Frogs are a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (Ancient Greek an-, without + oura, tail). The oldest fossil "proto-frog" appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian, 265 million years ago. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is found in tropical rainforests. There are approximately 4,800 recorded species, making them among the most diverse vertebrate groups.
The body plan of an adult frog is generally characterized by a stout body, protruding eyes, cleft tongue, limbs folded underneath and the absence of a tail. Besides living in fresh water and on dry land, the adults of some species are adapted for living underground or in trees. The skin of the frog is glandular, with secretions ranging from distasteful to toxic. Warty species of frog tend to be called toads. Frog warts are elevations in the skin where glandular toxins tend to concentrate. The distinction between frogs and toads is based on informal naming conventions concentrating on the warts rather than taxonomy or evolutionary history; some toads are more closely related to frogs than other toads. Frogs' skins vary in colour from well-camouflaged dappled brown, grey and green to vivid patterns of bright red or yellow and black to advertise toxicity and warn off predators.
Frogs typically lay their eggs in water. The eggs hatch into aquatic larvae, called tadpoles, that have tails and internal gills. They have highly specialized rasping mouth parts suitable for herbivorous, omnivorous or planktivorous diets. The life cycle is completed when they metamorphose into adults. A few species deposit eggs on land or bypass the tadpole stage. Adult frogs generally have a carnivorous diet consisting of small invertebrates, but omnivorous species exist and a few feed on fruit. Frogs are extremely efficient at converting what they eat into body mass, which makes them an important food source for predators. Frogs are a keystone group in the food web dynamics of many of the world's ecosystems. The skin is semi-permeable, making frogs susceptible to dehydration, so they either live in moist places or have special adaptations to deal with dry habitats. Frogs produce a wide range of vocalizations, particularly in their breeding season, and exhibit many different kinds of complex behaviours to attract mates, to fend off predators and to generally survive.
Frog populations around the world have declined significantly since the 1950s. More than one third of species are considered to be threatened with extinction and over one hundred and twenty are believed to have become extinct since the 1980s. The number of malformations among frogs is on the rise and an emerging fungal disease, chytridiomycosis, has spread around the world. Conservation biologists are working to understand the causes of these problems and to resolve them.
Frogs are valued as food by humans and also have many cultural roles in literature, symbolism and religion.
Other articles related to "frog, frogs":
... Three amphibians are found in Ireland, the common European brown frog, the smooth newt, and the natterjack toad ... There are questions over whether the frog is actually native to Ireland with some historic accounts stating that the frog was introduced in the 18th century ...
2000 Austrochaperina adelphe (Zweifel, 1985) Peeping Land Frog Austrochaperina aquilonia Zweifel, 2000 Austrochaperina archboldi Zweifel, 2000 ...
... hainanensis Amolops himalayanus Amolops hongkongensis – Hong Kong Cascade Frog Amolops iriodes Amolops jaunsari Amolops jinjiangensis Amolops kangtingensis Amolops kaulbacki Amolops ... is a junior synonym of Odorrana nasica, the Long-snout Torrent Frog ... The Concave-eared Torrent Frog, formerly A ...
... For more details on this topic, see Frogs in popular culture ... Frogs feature prominently in folklore, fairy tales and popular culture ... Frog, The Frog Prince and Kermit the Frog ...
... The pig frog (Rana grylio) is a species of aquatic frog found in the Southeastern United States, from South Carolina to Texas ... Some sources also refer to it as the lagoon frog or the southern bullfrog ...
Famous quotes containing the word frog:
“I feel like a white granular mass of amorphous crystalsmy formula appears to be isomeric with Spasmotoxin. My aurochloride precipitates into beautiful prismatic needles. My Platinochloride develops octohedron crystals,with a fine blue florescence. My physiological action is not indifferent. One millionth of a grain injected under the skin of a frog produced instantaneous death accompanied by an orange blossom odor.”
—Lafcadio Hearn (18501904)
“A frog he would a-wooing go,
Heigh ho! says Rowley,
Whether his mother would let him or no.
With a rowley, powley, gammon and spinach,
Heigh ho! says Anthony Rowley.”
—Mother Goose (fl. 17th18th century. A frog he would a-wooing go (l. 15)
“The owl is abroad, the bat and the toad,
And so is the cat-a-mountain;
The ant and the mole sit both in a hole,
And frog peeps out o the fountain.”
—Ben Jonson (15721637)