Salientia (Latin salere ( salio), "to jump") is a stem group including modern frogs in the order Anura and their close fossil relatives the "proto-frogs" (e.g., Triadobatrachus and Czatkobatrachus). These include around 4,810 species in 33 families, of which the Leptodactylidae (1,100 spp.), Hylidae (800 spp.) and Ranidae (750 spp.) are the richest in species. Approximately 88% of amphibian species are classified in the order Anura. The name frog derives from Old English frogga, abbreviated to frox, forsc and frosc (compare Old Norse frauki, German Frosch, older Dutch spelling kikvorsch), probably deriving from Proto-Indo-European preu = "to jump". Conservation biologists are working to understand the causes of these problems and to resolve them.įrogs are valued as food by humans and also have many cultural roles in literature, symbolism and religion. The number of malformations among frogs is on the rise and an emerging fungal disease, chytridiomycosis, has spread around the world. In 2006, one third of all frog and salamander species that depend on water during some stage of their life cycle were considered to be globally threatened or extinct. There is a significant decline in amphibian populations affecting many regions. 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. 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 are a keystone group in the food web dynamics of many of the world's ecosystems. Frogs are extremely efficient at converting what they eat into body mass, which makes them an important food source for predators. Adult frogs generally have a carnivorous diet consisting of small invertebrates, but omnivorous species exist and a few feed on fruit. A few species deposit eggs on land or bypass the tadpole stage. The life cycle is completed when they metamorphose into adults. They have highly specialized rasping mouth parts suitable for herbivorous, omnivorous or planktivorous diets. The eggs hatch into aquatic larvae, called tadpoles, that have tails and internal gills. 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.įrogs typically lay their eggs in water. 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. Frog warts are elevations in the skin where glandular toxins tend to concentrate. Warty species of frog tend to be called toads. The skin of the frog is glandular, with secretions ranging from distasteful to toxic. Besides living in fresh water and on dry land, the adults of some species are adapted for living underground or in trees. 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. There are approximately 4,800 recorded species, making them among the most diverse vertebrate groups. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is found in tropical rainforests. 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. Australian green tree frog ( Litoria caerulea)įrogs are a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura ( Ancient Greek an-, without + oura, tail).
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