wikipedia_id stringlengths 2 8 | wikipedia_title stringlengths 1 243 | url stringlengths 44 370 | contents stringlengths 53 2.22k | id int64 0 6.14M |
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655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
table strewn with dust definition is popular, there are those that do not place credence in this at all and in fact state that it is not proven. Greek itself is probably a borrowing of a Northwest Semitic, perhaps Phoenician, word akin to Hebrew "ʾābāq" (), "dust" (or in post-Biblical sense meaning "sand used as... | 27,900 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
number system.
Some scholars point to a character from the Babylonian cuneiform which may have been derived from a representation of the abacus. It is the belief of Old Babylonian scholars such as Carruccio that Old Babylonians "may have used the abacus for the operations of addition and subtraction; however, t... | 27,901 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
been used as counters. However, wall depictions of this instrument have not been discovered.
## Persian.
During the Achaemenid Empire, around 600 BC the Persians first began to use the abacus. Under the Parthian, Sassanian and Iranian empires, scholars concentrated on exchanging knowledge and inventions with t... | 27,902 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
mentions an abacus and pebbles for accounting, and both Diogenes and Polybius mention men that sometimes stood for more and sometimes for less, like the pebbles on an abacus. The Greek abacus was a table of wood or marble, pre-set with small counters in wood or metal for mathematical calculations. This Greek aba... | 27,903 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
of the tablet is a set of 5 parallel lines equally divided by a vertical line, capped with a semicircle at the intersection of the bottom-most horizontal line and the single vertical line. Below these lines is a wide space with a horizontal crack dividing it. Below this crack is another group of eleven parallel ... | 27,904 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
hand while manipulating counters on a table with the other.
## Chinese.
The earliest known written documentation of the Chinese abacus dates to the 2nd century BC.
The Chinese abacus, known as the "suanpan" (算盤, lit. "calculating tray"), is typically tall and comes in various widths depending on the operator.... | 27,905 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
a quick movement along the horizontal axis to spin all the beads away from the horizontal beam at the center.
The prototype of the Chinese abacus appeared during the Han Dynasty, and the beads are oval. The Song Dynasty and earlier used the 1:4 type or four-beads abacus similar to the modern abacus commonly kno... | 27,906 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
time included the Chinese catty equal to sixteen tael（一斤十六兩）.
Various calculation techniques were devised for "Suanpan" enabling efficient calculations. There are currently schools teaching students how to use it.
In the long scroll "Along the River During the Qingming Festival" painted by Zhang Zeduan during ... | 27,907 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
and the similarity of the abacuses may be coincidental, both ultimately arising from counting with five fingers per hand. Where the Roman model (like most modern Korean and Japanese) has 4 plus 1 bead per decimal place, the standard "suanpan" has 5 plus 2. (Incidentally, this allows use with a hexadecimal numera... | 27,908 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
holder. The zero was probably introduced to the Chinese in the Tang dynasty (618–907) when travel in the Indian Ocean and the Middle East would have provided direct contact with India, allowing them to acquire the concept of zero and the decimal point from Indian merchants and mathematicians.
## Roman.
The nor... | 27,909 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
limited use into the nineteenth century. Due to Pope Sylvester II's reintroduction of the abacus with modifications, it became widely used in Europe once again during the 11th century This abacus used beads on wires, unlike the traditional Roman counting boards, which meant the abacus could be used much faster.
... | 27,910 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
either one or no beads in each. The groove marked I indicates units, X tens, and so on up to millions. The beads in the shorter grooves denote fives –five units, five tens etc., essentially in a bi-quinary coded decimal system, related to the Roman numerals. The short grooves on the right may have been used for ... | 27,911 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
one thousand means it is a thousand". It is unclear exactly what this arrangement may have been. Around the 5th century, Indian clerks were already finding new ways of recording the contents of the Abacus. Hindu texts used the term "śūnya" (zero) to indicate the empty column on the abacus.
## Japanese.
In Japa... | 27,912 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
circa 1930, and became widespread as the Japanese abandoned hexadecimal weight calculation which was still common in China.
Today's Japanese abacus is a 1:4 type, four-bead abacus was introduced from China in the Muromachi era. It adopts the form of the upper deck one bead and the bottom four beads. The top bea... | 27,913 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
consistently use the division multiplication. Later, Japan had a 3:5 abacus called天三算盤, which is now the Ize Rongji collection of Shansi Village in Yamagata City. There were also had 2:5 beads abacus.
With the four-bead abacus spread, it is also common to use Japanese abacus around the world. There are also imp... | 27,914 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
in Japan today even with the proliferation, practicality, and affordability of pocket electronic calculators. The use of the soroban is still taught in Japanese primary schools as part of mathematics, primarily as an aid to faster mental calculation. Using visual imagery of a soroban, one can arrive at the answe... | 27,915 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
from China during the Ming Dynasty.
## Native American.
Some sources mention the use of an abacus called a "nepohualtzintzin" in ancient Aztec culture. This Mesoamerican abacus used a 5-digit base-20 system.
The word Nepōhualtzintzin comes from Nahuatl and it is formed by the roots; "Ne" – personal -; "pōhual... | 27,916 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
In the left part there were four beads, which in the first row have unitary values (1, 2, 3, and 4), and in the right side there are three beads with values of 5, 10, and 15 respectively. In order to know the value of the respective beads of the upper rows, it is enough to multiply by 20 (by each row), the value... | 27,917 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
lasts, two Nepōhualtzitzin (182) is the number of days of the corn's cycle, from its sowing to its harvest, three Nepōhualtzintzin (273) is the number of days of a baby's gestation, and four Nepōhualtzintzin (364) completed a cycle and approximate a year (1 days short). When translated into modern computer arith... | 27,918 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
instrument and reconstructed several of them made in gold, jade, encrustations of shell, etc. There have also been found very old Nepōhualtzintzin attributed to the Olmec culture, and even some bracelets of Mayan origin, as well as a diversity of forms and materials in other cultures.
George I. Sanchez, "Arithm... | 27,919 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
was a system of colored knotted cords used to record numerical data, like advanced tally sticks – but not used to perform calculations. Calculations were carried out using a yupana (Quechua for "counting tool"; see figure) which was still in use after the conquest of Peru. The working principle of a yupana is un... | 27,920 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
would keep the number of grains within any one field at a minimum.
## Russian.
The Russian abacus, the "schoty" (, plural from , counting), usually has a single slanted deck, with ten beads on each wire (except one wire, usually positioned near the user, with four beads for quarter-ruble fractions). Older mode... | 27,921 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
the left. For easy viewing, the middle 2 beads on each wire (the 5th and 6th bead) usually are of a different color from the other eight beads. Likewise, the left bead of the thousands wire (and the million wire, if present) may have a different color.
As a simple, cheap and reliable device, the Russian abacus ... | 27,922 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
to lose popularity only after the mass production of microcalculators had started in the Soviet Union in 1974. Today it is regarded as an archaism and replaced by the handheld calculator.
The Russian abacus was brought to France around 1820 by the mathematician Jean-Victor Poncelet, who served in Napoleon's arm... | 27,923 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
Russian schoty. It was named a "coulba" by the Turks and a "choreb" by the Armenians.
# School abacus.
Around the world, abacuses have been used in pre-schools and elementary schools as an aid in teaching the numeral system and arithmetic.
In Western countries, a bead frame similar to the Russian abacus but w... | 27,924 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
on the 8th wire, so numbers up to 100 may be represented). Teaching multiplication, e.g. 6 times 7 may be represented by shifting 7 beads on 6 wires. In the bead frame shown, the gap between the 5th and 6th wire, corresponding to the color change between the 5th and the 6th bead on each wire, suggests the latter... | 27,925 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
which becomes faster and more accurate in doing large number calculations. Abacus‐based mental calculation (AMC) was derived from the abacus which means doing calculation, including addition, subtraction, multiplication, and division, in mind with an imagined abacus. It is a high-level cognitive skill that run t... | 27,926 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
of the imaginary bead. Since the only thing needed to be remembered is the finial position of beads, it takes less memory and less computation time.
# Uses by the blind.
An adapted abacus, invented by Tim Cranmer, called a Cranmer abacus is still commonly used by individuals who are blind. A piece of soft fabr... | 27,927 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
to these students in early grades, both in public schools and state schools for the blind. Blind students also complete mathematical assignments using a braille-writer and Nemeth code (a type of braille code for mathematics) but large multiplication and long division problems can be long and difficult. The abacu... | 27,928 |
655 | Abacus | https://en.wikipedia.org/w/index.php?title=Abacus | Abacus
rs manipulate numbers. The abacus shows how numbers, letters, and signs can be stored in a binary system on a computer, or via ASCII. The device consists of a series of beads on parallel wires arranged in three separate rows. The beads represent a switch on the computer in either an "on" or "off" position.
# Se... | 27,929 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
Michael Schwerner
Michael Henry "Mickey" Schwerner (November 6, 1939 – June 21, 1964), was one of three Congress of Racial Equality (CORE) field/social workers killed in Philadelphia, Mississippi, by members of the Ku Klux Klan. Schwerner and two others were killed in response to their civil rights w... | 27,930 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
was a businessman. Schwerner attended Michigan State University, originally intending to become a veterinarian. He transferred to Cornell University and switched his major to rural sociology. While an undergraduate at Cornell, he was initiated into the school's chapter of Alpha Epsilon Pi Fraternity. ... | 27,931 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
on the Lower East Side of Manhattan, called "Downtown CORE." He participated in a 1963 effort to desegregate Gwynn Oak Amusement Park in Maryland. As activism increased in the South, Schwerner and his wife Rita Schwerner Bender volunteered to work for National CORE in Mississippi, under the tutelage o... | 27,932 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
to vote in the state, what they called "Freedom Summer". Many volunteers, mostly college students and young adults, had been recruited from local communities and northern/western states to work on this project.
Civil rights activists were resented and held under suspicion in Mississippi. Spies paid b... | 27,933 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
about the workers, including their car license number, to the Commission. Records showed the Commission passed the information on to the Sheriff of Neshoba County, who was implicated in the murders.
The Ku Klux Klan targeted Schwerner after he and his wife, Rita, had taken over the Meridian CORE fiel... | 27,934 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
Chaney, Andrew Goodman, and Michael Schwerner were murdered near the town of Philadelphia, Mississippi. They were investigating the burning of Mt. Zion Methodist Church, which had been a site of a CORE Freedom School, in a nearby community. Parishioners had been beaten in the wake of Schwerner and Cha... | 27,935 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
traffic violation and took them to the jail in Neshoba County. They were released that evening, without being allowed to telephone anyone. On the way back to Meridian, they were stopped by patrol lights and two carloads of KKK members on Highway 19, then taken in Price's car to another remote rural ro... | 27,936 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
Navy sailors and other forces to aid in the search.
Schwerner's widow Rita, who also worked for CORE in Meridian, expressed indignation publicly at the way the story was handled. She said she believed that if only Chaney (who was black) was missing and the two older white men from New York had not be... | 27,937 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
Reinvestigation.
Journalist Jerry Mitchell, an award-winning investigative reporter for the "Jackson Clarion-Ledger" had written extensively about the case for many years in the late 20th century. Mitchell had earned renown for helping secure convictions by his investigation of several other high-pro... | 27,938 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
documentary, produced for the National History Day contest, presented important new evidence and compelling reasons for reopening the case. Bradford also obtained an interview with Edgar Ray Killen, which helped convince the State to reinvestigate. Mitchell was able to determine the identity of "Mr. X... | 27,939 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
2005. He was sentenced to sixty years in prison—twenty years for each count, served consecutively.
# Personality.
Schwerner "was described by family and friends as friendly, good-natured, gentle, mischievous, and 'full of life and ideas'. He believed all people were essentially good. He loved sports... | 27,940 |
206712 | Michael Schwerner | https://en.wikipedia.org/w/index.php?title=Michael%20Schwerner | Michael Schwerner
of older boys; one of them was Michael Schwerner. Reich cites this event as an inspiration to "fight the bullies, to protect the powerless, to make sure that the people without a voice have a voice."
# Legacy and honors.
## Schwerner.
- In 2008, his hometown of Pelham, New York renamed a section of... | 27,941 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
Amphibian
Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. Modern amphibians are all Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae l... | 27,942 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in recent decades there has been a dramatic decline in amphibian populations for many species aroun... | 27,943 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
only the modern subclass Lissamphibia.
The three modern orders of amphibians are Anura (the frogs and toads), Urodela (the salamanders), and Apoda (the caecilians). The number of known amphibian species is approximately 8,000, of which nearly 90% are frogs. The smallest amphibian (and vertebrate) in the worl... | 27,944 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
word "amphibian" is derived from the Ancient Greek term ἀμφίβιος ("amphíbios"), which means "both kinds of life", "ἀμφί" meaning "of both kinds" and "βιος" 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. Traditiona... | 27,945 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
Lissamphibia (all modern amphibians, including frogs, toads, salamanders, newts and caecilians)
- Salientia (frogs, toads and relatives): Jurassic to present—6,200 current species in 53 families
- Caudata (salamanders, newts and relatives): Jurassic to present—652 current species in 9 families
- Gymnophion... | 27,946 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 amphibian species as of March 31, 2019 is exactly 8,000, of which nearly 90% are frogs.
With the phylogenetic classification, the taxon Labyrinthodontia ... | 27,947 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 Labyrinthod... | 27,948 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 and toads), Caudata (or Urodela, the salamanders), and ... | 27,949 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
Jurassic Kayenta Formation of Arizona. It is anatomically very similar to modern frogs. The oldest known caecilian is another Early Jurassic species, "Eocaecilia micropodia", also from Arizona. The earliest salamander is "Beiyanerpeton jianpingensis" from the Late Jurassic of northeastern China.
Authorities ... | 27,950 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
plus the Triassic proto-frog, "Triadobatrachus".
# 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-joint... | 27,951 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 ... | 27,952 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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... | 27,953 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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... | 27,954 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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, occupying the ecological position currently held by the crocodile. Though equipped with limbs and the ability to breathe air, most still had a long tapering body and strong ... | 27,955 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 ext... | 27,956 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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.
The ori... | 27,957 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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, b... | 27,958 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
years ago, and that stereospondyls are the closest relatives to the caecilians.
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,... | 27,959 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 wa... | 27,960 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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, amphibian... | 27,961 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
("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 an... | 27,962 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 a... | 27,963 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 ... | 27,964 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 amau... | 27,965 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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... | 27,966 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
suborder and includes the remaining families of modern frogs, including most common species. Ninety-six percent of the over 5,000 extant species of frog are neobatrachians.
## Caudata.
The order Caudata (from the Latin "cauda" meaning "tail") consists of the salamanders—elongated, low-slung animals that mos... | 27,967 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 ... | 27,968 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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.
The suborder Cryp... | 27,969 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 lung... | 27,970 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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... | 27,971 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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.
## Gymnophiona.
The order Gymnophiona (from the Greek "gymnos" meaning "naked" and "ophis" meaning "serpent") or Apoda com... | 27,972 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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... | 27,973 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
in tropical regions of Africa, Asia and Central and South America.
# 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 t... | 27,974 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 ... | 27,975 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 paratoids, produce the neurotoxin bufotoxin and ... | 27,976 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 ... | 27,977 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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, ... | 27,978 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 fro... | 27,979 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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, particular... | 27,980 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
a means of propulsion. Adult frogs do not have tails and caecilians have only very short ones.
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 u... | 27,981 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
(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 h... | 27,982 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
the same as in other vertebrates, with a central brain, a spinal cord, and nerves throughout the body. The amphibian brain is less well developed than that of reptiles, birds and mammals but is similar in morphology and function to that of a fish. It is believed amphibians are capable of perceiving pain. The ... | 27,983 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
The brain sends signals through the spinal cord and nerves to regulate activity in the rest of the body. 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 ance... | 27,984 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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, uniqu... | 27,985 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 ... | 27,986 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 ch... | 27,987 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 bla... | 27,988 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
acid.
## Respiratory system.
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, howeve... | 27,989 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 tadpo... | 27,990 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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... | 27,991 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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, usu... | 27,992 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
that are not yet reproductively active.
In caecilians, fertilisation is internal, the male extruding an intromittent organ, the phallodeum, 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 an... | 27,993 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 t... | 27,994 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 m... | 27,995 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 oc... | 27,996 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
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 region... | 27,997 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
number of females.
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,... | 27,998 |
621 | Amphibian | https://en.wikipedia.org/w/index.php?title=Amphibian | Amphibian
is regulated by thyroxine concentration in the blood, which stimulates metamorphosis, and prolactin, which counteracts thyroxine's effect. Specific events are dependent on threshold values for different tissues. Because most embryonic development is outside the parental body, it is subject to many adaptations... | 27,999 |
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