Frogs - History And Fossil Record, Adult Morphology, Ecology, Life History And Behavior, Classification, Frogs And Humans - Morphology, Larval morphology
animals amphibians includes toads
Frogs are tail-less amphibians (class Amphibia, order Anura). With some 3,500 living species, frogs are the most numerous and best known of amphibians. They are found on all continents except Antarctica and are common on many oceanic islands. The terms "frog" and "toad" are derived from early usage in England and northern Europe, where two families of the order Anura occur. One includes slender, long-legged, smooth-skinned animals that live near water: frogs; the other includes short-legged warty animals that live in fields and gardens: toads. When other kinds of animals of this group were discovered elsewhere, such as tree-frogs, fire-bellied toads, and others, it was realized that these various forms actually represented one major group. This group, the anurans, is now commonly referred to as frogs.
Frogs are amphibians, a term derived from two Greek words: amphi meaning double and bios meaning life. The double life of frogs involves living in water and also on land. Because of this amphibious habit, they must have adaptations for each environment. As in other animals that have a separate larval stage and a complex life cycle, frogs have two extremely different morphologies.
Tadpoles, the larval stage of frogs, are adapted to a purely aquatic life. They are seemingly reduced to the essentials, which in this case includes a globular body with a muscular, finned tail. Typically, tadpoles have no bones but rather a simple cartilaginous skull and skeleton. They also have no true teeth, instead having rows of denticles and a beak of keratin (a fingernail-like substance). The globular body is mainly filled with a long, highly coiled intestine.
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If frogs were not so common and familiar, they would be regarded as among the strangest of vertebrate animals. The typical frog has a broad head with an enormous mouth and protruding eyes. The body is short and plump, and there is no tail. The forelegs are rather short but normal-looking, and are used mainly for propping up the front part of the body and for stuffing food into the mouth. The hind …
Like other amphibians, such as salamanders (order Caudata) and caecilians (order Gymnophiona), most frogs hatch from a shell-less egg into a gilled, water-dwelling, larval stage (a tadpole). After a period of growth they metamorphose into the adult form. Most species of tadpoles are vegetarians, feeding upon algae and other plant material. All adult frogs, however, are carnivores, most of them fee…
During the 200 million years of their existence, frogs have been evolving in response to varying environmental conditions. Common elements of their adaptations have given rise to clusters of species that share certain morphological, physiological, and behavioral traits. A system of classification has been established, mostly based on morphological features of adult frogs and their larvae. In the o…
Frogs and humans have interacted for many thousands of years. Toads are referred to in ancient writings, as: a "rain of toads," the "eye of toad" as part of a witch's brew, and in many other relationships. Frogs are also used in research, and to teach biology. A core element of many high school and college biology classes in the United States might involve each s…
Judging by recent observations, the prospects for many species of frogs is grim. During the 1990s, numerous species of frogs apparently vanished from nature without any obvious cause of their demise. For example, a newly described, extremely unusual Australian frog, (Rheobatrachus silus), could not be found in its only known habitat the following year. Numerous other Australian frogs have also dis…
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