Chordata : Amphibia
Amphibians are the first cold blooded vertebrates which can live on land and water.
They are carnivorous, tetrapodus, pentadactylate and dicondylic.
Ear consists of middle and internal ear; and the eyes have eyelids. Skin is rich in glands and chromatophores (pigment cells). They have large mouth with protrusible tongue. Amphibians have two jaws present with teeth which are;homodont that is all teeth are similar, acrodont that is, the teeth are directly attached to bone, and polyphyodont that is, the teeth are present in many sets.
In amphibians respiration occurs by skin, lungs, buccopharyngeal cavity. Gills are present during larval stage for respiration. Their heart is three chambered. The kidney is mesonephric with nephrostome present as an excretory organ. Nervous system consists of less developed brain and ten pairs of cranial nerves.
Animals are dioecious and show external fertilisation. Eggs are laid in water with a gelatinous covering. Water is required for breeding as fertilisation is external (in water). So, amphibians need water to complete their life-cycle. Development is indirect in which tadpole larva transforms into adult through the process of metamorphosis.
Amphibians enter a state of dormancy during unfavourable conditions, when conditions are better they emerge from dormancy.
Such states of inactivity are called as hibernation in winter and aestivation in summer.
Some of the examples of Amphibians include: Ichthyophis, Rana (bull frog), Amphiuma, Nectaurus and Hyla (tree frog)
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