http://www.talkorigins.org/faqs/genetic-drift.html
The above is an article on genetic drift.
There are no boundaries to accumulated genetic change. If a chromosome breaks up or comes together and transfers to a litter of animals in the sexual process, it might be the basis for a new chromosome number in a new species.
Since naturally occurring speciations only occur about 4 times in a million years in a given population, it is rather difficult to observe. Many speciations have been observed. Species do not necessarily have different numbers of chromosomes, however. I hope you don't think that is what constitutes a species.
Mother and daughter species are generally so close in characteristics it is difficult for anyone but experts to tell them apart. That is one reason why the nonsense the creationists put out about no speciation occurring is so dishonest. No one can tell a species differentiation in a skeletal structure. Only larger differences are apparent.
Thus, it may appear to the laymen that life forms jump by Family differences from one thing to another. This is just not true. Everything is done in species steps. This is what is known as "gradualism". It is only looking back in the fossil record and seeing the history of changes that scientists can observe large scale changes from one Class to another. The Reptile to Mammal changes are well documented. There is a paper on talk origins that discusses that too.
To be fully versed in paleontology or genetics to be conversant with all the details of even part of one of these subparts takes a lifetime of study.
If you like, besides talk origins there are many good sites that discuss various aspects of biological knowledge that I can give you. It would take weeks of reading to fully understand the basic principles and supporting data for evolution.
My most detailed knowledge is in invertebrates, especially Insecta and parasitology. But every biologist must know the principles of evolution to understand the big picture of how life functions and changes by interactions within its ecosystem.
One good general book you might enjoy is Darwin's Ghost. Another interesting book on a specific topic is Parasite Rex.
No, I know better than that. I was just looking for a discrete, measurable event that I could hold for discussion.
I hope you don't take this the wrong way...but I would find myself responding to you more favorably if you would stop disparaging my intelligence. You seem to take me for a creationist, which is no doubt the source of your disdain; what I am, however, is a layman with no vested interest in either direction.