To warn potential predators, the most toxic amphibians are also the most brightly colored. Curare [kyoo-RAW-ree], for example, is found on the skin of colorful poison dart frogs. Another special feature of most amphibians is their egg-larva-adult life cycle. The larvae are aquatic and free-swimming—frogs and toads at this stage are called tadpoles.
At a certain size, the young develop limbs and lungs. Some also lose their tails. Eventually, they hop or climb out of the water as adults, and spend the rest of their lives on land. This process is known as metamorphosis. Like reptiles, amphibians are cold-blooded. Because of their special skin, they require very specific living conditions. Frogs and toads, also known as the tailless amphibians, live on every continent except Antarctica.
Currently, there are more than 3, species of frogs worldwide. Because frogs are the only amphibians that can hear, they are also the only amphibians that have a voice box or larynx. During the summer, if there are frogs in the area you can often walk outside and hear frogs calling to establish their territory or to find a mate. Salamanders usually have a long tail and four legs. Many people mistake salamanders for lizards and lizards for salamanders, but they are very different.
Salamanders, unlike lizards, have smooth, slimy skin and a larva stage. Salamanders also do not have ears or a voice box. The different species of salamanders worldwide are usually found in the cooler forested areas in the Northern Hemisphere. Adult amphibians are carnivores and predators. They eat a variety of food including spiders, beetles, and worms. Some of them, like frogs, have long tongues with sticky ends that they flick out to catch their prey. The larvae of many amphibians mostly eat plants.
Frogs have teeth, but toads do not. Most frogs have teeth on the upper jaw, yet they none on the lower jaw. Frogs' skin is slimy because they have protective skin secretions that ooze out of their bodies. Whereas frogs have smooth skin, toads' skin is rough and bumpy, due to special structures that secrete poisonous fluids from their skin.
Amphibian - a cold-blooded vertebrate that spends some time on land but must breed and develop into an adult in water camouflaged - devices designed to conceal by imitating the colours of the surrounding environment carnivores - an animal that eats other animals.
Need help? How to videos Why join? There are three types of amphibians: frogs, salamanders and caecilians. Generally, frogs have a short body, webbed fingers and toes, bulging eyes, and no tail. Frogs are good jumpers with long powerful legs. But what exactly are they…? Are all of them the same? Most eggs hatch into aquatic, legless, gilled larvae, which eventually metamorphosis into four-legged, air-breathing adults.
Interestingly, some frogs and toads hatch as mini adults. There are even some salamanders that never advance beyond the gilled larval stage. The life cycle of frogs, as other amphibians, consists of two distinct stages: the larval stage followed by metamorphosis to an adult stage. The larval stage of a frog, the tadpole , is often a filter-feeding herbivore. Tadpoles usually have gills, a lateral line system, long-finned tails, and lack limbs.
During this stage, the gills, tail, and lateral line system disappear, and four limbs develop. The jaws become larger and are suited for carnivorous feeding, and the digestive system transforms into the typical short gut of a predator.
An eardrum and air-breathing lungs also develop. These changes during metamorphosis allow the larvae to move onto land in the adult stage. An estimated species comprise caecilians , a group of amphibians that belong to the order Apoda. Although they are vertebrates, a complete lack of limbs leads to their resemblance to earthworms in appearance. They are adapted for a soil-burrowing or aquatic lifestyle, and they are nearly blind. They have vestigial limbs, evidence that they evolved from a legged ancestor.
The climate and geography of Earth was vastly different during the Paleozoic Era, when vertebrates arose, as compared to today. The Paleozoic spanned from approximately to million years ago. The landmasses on Earth were very different from those of today.
As the Paleozoic progressed, glaciations created a cool global climate, but conditions warmed near the end of the first half of the Paleozoic. During the latter half of the Paleozoic, the landmasses began moving together, with the initial formation of a large northern block called Laurasia. This contained parts of what is now North America, along with Greenland, parts of Europe, and Siberia.
Eventually, a single supercontinent, called Pangaea, was formed, starting in the latter third of the Paleozoic. During the early Paleozoic, the amount of carbon dioxide in the atmosphere was much greater than it is today. This may have begun to change later, as land plants became more common. As the roots of land plants began to infiltrate rock and soil began to form, carbon dioxide was drawn out of the atmosphere and became trapped in the rock.
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