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 name amphibian is derived from the Greek word "amphibious" meaning living a dual life.

• 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