Which of these organisms undergoes metamorphosis: a bear, a fish, a moth, or a dog?

 The term metamorphosis comes from the Greek language.  Meta- means "change" and morph means "shape." It describes a literal and dramatic change in the form of an organism.  A tadpole becoming a frog, a maggot becoming a fly, and a caterpillar becoming either a butterfly or a moth (depending on the species) are all examples of metamorphosis.  These changes are usually accompanied by a new set of behaviors and habitat for the organism. 

 Other animals, like the bear, fish, dog, or humans, do not undergo such drastic changes.  Sure, each of these organisms will mature and undergo puberty, which is still a pretty big change, but it will retain the same basic form.  Humans, for example, start and end life with a head, an abdomen, two arms, two legs, and no tail.