Does the mutation on the evolution theory are based on pure hazard or it depends on the environmental changes?

By hazard, I assume you're referring to 'accidental change' within the genetic makeup...

DNA replication is like a copy machine, which is prone to make a certain amount of error, as the ink fades, so that the original changes slightly over time!

Barring radio-active alteration to DNA, there is a natural drift which occurs, and is represented by a successful mutation which can effect the population of a species through natural selection!

SoSo is correct. Mutation is usually a product of random genetic drift. The environment only affects the survivability of a mutation, both in the long-term and short-term. However, as Mr P points out, there are exceptions - in the form of mutagenic substances (such as radioactive checmicals). Here is a recent answer I gave to a similar question which discusses these issues in greater depth.

1st limitation: Most mutations are biologically meaningless and have no appreciable effect on evolution.

2nd limitation: For a mutation to be passed on to offspring, it must be attached to a sex cell. This does not happen all that often, and is only possible when the mutation occurs in the female of the mating pair.

3rd limitation: Mutations are more or less random genetic drift (except for mutations caused by mutagenic substances), so environments do not, generally, cause them or even affect their timing and how they play out.

Once a mutation occurs in a sex cell, the constraints discussed by Jerihuana above can take hold. The only difference between his opinion regarding the subsequent behavior of natural selection and my own vis a vis mutations is that I would argue that selective pressure does not really favor beneficial mutations, but rather simply filters out that which does not fit in the ecological niche occupied by the organism. In other words - it's not necessarily survival of the fittest, but survival of the adequate.

In summary, most mutations end up having no net effect on evolution. Under very specific circumstances, mutations may be passed on to offspring (whether or not they are beneficial). Most mutations which are passed on will not effect the organism's fitness. Once a mutation has a stable breeding population associated with it:

* if the mutation is beneficial it may give that population a competitive advantage

* if it is irrelevant it may continue to be passed on

* if it reduces the organism's fitness in its ecosystem, the organism may either move to a niche where the mutation is less of a problem or may become extinct.

There is more to all of this, but these are the basics. Note also that some people will disagree with my argument against "survival of the fittest" (which I view as a myth of progress). That's fine, but I strongly recommend reading Darwin and Stephen J Gould for a start before developing strong opinions on this subject.

Pure hazard. Environmental changes are the cause of natural selection and evolution, which means that the species will adapt to the environment. Mutation happens when a trait or characteristic is changed in the DNA. THe funny thing is, I just sdtudied that in Science today. =D I hope my answer helped you!

New Scientist article recons that land life started on a radioactive beach - work that one out!

eh?