A simple eye consists of a few light-sensitive cells. ThatÃ¢â‚¬â„¢s it. The next step in complexity is some sort of lens, so that an image can be focused.
A "reaction to visible light" is not an eye.
Why would it result in resistance? As I already explained, the animal would be exposed to the same amount of light whether it could see it or not. Even if UV light is very harmful to the animal, there would be no reason for it to lose the ability to detect it. In fact, that would be a reason for light sensitivity to stick around in that animal. When we touch something thatÃ¢â‚¬â„¢s hot, we burn our hands. We havenÃ¢â‚¬â„¢t developed a resistance to the pain associated with burns, because itÃ¢â‚¬â„¢s useful to our survival.
Even if these reactions result in better resistance, which is rationally all that would ever happen, they don't produce an eye.
Chemistry. More specifically, the laws of kinetics and thermodynamics that determine which direction a reaction will proceed in, and which way a protein will fold.
You said, "If the right components were placed next to each other,...", what/Who "places" those "components next to each other"?
When I posted the OP I really did have in mind what we observe today as eyes and ears
If thatÃ¢â‚¬â„¢s what you had in mind, then you were already setting yourself up to believe that eye evolution is impossible. Of course something is impossible when you take out all the steps in between, the first of which would be the development of a reactive pigment. You canÃ¢â‚¬â„¢t go from no eyes to complex eyes and brains in a single step.
I already agreed with you on that. But as I said, hearing is nothing more than sensitivity to pressure changes. If you can detect the changes in air pressure which correspond to sound waves, you can hear.
And that a thing can sense air pressure changes doesn't mean it can "hear".
IÃ¢â‚¬â„¢ve given you an explanation. IÃ¢â‚¬â„¢ve explained how a mutation could lead to a pigment which reacts with light. IÃ¢â‚¬â„¢ve explained how pressure sensitivity is useful, and the most sensitive animals will be more likely to survive.
There is no explanation, from evolution, that gives us the reason why/how eyes and/or ears ever came into existence.