digestion are used for smother land by reptile & smother is a mean of kaput ->  lungs perform the function of breathing in birds  bone is used for smother land by sand & smother is a mean of kaput ->  skin performs the function of breathing in frogs  lungs perform the function of breathing in birds & skin performs the function of breathing in frogs ->  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