Anura (the frogs and toads), Urodela (the salamanders), and Apoda (the caecilians).
These characteristics are scales and amniotic eggs. Reptiles are one of the six basic animal groups. Other basic animal groups include amphibians, birds, fish, invertebrates, and mammals. This alligator is among about 23 species of crocodilians alive today. Reptiles are a group of four-legged vertebrates (also known as tetrapods) that diverged from ancestral amphibians approximately 340 million years ago. Making the world better, one answer at a time. 1)Frogs and Toads 2)Salamanders and Newts 3)Caecilians. Salamanders, Frogs and Caecilians, are three living groups of Amphibia. The three types of Amphibians are; Caudata, salamanders and newts; Anura, frogs and toads; and Apoda, legless caecilians. Amphibians are a group of tetrapod vertebrates that include modern-day frogs and toads, caecilians, and newts and salamanders. The first amphibians evolved from lobe-finned fishes approximately 370 million years ago during the Devonian Period. In this article, we'll take a look at six groups of amphibians, their characteristics and the organisms that belong to each group. Amphibians are one of the six basic animal groups. Other basic animal groups include birds, fish, invertebrates, mammals, and reptiles. Smooth Newt-Lissotriton vulgaris. The earliest tetrapods, called basal or stem tetrapods, such as the species Acanthostega, are more primitive than the common ancestor of all tetrapods alive today, and so do not fall into any of the main tetrapod groups. There are only a few dozen species in this classification, and they are all long extinct. Aside from the basal tetrapods, there are three major groups of tetrapods: amphibians, synapsids (meaning fused arch, mammals are the only synapsids alive today), and sauropsids (meaning lizard face).  The three modern orders of amphibians are Anura (the frogs and toads), Urodela (the salamanders), and Apoda (the caecilians). The number of known amphibian species is approximately 7,000, of which nearly 90% are frogs. The smallest amphibian (and vertebrate) in the world is a frog from New Guinea (Paedophryne amauensis) with a length of just 7.7 mm (0.30 in). Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. The largest living amphibian is the 1.8 m (5 ft 11 in) Chinese giant salamander (Andrias davidianus), but this is dwarfed by the extinct 9 m (30 ft) Prionosuchus from the middle Permian of Brazil. The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. The lungs and breathing tubes enabled them to breathe air. Their sternum formed a bony shield that supports and protects the internal organs, especially the lungs. Their hearts have two atriums and one ventricle. The three groups of amphibians alive today are salamanders, frogs and toads, and caecilians. Objectives: - Students will learn to describe what an amphibian is and summarize the events on their evolution by observation and instruction. - Students will learn how amphibians are adapted for life on land and the name of the three main groups of living amphibians by visualization and explanation.  Amphibians include newts and salamanders, frogs and toads, and caecilians. There are between 5000 and 6000 species of known amphibians alive today. Amphibian species are in decline around the world due to a variety of threats including of invasive species, habitat destruction, disease, climate change, and toxins. Frogs and Toads. Frogs and toads belong to the largest of the three groups of amphibians. There are more than 4,000 species of frogs and toads alive today. The earliest known frog-like ancestor is Gerobatrachus, a toothed amphibian that lived about 290 million years ago. In this article, we'll take a look at six groups of amphibians, their characteristics and the organisms that belong to each group. Amphibians are one of the six basic animal groups. Other basic animal groups include birds, fish, invertebrates, mammals, and reptiles. Smooth Newt-Lissotriton vulgaris.
http://animals.about.com/od/reptiles/tp/reptilegroups.htm http://www.answers.com/Q/What_are_the_three_groups_of_amphibians http://animals.about.com/od/amphibians/tp/amphibiangroups.htm http://www.wisegeek.com/what-are-the-major-groups-of-tetrapods.htm https://en.wikipedia.org/wiki/Amphibian https://en.wikipedia.org/wiki/Amphibian http://www.digitalfrog.com/resources/vilmalop.pdf http://www.youtube.com/watch?v=JKX3aSSu9C0 http://animals.about.com/od/amphibians/tp/amphibiangroups.htm
what are the three major groups of amphibians alive today