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Frogs are amphibians
of the family Ranidae, in the Order Anura. They are closely related
to toads. The Ranidae are sometimes called the "true frogs"
since a few members of other families also have common names including
the word "frog." Frogs are a diverse group with some
4800 species. Most spend their lives in or near a source of water
(water frogs), although tree frogs live in moist environments
that are not actually aquatic. The requirement for water becomes
most acute for egg and tadpole stages of the frog, yet here again
some species are able to utilize temporary pools and water collected
in the axils of plants. The most familiar frogs are Common frogs,
Bullfrogs, Edible frogs, Leopard frogs, Spring Peepers, Poison
dart frogs, and Green Frogs.
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Some adult frogs
are smaller than a person's thumb.Frogs range in size from less
than 50mm (2.0 in) to 300mm (11.8 in) in Conraua goliath, which
is the largest known frog. All frogs have horizontal pupils, smooth
skin and long legs with webbing between their toes. This family
has a bicornuated tongue that is attached in front: They also
have a tympanum on each side of their head, which is involved
in hearing. Most frogs have deep, booming calls, or croaks, with
some being onomatopoeically represented by the sound (for English
speakers), "ribbet" or "ribbit." The Ancient
Greeks, via Aristophanes, transcribed the sound of a croaking
frog as, "korax." Many species of frog secrete toxins
from their skin. These toxins deter predatory animals from eating
them, and some are extremely poisonous to humans. The natives
of the Amazon area extract arrow-poison from the arrow-poison
frog. Some toads also secrete toxins from their skins, the cane
toad being a well known example.
001-013.jpg
courtesy Us Fish and Wildlife Service
014-016.jpg courtesy: National Undersea Research Program
017-018.jpg courtesy: pdphoto.org
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