Amphibian - Wikipedia. Amphibians are ectothermic, tetrapodvertebrates of the class. Amphibia. Modern amphibians are all Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquaticecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this. The young generally undergo metamorphosis from larva with gills to an adult air- breathing form with lungs. 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 lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in recent decades there has been a dramatic decline in amphibian populations for many species around the globe. The earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony- limbed fins, features that were helpful in adapting to dry land. They diversified and became dominant during the Carboniferous and Permian periods, but were later displaced by reptiles and other vertebrates. Over time, amphibians shrank in size and decreased in diversity, leaving only the modern subclass Lissamphibia. 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 7,0. The smallest amphibian (and vertebrate) in the world is a frog from New Guinea (Paedophryne amauensis) with a length of just 7. The largest living amphibian is the 1. Chinese giant salamander (Andrias davidianus), but this is dwarfed by the extinct 9 m (3. Prionosuchus from the middle Permian of Brazil. Find recipes for every meal, easy ideas for dinner tonight, cooking tips and expert food advice. Gluten is incredible for its ability to piss off a diverse spectrum of people: Folks who are giving it up for a diet, folks who say it’s stupid to give up gluten. Habitat: This small, vampire-looking species of deer is endemic to China and Myanmar (Burma). Lifestyle: Tufted deer are herbivores. Their diet consists of fruit. Page last updated: 2006.11.08. For as long as I can remember, I've loved video games. And when a video game happened to have some vore content in. ![]() Must-have 'fatbit' fitness gadgets can exaggerate your step count by 25% every day Some gadgets register 'movements' when people sit at desks or stand still.The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology. Classification. The term was initially used as a general adjective for animals that could live on land or in water, including seals and otters. Amphibia in its widest sense (sensu lato) was divided into three subclasses, two of which are extinct. The two most common systems are the classification adopted by the website Amphibia. Web, University of California, Berkeley and the classification by herpetologist. Darrel Frost and the American Museum of Natural History, available as the online reference database . Classification varies according to the preferred phylogeny of the author and whether they use a stem- based or a node- based classification. Traditionally, amphibians as a class are defined as all tetrapods with a larval stage, while the group that includes the common ancestors of all living amphibians (frogs, salamanders and caecilians) and all their descendants is called Lissamphibia. The phylogeny of Paleozoic amphibians is uncertain, and Lissamphibia may possibly fall within extinct groups, like the Temnospondyli (traditionally placed in the subclass Labyrinthodontia) or the Lepospondyli, and in some analyses even in the amniotes. This means that advocates of phylogenetic nomenclature have removed a large number of basal Devonian and Carboniferous amphibian- type tetrapod groups that were formerly placed in Amphibia in Linnaean taxonomy, and included them elsewhere under cladistic taxonomy. The three modern orders are Anura (the frogs and toads), Caudata (or Urodela, the salamanders), and Gymnophiona (or Apoda, the caecilians). It has been suggested that salamanders arose separately from a Temnospondyl- like ancestor, and even that caecilians are the sister group of the advanced reptiliomorph amphibians, and thus of amniotes. It is anatomically very similar to modern frogs. The Lissamphibia are traditionally divided into three orders, but an extinct salamander- like family, the Albanerpetontidae, is now considered part of Lissamphibia alongside the superorder Salientia. Furthermore, Salientia includes all three recent orders plus the Triassic proto- frog, Triadobatrachus. Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required. Eventually, their bony fins would evolve into limbs and they would become the ancestors to all tetrapods, including modern amphibians, reptiles, birds, and mammals. Despite being able to crawl on land, many of these prehistoric tetrapodomorph fish still spent most of their time in the water. They had started to develop lungs, but still breathed predominantly with gills. Ichthyostega was one of the first primitive amphibians, with nostrils and more efficient lungs. It had four sturdy limbs, a neck, a tail with fins and a skull very similar to that of the lobe- finned fish, Eusthenopteron. Their lungs improved and their skeletons became heavier and stronger, better able to support the weight of their bodies on land. It is thought they may have propelled themselves with their forelimbs, dragging their hindquarters in a similar manner to that used by the elephant seal. Extensive swamps developed with mosses, ferns, horsetails and calamites. Air- breathing arthropods evolved and invaded the land where they provided food for the carnivorous amphibians that began to adapt to the terrestrial environment. There were no other tetrapods on the land and the amphibians were at the top of the food chain, occupying the ecological position currently held by the crocodile. Though equipped with limbs and the ability to breathe air, most still had a long tapering body and strong tail. They still needed to return to water to lay their shell- less eggs, and even most modern amphibians have a fully aquatic larval stage with gills like their fish ancestors. It was the development of the amniotic egg, which prevents the developing embryo from drying out, that enabled the reptiles to reproduce on land and which led to their dominance in the period that followed. According to the fossil record, Lissamphibia, which includes all modern amphibians and is the only surviving lineage, may have branched off from the extinct groups Temnospondyli and Lepospondyli at some period between the Late Carboniferous and the Early Triassic. The relative scarcity of fossil evidence precludes precise dating. A 2. 00. 5 molecular phylogeny, based on r. DNA analysis, suggests that salamanders and caecilians are more closely related to each other than they are to frogs. It also appears that the divergence of the three groups took place in the Paleozoic or early Mesozoic (around 2. Pangaea and soon after their divergence from the lobe- finned fish. The briefness of this period, and the swiftness with which radiation took place, would help account for the relative scarcity of primitive amphibian fossils. Molecular analysis suggests that the frog–salamander divergence took place considerably earlier than the palaeontological evidence indicates. In the water, the sideways thrusts of their tails had propelled them forward, but on land, quite different mechanisms were required. Their vertebral columns, limbs, limb girdles and musculature needed to be strong enough to raise them off the ground for locomotion and feeding. Terrestrial adults discarded their lateral line systems and adapted their sensory systems to receive stimuli via the medium of the air. They needed to develop new methods to regulate their body heat to cope with fluctuations in ambient temperature. They developed behaviours suitable for reproduction in a terrestrial environment. Their skins were exposed to harmful ultraviolet rays that had previously been absorbed by the water. The skin changed to become more protective and prevent excessive water loss. Characteristics. They are not found in the sea with the exception of one or two frogs that live in brackish water in mangrove swamps. It has an average length of 7. Their metabolic rate is low and as a result, their food and energy requirements are limited. In the adult state, they have tear ducts and movable eyelids, and most species have ears that can detect airborne or ground vibrations. They have muscular tongues, which in many species can be protruded. Modern amphibians have fully ossified vertebrae with articular processes. Their ribs are usually short and may be fused to the vertebrae. Their skulls are mostly broad and short, and are often incompletely ossified. Their skin contains little keratin and lacks scales, apart from a few fish- like scales in certain caecilians. The skin contains many mucous glands and in some species, poison glands (a type of granular gland). The hearts of amphibians have three chambers, two atria and one ventricle. They have a urinary bladder and nitrogenous waste products are excreted primarily as urea. Most amphibians lay their eggs in water and have aquatic larvae that undergo metamorphosis to become terrestrial adults. Amphibians breathe by means of a pump action in which air is first drawn into the buccopharyngeal region through the nostrils. These are then closed and the air is forced into the lungs by contraction of the throat. They supplement this with gas exchange through the skin. The order Anura (from the Ancient Greek a(n)- meaning . They usually have long hind limbs that fold underneath them, shorter forelimbs, webbed toes with no claws, no tails, large eyes and glandular moist skin. Members of this order with smooth skins are commonly referred to as frogs, while those with warty skins are known as toads. The difference is not a formal one taxonomically and there are numerous exceptions to this rule. Members of the family Bufonidae are known as the . They are found worldwide except for polar areas. Future molecular studies should provide further insights into their evolutionary relationships. AOL Food - Recipes, Cooking and Entertaining. Inside- out breakfast sandwich will make your mouth water. Topped with fried pork, gooey brie and egg, it's the ultimate way to start the morning.
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