Summations Only

It had proved beyond any doupt that stress causes genes mutations.

So the mechanism for it exists in metazoa.

"Although most mutations are believed to be caused by replication errors, they can also be caused by various environmentally induced and spontaneous changes to DNA that occur prior to replication but are perpetuated in the same way as unfixed replication errors. As with replication errors, most environmentally induced DNA damage is repaired, resulting in fewer than 1 out of every 1,000 chemically induced lesions actually becoming permanent mutations. The same is true of so-called spontaneous mutations. "Spontaneous" refers to the fact that the changes occur in the absence of chemical, radiation, or other environmental damage. Rather, they are usually caused by normal chemical reactions that go on in cells, such as hydrolysis. These types of errors include depurination, which occurs when the bond connecting a purine to its deoxyribose sugar is broken by a molecule of water, resulting in a purine-free nucleotide that can't act as a template during DNA replication, and deamination, which results in the loss of an amino group from a nucleotide, again by reaction with water. Again, most of these spontaneous errors are corrected by DNA repair processes. But if this does not occur, a nucleotide that is added to the newly synthesized strand can become a permanent mutation."

I see a lot of vague claims but zero evidence.

So environment causes gene mutations!

In that case we would have a serious evidence or not of guided mutations.

zi ko writes:In that case we would have a serious evidence or not of guided mutations.

Catholic Scientist writes: Sure, but it really doesn't have any impact on the evolution of species.

I'm guessing you really meant to something about guided evolution since any mutation, regardless of ultimate cause, can have an impact on evolution.

Catholic Scientist writes:Your right. What I meant was that environment caused mutations aren't really that important when we're considering the evolution of speices. Sure, they aren't non-existant, but do they really matter? Meh, not so much. They don't really (read: an appreciable amount) affect evolution.

You may be unduly minimizing the impact of environmentally caused mutations on evolution.

Environmental stress can increase mutation rates.

A population under environmental stress and possibly facing eventual extinction has a better chance of evolving it's way out of its predicament if it has a higher mutation rate.

I think the current understanding is that environmentally caused mutations can matter a great deal.

So environment causes gene mutations!

There isn't any relation as to if the error repairing actions are directed to special types of mutations, leaving others to perpatuate.

How's that work? What's the mechanism?

But a particular mutation isn't caused by the enivronment in these cases, is it? I know it is possible for the evnironment to directly cause a mutation, but that's not the same thing as the environment increasing mutation rates. And an environmentally increased mutation rate doesn't have anything to do with guided evolution.

What has this to do with how novel features evolve?

zi ko writes:If cells are directing repairing mechanisms only to some specific DNA damage and not all, then there is surely a matter of guided evolution.

I think the current understanding is that environmentally caused mutations can matter a great deal

Yes, and those mutations are random with respect to fitness. We are all aware that chemical mutagens and radiation cause mutations. We are also aware of things like the SOS response in E. coli. In each case, the mutations that are produced are random with respect to fitness.