[kahljorn]

"Also, anything foreign to the body could possibly also induce the same changes. New makes new? Maybe."

Adding to that; if an organism was at first built to survive off of certain chemicals or gases or molecules, like oxygen and carbon dioxide, what would the long term exposure to something it's not built to handle cause? Obviously, it has to have some sort of effect, if the body is exposed to anything it has to react, no matter what it is. Something as simple as being born at the bottom of the sea next to a volcanic vent would likely be used to high water pressure, while surfacing would create a different atmosphere entirely, exposing them to sunlight and possibly other chemicals/gases.
Again, the body HAS to react to these effects, whether it's a simple matter of drowning or being crushed by high pressure, or by being poisoned as a result of exposure to foreign gases and chemicals.
Anyway, go with what i said before off of shit like that. Different chemicals and gases, different minerals, yada yada, body using them for bodily material, yada yada stuff happening and stuff. Eatting foods it's not supposed to, stuff. stuff. yea.