Rats, lost a post when the site was being a bit glitchy earlier.
Okay, your post tells me that you do not understand variation. One of the main sources of variation is mutations that arise through reproduction. You have on the order of 100 mutations in the genome that you inherited from your parents. Most do nothing. In fact it is possible for all of them to be totally benign, neither advantageous or disadvantageous. Those that have an effect tend to be very small ones. If they are positive changes they increase the odds of being passed on. Negative ones reduce that possibility. These are all rather basic ideas that I will gladly support if needed. And I am sure that you know that mutations that have a strong effect are almost always negative mutations. It would actually take energy to prevent these variations. That is why I said that variation appears naturally.
As to a "system changing". You appear to be talking about an accumulation of changes that causes a noticeable difference. Those changes that are finally noticed are merely the accumulated small changes that were positive which are all but indiscernible when the mutations that caused them first appeared. Also most traits arise by the slow change of existing "systems". They do not appear full blown. And to understand this it helps to understand what a Vestigial Organ is. They are not the strawman version that creationists give of an organ that has lost all function. That does not tend to happen. A vestigial organ is an organ that has lost much of its original function. It often picks up a secondary function in the meantime. For example the stapes bone is technically a vestigial organ since it does not do a job that it had in the past. And the evolution of the mammalian ear is well known and can be traced through the fossil record.
Evolution of mammalian auditory ossicles - Wikipedia
The idea of sudden changes does not tend to occur very often at all. I see that
@pitabread brought up horizontal gene transfer. That is an example of variation that is sudden, but those genes had to arise by a slow process themselves. And they tend to occur mostly in single celled life. For multicellular life it is merely an accumulation of changes that occurred randomly and were put through the sieve of natural selection.
There is of course energy involved in growing, selection and reproduction. What I objected to is your idea that variation, the one process that occurs naturally and would take energy to prevent would ever stop.
Any questions? Just one at a time please since this is getting to be a more complex idea.