Everything you need to understand or teach There Is a Wolf in My Time Machine by Larry Niven.
Hanville Svetz is a wanderer through time, usually very lost without knowing it.
His job is to ride a time machine, an "extension cage," back to the pre-Atomic era and retrieve extinct animals for display. Eleven hundred years after the Atomic era, little is known about animals. Humanity has so polluted the world that only humans and dogs, both of whom have adapted their lungs and digestions to the pollution, survive. When sent back for a horse, he retrieves a unicorn, but with no one having seen a horse in thousands of years, the unicorn is accepted as a horse. What we readers quickly realize, but Svetz and the engineers of the time machine do not realize, is that Svetz is retrieving animals that never existed; they are products of myth, legend, and fiction. (Moby Dick makes a cameo appearance in another story about Svetz, "Leviathan!")