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Saturday, September 26, 2020

Class Amphibia- NEET-Biology

 Class Amphibia

Class: Amphibia

  • Amphibians are vertebrates, that can live in both aquatic (water) as well as terrestrial (land) environments.
  • The first amphibian came into existence in the Devonian period.

Important characteristics:

  • Soft, moist (without scales) & glandular skin.
  • Endoskeleton mostly bony.
  • Notochord does not persist.
  • The eyes have eyelids.
  • A tympanum represents the ear.
  • Respiration is by gills, lungs, and through the skin.
  • Larvae with external gills which may persist in some aquatic adults (like salamanders).
  • The heart is three-chambered (two auricles & one ventricle).
  • The alimentary canal, urinary & reproduction tracts open into a common chamber called cloaca which opens to the exterior.
  • Kidneys are mesonephric.
  • Excretion is ureotelic.
  • They are cold-blooded animals.
  • Sexes are separate. Fertilization is external.
  • They are oviparous & development is direct or indirect.
  • Example: Ichthyophis (blind-worm), Ambystoma (American salamander), Hyla (tree frog), Necturus (Mudpuppy), Alytes (Midwife toad), Bufo (Toad), Rana tigrina (Indian Bullfrog)
Fig: Rana tigrina



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