An animal's teeth is an adaptation for the food that it eats.

If herbivore jaws are available:
Look at the herbivore jaw bones and teeth. (Photo shows lower jaws of herbivores, from top to bottom: moose, vole, deer.)
Herbivores have teeth that are adapted to smash up plants. Their incisors at the front of the jaw (these are often missing from a found jaw) snip off the plant stems and leaves. To grind the plants they use their molars, which have sharp ridges on the top and fit together perfectly to smash the plant cells open.
3D view of positioning teeth in a mouse jaw: https://www.youtube.com/watch?v=oLn70NiouS4

With a skull and associated jaws:
Insert the jaw bones in the skull and show how tightly the teeth fit together. Show how the jaw moves sideways to mash plants between the teeth.

If carnivore jaws are available:
Carnivores need sharp teeth to catch prey and rip meat. Canines are huge, and even on domestic animals they can be terrifying (show cat and dog photo). Incisors are tiny. The molars are sharp to shred meat.
Look at real carnivore skull to see teeth (e.g. I have cat skull with upper jaw including canines)

Look at human teeth:
We are omnivores - are jaws and teeth are adapted to eat both meat and plants.
Students use a mirror to find the different kinds of teeth in their mouth: incisors, canines, molars (use illustrations to show the different types)
Canines are there but small - between the two.
Incisors are more like herbivores though no where near as big.
Molars are between the two.
We are omnivores. (Same as bears and racoons.)