Amphibians, or amphibians, are distinguished from other animals primarily by the fact that they are the first and smallest members of the four-legged vertebrate class.
Amphibians are the smallest class of vertebrates, comprising only about 6200 modern species, which are divided into three orders: the tailed, the tailless or dancing, and the legless.
The tailless or jumping amphibians (Anura) have the largest number of species, about 5 400, and are adapted to move over land by jumping due to their elongated hind limbs. This order includes a wide variety of frogs, toads, garlic crabs, hammerheads, jellyfish and others. The tailless fishes are found on all continents except Antarctica.
The tailed amphibians (Urodela or Caudata) are more primitive. This order includes the various salamanders and newts, which are almost exclusively restricted to the northern hemisphere.
The legless amphibians (Apoda) comprise about 170 species of tropical worm-eating amphibians, most of which live under land.
Gabarites
The vast majority of amphibians are very small. The largest are large salamanders (75-150 cm) and some legless worms (up to 135 cm). The largest frogs (Giant Frogs) are 33-42 cm long and weigh more than 3.5-5 kg. The smallest amphibian is the leaf frog, which is at most 1 cm long. The maximum lifespan was reached by the giant Japanese salamander, which survived 55 years in captivity. The longest-lived amphibian among the tailless amphibians is the grey toad, with an average life expectancy of 36 years. Other species have life spans ranging from 5 to 20 years.
Feeding chain
Amphibians feed on insects as well as small mammals, other amphibians, fish and crustaceans. Meanwhile, amphibians themselves are eaten by reptiles, birds, mammals and humans.
Evolution
Some 300 million years ago, amphibians were the first vertebrates to emerge from the water and become land animals.ventoys. Until the advent of reptiles, amphibians were the only vertebrates on Earth. In the evolutionary chain, amphibians are intermediate between fish and reptiles.
Breeding
Like fish, amphibians reproduce by laying eggs. Amphibian eggs do not have shells to protect them from drying out and are usually only able to develop in or near water. Amphibian development takes place through metamorphosis (metamorphosis), during which the aquatic larva transforms into a terrestrial animal. Within a few weeks, amphipods go through all the stages of the evolutionary process, lose their gills and tail (frogs and toads), grow limbs and come out on land. Some species, such as the ambistomines, remain in the larval stage throughout their lives. The ability to reproduce in the early stages of development is called neoteny.