🐸Amphibians flourished during the Carboniferous period.
🐸They live partly in water and partly on land, and hencethe name Amphibia (Greek: amphi - double, dual; bios - life) to the class.
🐸Most of the amphibians are now extinct.
🐸Cold blooded or poikilothermic vertebrates. Breed and develop in freshwater.Adult is terrestrial or partly aquatic.
🐸Skin moist and glandular.
🐸Exoskeleton absent. In some forms (apoda), concealed dermal scales are present.
🐸Two pairs of pentadactyl limbs are present. Digits are clawless. In someamphibians (apoda) limbs are absent.
🐸Skull dicondylic. i.e. two occipital condyles are present.
🐸Vertebrae are procoelous, amphicoelous or opisthocoelous.
🐸Respiratory organs in terrestrial adults are skin, lungs and buccal lining. Inaquatic larvae, gills are the respiratory organs.
🐸Heart is three-chambered.
The chambers are two atria and one ventricle.
🐸There are three pairs of aortic arches, namely, carotid, systemic and pulmocutaneous.
🐸Nostrils open into the buccal cavity.
🐸External ear is absent. Middle ear has tympanum (ear drum), eusta chian tube and columella auris (modified hyomandibular).
🐸Kidney is mesonephric. Urinary bladder is large.
🐸Amphibians are ureotelic(urea is excreted).
🐸Mouth is large. Upper jaw or both jaws bear homodont teeth. Tongue protrusible.
🐸Eggs are laid in fresh water or moist places. Eggs are covered with gelatinous material.
,are rudimentary or absent.
🐸Teeth are present on the upper jaw only or absent.
🐸In adult, gills or gill openings are absent.
🐸Skin is naked, scaleless and glandular.
🐸Skull is dicondylic (two occipital condyles are present).
🐸Tympanum (eardrum) and middle ear cavity are present.
🐸Vocal cords are present.
🐸Fertilization and development are external.Development is indirect. Fish-like, gill breathing aquatic tadpole larva metamorphoses into adult.
Examples: Frog (Rana hexadactyla), Toad (Bufo)
