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| − | {{alternateuses}} *[[Category:Frogs| ]]
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| | + | ===Frogs=== <!--T:1--> |
| | + | [[Image:Frogspawn closeup.jpg|190px|thumb|Frogspawn]] |
| | + | [[Image:Tadpoles 10 days.jpg|190px|thumb||10 days: Tadpoles]] |
| | + | [[Image:Frog-Zhe.jpg||190px|thumb|8–12 weeks: Froglet]] |
| | + | [[Image:Green-leopard-frog-in-swamp.jpg||190px|thumb|12–16 weeks: Adult frog]] |
| | + | The life cycle of frogs, like that of other amphibians, consists of four main stages: egg, tadpole, metamorphosis and adult. The reliance of frogs on an aquatic environment for the egg and tadpole stages gives rise to a variety of breeding behaviors that include the well-known mating calls used by the males of most species to attract females to the bodies of water that they have chosen for breeding. Some frogs also look after their eggs—and in some cases even the tadpoles—for some time after laying. |
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| − | [[Image:Pobblebonk.jpg|thumb|250px|[[Pobblebonk]], Australia]]
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| | + | The life cycle of a frog starts with an egg. Eggs are generally laid in water, and an individual female may lay egg masses containing thousands of eggs. While the length of the egg stage depends on the species and environmental conditions, aquatic eggs generally hatch within one week. |
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| − | '''Frogs''' are [[Amphibia|amphibians]] in the [[order (biology)|Order]] [[Anura]], which includes frogs and [[toad]]s. The term "frog" is a popular name for [[animal]]s that look like toads, but are generally more slender, have a less warty and dry skin, have long legs adapted for leaping and are more aquatic. It has no meaning in animal [[systematics]], since many anuran families include both "frogs" and "toads". The [[true frog]]s are the Ranidae and the [[true toad]]s are the Bufonidae. | + | <!--T:3--> |
| | + | Some frogs do not have the tadpole stage going from egg to adult shape e.g. New Zealand's native frogs (pepeketua) belong to the genus Leiopelma. |
| | + | Eggs hatch and continue life as tadpoles (occasionally known as polliwogs). Tadpoles are aquatic, lack front and hind legs, and have gills for breathing and tails with fins for swimming. Tadpoles are typically herbivorous, feeding mostly on algae, including diatoms that are filtered from the water through the gills. Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles and fish. The tadpole stage may be as short as a week, or tadpoles may overwinter and metamorphosis the following year in some species, such as the Midwife toad (''Alytes obstetricans'') and the Common Spadefoot (''Pelobates fuscus''). |
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| | + | At the end of the tadpole stage, frogs undergo metamorphosis, in which they transition into adult form. Metamorphosis involves a dramatic transformation of body shape and function, as tadpoles develop hind legs and then front legs, lose their gills and develop lungs. Their intestines shorten as they shift from an herbivorous to a carnivorous diet. The final stage of development from froglet to adult frog involves the loss of the tail. |
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| − | ==Characteristics==
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| − | Frogs range in size from less than 50mm (2.0 in) to 300mm (11.8 in) in ''Conraua goliath'', the [[Goliath frog]] from [[Cameroon]], which is the largest known frog. Frogs can have horizontal [[pupil]]s, like tree frogs and true frogs, or vertical pupils, like the painted frogs.
| + | After metamorphosis, young adults may leave the water and disperse into terrestrial habitats, or continue to live in the aquatic habitat as adults. Almost all species of frogs are carnivores as adults, eating invertebrates such as spiders, insects, snails, and slugs. A few of the larger species may eat prey such as small mammals, fish and smaller frogs. Some frogs use their sticky tongues to catch fast-moving prey, while others capture their prey and force it into their mouths with their hands. However, there are a very few species of frogs that primarily eat plants. Adult frogs are themselves preyed upon by birds, large fish, snakes, otters, foxes, badgers, coatis, and other animals. |
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| − | The skin is smooth, unkeratinized and hangs loosely on the body because of the lack of [[loose connective tissue]].
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| − | Generally, frogs have long legs with webbed toes. The true frogs have a tongue with two lobes on its free end; it is attached in front. Frogs have three eyelid membranes: one transparent to protect the eyes underwater, and two which are translucent to opaque like human eyelids. They have a [[tympanum]] on each side of their head, which is involved in hearing.
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| − | ===Croaking===
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| − | Many species of frog (and toad) have deep calls, or croaks. Frog noise tends to be spelt (for English speakers) as "crrrrk" in Britain and "ribbit" in the USA. This difference is due to Britain and the USA having different species of frogs (e.g. ''Rana temporaria'' in Britain and ''Rana pipiens'' (leopard frog) etc in the USA.) The croak of the American [[bullfrog]] ''Rana catesbiana'' is sometimes spelt "jug o' rum". The [[Ancient Greeks]] (for example [[Aristophanes]]) spelt the croak of the usual Greek species of frog as "korax" or "brekekekex co-ax co-ax": that species is probably ''Rana ridibunda''. Small tropical frogs tend to have higher-pitched calls. [[Rigveda]] book 7 hymn 103 describes frogs with different calls (''g<u>o</u>māyu'' = "having a voice like a cow's" and ''aj<u>a</u>māyu'' = "having a voice like a goat's") calling when the rains bring the breeding season.
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| − | ===Poison===
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| − | Some species of frog secrete [[toxin]]s from their skin. These toxins deter predatory animals from eating them, and some are extremely poisonous to humans. Some natives of the [[Amazon_Rainforest|Amazon]] area extract poison from the [[poison dart frog]] and put it on their [[arrow]]heads when hunting.
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| − | ==Distribution and status==
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| − | [[Image:Frog.jpg|thumb|right|Australian Frog]]
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| − | Frogs are found nearly worldwide, but they do not occur in antarctica and are not present on most oceanic islands.
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| − | In many parts of the world the frog populations have [[Decline in frog populations|declined]] drastically over the last few decades. Many environmental scientists feel that amphibians, and frogs in particular, may be excellent biological indicators of ecosystem function because of their place in the food web, their permeable skins, their typically bi-phasic life history (in both water and on land), and how diverse and dense they have historically been in many areas. Although habitat loss is certainly one of the most important features of most declines, pollutants, climate change, parasitic infestation, introduction of non-indigenous predators/competitors, and infectious diseases (see Chitrid fungus) have also been implicated.
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| − | ==Frog zoology==
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| − | ''Main Article: [[Frog zoology]]''
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| − | ==Life cycle==
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| − | {| align=right
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| − | |[[Image:Frogspawn closeup.JPG|thumb|Frogspawn]]
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| − | |[[image:Tadpoles 10 days.JPG|thumb|The tadpoles, ten days later]]
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| − | |[[Image:Frog-Zhe.jpg|thumb|Froglet]]
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| − | |[[image:Green-leopard-frog-in-swamp.jpg|thumb|right|Adult frog]]
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| − | |}
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| − | The life cycle of a frog involves several stages. Typically adult frogs gather in suitable pools, the first to arive usually being the males. Their croaking may well encourage the females to arrive. A female would wish to avoid arriving at a pond which did not have any males in attendance. Gravid female frogs are actively and persistently sought out by males and many males will often try to attach themselves to a single female but eventually one male will secure possession. [[Amplexus]] is the process wherein the male grasps the female while she lays her eggs. At the same time, he fertilizes them with a fluid containing sperm. The eggs are about 2.0 to 2.8 millimetres in diameter and are dark brown and are covered in an outer shell of gelatinous transparent material which swells in contact with water. The female frog lays her [[Egg (biology)|egg]]s in a shallow [[pond]] or creek, where they will be sheltered from the current and from predators. The eggs, known as ''frogspawn'' hatch into [[tadpole]]s. The tadpole stage develops gradually into a froglet, resembling an adult but retaining a vestigial tail. Finally the froglet develops into an adult frog. Typically, tadpoles are [[herbivore]]s, feeding mostly on [[alga]]e, whereas juvenile and adult frogs are rather voracious [[carnivore]]s.
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| − | Most temperate species of frog reproduce in the period between late autumn to early spring. In the [[UK]] most Common Frog populations produce frogspawn in February although there is wide variation in timing. Water temperatures at this time of year are relatively low and typically between four and 10 degrees celsius. Reproducing in these conditions helps the developing tadpoles because dissolved oxygen concentrations in the water are highest at cold temperatures. More importantly, reproducing early in the season ensures that appropriate food is available to the developing frogs at the right time.
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| − | ==Diet==
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| − | Most frogs eat [[insect]]s such as [[mosquito]]es, earthworms and small fish such as [[minnow]]s; however, a few of the bigger ones may tackle larger prey, such as [[mice]]. Some frogs use their sticky tongues effectively in catching fast-moving prey. Still others capture their prey in their mouth with speed and agility. Certain big frogs eat small frogs.
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| − | ==Predators==
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| − | Many animals eat frogs. These include [[heron]]s, [[stork]], large [[fish]], [[snake]]s [[otter]]s, [[fox]]es, [[badger]]s, [[coati]]s, etc etc. Large domestic [[duck]]s are built for [[dredging]] rather than [[fishing]], but routinely catch and swallow frogs, as commemorated in the song [[Froggy would a-wooing go]].
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| − | ==A new frog==
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| − | ''Main article: [[Purple Frog]]''
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| − | In 2003, Franky Bossuyt of the ''[[Vrije Universiteit Brussel]]'' (Free University of Brussels) and S.D. Biji of the Tropical Botanic Garden and Research Institute in [[Palode]], [[India]] reported the discovery of a new [[species]] of frog so distinct in appearance and [[DNA]] that it merited its own new [[Scientific classification|family]], the first new family for frogs since [[1926]]. This new species, dubbed ''[[Purple Frog|Nasikabatrachus sahyadrensis]]'' (commonly ''Purple Frog'' or ''Pignose Frog''), is dark purple in color, seven centimeters in length, and has a small head and a pointy snout. Genetically, its closest living relatives are the [[sooglossid]]s found in the [[Seychelles]]. The new species was discovered in the [[Sahyadri]] (Western Ghats) Mountains in India.
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| − | * [http://news.bbc.co.uk/1/hi/sci/tech/3200214.stm BBC article with photos of the Purple Frog]
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| − | ==Frogs in popular culture==
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| − | *Frogs feature prominently in [[folklore]] and [[fairy tale|fairy tales]] in many cultures, such as the story of ''[[The Frog Prince]]''. Similarly, numerous [[fantasy]] settings (such as the [[Final Fantasy]] [[videogames]]) include [[magic]] spells that turn people into frogs. Similarly, [[Frog (Chrono Trigger)|a frog]] is a playable character in the [[videogame]] [[Chrono Trigger]]. In the 1992 animated movie [[Freddie as FRO7]], Frederick, an enchanted frog prince with magical powers, becomes a modern-day secret agent.
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| − | *Probably the most famous frog in the entertainment world is the [[Muppet]] character [[Kermit the Frog]].
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| − | *Until recently, the American TV network The WB ([[Warner Brothers]]) used [[Michigan J. Frog]], a frog in a tuxedo as their logo. Michigan J. Frog was the singing, dancing star of the [[1955]] Warner cartoon, "[[One Froggy Evening]]".
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| − | *''[[Frogger]]'' is an early electronic [[arcade game]] which features a frog that must cross a busy road and river.
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| − | *Frogs fall from the sky in various urban myths and notably in the movie [[Magnolia]]. This may derive from incidents when frogs are picked up by a [[tornado]], or when a sudden migration of frogs happens overnight.
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| − | *The behavior of frogs illustrating nonaction is a myth. ("Take a pot of hot water and a frog. Throw the frog into the pot. What do you think will happen? The obvious, of course: the frog will jump out. Who likes hanging around in a pot of hot water? Now ... [t]ake a pot of cold water, put the frog in it, and place the pot on the stove. Turn on the heat. This time something different will occur. The frog, because of the incremental change in temperature, will not notice that it is slowly being boiled." from "Life and Death in the Executive Fast Lane" by Manfred Kets de Vries) Professor Doug Melton, Harvard University Biology Department, says, "If you put a frog in boiling water, it won't jump out. It will die. If you put it in cold water, it will jump before it gets hot -- they don't sit still for you." [http://www.fastcompany.com/online/01/frog.html] A frog put anywhere that doesn't kill it will jump, "they don't sit still for you."
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| − | *[[Paul McCartney]]'s "[[Rupert the Bear| Rupert]] and the Frog Song" was released in [[1984]] and reached no.3 in the British Charts.
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| − | ==External links== | |
| − | * [http://www-itg.lbl.gov/ITG.hm.pg.docs/Whole.Frog/Whole.Frog.html The Whole Frog Project] ~ Virtual frog dissection and anatomy
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| − | * ''[http://raysweb.net/specialplaces/pages/frogsdecline.html Disappearance of toads, frogs has some scientists worried]'' ~ ''San Francisco Chronicle'', April 20, 1992
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| − | *[http://www.thelilypad.org/ The Lily Pad] - Frog information, care, and culture.
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| − | * [http://www.frogsonice.com/froggy/ The Froggy Page] ~ Frog fun
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| − | * [http://www.dartden.com Dart Den] ~ Dart frog resource and forums
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| − | * [http://www.xenbase.org/ Xenbase] ~ A <i>Xenopus laevis</i> and <i>tropicalis</i> Web Resource
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| − | * [http://markus.nolf.org/blog.php?p=160 Time-lapse video showing the egg's development until hatching]
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| − | [[ar:ضفدع]]
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| − | [[ast:Xaronca]]
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| − | [[ca:Granota]]
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| − | [[da:Frø (padde)]]
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| − | [[de:Froschlurche]]
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| − | [[es:Rana]]
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| − | [[eo:Rano]]
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| − | [[fr:Grenouille]]
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| − | [[li:Kwakkers]]
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| − | [[nl:Kikker]]
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| − | [[no:Frosk]]
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| − | [[ja:カエル]]
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| − | [[pl:żaba]]
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| − | [[pt:Rã]]
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| − | [[simple:frog]]
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| − | [[sv:Grodor]]
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Frogs
The life cycle of frogs, like that of other amphibians, consists of four main stages: egg, tadpole, metamorphosis and adult. The reliance of frogs on an aquatic environment for the egg and tadpole stages gives rise to a variety of breeding behaviors that include the well-known mating calls used by the males of most species to attract females to the bodies of water that they have chosen for breeding. Some frogs also look after their eggs—and in some cases even the tadpoles—for some time after laying.
The life cycle of a frog starts with an egg. Eggs are generally laid in water, and an individual female may lay egg masses containing thousands of eggs. While the length of the egg stage depends on the species and environmental conditions, aquatic eggs generally hatch within one week.
Some frogs do not have the tadpole stage going from egg to adult shape e.g. New Zealand's native frogs (pepeketua) belong to the genus Leiopelma.
Eggs hatch and continue life as tadpoles (occasionally known as polliwogs). Tadpoles are aquatic, lack front and hind legs, and have gills for breathing and tails with fins for swimming. Tadpoles are typically herbivorous, feeding mostly on algae, including diatoms that are filtered from the water through the gills. Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles and fish. The tadpole stage may be as short as a week, or tadpoles may overwinter and metamorphosis the following year in some species, such as the Midwife toad (Alytes obstetricans) and the Common Spadefoot (Pelobates fuscus).
At the end of the tadpole stage, frogs undergo metamorphosis, in which they transition into adult form. Metamorphosis involves a dramatic transformation of body shape and function, as tadpoles develop hind legs and then front legs, lose their gills and develop lungs. Their intestines shorten as they shift from an herbivorous to a carnivorous diet. The final stage of development from froglet to adult frog involves the loss of the tail.
After metamorphosis, young adults may leave the water and disperse into terrestrial habitats, or continue to live in the aquatic habitat as adults. Almost all species of frogs are carnivores as adults, eating invertebrates such as spiders, insects, snails, and slugs. A few of the larger species may eat prey such as small mammals, fish and smaller frogs. Some frogs use their sticky tongues to catch fast-moving prey, while others capture their prey and force it into their mouths with their hands. However, there are a very few species of frogs that primarily eat plants. Adult frogs are themselves preyed upon by birds, large fish, snakes, otters, foxes, badgers, coatis, and other animals.
