Frog Fossil range: Triassic - Recent
White's Tree Frog (Litoria caerulea)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Amphibia Order: Anura Merrem, 1820
Distribution of frogs (in black)
Suborders
Archaeobatrachia Mesobatrachia Neobatrachia - List of Anuran families

The frog is an amphibian in the order Anura (meaning "tail-less", from Greek an-, without + oura, tail), formerly referred to as Salientia (Latin saltare, to jump). The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago The Holocene is a Geological epoch which began approximately 10000 years ago (about 8000 BC The Australian Green Tree Frog, simply Green Tree Frog in Australia White's Tree Frog, or Dumpy Tree Frog ( Litoria caerulea) is a Species Chordates ( Phylum Chordata) are a group of Animals that includes the Vertebrates together with several closely related Invertebrates Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and Blasius Merrem ( February 4, 1761 - February 23, 1824) was a German naturalist. Archaeobatrachia is a suborder of Anura containing various primitive Frogs and Toads As the name literally suggests these are the most primitive frogs Mesobatrachia is the second largest of the Anura Suborders of amphibians Neobatrachia are a suborder of order Anura, ie of frogs or toads Wikipedia talkFeatured lists for an explanation of this and other inclusion tags below -->This list of Anuran families shows all extant families Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and The name frog derives from Old English frogga,^[1] (compare Old Norse frauki, German Frosch, older Dutch spelling kikvorsch), cognate with Sanskrit plava (frog), probably deriving from Proto-Indo-European praw = "to jump". Old Norse is the North Germanic language that was spoken by inhabitants of Scandinavia and inhabitants of their overseas settlements during the Viking Age The German language (de ''Deutsch'') is a West Germanic language and one of the world's major languages. Dutch ( is a West Germanic language spoken by around 24 million people 22 million of which are from the Netherlands, Belgium and Suriname Sanskrit (sa संस्कृता वाक् saṃskṛtā vāk, for short sa संस्कृतम् saṃskṛtam) is a historical ^[2]

Adult frogs are characterised by long hind legs, a short body, webbed digits, protruding eyes and the absence of a tail. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain The tail is the section at the rear end of an Animal 's Body; in general the term refers to a distinct flexible Appendage to the Torso. Most frogs have a semi-aquatic lifestyle, but move easily on land by jumping or climbing. They typically lay their eggs in puddles, ponds or lakes, and their larvae, called tadpoles, have gills and develop in water. In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. A pond is a body of water smaller than a Lake, both being examples of Terrain features Although the term pond is universally used to describe waterbodies that A lake (from Latin lacus) is a Terrain feature (or Physical feature) a body of Liquid on the surface of a world that is localized to the A larva ( Latin; plural larvae) is a juvenile form of Animal with indirect development, undergoing Metamorphosis (for example A tadpole or polliwog (also pollywog, polliwig, polewig, or polwig) is the wholly aquatic larval stage in the life cycle of A gill is an anatomical structure found in many aquatic organisms Water is a common Chemical substance that is essential for the survival of all known forms of Life. Adult frogs follow a carnivorous diet, mostly of arthropods, annelids and gastropods. A carnivore (ˈkɑrnɪvɔər meaning 'meat eater' ( Latin carne meaning 'flesh' and vorare meaning 'to devour' is any animal with a diet consisting Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " The annelids, collectively called Annelida (from Latin anellus "little ring" are a large phylum of Animals comprising The class Gastropoda or the gastropods, also previously known as gasteropods, or univalves, and more commonly known as Snails Frogs are most noticeable by their call, which can be widely heard during the night or day, mainly in their mating season. Oestrus is also the biological genus name of the gadfly. The estrous cycle (also oestrous cycle; derived from Latin

The distribution of frogs ranges from tropic to subarctic regions, but most species are found in tropical rainforests. The Tropics are centered on the Equator and limited in Latitude by the Tropic of Cancer in the northern hemisphere at approximately 23°26' (23 The Subarctic is a region in the Northern Hemisphere immediately south of the true Arctic and covering much of Alaska, Canada and Tropical rainforests are generally found near the Equator. They are common in Asia, Australia, Africa, South America, Central Consisting of more than 5,000 species described, they are among the most diverse groups of vertebrates. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes However, populations of certain frog species are significantly declining. Dramatic declines in Amphibian populations, including Population crashes and mass localized Extinctions have been noted since the 1980s from locations all

A distinction is often made between frogs and toads on the basis of their appearance, caused by the convergent adaptation among so-called toads to dry environments; however, this distinction has no taxonomic basis. A toad can refer to a number of Species of Amphibians in the order Anura. Convergent evolution describes the acquisition of the same biological trait in unrelated lineages The only family exclusively given the common name "toad" is Bufonidae, but many species from other families are also called "toads," and the species within the toad genus Atelopus are referred to as "harlequin frogs. A toad can refer to a number of Species of Amphibians in the order Anura. Atelopus is a large Genus of true toads natively distributed in Costa Rica to Bolivia and French Guiana. "

Contents 1 Taxonomy 2 Morphology and physiology 2.1 Feet and legs 2.2 Skin 2.3 Poison 2.4 Respiration and circulation 3 Natural history 3.1 Life cycle 3.2 Reproduction of frogs 3.3 Parental care 3.4 Call 4 Distribution and conservation status 5 Evolution 6 Uses in agriculture and research 7 Cultural beliefs 8 Cited references 9 General references 10 External links

Taxonomy

For more details on this topic, see List of Anuran families. The European Fire-bellied Toad Bombina bombina is a Fire-bellied toad native to mainland Europe. Wikipedia talkFeatured lists for an explanation of this and other inclusion tags below -->This list of Anuran families shows all extant families

The order Anura contains 5,250 species in 33 families, of which the Leptodactylidae (1100 spp. Leptodactylidae are a diverse Family of Frogs that probably diverged from other hyloids during the Cenozoic era or possibly at the end of ), Hylidae (800 spp. Hylidae are a family of Frogs with tree dwelling adaptations and include several species commonly called " Treefrogs and their allies" ) and Ranidae (750 spp. The true frogs, family Ranidae, have the widest distribution of any Frog family ) are the richest in species. About 88% of amphibian species are frogs. Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and

The use of the common names "frog" and "toad" has no taxonomic justification. From a taxonomic perspective, all members of the order Anura are frogs, but only members of the family Bufonidae are considered "true toads". The use of the term "frog" in common names usually refers to species that are aquatic or semi-aquatic with smooth and/or moist skins, and the term "toad" generally refers to species that tend to be terrestrial with dry, warty skin. An exception is the fire-bellied toad (Bombina bombina): while its skin is slightly warty, it prefers a watery habitat. The Fire-bellied Toads is a group comprising eight species of small Toads (typically 4-7cm in length belonging to the genus Bombina.

Frogs and toads are broadly classified into three suborders: Archaeobatrachia, which includes four families of primitive frogs; Mesobatrachia, which includes five families of more evolutionary intermediate frogs; and Neobatrachia, by far the largest group, which contains the remaining 24 families of "modern" frogs, including most common species throughout the world. Archaeobatrachia is a suborder of Anura containing various primitive Frogs and Toads As the name literally suggests these are the most primitive frogs Mesobatrachia is the second largest of the Anura Suborders of amphibians Neobatrachia are a suborder of order Anura, ie of frogs or toads Neobatrachia is further divided into the Hyloidea and Ranoidea. ^[3] This classification is based on such morphological features as the number of vertebrae, the structure of the pectoral girdle, and the morphology of tadpoles. The pectoral girdle is the set of bones which connect the upper limb to the axial skeleton on each side While this classification is largely accepted, relationships among families of frogs are still debated. Future studies of molecular genetics should soon provide further insights to the evolutionary relationships among frog families. Molecular genetics is the field of Biology which studies the structure and function of Genes at a molecular level ^[4]

Some species of anurans hybridise readily. In Biology, hybrid has two meanings The first meaning is the result of interbreeding between two animals or plants of different taxa. For instance, the edible frog (Rana esculenta) is a hybrid of the pool frog (R. The Edible Frog ( Pelophylax kl esculentus) is a name for a common European Frog, also known as the common water frog or green frog (however this latter The Pool Frog ( Rana lessonae) is a European Frog. It is one of only three Amphibian Species recognized by the UK lessonae) and the marsh frog (R. The Marsh Frog ( Rana ridibunda) is the largest Frog native to Europe, and belongs to the family of True frogs It is very similar in appearance ridibunda). Bombina bombina and Bombina variegata similarly form hybrids, although these are less fertile, giving rise to a hybrid zone. A hybrid zone exists where the ranges of two Interbreeding Species meet

Morphology and physiology

For more details on this topic, see Frog zoology. Introduction to phylum Around 400 million years ago some members of the sarcopterygian group of Fish moved onto land

The morphology of frogs is unique among amphibians. The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism Compared with the other two groups of amphibians, (salamanders and caecilians), frogs are unusual because they lack tails as adults and their legs are more suited to jumping than walking. Salamander (orig from Persian: sām, "fire" and andarūn, "within" is the common name for a group of approximately 500 Species Apoda redirects here For the Moth Genus, see Apoda (moth. For the bishop of Carthage see Caecilianus. The physiology of frogs is generally like that of other amphibians (and differs from other terrestrial vertebrates) because oxygen can pass through their highly permeable skin. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes This unique feature allows frogs to "breathe" largely through their skin. Because the oxygen is dissolved in an aqueous film on the skin and passes from there to the blood, the skin must remain moist at all times; this makes frogs susceptible to many toxins in the environment, some of which can similarly dissolve in the layer of water and be passed into their bloodstream. This may be cause of the decline in frog populations. Dramatic declines in Amphibian populations, including Population crashes and mass localized Extinctions have been noted since the 1980s from locations all

Many characteristics are not shared by all of the approximately 5,250 described frog species. However, some general characteristics distinguish them from other amphibians. Frogs are usually well suited to jumping, with long hind legs and elongated ankle bones. They have a short vertebral column, with no more than ten free vertebrae, followed by a fused tailbone (urostyle or coccyx), typically resulting in a tailless phenotype. The coccyx (pronounced kok -siks (Latin os coccygis) commonly referred to as the tailbone, is the final segment of the human vertebral column

Frogs range in size from 10 mm (Brachycephalus didactylus of Brazil and Eleutherodactylus iberia of Cuba) to 300 mm (goliath frog, Conraua goliath, of Cameroon). The Brazilian Gold Frog ( Brachycephalus didactylus) also known as Izecksohn's Toad, is the smallest Frog in the Southern Hemisphere |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld At just over 3/8 inches (96 - 98 mm long the Monte Iberia Eleuth ( Eleutherodactylus iberia) is the smallest living Frog The Republic of Cuba (ˈkjuːbə or) consists of the island of Cuba (the largest and second-most populous island of the Greater Antilles) Isla de la The goliath frog, Conraua goliath is the largest extant anuran on Earth. The Republic of Cameroon is a unitary republic of central and western Africa. The skin hangs loosely on the body because of the lack of loose connective tissue. Areolar tissue (a type of "loose connective tissue" exhibits loosely organized fibers abundant blood vessels and a lot of seemingly empty space Skin texture varies: it can be smooth, warty or folded. Frogs have three eyelid membranes: one is transparent to protect the eyes underwater, and two vary from translucent to opaque. Frogs have a tympanum on each side of the head, which is involved in hearing and, in some species, is covered by skin. The tympanum is an external hearing structure in Frogs and Toads located just behind the eye Most frogs do in fact have teeth of a sort. They have a ridge of very small cone teeth around the upper edge of the jaw. These are called maxillary teeth. Frogs often also have what are called vomerine teeth on the roof of their mouth. They do not have anything that could be called teeth on their lower jaw, so they usually swallow their food whole. The so-called "teeth" are mainly used to hold the prey and keep it in place till they can get a good grip on it and squash their eyeballs down to swallow their meal. Toads, however, do not have any teeth.

Feet and legs

The structure of the feet and legs varies greatly among frog species, depending in part on whether they live primarily on the ground, in water, in trees, or in burrows. Frogs must be able to move quickly through their environment to catch prey and escape predators, and numerous adaptations help them do so.

Many frogs, especially those that live in water, have webbed toes. The degree to which the toes are webbed is directly proportional to the amount of time the species lives in the water. For example, the completely aquatic African dwarf frog (Hymenochirus sp. African dwarf frogs of genus Hymenochirus, also known as dwarf aquatic frogs (ADF or DAF for short are Frogs native to Sub Saharan Africa ) has fully webbed toes, whereas the toes of White's tree frog (Litoria caerulea), an arboreal species, are only a half or a quarter webbed. The Australian Green Tree Frog, simply Green Tree Frog in Australia White's Tree Frog, or Dumpy Tree Frog ( Litoria caerulea) is a Species

Arboreal frogs have "toe pads" to help grip vertical surfaces. A tree frog or tree toad is any Frog that spends a major portion of its lifespan in an Arboreal state These pads, located on the ends of the toes, do not work by suction. Rather, the surface of the pad consists of interlocking cells, with a small gap between adjacent cells. When the frog applies pressure to the toe pads, the interlocking cells grip irregularities on the substrate. The small gaps between the cells drain away all but a thin layer of moisture on the pad, and maintain a grip through capillarity. Capillary action, capillarity, capillary motion, or wicking is the ability of a substance to draw another substance into it This allows the frog to grip smooth surfaces, and does not function when the pads are excessively wet. ^[5]

In many arboreal frogs, a small "intercalary structure" in each toe increases the surface area touching the substrate. Furthermore, since hopping through trees can be dangerous, many arboreal frogs have hip joints that allow both hopping and walking. Some frogs that live high in trees even possess an elaborate degree of webbing between their toes, as do aquatic frogs. In these arboreal frogs, the webs allow the frogs to "parachute" or control their glide from one position in the canopy to another. ^[6]

Ground-dwelling frogs generally lack the adaptations of aquatic and arboreal frogs. Most have smaller toe pads, if any, and little webbing. Some burrowing frogs have a toe extension—a metatarsal tubercle—that helps them to burrow. The metatarsus consists of the five long Bones of the Foot, which are numbered from the medial side ( ossa metatarsalia I tubercle (anatomyA tubercle is generally a wart-like projection but it has slightly different meaning depending on which family of plants or animals it is used to refer to The hind legs of ground dwellers are more muscular than those of aqueous and tree-dwelling frogs.

While frog species can use a variety of locomotor modes (running, walking, gliding, swimming and climbing), more are either proficient at jumping or descended from ancestors who were, with much of the musculo-skeletal morphology modified for this purpose. Running is a means for an animal to move on Foot. It is defined in Sporting terms as a Gait in which at some point all feet are off the ground Walking (also called ambulation) is the main form of Animal Locomotion on land, distinguished from Running and crawling Gliding is a Recreational activity and competitive Sport in which pilots fly un-powered aircraft known as Gliders or sailplanes Swimming is the movement by humans or animals through Water, usually without artificial assistance UserStan Shebs for a timetable --> Climbing is the activity of using one's hands and feet (or Jumping or leaping is an ability that most Humans and many Animals share to some degree The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism The tibia, fibula and tarsals have been fused into a single, strong bone, as have the radius and ulna in the forelimbs (which must absorb the impact of landing). The tibia, shinbone, or shankbone is the larger and stronger of the two Bones in the Leg below the Knee in vertebrates and connects For other uses see Fibula (disambiguation The fibula or calf bone is a Bone located on the lateral side of the Tibia Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce The metatarsals have become elongated to add to the leg length and allow the frog to push against the ground for longer during a jump. The metatarsus consists of the five long Bones of the Foot, which are numbered from the medial side ( ossa metatarsalia I A leg is a limb on an Animal 's Body that supports the rest of the animal above the ground between the Ankle and the Hip and is used for The illium has elongated and formed a mobile joint with the sacrum which, in specialist jumpers such as Ranids or Hylids, functions as an additional limb joint to further power the leaps. The ilium of the Pelvis is divisible into two parts the body and the ala the separation is indicated on the top surface by a curved line the arcuate line and on the The sacrum is a large triangular bone at the base of the spine and at the upper and back part of the Pelvic cavity, where it is inserted like a wedge between The true frogs, family Ranidae, have the widest distribution of any Frog family Hylidae are a family of Frogs with tree dwelling adaptations and include several species commonly called " Treefrogs and their allies"

Skin

Many frogs are able to absorb water and oxygen directly through the skin, especially around the pelvic area. However, the permeability of a frog's skin can also result in water loss. Some tree frogs reduce water loss with a waterproof layer of skin. Others have adapted behaviours to conserve water, including engaging in nocturnal activity and resting in a water-conserving position. As an Animal behavior, nocturnality describes sleeping during the Daytime and being active at Night - the opposite of the diurnal This position involves the frog lying with its toes and fingers tucked under its body and chin, respectively, with no gap between the body and substrate. Some frog species will also rest in large groups, touching the skin of the neighbouring frog. This reduces the amount of skin exposed to the air or a dry surface, and thus reduces water loss. These adaptations only reduce water loss enough for a predominantly arboreal existence, and are not suitable for arid conditions.

Camouflage is a common defensive mechanism in frogs. Camouflage is a method of cryptic or concealing coloration that allows an otherwise visible Organism Most camouflaged frogs are nocturnal, which adds to their ability to hide. Nocturnal frogs usually find the ideal camouflaged position during the day to sleep. Some frogs have the ability to change colour, but this is usually restricted to shades of one or two colours. For example, White's tree frog varies in shades of green and brown. Features such as warts and skin folds are usually found on ground-dwelling frogs, where a smooth skin would not disguise them effectively. Skin folds are areas of Skin where it folds Many skin folds are distinct heritable anatomical features and may be used for identification of animal Species, while Arboreal frogs usually have smooth skin, enabling them to disguise themselves as leaves.

Certain frogs change colour between night and day, as light and moisture stimulate the pigment cells and cause them to expand or contract.

Poison

Many frogs contain mild toxins that make them unpalatable to potential predators. A toxin ( Greek:, toxikon, lit (poison for use on arrows is a Poisonous substance produced by living cells or organisms that is active at very low For example, all toads have large poison glands—the parotid glands—located behind the eyes on the top of the head. Some frogs, such as some poison dart frogs, are especially toxic. Poison dart frog (also dart frog, poison frog or formerly poison arrow frog) is the common name of a group of Frogs in the family The chemical makeup of toxins in frogs varies from irritants to hallucinogens, convulsants, nerve poisons, and vasoconstrictors. The general group of pharmacological agents commonly known as hallucinogens can be divided into three broad categories Psychedelics, Dissociatives An epileptic seizure is caused by excessive and/or hypersynchronous electrical Neuronal activity and is usually self-limiting A neurotoxin is a Toxin that acts specifically on nerve cells ( Neurons, usually by interacting with Membrane proteins such as Ion channels Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels particularly the large Arteries, Arterioles Many predators of frogs have adapted to tolerate high levels of these poisons. Others, including humans, may be severely affected.

Some frogs obtain poisons from the ants and other arthropods they eat;^[7] others, such as the Australian Corroboree Frogs (Pseudophryne corroboree and Pseudophryne pengilleyi), can manufacture an alkaloid not derived from their diet. The Corroboree frogs are two species of small ground dwelling Frogs native to Southern Tablelands of Australia. This article is about the chemical compounds alkaloids For the Pharmaceutical company in the Republic of Macedonia see Alkaloid (company. ^[8] Some native people of South America extract poison from the poison dart frogs and apply it to their darts for hunting,^[9] although few species are toxic enough to be used for this purpose. It was previously a misconception the poison was placed on arrows rather than darts. The common name of these frogs was thus changed from "poison arrow frog" to "poison dart frog" in the early 1980s. Poisonous frogs tend to advertise their toxicity with bright colours, an adaptive strategy known as aposematism. There are at least two non-poisonous species of frogs in tropical America (Eleutherodactylus gaigei and Lithodytes lineatus) that mimic the colouration of dart poison frogs' coloration for self-protection (Batesian mimicry). Batesian mimicry is a form of Mimicry typified by a situation where a harmless species has evolved to imitate the warning signals of a harmful species directed at a common ^[10][11]

Because frog toxins are extraordinarily diverse, they have raised the interest of biochemists as a "natural pharmacy". The alkaloid epibatidine, a painkiller 200 times more potent than morphine, is found in some species of poison dart frogs. Epibatidine is an Alkaloid that originally is found in the skin of a neotropical poisonous Frog, ''Epipedobates tricolor'', found in modern Ecuador Medical uses Morphine can be used as an analgesic in hospital settings to relieve pain in Myocardial infarction pain in Other chemicals isolated from the skin of frogs may offer resistance to HIV infection. Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome ^[12] Arrow and dart poisons are under active investigation for their potential as therapeutic drugs. ^[13]

The skin secretions of some toads, such as the Colorado River toad and cane toad, contain bufotoxins, some of which, such as bufotenin, are psychoactive, and have therefore been used as recreational drugs. The Colorado River Toad or Bufo alvarius, also known as the Sonoran Desert Toad, is a Psychoactive toad found in the Southwestern United Bufotoxins are a family of toxic substances found in the Parotoid glands skin and venom of many Toads ( Genus Bufo) other amphibians and other Bufotenin (also known as bufotenine) is a Tryptamine related to the Neurotransmitter Serotonin. Typically, the skin secretions are dried and smoked. Skin licking is especially dangerous, and appears to constitute an urban myth. An urban legend or urban myth is a form of modern Folklore consisting of stories thought to be factual by those circulating them See psychoactive toad. Psychoactive toad is a name used for Toads from which Psychoactive substances from the family of Bufotoxins can be derived

Respiration and circulation

The skin of a frog is permeable to oxygen and carbon dioxide, as well as to water. There are a number of blood vessels near the surface of the skin. When a frog is underwater, oxygen is transmitted through the skin directly into the bloodstream. On land, adult frogs use their lungs to breathe. Their lungs are similar to those of humans, but the chest muscles are not involved in respiration, and there are no ribs or diaphragm to support breathing. In Vertebrate Anatomy, ribs ( Latin costae) are the long curved Bones which form the ribcage. For other types of diaphragm see Diaphragm. In the Anatomy of Mammals the thoracic diaphragm is a sheet of Muscle Frogs breathe by taking air in through the nostrils (causing the throat to puff out), and compressing the floor of the mouth, which forces the air into the lungs. In August 2007 an aquatic frog named Barbourula kalimantanensis was discovered in a remote part of Indonesia. The Bornean Flat-headed Frog (B. UserPolbot. -->The Bornean Flat-headed Frog ( Barbourula kalimantanensis) is a species of Toad in the kalimantanensis) is the first species of frog known to science without lungs. ^[14]

Frogs are known for their three-chambered heart, which they share with all tetrapods except birds and mammals. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic Tetrapods ( Greek τετραποδη tetrapoda, Latin Quadruped, "four-footed" are Vertebrate Animals Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands In the three-chambered heart, oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enter by separate atria, and are directed via a spiral valve to the appropriate vessel—aorta for oxygenated blood and pulmonary vein for deoxygenated blood. In Animal physiology, respiration is the transport of Oxygen from the outside air to the cells within tissues and the transport of Carbon dioxide In Anatomy, the atrium (plural atria) refers to a chamber or space The four pulmonary veins carry Oxygen -rich Blood from the Lungs to the left atrium of the Heart. This special structure is essential to keeping the mixing of the two types of blood to a minimum, which enables frogs to have higher metabolic rates, and to be more active than otherwise.

Natural history

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 behaviours 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.

Life cycle

The life cycle of a frog starts with an egg. Leopard frogs are also called meadow frogs or cow frogs. They are the archetypal " Grass frogs quot of North America, a collection A female generally lays frogspawn, or egg masses containing thousands of eggs, in water. The eggs are highly vulnerable to predation, so frogs have evolved many techniques to ensure the survival of the next generation. In colder areas of the first, the embryo is black to absorb more heat from the sun, which speeds up the development. Most commonly, this involves synchronous reproduction. Many individuals will breed at the same time, overwhelming the actions of predators; the majority of the offspring will still die due to predation, but there is a greater chance some will survive. Another way in which some species avoid the predators and pathogens eggs are exposed to in ponds is to lay eggs on leaves above the pond, with a gelatinous coating designed to retain moisture. In these species the tadpoles drop into the water upon hatching. The eggs of some species laid out of water can detect vibrations of nearby predatory wasps or snakes, and will hatch early to avoid being eaten. ^[15] Some species, such as the Cane Toad (Bufo marinus), lay poisonous eggs to minimise predation. While the length of the egg stage depends on the species and environmental conditions, aquatic eggs generally hatch within one week. Other species goes through their whole larval phase inside the eggs or the mother, or they have direct development.

Eggs hatch and continue life as tadpoles (occasionally known as polliwogs). A tadpole or polliwog (also pollywog, polliwig, polewig, or polwig) is the wholly aquatic larval stage in the life cycle of At least one species (Nannophrys ceylonensis) has tadpoles that are semi-terrestrial and lives among wet rocks^[16][17], but as a general rule, free living larvae are fully aquatic. They lack lungs, eyelids, front and hind legs, and have a cartilaginous skeleton, a lateral line system, gills for respiration (external gills at first, internal gills later) and tails with folds of skin fins for swimming^[18]. In Fish, the lateral line is a Sense organ used to detect movement and vibration in the surrounding water Some species who goes through the metapormhosis inside the egg and hatches to small frogs never develops gills, instead there are specialised areas of skin that takes care of the respiration. Tadpoles also lack true teeth, but the jaws in most species usually have two elongate, parallel rows of small keratinized structures called keradonts in the upper jaw while the lower jaw has three rows of keradonts, surrounded by a horny beak, but the number of rows can be lower or absent, or much higher[2]. Keratins are a family of fibrous structural proteins; tough and insoluble they form the hard but nonmineralized structures found in Reptiles Birds Keratins are a family of fibrous structural proteins; tough and insoluble they form the hard but nonmineralized structures found in Reptiles Birds Tadpoles are typically herbivorous, feeding mostly on algae, including diatoms filtered from the water through the gills. Herbivory is a form of Predation in which an Organism, known as a herbivore, consumes principally Autotrophs ref name=Campbell>Campbell Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i A gill is an anatomical structure found in many aquatic organisms Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles, and fish. Tadpoles are highly vulnerable to predation by fish, newts, predatory diving beetles and birds such as kingfishers. A newt is an Amphibian of the Salamandridae family order Urodela or Caudata, found in North America, Europe, and Dytiscidae &ndash based on the Greek dytikos (δυτικός "able to dive" &ndash are the predaceous diving beetles, a family of Kingfishers are small bright colored Birds of the three families Alcedinidae ( River kingfishers, Halcyonidae ( Tree kingfishers, and Cerylidae ( Water Cannibalism has been observed among tadpoles. Cannibalism (from Spanish es ''caníbal'' in connection with cannibalism among the Antillean Caribs, also called anthropophagy (from Greek ἄνθρωπος Poisonous tadpoles are present in many species, such as Cane Toads. The tadpole stage may be as short as a week, or tadpoles may overwinter and metamorphose the following year in some species, such as the midwife toad (Alytes obstetricans) and the common spadefoot (Pelobates fuscus). Midwife toads ( Alytes) are a genus of Frogs in the Discoglossidae family and are found in most of Europe and northwestern Africa In the Pipidae, with the exception for Hymenochirus, the tadpoles have paired anterior barbells which makes the resemple small catfish^[19]. The Pipidae are a family of primitive Tongueless Frogs The thirty species in the family Pipidae are found in tropical South America (genus Catfish ( order Siluriformes) are a very diverse group of bony Fish.

With the exception of the base of the tail, where a few vertebral structures develops to give rise to the urostyle later in life, the tails lacks completely solid, segmental skeletal elements of cartilage or bony tissue that is so typical for other vertebrates, althought it does contains a notochord^[20]

At the end of the tadpole stage, frogs undergo metamorphosis, in which they transition into adult form. The notochord is a flexible rod-shaped body found in Embryos of all Chordates It is composed of cells derived from the Mesoderm and defines the Metamorphosis is a Biological process by which an Animal physically develops after Birth or hatching involving a conspicuous and relatively Metamorphosis involves a dramatic transformation of morphology and physiology, as tadpoles develop hind legs, then front legs, lose their gills and develop lungs. Their intestines shorten as they shift from an herbivorous to a carnivorous diet. Eyes migrate rostrally and dorsally, allowing for binocular vision exhibited by the adult frog. This shift in eye position mirrors the shift from prey to predator, as the tadpole develops and depends less upon a larger and wider field of vision and more upon depth perception. The final stage of development from froglet to adult frog involves apoptosis (programmed cell death) and resorption 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 carnivorous as adults, eating invertebrates such as arthropods, annelids and gastropods. A carnivore (ˈkɑrnɪvɔər meaning 'meat eater' ( Latin carne meaning 'flesh' and vorare meaning 'to devour' is any animal with a diet consisting Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " The annelids, collectively called Annelida (from Latin anellus "little ring" are a large phylum of Animals comprising The class Gastropoda or the gastropods, also previously known as gasteropods, or univalves, and more commonly known as Snails A few of the larger species may eat prey such as small mammals, fish and smaller frogs. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two 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. ^[21] Adult frogs are themselves preyed upon by birds, large fish, snakes, otters, foxes, badgers, coatis, and other animals. Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two A snake is an elongate Reptile of the suborder Serpentes Like all reptiles snakes are covered in scales. Otters are semi- aquatic (or in one case aquatic) fish-eating Mammals The otter subfamily Lutrinae forms part of the family A fox is an Animal belonging to any one of about 27 Species (of which only 12 actually belong to the Vulpes genus or 'true foxes' of small Badger is the Common name for any animal of three subfamilies which belong to the family Mustelidae: the same Mammal family as the The coati, genera Nasua and Nasuella, also known as the hog-nosed coon snookum bear and Brazilian Aardvark is a member of the Raccoon family ( Procyonidae Frogs are also eaten by people (see section on uses in agriculture and research, below).

Frogs and toads can live for many years; though little is known about their life span in the wild, captive frogs and toads are recorded living up to 40 years ^[22].

Although it is not common knowledge, some species of frog in their tadpole stage are known to be carnivorous. Early developers who gain legs may be eaten by the others, so the late bloomers survive longer. This has been observed in England in the species Rana temporaria (common frog). ^[23]

Unlike salamanders and newts, frogs and toads never become sexually mature while still in their larval stage.

Reproduction of frogs

Once adult frogs reach maturity, they will assemble at a water source such as a pond or stream to breed. Many frogs return to the bodies of water where they were born, often resulting in annual migrations involving thousands of frogs. In continental Europe, a large proportion of migrating frogs used to die on roads, before special fences and tunnels were built for them.

Once at the breeding ground, male frogs call to attract a mate, collectively becoming a chorus of frogs. The Common Toad ( Bufo bufo) or European Toad is widespread throughout Europe, with the exception of Ireland and some Mediterranean Amplexus (Latin "embrace" is a form of Pseudocopulation in which a male Frog grasps a female with his front legs while she lays her eggs The call is unique to the species, and will attract females of that species. Some species have satellite males who do not call, but intercept females that are approaching a calling male.

The male and female frogs then undergo amplexus. Amplexus (Latin "embrace" is a form of Pseudocopulation in which a male Frog grasps a female with his front legs while she lays her eggs This involves the male mounting the female and gripping her tightly. Fertilization is external: the egg and sperm meet outside of the body. External fertilization is a form of Fertilization in which a Zilo cell is united with an Egg cell external to the body of the female An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known The female releases her eggs, which the male frog covers with a sperm solution. The eggs then swell and develop a protective coating. The eggs are typically brown or black, with a clear, gelatin-like covering. Gelatin (also gelatine, from French gélatine) is a translucent colourless brittle nearly tasteless solid substance, extracted from the

Most temperate species of frogs reproduce between late autumn and early spring. In the UK, most common frog populations produce frogspawn in February, although there is wide variation in timing. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Water temperatures at this time of year are relatively low, typically between four and 10 degrees Celsius. The Celsius Temperature scale was previously known as the centigrade scale. 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.

Parental care

Although care of offspring is poorly understood in frogs, it is estimated that up to 20% of amphibian species may care for their young in one way or another, and there is a great diversity of parental behaviours. ^[24] Some species of poison dart frog lay eggs on the forest floor and protect them, guarding the eggs from predation and keeping them moist. The frog will urinate on them if they become too dry. After hatching, a parent (the sex depends upon the species) will move them, on its back, to a water-holding bromeliad. The parent then feeds them by laying unfertilized eggs in the bromeliad until the young have metamorphosed. Other frogs carry the eggs and tadpoles on their hind legs or back (e. g. the midwife toads, Alytes spp. Midwife toads ( Alytes) are a genus of Frogs in the Discoglossidae family and are found in most of Europe and northwestern Africa ). Some frogs even protect their offspring inside their own bodies. The male Australian Pouched Frog (Assa darlingtoni) has pouches along its side in which the tadpoles reside until metamorphosis. The Pouched Frog ( Assa darlingtoni) is a small terrestrial Frog found in rainforests in mountain areas of south-eastern Queensland and The female Gastric-brooding Frogs (genus Rheobatrachus) from Australia, now probably extinct, swallows its tadpoles, which then develop in the stomach. The gastric-brooding frogs or Platypus frogs ( Rheobatrachus) were a Genus of ground-dwelling Frogs native to Queensland in eastern For a topic outline on this subject see List of basic Australia topics. To do this, the Gastric-brooding Frog must stop secreting stomach acid and suppress peristalsis (contractions of the stomach). Gastric acid is one of the main Secretions of the Stomach, together with several Enzymes and Intrinsic factor. In the Esophagus After food is chewed into a bolus it is swallowed to move it into the esophagus Darwin's Frog (Rhinoderma darwinii) from Chile puts the tadpoles in its vocal sac for development. Darwin's Frog ( la Rhinoderma darwinii) is a frog native to the forest streams of Chile and Argentina. Chile, officially the Republic of Chile ( Spanish:) is a country in South America occupying a long and narrow Coastal strip wedged between the Some species of frog will leave a 'babysitter' to watch over the frogspawn until it hatches.

Call

Some frog calls are so loud, they can be heard up to a mile away. ^[25]The call of a frog is unique to its species. Frogs call by passing air through the larynx in the throat. The larynx (plural larynges) colloquially known as the voicebox, is an organ in the Neck of Mammals involved in protection of the In most calling frogs, the sound is amplified by one or more vocal sacs, membranes of skin under the throat or on the corner of the mouth that distend during the amplification of the call. The vocal sac is the flexible Membrane of skin possessed by most male Frogs The purpose of the vocal sac is usually as an amplification of their mating or advertisement The field of neuroethology studies the neurocircuitry that underlies frog audition. Neuroethology ("neuro" Greek related to Nerve cells, "ethos" Greek habit or custom is an evolutionary and comparative approach to the study of animal behavior

Some frogs lack vocal sacs, such as those from the genera Heleioporus and Neobatrachus, but these species can still produce a loud call. Their buccal cavity is enlarged and dome-shaped, acting as a resonance chamber that amplifies their call. A resonance chamber uses Resonance to amplify Sound. The chamber has interior surfaces which reflect an acoustic wave Species of frog without vocal sacs and that do not have a loud call tend to inhabit areas close to flowing water. The noise of flowing water overpowers any call, so they must communicate by other means.

The main reason for calling is to allow males to attract a mate. Males call either individually or in a group called a chorus. Females of many frog species, for example Polypedates leucomystax, produce calls reciprocal to the males', which act as the catalyst for the enhancement of reproductive activity in a breeding colony. ^[26] A male frog emits a release call when mounted by another male. Tropical species also have a rain call that they make on the basis of humidity cues prior to a rain shower. Many species also have a territorial call that is used to chase away other males. All of these calls are emitted with the mouth of the frog closed.

A distress call, emitted by some frogs when they are in danger, is produced with the mouth open, resulting in a higher-pitched call. The effectiveness of the call is unknown; however, it is suspected the call intrigues the predator until another animal is attracted, distracting them enough for its escape.

Many species of frog have deep calls, or croaks. The English onomatopoeic spelling is "ribbit". Onomatopoeia (also spelled onomatopœia, from Greek: ονοματοποιΐα is a Word or a grouping of words that imitates the sound it is describing The croak of the American bullfrog (Rana catesbiana) is sometimes spelt "jug o' rum". The American Bullfrog ( Rana catesbeiana) is an aquatic Frog, a member of the family Ranidae, or "true frogs" native to much of North Other examples are Ancient Greek brekekekex koax koax for probably Rana ridibunda, and the description in Rigveda 7:103. The Marsh Frog ( Rana ridibunda) is the largest Frog native to Europe, and belongs to the family of True frogs It is very similar in appearance The Rigveda ( Sanskrit sa ऋग्वेद ṛgveda, a compound of ṛc "praise verse" and veda "knowledge" 6 gómāyur éko ajámāyur ékaħ = "one [has] a voice like a cow's, one [has] a voice like a goat's".

Distribution and conservation status

The habitat of frogs extends almost worldwide, but they do not occur in Antarctica and are not present on many oceanic islands. The golden toad WikipediaNaming conventions (fauna --> ( Bufo periglenes) was a small shiny bright True ^[27][28] The greatest diversity of frogs occurs in the tropical areas of the world, where water is readily available, suiting frogs' requirements due to their skin. Some frogs inhabit arid areas such as deserts, where water may not be easily accessible, and rely on specific adaptations to survive. The Australian genus Cyclorana and the American genus Pternohyla will bury themselves underground, create a water-impervious cocoon and hibernate during dry periods. Cyclorana is a subgenus of the Frog genus Litoria in the family Hylidae (tree frogs whose members are found in most Pternohyla was a genus of Frogs in the Hylidae family but the genus is now considered invalid and the two species have been removed to the genus For the ability of certain operating systems see Hibernate (OS feature Hibernation is a state of inactivity and metabolic depression Once it rains, they emerge, find a temporary pond and breed. Egg and tadpole development is very fast in comparison to most other frogs so that breeding is complete before the pond dries up. Some frog species are adapted to a cold environment; for instance the wood frog, whose habitat extends north of the Arctic Circle, buries itself in the ground during winter when much of its body freezes. Wood frog is the common name given to Rana sylvatica. The wood frog has a broad North American distribution extending from the southern Appalachians to the boreal forest The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth.

Frog populations have declined dramatically since the 1950s: more than one third of species are believed to be threatened with extinction and more than 120 species are suspected to be extinct since the 1980s. Dramatic declines in Amphibian populations, including Population crashes and mass localized Extinctions have been noted since the 1980s from locations all ^[29] Among these species are the golden toad of Costa Rica and the Gastric-brooding frogs of Australia. The golden toad WikipediaNaming conventions (fauna --> ( Bufo periglenes) was a small shiny bright True Habitat loss is a significant cause of frog population decline, as are pollutants, climate change, the introduction of non-indigenous predators/competitors, and emerging infectious diseases including chytridiomycosis. Chytridiomycosis is an Infectious disease of Amphibians, caused by the Chytridaceous fungus Batrachochytrium dendrobatidis. Many environmental scientists believe that amphibians, including frogs, are excellent biological indicators of broader ecosystem health because of their intermediate position in food webs, permeable skins, and typically biphasic life (aquatic larvae and terrestrial adults). An indicator species is any Biological species that defines a trait or Characteristic of the environment ^[30] It appears that it is the species with both aquatic eggs and aquatic larvae that are most affected by the decline, while those with direct development are the most resistant^[31]

A Canadian study conducted in 2006 proposed heavy traffic near frog habitats as a large threat to frog populations. ^[32]

In a few cases, captive breeding programs have been attempted to alleviate the pressure on frog populations, and these have proved successful. ^[33][34][35] In May 2007, it was reported the application of certain probiotic bacteria could protect amphibians from chytridiomycosis. ^[36]

Zoos and aquariums around the world have named 2008 the Year of the Frog, to draw attention to the conservation issues. ^[37]

Evolution

Until the discovery of the Early Permian Gerobatrachus hottoni, a stem-batrachian with many salamander-like characteristics, the earliest known proto-frog was Triadobatrachus massinoti, from the 250 million year old early Triassic of Madagascar. The Permian is a geologic period and system that extends from 299 Gerobatrachus, also referred to as a frogamander is an Extinct Genus of early toothed Amphibian, a stem-batrachian that lived Salamander (orig from Persian: sām, "fire" and andarūn, "within" is the common name for a group of approximately 500 Species Triadobatrachus is an extinct genus of Frog, including only one known species Triadobatrachus massinoti. The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago Madagascar, or Republic of Madagascar (older name Malagasy Republic) is an Island nation in the Indian Ocean off the southeastern The skull is frog-like, being broad with large eye sockets, but the fossil has features diverging from modern amphibia. These include a different ilium, a longer body with more vertebrae, and separate vertebrae in its tail (whereas in modern frogs, the tail vertebrae are fused, and known as the urostyle or coccyx). The ilium of the Pelvis is divisible into two parts the body and the ala the separation is indicated on the top surface by a curved line the arcuate line and on the A vertebra (plural vertebrae) is an individual Irregular bone in the spinal or Vertebral column ( aka ischis a flexuous and flexible column The tibia and fibula bones are unfused and separate, making it probable Triadobatrachus was not an efficient leaper. The tibia, shinbone, or shankbone is the larger and stronger of the two Bones in the Leg below the Knee in vertebrates and connects For other uses see Fibula (disambiguation The fibula or calf bone is a Bone located on the lateral side of the Tibia

Another fossil frog, discovered in Arizona and called Prosalirus bitis, was uncovered in 1985, and dates from roughly the same time as Triadobatrachus. The State of Arizona ( is a state located in the southwestern region of the United States. Prosalirus bitis is the name given to a fossil proto-frog found in Arizona in 1995 which has primitive features but has mostly lost the salamander-like traits Like Triadobatrachus, Prosalirus did not have greatly enlarged legs, but had the typical three-pronged pelvic structure. The pelvis (pl pelvises or pelves) or pelvic girdle is the irregular bony structure located at the base of the spine (properly known Unlike Triadobatrachus, Prosalirus had already lost nearly all of its tail.

The earliest true frog is Vieraella herbsti, from the early Jurassic (188–213 million years ago). The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning It is known only from the dorsal and ventral impressions of a single animal and was estimated to be 33 mm from snout to vent. In Anatomy, the dorsum is the upper side of animals that typically run fly or swim in a horizontal position and the back side of animals (like humans that walk upright In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species Notobatrachus degiustoi from the middle Jurassic is slightly younger, about 155–170 million years old. It is likely the evolution of modern Anura was completed by the Jurassic period. The main evolutionary changes involved the shortening of the body and the loss of the tail.

The earliest full fossil record of a modern frog is of sanyanlichan, which lived 125 million years ago and had all modern frog features, but bore 9 presacral vertebrae instead of the 8 of modern frogs, apparently still being a transitional species. "Sanyanlichan" is the name given to a fossil that represents the earliest known "modern" Frog.

Frog fossils have been found on all continents, including Antarctica.

Uses in agriculture and research

For more details on this topic, see animal testing on frogs. Frogs have been used in animal tests throughout the history of biomedical science

Frogs are raised commercially for several purposes. Frogs are used as a food source; frog legs are a delicacy in China, France, the Philippines, the north of Greece and in many parts of the American South, especially Louisiana. Frogs legs are one of the better-known delicacies of French and Chinese cuisine China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National This article is about the country For a topic outline on this subject see List of basic France topics. The Philippines ( Filipino: Pilipinas, officially known as the Republic of the Philippines (fil ''Republika ng Pilipinas'' RP Greece (Ελλάδα transliterated: Elláda, historically, Ellás,) officially the Hellenic Republic (Ελληνική Δημοκρατία The Southern United States &mdashcommonly referred to as the American South, Dixie, or simply the South &mdashconstitutes a large distinctive The State of Louisiana ( or, État de Louisiane, pronounced) is a state located in the southern region of the United States of America Dead frogs are sometimes used for dissections in high school and university anatomy classes, often after being injected with coloured plastics to enhance the contrast between the organs. Dissection (also called anatomization) is usually the process of disassembling and observing something to determine its internal structure and as an aid to discerning the function In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument This practice has declined in recent years with the increasing concerns about animal welfare. Animal welfare refers to the viewpoint that it is morally acceptable for humans to use nonhuman animals for food in animal research, as clothing and in entertainment

Frogs have served as important model organisms throughout the history of science. Eighteenth-century biologist Luigi Galvani discovered the link between electricity and the nervous system through studying frogs. Luigi Galvani was an Italian Physician and Physicist who lived and died in Bologna. The nervous system is a Network of specialized cells that communicate information about an animal's surroundings and itself The African clawed frog or platanna (Xenopus laevis) was first widely used in laboratories in pregnancy assays in the first half of the 20th century. The African clawed frog ( Xenopus laevis, also known as platanna) is a species of South African aquatic Frog of the genus Xenopus When human chorionic gonadotropin, a hormone found in substantial quantities in the urine of pregnant women, is injected into a female X. Human chorionic gonadotropin ( hCG) is a Glycoprotein Hormone produced in Pregnancy that is made by the Embryo soon after conception Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body Urine is a liquid waste product of the body secreted by the Kidneys by a process of filtration from Blood and Excreted through the Urethra. laevis, it induces them to lay eggs. In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. In 1952, Robert Briggs and Thomas J. King cloned a frog by somatic cell nuclear transfer, the same technique later used to create Dolly the Sheep, their experiment was the first time successful nuclear transplantation had been accomplished in metazoans. Robert Briggs ( December 10, 1911 — March 4, 1983) was a scientist who in 1952 together with Thomas J Thomas J King ( 1921 - October 25, 2000) was an American Biologist. Genetics and Developmental biology, somatic cell nuclear transfer ( SCNT) is a Laboratory technique for creating an Ovum with a donor Dolly was a ewe ( July 5, 1996 – February 14, 2003) that was the first Animal to be cloned from an adult ^[38]

Frogs are used in cloning research and other branches of embryology because frogs are among the closest living relatives of man to lack egg shells characteristic of most other vertebrates, and therefore facilitate observations of early development. Embryology (from Greek grc ἔμβρυον embryon, "unborn embryo" and grc -λογία -logia) is the study of the development Although alternative pregnancy assays have been developed, biologists continue to use Xenopus as a model organism in developmental biology because it is easy to raise in captivity and has a large and easily manipulatable embryo. A model organism is a Species that is extensively studied to understand particular biological Phenomena, with the expectation that discoveries made Developmental Biology is the official journal of the Society for Developmental Biology. Recently, X. laevis is increasingly being displaced by its smaller relative X. tropicalis, which reaches its reproductive age in five months rather than one to two years (as in X. laevis),^[39] facilitating faster studies across generations. The genome sequence of X. Genome projects are Scientific endeavours that ultimately aim to determine the complete Genome sequence of an Organism (be it an Animal, a tropicalis will probably be completed by 2015 at the latest. ^[40]

Cultural beliefs

For more details on this topic, see Frogs in popular culture. Frogs feature prominently in Folklore and Fairy tales in many cultures such as the story of The Frog Prince, up to modern-day popular culture

Frogs feature prominently in folklore, fairy tales and popular culture. History The concept of folklore developed as part of the 19th century ideology of Romantic nationalism, leading to the reshaping of oral traditions to serve modern ideological A fairy tale or fairy story is a fictional Story that may feature folkloric characters (such as fairies, enchantments]] often involving They tend to be portrayed as benign, ugly, clumsy, but with hidden talents. Examples include Michigan J. Frog, The Frog Prince, and Kermit the Frog. Michigan J Frog is an Animated cartoon character who debuted in the Looney Tunes cartoon One Froggy Evening ( December 31 The Frog King or Iron Heinrich (German Der Froschkönig oder der eiserne Heinrich) also known as The Frog Prince, is a Fairy tale, best known through Kermit the Frog is a Muppet, one of Puppeteer Jim Henson 's most famous and beloved creations first introduced in 1955 Michigan J. Frog, featured in a Warner Brothers cartoon, only performs his singing and dancing routine for his owner. Warner Bros Entertainment Inc (or Warner Bros, Warner Bros Pictures) is one of the world's largest producers of Film and Once another person looks at him, he will return to a frog-like pose. "The Frog Prince" is a fairy tale of a frog who turns into a handsome prince once kissed. A kiss is the touching of one person's lips to another place which is used as an expression of Affection, Respect, Greeting, Farewell Kermit the Frog, on the other hand, is a conscientious and disciplined character of Sesame Street and The Muppet Show; while openly friendly and greatly talented, he is often portrayed as cringing at the fanciful behaviour of more flamboyant characters. Sesame Street is an American educational Children's television series and a pioneer of the contemporary educational television standard combining The Muppet Show is an American Television program featuring a cast of Muppets which was produced by Jim Henson and his team from

The Moche people of ancient Peru worshipped animals and often depicted frogs in their art. The Moche civilization (alternately the Mochica culture Early Chimu Pre-Chimu Proto-Chimu etc Peru (Perú Piruw Piruw officially the Republic of Peru ( reˈpuβlika del peˈɾu is a country in western South America. ^[41]

Cited references

General references

External links

• The Whole Frog Project - Virtual frog dissection and anatomy
• Disappearance of toads, frogs has some scientists worried - San Francisco Chronicle, April 20, 1992
• Xenbase - A Xenopus laevis and tropicalis web resource
• Amphibia web
• Time-lapse video showing the egg's development until hatching
• Frog calls - Short video clips of calling frogs and interviews with scientists about frog issues
• Frog calls - Canada
• eastern United States frog calls - eastern United States
• Recording UK frogspawn sightings - Springwatch 2006
• Frogwatch USA Volunteer frog and toad monitoring program by National Wildlife Federation and USGS, includes links to frog calls of the United States
• Amphibian photo gallery by scientific name - features many unusual frogs
• Scientific American: Researchers Pinpoint Source of Poison Frogs' Deadly Defenses

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