but that's the basic flaw with your understanding of evolution - why would a cat become a dog ?
Oh boy.. If you can't grasp the concept of examples then it's no wonder you believe in evolution!
Oh, and, given what should be possible with evolution, why would a dog or cat not be able to evolve into the other? Given the right environmental pressures etc... Or do you think cats would only evolve into rather vain human-like creatures, over oh.. 3 million years in space or so?