Amphibians

Evolutionary Perspective of Amhibian's!

(amphibia means living a double life)

                                Class amphibia includes frogs, roads, salamandars, andcaecilians.Class name shows that amphibians move between water and land.They spend one stage of their life in water and another on land.

   

Philogenetic Relationships of  amphibians!

Evolution of land vertebrates:

                                               Many adaptive radiations are produced in vertebrates during first  250 milion years of vertebrates history.Thus the vertebrates filled most aquatic habitats .Prehistoric water contained many active powerfull predators.However vertebrates were absent on land.Only some arthropods lived there as predators.Therefore,there was no vertebrate predator on land to capture animals that moved near the edge.Some vertebrates developed luns for breathing and muscular fins for moving.These animals found ample food on land in the form of arthropods.The arthropods are the major of the diet of most modern amphibians.Thus evolution of amphibians took place.Then adaptive radiations were produced in amphibians .It produced greater variety of amphibians than exists today .Later convergent and parallel evolution took place in amphibians .Then widespread extinction took place .

                            Lungs of Frog!

First Amphibian:

                          No one knows what the first amphibian was .The structure of limbs,skulls and teeth of  lchthyostega are similar to the earliest amphibians. Two lineages of amphibians are formed in the late Devonian and early Carboniferous periods. These lineages can be differentiated by the structure of roof  and the attachment of posterior potion of the skull to each other. 

1. Amniotic lineage: One lineage of amphibians became extinct in the late carboniferous periods. An amniotic egg evolved in this group. It resisted dryness. This lineage is called the amniotic lineage .This lineage forms reptiles,birds and mammals.