How does evolution explain the formation of the eye?

Answer 1

It happened over a few steps;
1. A light sensitive area formed allowing the animal (actually it was just a lump of slime, but I'll be nice ot it) to detect the amount of light directly. This is important for regulation of processes like photosynthesis.
2. The light sentsitive patch became concave, allowing direction to be determined. This helped the animal become aware of it's surroundings. If there is another object casting a shadow, it can roughly see it. (Some of them formed convex to acheive the same end, but they didn't evolve further.)
3. The concave patch became deeper, allowing for better definition, then the mouth started to close in which allowed an image to be formed. The only problem with this is that the image is quite dark, so it's very difficult to see in dim light.
4. A lens goes in, making the image brighter, and you basically have the eye that we all know and love today. :)

Answer 2

Actually, the eye is a great example FOR evolution, not against it.

Technically, the light comes from the wrong direction for the photoreceptors to hit it optimally.

That is because the eye folded out from the brain. In a process of evolution.

The other optical properties are terrible, too. If you circumvent the optics of the eye, you can see 100 cycles per degree of spatial frequency, in other words, like an eagle. We're working on that.

So in terms of design, the design of the eye is not very intelligent at all.

Answer 3

This is a very interesting question. It has recently been discovered that the DNA codes for "light sensing nerve cell" are the essentially identical in jellyfish and in humans and in fruit flies and in all other animals that have any light sensing capability at all. It seems that this was the essential ingredient, and various forms of eyes have evolved independently around this light sensing ability with a huge variety of results. The most interesting thing to me is the eye of the squid and/or octopus, which is essentially identical to our own but clearly evolved independently. If we ever encounter intelligent aliens, I think there is a good chance they too will have something closely resembling our eyes.

Answer 4

Imagine a creature with a single light-sensitive cell. Such visual systems exist (flatworm, was it?).

There are 2 very general styles of scaling up from this seen in animals:
something like the compound eye of a fly; and
something like my eye, which is very like those of other vertebrates.

Both of these are like bundling together very many of the flatworms' eyespots into one. Good idea. A simple design, and you see how effective it is... The complexity of the eye is not complexity of design, but of the sort of inefficiency that comes from relying on evolutionary algorithms. (If God had designed our eyes, He'd have used less parts -- it'd be more like a video camera (incidentally, the way wE apparently would design an eye)).

It is not necessarily that natural selection will favour better vision. Indeed, often an animal's needs are better served by shorter vision. Hence, eagles are sharper seers than we, not because their eyes have been evolving longer (obviously, their eyes have been evolving precisely as long as ours have).

Answer 5

An eye is a superb light sensing device. Numerous animals today have patches of light sensitive cells. Needless to say, vision is an extremely useful ability for any creature so even the tiniest mutation towards better eyesight will confer an immediate advantage. The superb complexity of such a useful organ is actually evidence in favour of natural selection.

Answer 6

This is a question usually raised by ignorant fundamentalists who are seeking to discredit the Theory of Evolution. Fortunately there are good explainations for the evolutionary development of the eye. Several earlier replies to your question supply good answeres. But you will want to do more studying to become familiar with this issue as it is only one of several attempts by ignorant fundamentalists to ridicule something they don't understand.

Answer 7

The human eye is actually poorly designed if you were to do it yourself.
A good design would see farther into the infrared and ultraviolet wavelengths and would be able to see at much lower light levels.
Too bad there was no intelligent design at work here.

Answer 8

I don't know all the details, but I think it has to do with symbiotic co-operation and co-evolution.