two chains
amphibian
A porcupine is a mammal because it does'nt meet all the characteristics of the others
Because it is. There's not really a "why". If you mean "what are the characteristics of a dolphin that show that it's a mammal and not a fish or amphibian", it's warm-blooded, produces milk, and gives birth to live young.
amphibian
No, a dolphin is a mammal, not an amphibian.
A rhinoceros is a mammal, not an amphibian.
An orangutan is a mammal.
MAMMAL
A chimpanzee is a mammal
A bat is a mammal.
The donkey is a mammal. The frog is an amphibian.
Frogs are amphibian. Not a reptile an not a mammal but a amphibian