Evolution of the eye

[dimreepr]

First, we need to know :

1. Electromagnetic radiation:

The energy of photons, having properties of both particles and waves. The major wavelength bands are, from short to long: cosmic, ultraviolet, visible or "light," infrared, and radio.

2. Quantum:

The amount of radiant energy in the different orbits of an electron around the nucleus of an atom.

3. Quantum mechanics:

The theory that has been developed from Max Planck's quantum principle to describe the physics of the very small. The quantum principle basically states that energy only comes in certain indivisible amounts designated as quanta. Any physical interaction in which energy is exchanged can only exchange integral numbers of quanta.

Now, The visible light that we see, the x rays that dentists use, and the radio waves that carry music to our radios are all forms of electromagnetic radiation. Other forms include the microwaves which we use to cook food and gamma rays which are produced when radioactive elements disintegrate. Although they seem quite different, all types of electromagnetic radiation behave in similar ways. If you think about it, the shadows of our teeth that are produced by x rays and captured on special film are really not that different from our visible shadows cast by the sun. If x rays and light are essentially the same, why is one visible to our eyes and the other invisible?

We know that visible light comes in many different colors, like those we see in a rainbow. The colors can be understood by thinking of light as a vibration moving through space. Any vibration, or oscillation, repeats itself with a certain rhythm, or frequency. For light, every shade of every color corresponds to a different frequency, and the vibration of blue light, for example, has a higher frequency than that of red light.

It turns out that our eyes can only detect electromagnetic radiation for a relatively narrow range of frequencies, and so only those vibrations are "visible."

However, other forms of electromagnetic radiation are all around us with frequencies our eyes cannot detect.

If our eyes could detect very high frequencies, we could see the x rays which can pass through many solid objects just like visible light passes through tinted glass.

Originally, vibrations of light were thought to be somehow similar to water waves. The energy carried by that kind of vibration is related to the height of the wave, so a brighter source of light would seem to simply produce bigger waves. This idea provided a very effective way of understanding electromagnetic radiation until about 100 years ago. At that time several phenomena were found which could only be explained if light was considered to be made up of extremely small pieces or "wave packets," which still had some of the properties of waves. One of the most important phenomena was the photoelectric effect. It was discovered that when visible light shined on certain metals, electrons were ejected from the material. Those free electrons were called photoelectrons. It was also found that it took a certain minimum amount of energy to release electrons from the metal. The original vibration concept suggested that any color(frequency) of light would do this if a bright enough source (lamp) was used. This was because eventually the waves of light would become large enough to carry enough energy to free some electrons. However, this is not what happened! Instead it was found that, for example, even dim blue light could produce photoelectrons while the brightest red light could not. The original vibration theory of light could not explain this so another idea was needed.

In 1905 Albert Einstein suggested that this effect meant that the vibrations of light came in small pieces or "wave packets." He also explained that each packet contained a predetermined amount (or quantum) of energy which was equal to a constant multiplied by the frequency of the light. This meant that a bright source of a particular color of light just produced more packets than a dim source of the same color did.

If the energy, and therefore the frequency, of a packet was large enough, an electron could be freed from the metal. More packets of that frequency would release more electrons. On the other hand when the energy of a packet was too small, it did not matter how many packets struck the metal, no electrons would be freed.

This new idea explained all the newly discovered phenomena and also agreed with effects that had been known for hundreds of years. Einstein's wave packets became known as photons, which are somehow like indivisible pieces (like small particles) and also like vibrations. The discovery of this split personality was one of the factors that led to the theory of quantum mechanics.

Light from a lamp consists of photons. Why does the light we see appear to be reaching us continuously instead of in lumps?

Well, this is actually easy to understand by performing an experiment with sand. First, we need to fill a plastic bucket with sand and hold it over a bathroom scale. Next, we make a small hole in the bottom of the bucket so that sand will slowly drain out and fall on the scale. As more and more sand collects on the scale, we will see that the weight increases in an apparently continuous manner. However, we know that sand is made up of particles and so the weight on the scale must really be increasing by jumps (whenever a new grain of sand lands on the scale). The trick is that the size of the grains is so small that the individual increments by which the weight changes are too small for us to detect. The same thing happens with light, only in a more exaggerated way. If we look into a lamp (not recommended) there are billions photons reaching our eyes in every second, with each photon carrying only a small amount of energy.

 

Why would evolution over design the eye, evolution responds only to need.

[muhammad]

Why would evolution over design the eye, evolution responds only to need.

Actually, I do not believe in the" evolution theory"; since the anatomy of our eye is the same as the one of a human lived 10000 years ago. So "evolution" has nothing to do with this topic.

[immijimmi]

Actually, I do not believe in the" evolution theory"; since the anatomy of our eye is the same as the one of a human lived 10000 years ago. So "evolution" has nothing to do with this topic.

 

Sorry, I have to butt in here against my better judgement to say that evolution is slightly more than a theory, to put it lightly. For some reason science differs from other subjects and disciplines in that its 'theories' are backed by evidence. We have discovered fossils for practically every possible evolutionary stage from caveman to modern-day human, for example. And yet, some people refuse to believe that this means anything because they are ignorant of the facts. I don't like ranting, and I certainly won't force beliefs on you, but please, please look at the information available before you make up your mind. Also, according to evolutionary theory the anatomy of our eyes has changed over time significantly, so it is relevant.

[dimreepr]

Actually, I do not believe in the" evolution theory"; since the anatomy of our eye is the same as the one of a human lived 10000 years ago. So "evolution" has nothing to do with this topic.

 

 

Your belief is quite irreleveant here, but even if your statement, that the eye hasn't changed for this period of time only establishes the fact that need is necasary for evolution to work.

[dimreepr]

Actually, I do not believe in the" evolution theory"; since the anatomy of our eye is the same as the one of a human lived 10000 years ago. So "evolution" has nothing to do with this topic.

 

 

Ok so why would the creator over design the eye?

[IM Egdall]

Actually, I do not believe in the" evolution theory"; since the anatomy of our eye is the same as the one of a human lived 10000 years ago. So "evolution" has nothing to do with this topic.

 

I recommend you read Kenneth Miller's book, Finding Darwin's God. It is a compelling case (overwhelming case actually) for evolution, based on actual evidence. And Miller gives a clever explanation of how his religious beliefs on God fit with the science. Plus Miller explains the evolution of the eye.

Edited January 7, 2012 by IM Egdall

[Moontanman]

Actually, I do not believe in the" evolution theory"; since the anatomy of our eye is the same as the one of a human lived 10000 years ago. So "evolution" has nothing to do with this topic.

 

 

Eyes had already evolved far before humans did and we inherited those eyes from our ancestors, eyes did not originally evolve in humans and humans do not have the best eyes in the animal kingdom...

[questionposter]

This is going off topic, and besides evolution isn't a theory, its a sequence of chaos, of random changes on multiple levels simultaneously.

Edited January 7, 2012 by questionposter

[swansont]

!

Moderator Note

Split from http://www.scienceforums.net/topic/62690-photon/page__gopid__649500#entry649500

[questionposter]

Why would evolution over design the eye, evolution responds only to need.

 

Evolution doesn't "respond", things can happen that cause a species to evolve, but evolution as a whole doesn't respond, it's just genes being altered and some happen to be more successful for surviving the environment they are in making it more likely for them to get passed on. The evolution of eyes took a very long time, at first eyes were only exterior organs that told an organism just whether or not it was bright out. After a lot of gradual alterations through millions of years, we get the eyes we see today. Eyes help things survive by letting organisms know what outside of themselves, so better eyes having the ability to help organism survive will be likely to get passed on where they have a chance to get mutated into even better eyes.

[Sorcerer]

Cephalopods eyes are better than ours. We have a blind spot where the optic nerve runs through our retina. Also we can only see in a small range of the spectrum, our eyes are not perfect - this shows evolution at work, why would a creator design anything less than perfect?

[Greg Boyles]

Actually, I do not believe in the" evolution theory"; since the anatomy of our eye is the same as the one of a human lived 10000 years ago. So "evolution" has nothing to do with this topic.

 

http://en.wikipedia.org/wiki/Evolution_of_the_eye

 

Compound eyes first evolved in the Cambrian period some 500 million years ago. The extinct triloites were among the first life forms to possess them and in fact their compound eyes are unique in evolutionary history in that they had lenses composed of calcite......calcium carbonate........effectively stone.

 

Since then complex lensed eyes have evolved independantly many times in many different types of animals and thet all share common components and common genes.

 

While it is impossible for a complex eye to evolve in a given species in 100s or 1000s of years, leading you to the false conclusion they must have been created by your god, it is highly likely that they might evolve in a given species in 100s of millions of years. 100s of millions of years is a LOOOOOONG time for tiny genetic and anatomical changes to imperceptibly accumulate and produce a functional complex eye.

[Fuzzwood]

That is the trouble with creationists, they see evolution as a sentient entity, while science has labeled it as a phenomenon. Get off your high stick that the eye was suddenly there. It wasn't. The very first eye was most likely a simple light receptor to figure out if it was day or not.

Edited January 8, 2012 by Fuzzwood

[Greg Boyles]

The very first eye was most likely a simple light receptor to figure out if it was day or not.

Not most likely but definitely.

 

I believe some flat worms and clams have simple eye spots that do no more than detect light or shadow.

[CharonY]

The first photoreceptors can be found in bacteria. Usually in photosynthetically active ones that also exhibit phototaxis.

[Tres Juicy]

Why would evolution over design the eye, evolution responds only to need.

 

 

The first basic light sensing cells (which would have occurred as a result of random mutation) were obviously usefull and were passed on to the next generation. As time went on the creatures with the more sensitive light sensing cells obviously did better than the ones without or with less sensitivity to light, so passed on their dna more often -eventually resulting in the complex eyes we have today - hence evolution at work

[Laurens]

Read 'Climbing Mount Improbable' by Richard Dawkins, he explains how the eye could have evolved. It's really not much of a problem for evolution.

[Tres Juicy]

Read 'Climbing Mount Improbable' by Richard Dawkins, he explains how the eye could have evolved. It's really not much of a problem for evolution.

 

 

Good call

[iNow]

Or, watch the video from more than 20 years ago:

 

[Tres Juicy]

Or, watch the video from more than 20 years ago:

 

 

 

Even better!

[Edtharan]

The best eye I have heard of is the eye of the Mantis Shrimp. We have only 3 colour receptors in our eyes, they have 16 and can even see the differences in circularly polarised light (afaik no other animal can do this).

 

Compared to these guys, the human eye is severely underdeveloped.

[dimreepr]

The best eye I have heard of is the eye of the Mantis Shrimp. We have only 3 colour receptors in our eyes, they have 16 and can even see the differences in circularly polarised light (afaik no other animal can do this).

 

Compared to these guys, the human eye is severely underdeveloped.

 

 

This must take a huge percentage of it's brain to process.