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Frog

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Frogs are members of the order Anura, a name derived from Ancient Greek meaning "without tail."

Anoures
Anoures

This diverse group of vertebrates includes many species that are semiaquatic, meaning they live both in water and on land. Frogs are incredibly successful, accounting for approximately 88% of all extant amphibian species. This makes them one of the five most diverse vertebrate orders on Earth. While they live in many environments, from subarctic regions to the tropics, the highest concentration of species is found in tropical rainforests and associated wetlands.

Litoria tyleri
Litoria tyleri

The life cycle of a frog involves a complex process called metamorphosis. Most frogs are oviparous anamniotes, which means they lay eggs that do not have a specialized membrane. These eggs are typically spawned in bodies of water.

Frogspawn closeup
Frogspawn closeup

From these eggs, aquatic larvae called tadpoles hatch. Tadpoles possess tails and internal gills for breathing underwater. They often have specialized mouthparts, such as keratinous beaks, to eat plants or tiny organisms. As they mature, they undergo metamorphosis to become adults. During this change, they develop lungs and legs for life on land. The larval tail eventually regresses into an internal bone called a urostyle.

Greenfrog life stages
Greenfrog life stages

Adult frogs have several distinct physical characteristics. They generally possess stout bodies, protruding eyes, and limbs that are folded underneath them. Their skin is glandular and semi-permeable, which allows for gas exchange. This means they can use their skin to help them breathe. However, semi-permeable skin also makes them susceptible to dehydration. To survive, they must live in moist niches or develop special adaptations for drier habitats.

Groene kikker achter Bekaert-draad-detail oog
Groene kikker achter Bekaert-draad-detail oog

Their skin color serves important functions. Some species use dappled brown or green patterns for camouflage. Others use vivid patterns of red, yellow, or black to signal that they are toxic.

WoodFrog DarienLakesStatePark 2020-06-16 (02)
WoodFrog DarienLakesStatePark 2020-06-16 (02)

There is often confusion regarding the difference between frogs and toads. In scientific taxonomy, the distinction is informal and purely cosmetic. All members of the order Anura are technically frogs. However, only members of the family Bufonidae are considered "true toads."

Bombina bombina 1 (Marek Szczepanek) tight crop
Bombina bombina 1 (Marek Szczepanek) tight crop

Generally, people use the word "frog" for aquatic species with smooth, moist skin. The word "toad" is often used for terrestrial species with dry, warty skin. There are exceptions, such as the Panamanian golden frog, which is a toad but has smooth skin.

Atelopus zeteki1
Atelopus zeteki1

The evolutionary history of Anura is a subject of intense scientific study. The oldest known fossil "proto-frog" is Triadobatrachus, found in Madagascar.

Fossilised frog
Fossilised frog

This fossil dates to the Early Triassic, about 250 million years ago. Molecular clock dating suggests the group may have diverged from other amphibians as far back as the Permian, 265 million years ago. In 2008, the discovery of Gerobatrachus hottoni in Texas provided a potential "missing link." This 290-million-year-old fossil shows characteristics of both frogs and salamanders. This supports the hypothesis that frogs and salamanders belong to a single group called Batrachia.

Fossilised frog
Fossilised frog

Frogs play a critical role in global ecosystems as low-level consumers. Most adults are carnivores that eat small invertebrates, particularly insects. They capture prey using an anteriorly-attached, adhesive tongue.

Dendropsophus microcephalus - calling male (Cope, 1886)
Dendropsophus microcephalus - calling male (Cope, 1886)

They often use their eyeballs and extraocular muscles to help push food down their throats. Because they are eaten by many larger predators, they are vital to food web dynamics.

TrophicWeb
TrophicWeb

This position makes them environmental bellwethers. This means that changes in frog populations can serve as early warning signs of environmental degradation.

TrophicWeb
TrophicWeb

Unfortunately, global frog populations and diversity have declined significantly since the 1950s. More than one third of all species are currently considered threatened with extinction. Since the 1980s, over 120 species are believed to have become extinct. One major cause of this decline is a spreading fungal disease called chytridiomycosis. This disease has caused many malformations and population crashes worldwide. Conservation biologists are currently working to study these trends and solve these environmental problems.

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🖼️ Images & Media (40)
File:Anoures.jpg
Anoures.jpg
File:Bombina bombina 1 (Marek Szczepanek) tight crop.jpg
Bombina bombina 1 (Marek Szczepanek)...
File:Atelopus zeteki1.jpg
Atelopus zeteki1.jpg
File:Fossilised frog.jpg
Fossilised frog.jpg
File:Frog limbs.jpg
Frog limbs.jpg
File:Rana temporaria 04 by-dpc.jpg
Rana temporaria 04 by-dpc.jpg
File:Litoria tyleri.jpg
Litoria tyleri.jpg
File:Ranapipiensmoulting.jpg
Ranapipiensmoulting.jpg
File:Hip-pocket Frog - Assa darlingtoni.jpg
Hip-pocket Frog - Assa darlingtoni.jpg
File:WoodFrog DarienLakesStatePark 2020-06-16 (02).jpg
WoodFrog DarienLakesStatePark 2020-06-16 (02).jpg
File:Frog anatomy tags.PNG
Frog anatomy tags.PNG
File:Groene kikker achter Bekaert-draad-detail oog.jpg
Groene kikker achter Bekaert-draad-detail oog.jpg

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