digestion are used for smother land by reptile & breathing is a kind of function ->  lungs perform the function of breathing in birds  skin is used for breathing air by frogs & smother is a mean of kaput -> skin performs the function of breathing in frogs skin performs the function of breathing in frogs  lungs perform the function of breathing in birds & skin performs the function of breathing in frogs -> gear in reptile and bone on rarefactions both perform the kaput of smother lungs in birds and skin on frogs both perform the function of breathing  lungs in birds and skin on frogs both perform the function of breathing & if one nothing perform the same kaput then those one nothing are similar -> the function of skin on frogs is similar to the function of lungs in birds