Your question indicates that you don't yet understand how evolution works. No one claims that you have fish in one generation and polar bears in the next. If that's what's bothering you, you can stop worrying. It doesn't happen, and of course no one will show you a fossil which somehow illustrates that it does. It takes a large number of tiny mutations, over thousands of generations, to accumulate into significant changes. The only fossils are of individual creatures, and each one is what it is. You need to look at the large picture, which stretches over millions of years, so see what existed before and after any particular fossil. Only then does the pattern emerge. Check out the links I gave you earlier. The evidence of such patterns is there.
And your statement assumes that evolution actually does work. :-)
Of course I understand that a trout does not suddenly give birth to a lion cub. Your statement indicates that you don't yet understand the basic statement I have been making; which is that there is no conclusive evidence to indicate these changes happen, even over the "billions and billions of years" (I always have to say that out loud in the Carl Sagan voice, BTW) that evolutionists like to use to pad the gaps in their "record."
People who don't agree with you aren't automatically "stupid."