the co-princes, one by the Syndic General, and one by the ...
Foreign relations, defence and security. Andorra does not have its own armed forces, although there is a small ceremonial army. Responsibility for defending the nation rests primarily with France and Spain. However, in case of emergencies or natural disasters, the Sometent (an alarm) is called and all able-bodied men b...
Military. Andorra has a small army, which has historically been raised or reconstituted at various dates, but has never in modern times amounted to a standing army. The basic principle of Andorran defence is that all able-bodied men are available to fight if called upon by the summoning of the Sometent (a civil defence...
The army's role in internal security was largely taken over by the formation of the Police Corps of Andorra in 1931. Brief civil disorder associated with the elections of 1933 led to assistance being sought from the French National Gendarmerie, with a detachment resident in Andorra for two months under the command of R...
The only more recent general emergency call to the Sometent was given during the floods of 1982 in the Catalan Pyrenees (when 12 Andorran citizens perished), to help the population and establish a public order along with the local police units. Andorra in the Council of Europe. Andorra is one of the 46 member states of...
GIPA. The ' (GIPA) is a small special forces squad trained in counter-terrorism, and hostage recovery tasks. Although it is the closest in style to an active military force, it is part of the Police Corps, and not the army. As terrorist and hostage situations are a rare threat to the country, the GIPA is commonly assig...
The fire service maintains full-time cover with five fire crews on duty at any time: two at the brigade's headquarters in Santa Coloma, and one crew at each of the other three fire stations. Geography. Parishes. Andorra consists of seven parishes: Physical geography. Due to its location in the eastern Pyrenees mountain...
Important Bird Area. The whole country has been recognised as a single Important Bird Area (IBA) by BirdLife International, because it is important for forest and mountain birds and supports populations of red-billed choughs, citril finches and rock buntings. Climate. Andorra has alpine, continental and oceanic climate...
As a small mountainous country, Andorra is highly vulnerable to climate change. Temperatures in its high-altitude regions have risen by about 0.17 °C per decade, while annual rainfall has decreased by 49 mm. These shifts are impacting water resources and snow cover, which are key elements for Andorra's tourism-driven e...
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...
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 p...
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 Mar...
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%...
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 Musl...
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 educati...
Transport. 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 un...
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 ho...
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...
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 incl...
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. ...
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. Sports. Andorra is famous for its winter sports. Andorra ha...
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 cha...
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. Tourism. Skiing, hiking, cross-country running, and cycling are all popular sports tourism activities in A...
Arithmetic mean 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 s...
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 formula_1, the arithmetic mean is defined by the formula: In simpler terms, the formula for the ar...
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 direc...
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. Generalizations. Weighted average. A weighted average, or weighted mean, is an average in which some data points count more heav...
Continuous probability distributions. 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 distri...
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: In general application, such an oversight will lead to the average value artificially moving towards the middle of the numerical range...
American Football Conference 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 d...
Season structure. 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 agai...
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 ...
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, wh...
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 ...
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 wou...
Logo. 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 leagu...
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...
Animal Farm 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, a...
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 su...
"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 W...
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 har...
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 (be...
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 car...
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...
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 t...
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. Publication. Publishing. Orwell initially encountered difficulty...
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 liter...
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...
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 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 resp...
"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...
Analysis. 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 hum...
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 F...
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 ris...
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...
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 d...
Adaptations. Stage productions. 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 ...
Andy Serkis is directing an upcoming animated film adaptation. 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...
Amphibian 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 excluding the amniotes (tetrapods with an amniotic membrane, such as modern reptiles, birds and mammals). All extant (living) ...
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...
Classification. 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 ...
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 c...
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 ...
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 t...
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 themselve...
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 amphi...
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, lim...
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 rapi...
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 ear...
Anura. 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 s...
Caudata. 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, eith...
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") fro...
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 sir...
Anatomy and physiology. Skin. The 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, s...
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...
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. T...
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 attac...
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 caecilia...
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 vi...

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