Press [Shift] + [Alt] +C during game play.

You can also unlock special terrain maps by completing scenarios. For example, Rainforest Zoo will unlock the Rainforest zoo terrain.

You can unlock animals such as the Asian Black Bear, Przwlaski's Wild Horse, Albino Gorilla, Chinese Alligator, etc. Research the strongest fence and go to the bottom of the list of animals. All the ones after the Chinese Alligator are the ones that can be unlocked unlock during scenarios. Rainforest Zoo has the Przwlaski's Wild Horse and Asian Black Bear. Condition:Critical has the Albino Gorilla and Asian Black Bear.