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The Amphibians are creatures that have evolved from there fish ancestors but in the majority of cases are able to move onto dry land once the adult stages are reached. They return to the water to breed and the young invariably have gills to enable them to breath in water. Whereas the adults have lungs and nostrils to enable them to breath out of water. The amphibians include species like frogs, toads and newts plus others the lifestyles and cycles are all very similar so we shall discuss a general cycle.
Lets assume that it is breeding time and the adults have returned to the water to mate and spawn. After courtship the eggs are laid (fertilization can differ between species as to method) normally laid encapsulated in a gelentous covering,The eggs
which can be in masses or strings or even singularly deposited are then left to there own devices. Within a few days the eggs develop and soon tadpoles emerge, these are nothing like the adults as at this stage they have no legs and the propel themselves by the use of a tail. The delicate gill fronds which are external are used to process the oxygen from the water. Slowly the legs start to appear depending on species as to which develop first front or rear, at this stage the larvae are nearly ready to leave the water.
The last thing to change is the gills and once they have gone the miniature amphibian is air breathing and ready to leave the water. From this stage on they are able to survive away from the water and in some cases will not return again until ready to undertake there breeding cycle.
