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Amphibians are ectothermic , tetrapod vertebrates of the class Amphibia. All living amphibians belong to the group lissamphibia They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.

frog

salamander

frog

salamander

scientific Classification
Kingdom :	Animalia
Phyium :	Chordata
Class :	Amphibia
Clade :	batrachomorpha

Red-eyed tree frogs, Agalychnis callidryas, are colorful amphibians found in the tropical lowlands of Central America where the animals hunt after dark for their insect prey. The frogs are arboreal and are commonly be found on plants and trees. (Image credit: Julie Larsen Maher ©WCS) Frogs are amphibians that are known for their jumping abilities, croaking sounds, bulging eyes and slimy skin. They live all over the world and are among the most diverse animals in the world, with more than 6,000 species.
Frogs substantially outnumber the two other groups ofAmphibians — salamanders and caecilians. According to the American Museum of Natural History (AMNH) online reference site, Amphibian Species of the World, which is updated in real time, as of late April 2015, there are 6,482 species in the Anura order (frogs and toads), 691 species in the Caudata order (salamanders and newts) and 204 species in the Gymnophiona order (caecilians). Caecilians look like large worms or slick snakes,
according to the San Diego Zoo. They have no arms or legs, and live underground in a network of tunnels. Frogs vs. toads There is no scientific distinction between frogs and toads, according to the University of Michigan Museum of Zoology. Frog and toads both belong to the Anura order, but are found in different families. "True toads" make up the Bufonidae family, which includes 580 species.Frogs and toads do have specific traits that define them, however, according to the Maryland Zoo. For example, frogs are mostly aquatic; most toads live on land (but near water). Frogs have teeth; toads do not. Toads of both sexes have a rudimentary ovary called a bidder's organ. Frogs are also typically longer than toads.

Some frogs have toxic skin. Some South American frogs are so toxic that one drop of their skin secretions can kill an adult human. Poison frogs usually have bright colors to warn predators that their skin is toxic, according to the San Diego Zoo. Camouflage is another survival technique. Many frogs have mottled green or brown skin to help them blend in with their surroundings. [Gallery: Freaky Frog Photos: A Kaleidoscope of Colors] Since there are so many types of frogs, one size doesn't fit all . The largest frog is the Goliath frog, which is 13.5 inches long (30 centimeters) and weighs 6.6 lbs. (3 kilograms), according to the San Diego Zoo. The devil frog of Madagascar, now extinct, once held the title of largest frog. It was 16 inches long (41 cm) long and weighed 10 lbs. (4.5 kg), according to National Geographic. The smallest frog is the gold frog, which is a tiny 0.39 in (1 cm) long and only 7 ounces (200 grams), according to the San Diego Zoo. That's around the size of a dime.

Frogs need to be around areas with a water source to reproduce, but other than that, they are found on every continent except Antarctica and in almost every environment. The poison dart frog lives in the tropical forests of Central and South America. Northern leopard frogs live in the northern areas of North America in marshes and grasslands. The green-eyed tree frog lives in the moss-covered rain forests of Queensland, Australia, according to National Geographic. The desert rain frog lives exclusively in Namibia and South Africa, along the coast in sand dunes.

Frogs will often eat any living thing that will fit into their mouths. This includes bugs, spiders, worms, slugs, larvae and even small fish. To catch prey, their sticky tongues will dart from their mouths and pull the prey into the frog's mouth. This movement is so fast often the prey doesn't have a chance to escape. A frog's tongue can snap back into its mouth within 15/100ths of a second. Frogs and toads help keep the world's insect population under control, according to the San Diego Zoo. Their appetite for bugs is usually quite helpful, but sometimes it can lead to disaster. For example, in 1935, cane toads from Puerto Rico were introduced to Australia to kill sugarcane beetles. However, the cane toads, which can grow as large as a dinner plate, preferred to eat native frogs, small marsupials and snakes. The original 102 toads set out across the continent and have mushroomed in number to more than 1.5 billion, according to a 2010 Live Science article. Today, cane toads have conquered more than 386,000 square miles (1 million square kilometers) of Australia. This is equivalent to an area slightly larger than the states of Texas and Oklahoma combined.

Frogs are social creatures that live in groups. A group of frogs is called army, colony or a knot. Groups of young frogs will even swim together in schools, much like fish. Advertisement
During mating season, the male frogs in a group will croak quite loudly. Frogs croak to attract females. When the female finds a male croak she likes, the male will grab her and she will release eggs for him to fertilize.

Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela. Salamander diversity is highest in eastern North America and most species are found in the Holarctic realm, with some species present in the Neotropical realm.
Salamanders rarely have more than four toes on their front legs and five on their rear legs, but some species have fewer digits and others lack hind limbs. Their permeable skin usually makes them reliant on habitats in or near water or other cool, damp places. Some salamander species are fully aquatic throughout their lives, some take to the water intermittently, and others are entirely terrestrial as adults. They are capable of regenerating lost limbs as well
as other damaged parts of their bodies. Researchers hope to reverse engineer the remarkable regenerative processes for potential human medical applications, such as brain and spinal cord injury treatment or preventing harmful scarring during heart surgery recovery.[2] Members of the family Salamandridae are mostly known as newts and lack the costal grooves along the sides of their bodies typical of other groups. The skin of some species contains the powerful poison tetrodotoxin; these salamanders tend to be slow-moving and have bright warning coloration to advertise their toxicity. Salamanders typically lay eggs in water and have aquatic larvae, but great variation
occurs in their lifecycles. Some species in harsh environments reproduce while still in the larval state.

The skin lacks scales and is moist and smooth to the touch, except in newts of the Salamandridae, which may have velvety or warty skin, wet to the touch. The skin may be drab or brightly colored, exhibiting various patterns of stripes, bars, spots, blotches, or dots. Male newts become dramatically colored during the breeding season. Cave species dwelling in darkness lack pigmentation and have a translucent pink or pearlescent appearance.[3]An adult salamander generally resembles a small lizard, having a basal tetrapod body form with a cylindrical trunk, four limbs, and a long tail. Except in the family Salamandridae, the head, body, and tail have a number of vertical depressions in the surface which run from the mid-dorsal region to the ventral area and are known as costal grooves. Their function seems to be to help keep the skin moist by channeling water over the surface of the body.[5] Sirens have an eel-like appearance. Some aquatic species, such as sirens and amphiumas, have reduced or absent hind limbs, giving them an eel-like appearance, but in most species, the front and rear limbs are about the same length and project sidewards, barely raising the trunk off the ground. The feet are broad with short digits, usually four on the front feet and five on the rear. Salamanders do not have claws, and the shape of the foot varies according to the animal's habitat. Climbing species have elongated, square-tipped toes, while rock-dwellers have larger feet with short, blunt toes. The tree-climbing salamander (Bolitoglossa sp.) has plate-like webbed feet which adhere to smooth surfaces by suction, while the rock-climbing Hydromantes species from California have feet with fleshy webs and short digits and use their tails as an extra limb. When ascending, the tail props up the rear of the body, while one hind foot moves forward and then swings to the other side to provide support as the other hind foot advances.[6] In larvae and aquatic salamanders, the tail is laterally flattened, has dorsal and ventral fins, and undulates from side to side to propel the animal through the water. In the families Ambystomatidae and Salamandridae, the male's tail, which is larger than that of the female, is used during the amplexus embrace to propel the mating couple to a secluded location. In terrestrial species, the tail moves to counterbalance the animal as it runs, while in the arboreal salamander and other tree-climbing species, it is prehensile. The tail is also used by certain plethodontid salamanders that can jump, to help launch themselves into the air.[6] The tail is used in courtship and as a storage organ for proteins and lipids. It also functions as a defense against predation, when it may be lashed at the attacker or autotomised when grabbed. Unlike frogs, an adult salamander is able to regenerate limbs and its tail when these are lost.[6]

Although many salamanders have cryptic colors so as to be unnoticeable, others signal their toxicity by their vivid coloringa. Yellow, orange, and red are the colors generally used, often with black for greater contrast. Sometimes, the animal postures if attacked, revealing a flash of warning hue on its underside. The red eft, the brightly colored terrestrial juvenile form of the eastern newt (Notophthalmus viridescens), is highly poisonous. It is avoided by birds and snakes, and can survive for up to 30 minutes after being swallowed (later being regurgitated).[43] The red salamander (Pseudotriton ruber) is a palatable species with a similar coloring to the red eft. Predators that previously fed on it have been shown to avoid it after encountering red efts, an example of Batesian mimicry.[43] Other species exhibit similar mimicry. In California, the palatable yellow-eyed salamander (Ensatina eschscholtzii) closely resembles the toxic California newt (Taricha torosa) and the rough-skinned newt (Taricha granulosa), whereas in other parts of its range, it is cryptically colored.[44] A correlation exists between the toxicity of Californian salamander species and diurnal habits: relatively harmless species like the California slender salamander (Batrachoseps attenuatus) are nocturnal and are eaten by snakes, while the California newt has many large poison glands in its skin, is diurnal, and is avoided by snakes.[45]

Many salamanders do not use vocalisations,[55] and in most species the sexes look alike, so they use olfactory and tactile cues to identify potential mates, and sexual selection occurs. Pheromones play an important part in the process and may be produced by the abdominal gland in males and by the cloacal glands and skin in both sexes. Males are sometimes to be seen investigating potential mates with their snouts. In Old World newts, Triturus spp., the males are sexually dimorphic and display in front of the females. Visual cues are also thought to be important in some Plethodont species.[56] In about 90% of all species, fertilisation is internal. The male typically deposits a spermatophore on the ground or in the water according to species, and the female picks this up with her vent. The spermatophore has a packet of sperm supported on a conical gelatinous base, and often an elaborate courtship
behavior is involved in its deposition and collection. Once inside the cloaca, the spermatozoa move to the spermatheca, one or more chambers in the roof of the cloaca, where they are stored for sometimes lengthy periods until the eggs are laid. In the most primitive salamanders,
such as the Asiatic salamanders and the giant salamanders, external fertilization occurs, instead. In these species, the male releases sperm onto the egg mass in a reproductive process similar to that of typical frogs.[56] Three different types of egg deposition occur. Ambystoma and Taricha spp. spawn large numbers of small eggs in quiet ponds where many large predators are unlikely. Most dusky salamanders (Desmognathus) and Pacific giant salamanders (Dicamptodon) lay smaller batches of medium-sized eggs in a concealed site in flowing water, and these are usually guarded by an adult, normally the female. Many of the tropical climbing salamanders (Bolitoglossa) and lungless salamanders (Plethodontinae) lay a small number of large eggs on land in a well-hidden spot, where they are also guarded by the mother.[56] Some species such as the fire salamanders (Salamandra) are ovoviviparous, with the female retaining
the eggs inside her body until they hatch, either into larvae to be deposited in a water body, or into fully formed juveniles