Evolution of the Eye

[LJP07]

Evolution provides fascinating insights into how such things like the formation of the eye, wing formation and camouflage among other great adaptations evolve. However while the theory on how these form is desirable, I can't seem to fully comprehend the understanding for the explanation of the evolution of the eye.

 

For example, I fully understand the wikipedia article among many which describes the same thing:

 

Evolution of the eye - Wikipedia, the free encyclopedia

 

They all claim that a group of photosensitive cells existed first with the surrounding epithelium and that a pouch formed, filled with fluid, formed a lens and became more complex. But how did the first photosensitive cells evolve and what triggered their formation in the flat epithelium?

 

Likewise, how did a "Pair" of eyes form and why did the photosensitive cells form in symmetrical locations, I understand why it occurred in terms of survival, but in terms of evolution why did it occur this way?

[Thunderbird]

Evolution provides fascinating insights into how such things like the formation of the eye, wing formation and camouflage among other great adaptations evolve. However while the theory on how these form is desirable, I can't seem to fully comprehend the understanding for the explanation of the evolution of the eye.

 

For example, I fully understand the wikipedia article among many which describes the same thing:

 

Evolution of the eye - Wikipedia, the free encyclopedia

 

They all claim that a group of photosensitive cells existed first with the surrounding epithelium and that a pouch formed, filled with fluid, formed a lens and became more complex. But how did the first photosensitive cells evolve and what triggered their formation in the flat epithelium?

 

Likewise, how did a "Pair" of eyes form and why did the photosensitive cells form in symmetrical locations, I understand why it occurred in terms of survival, but in terms of evolution why did it occur this way?

 

 

 

The first part is how the cells differentiated into the group of photosensitive cells. Adaptation and natural selection are the main drivers of change, however when we attempt to gain an understanding of how these finely tuned structures could form it is apparent we need to fine tune our terms of adaptation. Terms like natural selection, adaptation, random mutation, are indeed accurate, but do not address directly how these instruments are so finely tuned to incoming information at large. Energy such as light contains variables. A spectrum. This spectrum represents and contain not only energy and information, but more aptly information about energy of the outside environment. The developing biological instruments forms around the information that flows though it, Therefore one could define an eye as a finely tuned persistent structure that can conduct information in a quantum wave form that also has its origins from that wave form, therefore only persist because of it.

 

As far as why their are two eyes, one needs to consider the nature of bilateral symmetry in morphology ,and how this relates to symmetry as a mathematical construct in general. Morphological geometry forms around a basic 3 dimensional axis's of movement, forward: right-left For the simple creature that begins to orient itself toward a target it needs to distinguish between dual incoming informational centers. This is why the body plan developed into two parts. The same would apply for ears. If you had only one ear you could hear but you would have no way to tell where the sound is coming from.

[Thunderbird]

One of the principles of self-organizing systems of evolution is a property quantum mechanics. Information in the form waves that can be split in two equal divisions but containing an equal spectrum that can be interfaced , or “braided” back together. This division and reunification creates an oscillation between the separate points of reference. These oscillations pit one system against the other to constantly seek an equilibrium. Since this equilibrium can never be reach to the fact the dual systems are separated as opposites they can only gain more information and subsequently more complexity.

[Moontanman]

Evolution provides fascinating insights into how such things like the formation of the eye, wing formation and camouflage among other great adaptations evolve. However while the theory on how these form is desirable, I can't seem to fully comprehend the understanding for the explanation of the evolution of the eye.

 

For example, I fully understand the wikipedia article among many which describes the same thing:

 

Evolution of the eye - Wikipedia, the free encyclopedia

 

They all claim that a group of photosensitive cells existed first with the surrounding epithelium and that a pouch formed, filled with fluid, formed a lens and became more complex. But how did the first photosensitive cells evolve and what triggered their formation in the flat epithelium?

 

The first creatures to develop photo sensitivity did so because it was an advantage to be able to orientate them selves to the light. Either they feed on light or they feed on creatures that used light or they had to migrate from light to dark for some reason of their biology. We do see this today in many creatures that other wise would have no use for eyes or photosensitivity at all.

 

Likewise, how did a "Pair" of eyes form and why did the photosensitive cells form in symmetrical locations, I understand why it occurred in terms of survival, but in terms of evolution why did it occur this way?

 

First it's important to understand that not all creatures have two eyes, a great many animals have lots of eyes, spiders have several, some other arthropods have more than two eyes. Two eyes are thought to be necessary to see in stereo (depth or distance) Two eyes are the minimum for stereo vision and in evolution animals seldom have more of anything than they actually need. This why cave animals are often blind, the energy necessary to grow eyes is used for other things. Two eyes in vertebrates is often thought to be universal on the earth but some reptiles have three. One in the middle of the two regular eyes, this eye is under the skin and not used for vision but it is sensitive to light. Eyes are on the head in vertebrates so an animals can see where it is going and be close to the brain. So although we have two eyes the more primitive animals often have more so the premise of why two eyes developed is not the correct idea to ask about. Two eyes did not develop from simple photosensitive cells, two eyes came later after the number of eyes had varied drastically among different life forms.

[Thunderbird]

Good point MoontanMan, not all creatures have two eyes such as the spider, but

they are symmetrically arranged bilaterally along the body plan. The number does not tell you as much as the geometry. This is an important point that should not be over looked.

[LJP07]

Thanks all, it makes much more sense now.

[Moontanman]

Good point MoontanMan, not all creatures have two eyes such as the spider, but

they are symmetrically arranged bilaterally along the body plan. The number does not tell you as much as the geometry. This is an important point that should not be over looked.

 

I hadn't thought of that, I was going to say the cyclops has only one eye but I think they have one big one and several tiny ones but I'm not sure.

[Thunderbird]

I hadn't thought of that, I was going to say the cyclops has only one eye but I think they have one big one and several tiny ones but I'm not sure.

:edepress: Have you been taking silly pills again?

[Moontanman]

:edepress: Have you been taking silly pills again?

 

Nope, I used to culture them as fish food, lots of vernal pool varieties too. some eat algae but most eat other tiny crustaceans.

[Thunderbird]

Nope, I used to culture them as fish food, lots of vernal pool varieties too. some eat algae but most eat other tiny crustaceans.

Ok,:hihi: I thought you were talking about the one that eat Greeks.:edepress:

Got any pictures? Are they like hydras?

[Moontanman]

Ok,:hihi: I thought you were talking about the one that eat Greeks.:edepress:

Got any pictures? Are they like hydras?

 

Google Image Result for http://www.scientificillustrator.com/art/microscopic/cyclops.jpg

[freeztar]

Google Image Result for http://www.scientificillustrator.com/art/microscopic/cyclops.jpg

 

Very interesting!

 

It's interesting to note that it still displays morphological bilateral symmetry.

 

Are there other examples of "uniphotos"?

[Thunderbird]

I like their shape, would make a good subject for a gem sculpture. Tiger eye or maybe jade.

[Moontanman]

I like their shape, would make a good subject for a gem sculpture. Tiger eye or maybe jade.

 

Lots of vernal pool shrimp are interstingly shaped. Clam shrimp, seed shrimp, tadpole shrimp and fairy shrimp.

[jab2]

The evolution of the eye, or rather spontaneous appearance as they want to argue, is one of the classic examples non-believers in evolution uses to "show" why evolution is a lie. It is thus with great interest that I try and follow all discussions pertaining to it.

 

The whole development from photo sensitive cells on a flat surface through all the different stages is always very well explained. There is however always the nagging question as to why cells needed to be sensitive to light in the first place and this is never not very well answered.

 

The following is pure speculation on my part, as I have never came across a proper explanation of why there were a need for photo sensitive cells on the outside of an organism.

 

If one look at chemistry, virtually all chemical reactions work better or faster when heated. As the molecular workings of any organism is pure chemistry, one can argue that gaining heat from the environment must have been beneficial for an organism, or at least the proto-cold blooded ones. This ability to find hotter environments would definitely favour organisms which were slightly sensitive to heat. But heat is "light" in the infra-red region of the spectrum, and heat and light as supplied by the sun are "cousins". They are both present at the same time, so organisms need not only favour the mutations that had heat sensitive outer covers to find heat, but mutations with a light sensitive skin will also have the ability to find heat. It is thus very easy to envision an evolutionary benefit for light sensitivity on the outside of an organism.

 

At danger of stealing LJP07's light, I mean thread, I would like to hear your comments on this argument. I would also appreciate pointers to resources on this issue, as I am sure I am not the first to argue this path of development.

[LJP07]

With respect Jab2, that's the primary point I was trying to ask, why is there a need for photosensitive cells and why do they occur in what seems to be randomness in terms of position and no satisfactory explanation as to why the photosensitive cells formed in the very initial first place with just a layer of skin.

[Moontanman]

With respect Jab2, that's the primary point I was trying to ask, why is there a need for photosensitive cells and why do they occur in what seems to be randomness in terms of position and no satisfactory explanation as to why the photosensitive cells formed in the very initial first place with just a layer of skin.

 

I think I answered this once but just in case, a limited area a of photo sensitivity allows an animal (bacterium or protozoa) to be able to figure out where the light is coming from. Just knowing it's light might be good enough for some bacteria but an animal who needs to follow the light for some reason needs to be able to know which direction the light is coming from. larger more complex animals have the same needs so most really primitive eyes are just light detectors that allow the animals to know where the light is coming from. If the entire animal was equally sensitive to light it wouldn't know where the light is coming from. Cells in a limited area allow the animal to not only know where the light is coming from it allows the animal to orient it's self to the light. the more specialized this area becomes the better the animal can follow the light. later light can be used as a passive way to find out about the environment, avoiding shadows to avoid predators, that sort of thing.