A frog is any member of a various and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (actually without tail in Historical Greek). The oldest fossil “proto-frog” appeared within the early Triassic of Madagascar, however, the molecular clock relationship suggests their origins could prolong additional again to the Permian, 265 million years in the past. Frogs are extensively distributed, starting from the tropics to subarctic areas, however, the biggest focus of species range is within the tropical rainforest. There are over 6,300 recorded species, accounting for around 87% of extant amphibian species. They’re additionally one of many 5 most numerous vertebrate orders. Warty frog species are usually known as toads, however, the distinction between frogs and toads is casual, not from taxonomy or evolutionary historical past. All toads are frogs, however, not all frogs are toads.
A grownup frog has a stout physique, protruding eyes, anteriorly-attached tongue, limbs folded beneath, and no tail (besides in tailed frogs). Frogs have glandular pores and skin, with secretions starting from distasteful to poisonous. Their pores and skin vary in color from well-camouflaged dappled brown, gray and inexperienced to vivid patterns of shiny crimson or yellow and black to point out toxicity and push back predators. Grownup frogs reside in freshwater and on dry land; some species are tailored for dwelling underground or in bushes.
Frogs usually lay their eggs in water. The eggs hatch into aquatic larvae known as tadpoles which have tails and inside gills. They’ve extremely specialized rasping mouth components appropriate for herbivorous, omnivorous, or planktivorous diets. The life cycle is accomplished after they metamorphose into adults. A number of species deposit eggs on land or bypass the tadpole stage. Grownup frogs typically have a carnivorous weight-reduction plan consisting of small invertebrates, however, omnivorous species exist and some feeds on plant matter. Frogskin has a wealthy microbiome which is essential to their well being.
Frogs are extraordinarily environment friendly at changing what they eat into physique mass. They’re an essential meal supply for predators and a part of the meals internet dynamics of most of the world’s ecosystems. The pores and skin are semi-permeable, making them inclined to dehydration so that they both reside in moist locations or have particular variations to cope with dry habitats. Frogs produce a variety of vocalizations, significantly of their breeding season, and exhibit many various sorts of complicated behaviors to draw mates, to fend off predators, and to typically survive.
Frogs are valued as meals by people and still have many cultural roles in literature, symbolism, and faith. They’re additionally seen as environmental bellwethers, with declines in frog populations usually considered as early warning indicators of environmental harm. Frog populations have declined considerably because of the 1950s. Multiple-third of species are thought-about to be threatened with extinction and over 120 are believed to have to turn out to be extinct because of the 1980s. The variety of malformations amongst frogs is on the rise and rising fungal illness, chytridiomycosis, has unfolded all over the world. Conservation biologists are working to grasp the causes of those issues and to resolve them.
Etymology and taxonomy
The usage of the widespread names “frog” and “toad” has no taxonomic justification. From a classification perspective, all members of the order Anura are frogs, however solely family members Bufonidae are thought-about “true toads”. The usage of the time period “frog” in widespread names often refers to species which can be aquatic or semi-aquatic and have clean, moist skins; the time period “toad” typically refers to species which can be terrestrial with dry, warty skins. There are quite a few exceptions to this rule. The European fire-bellied toad (Bombina bombina) has a barely warty pores and skin and prefers a watery habitat. whereas the Panamanian golden frog (Atelopus zeteki) is within the toad household Bufonidae and has a clean pores and skin.
The origin of the order title Anura — and its unique spelling Anoures — is the Historical Greek “alpha privative” prefix ἀν- (an-) “without”, and οὐρά (ourá), which means “animal tail”. It refers back to the tailless character of those amphibians.
The origins of the phrase frog are unsure and debated. The phrase is first attested in Previous English as frogga, however the typical Previous English phrase for the frog was frosc (with variants akin to frox and forsc), and it’s agreed that the phrase frog is in some way associated to this. Previous English frosc remained in dialectal use in English as frosh and frosk into the nineteenth century, and is paralleled extensively in different Germanic languages, with examples within the fashionable languages together with German Frosch, Icelandic froskur, and Dutch (Kik)vors. These phrases enable us to reconstruct a Widespread Germanic ancestor froskaz. The third version of the Oxford English Dictionary finds that the etymology of froskaz is unsure, however, agrees with arguments that it might plausibly derive from a Proto-Indo-European base alongside the strains of preu = “soar”.
How Previous English frosc gave rise to frogga is, nonetheless, unsure, as the event doesn’t contain a daily sound-change. As a substitute, plainly there was a pattern in Previous English to coin nicknames for animals ending in -g, with examples—themselves all of unsure etymology—together with canine, hog, pig, stag, and (ear)wig. Frog seems to have been tailored from frosc as a part of this pattern.
In the meantime, the phrase toad, first attested as Previous English tādige, is exclusive to English and is likewise of unsure etymology. It’s the foundation for the phrase tadpole, first attested as Center English tadpole, apparently which means ‘toad-head’.
About 88% of amphibian species are categorized within the order Anura. These embrace over 7,100 species in 55 households, of which the Craugastoridae (850 spp.), Hylidae (724 spp.), Microhylidae (688 spp.), and Bufonidae (621 spp.) are the richest in species.
The Anura contains all fashionable frogs and any fossil species that match throughout the anuran definition. The traits of anuran adults embrace 9 or fewer presacral vertebrae, the presence of a urostyle shaped of fused vertebrae, no tail, a protracted and forward-sloping ilium, shorter forelimbs than hind limbs, radius and ulna fused, tibia and fibula fused, elongated ankle bones, absence of a prefrontal bone, presence of a hyoid plate, a decreased jaw without tooth (except for Gastrotheca guentheri) consisting of three pairs of bones (angulosplenial, dentary, and mentomeckelian, with the final pair being absent in Pipoidea), an unsupported tongue, lymph areas beneath the pores and skin, and a muscle, the protractor lens, connected to the lens of the attention. The anuran larva or tadpole has a single central respiratory spiracle and mouthparts consisting of keratinous beaks and denticles.
Frogs and toads are broadly categorized into three suborders: Archaeobatrachia, which incorporates 4 households of primitive frogs; Mesobatrachia, which incorporates 5 households of extra evolutionary intermediate frogs; and Neobatrachia, by far the most important group, which accommodates the remaining households of contemporary frogs, together with commonest species all through the world. The suborder Neobatrachia is additional divided into the 2 superfamilies Hyloidea and Ranoidea. This classification is predicated on such morphological options because of the variety of vertebrae, the construction of the pectoral girdle, and the morphology of tadpoles. Whereas this classification is basically accepted, relationships amongst households of frogs are nonetheless debated
Some species of anurans hybridize readily. As an example, the edible frog (Pelophylax esculentus) is a hybrid between the pool frog (P. lessonae) and the marsh frog (P. ridibundus). The hearth-bellied toads Bombina bombina and B. variegata are related in forming hybrids. These are much less fertile than their dad and mom, giving rise to a hybrid zone the place the hybrids are prevalent.