Evolution never stops at one place. In Evolution: The Origin of Species you created toxic predators, hid them in holes, and built compound chains of interactions. Your animals accumulated fatty stock, ran into hibernation, and rejected tails.
The Evolution: Time to Fly expansion opens new space for experimentation and change. Now you can hide your animals in strong shells, teach them to emit ink, and (as the title suggests) take to the skies. With ever-increasing change in the animal kingdom, you might think twice before attacking a harmless animal as it might not be defenseless prey, but rather a dangerous predator using itself as bait to catch you.
Evolution: The Origin of Species allowed players to create more than 50,000 different animals; with Evolution: Time to Fly, the number of possible combinations tops 50 million – more than the number of kinds of living animals on Earth.