Characteristics Modern amphibians share the characteristics:
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MovementStandard tetrapod vertebrate body plan, with 4 limbs and bones providing leverage for muscles.
Frogs' skeletons are highly adapted for jumping. Forelimbs' bones have fused, unlike in mammals who have two separate bone. There are few vertebrae. |
CirculationSimilar to most vertebrates. They have 3 chambered heart, with double circulation. Oxygenated blood from the lungs mixes with deoxygenated blood from the body in the single ventricle of the heart.
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Oxygen ExchangeLarval amphibians exchange oxygen through gills and skin. Most lose their gills during metamorphosis and gain lungs. There is positive pressure breathing. Amphibian lungs are small and inefficient, so respiration through the skin is common.
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ReproductionThey have a very complex reproductive structure. Eggs are typically fertilized externally in nests. Eggs hatch a few days after fertilization into tadpoles (larva). Larvae slowly change into adults through a process called metamorphosis. Typical of most amphibians.
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Unusual Aspects of ReproductionSome salamanders (like axolotl) remain in larval stage their entire lives. Parental care is common.
Male Darwin's frogs (Rhinoderma darwinii) take eggs into vocal sacs where they hatch and undergo metamorphosis. Two frogs swallow their young and they grow and metamorphose in the stomach, which stops producing acid. Neotony is the retention, by adults in a species, of traits previously seen only in juveniles. There are several advantages of parental control. |
ExcretionSame as bony fish. Wastes are removed by kidney and will leave through the anus.
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ResponseSame as other vertebrates. Eyes are covered by movable nictating membrane, which helps protect the eye while allowing vision. Sound is detected by ears, covered with a tymponic membrane.
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Feeding/DigestionMany frogs have extendable tongues to catch prey. Amphibian digestive system is similar to most other vertebrate.
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Order Anura
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Order Gymnophiona
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