Evolution is most definitely considered credible -- to those who have made a study of the subject. You might take a look at this: mutations create new variation, which I found quickly, and it only hints at the information which is available on this subject.
Coming to this subject new, as you apparently are, it's easy to be unaware that all of your objections have been dealt with for generations. If your only source of information is what you glean from hanging out at creationist websites, then you are cheating yourself. Anyway, if you are interested in the subject, you ought to study it systematically. You would be amazed at how exposure to already-existing information will change your views.
I'm moving on now. Please, don't imagine it's because your objections to evolution have overwhelmed me and that you have thrown 150 years of biology into a tizzy. I just don't have the time for this thread right now. It's been good chatting with you.
That article is faulty in assuming that there was not the potential for variation in the orignial bacteria. Until scientists fully understand all of the bacteria's code and how it functions, they cannot claim that variation only comes from mutation and was not already inherent in the code in the one bacteria.
It's not sufficient to say they all came from one chromosome, because until you understand the functionality of recessive genes and all DNA (previously called junk DNA) you can't claim that the variation is exclusively mutations.
Nevertheless, I'm not saying variations don't arise from mutations, just that most of those are negative.
But I agree let's move on.