Evolve! Lite

Evolve! Lite (the "Lite" indicating the shareware version) is a life simulation game / simulator where two different life forms vie for supremacy. Rather than controlling the life forms directly, you change the environmental conditions and the creatures' behavior. The latter is controlled via a 3x3 grid of different actions the creature takes in different situations. The game is pretty slickly produced with a nice user interface and a decent help system with a tutorial. This is really not my kind of game but if the topic interests you, you'll likely find this to be an interesting piece of software.