A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura.
What is a frog?
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 in tropical rainforests. There are approximately 4,800 recorded species, accounting for over 85% of extant amphibian species. They are also one of the five most diverse vertebrate orders.
Frogs are valued as food by humans and also have many cultural roles in literature, symbolism and religion. Frog populations 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.
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 made by some species of poison dart frogs, although it can also cause death by lung paralysis. Other chemicals isolated from the skins of frogs may offer resistance to HIVinfection. Dart poisons are under active investigation for their potential as therapeutic drugs.
Frogs live on all the continents except Antarctica, but they are not present on certain islands, especially those far away from continental land masses. Many species are isolated in restricted ranges by changes of climate or inhospitable territory, such as stretches of sea, mountain ridges, deserts, forest clearance, road construction, or other man-made barriers.
Image: Photo by david clode
Text: Wikipedia contributors. “Frog.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 2 Aug. 2017. Web. 24 Aug. 2017.