Select the invertebrate.

 - pipevine swallowtail butterfly
 - human
 - whiptail lizard
 - cockatoo
A whiptail lizard is a reptile. Like other reptiles, a whiptail lizard is a vertebrate. It has a backbone.
A cockatoo is a bird. Like other birds, a cockatoo is a vertebrate. It has a backbone.
A human is a mammal. Like other mammals, a human is a vertebrate. It has a backbone.
A pipevine swallowtail butterfly is an insect. Like other insects, a pipevine swallowtail butterfly is an invertebrate. It does not have a backbone. It has an exoskeleton.