Re: why can't animals besides amphibians absorb oxygen through their skin?

All forms of life on earth have evolved through a process of adaptation to 
the environment, and the properties of each according to the surroundings 
in which it lives.
Amphibians are those which can live on both land as well as in water. To 
survive in such dual atmospheres requires certain adaptive tendencies. 
They have nostrils(nose) for use on land, ad while they are in water, they 
often just stay on the surface, their nostrils above the water level to 
help them breathe. But at the same time they also have a skin, which is 
like a memrane, helping in exchange of gases. 
Now take a look at birds and mammals and skme reptiles, whih are 
terrestrial, ie live only on land. Here, there is not much of a chance for 
them to go and start living in water. Hence, the skin in terrestrial 
creatures primarily serves the function of protection of the internal 
organs of the body.
Not that amphibians dont need such protection, but that is provided for in 
other forms such as camouflage.