But dido, speciation (that is, the process of one species turning into two species) does occur. It has even been observed by scientists--it's not in doubt. See this link for more information.
Here's the deal--that's evolution. Those things (selection of traits, environmental adaptation, mutation, speciation) ARE evolution. If you accept that they all exist, and it would be hard not to, then you accept evolution.
It's not nearly as sinister as you thought, is it? And really, if you believe in God, it's a wonderful testament to God's cunning and inventiveness. It's an amazing part of the natural world we live in, and it's yet one more glory to God.
Evolutionary biologists say a lot more things, though--they say the biological facts listed above mean that we share a common ancestor with chimpanzees, for example. Well, I doubt you'd disagree that humans are related to monkeys--our DNA is mostly the same, and our bodies and organs and even social patterns are very similar. If you're related to somebody, doesn't that mean that you share a common ancestor with them?
Whether you want to make that additional step is up to you. But you believe in evolution, as it stands--and you don't even have to give up God to do it. You might have some trouble making Genesis literally true, though...
But then nobody in the world thinks that every word in the entire Bible is literally true. Nobody.