Talk:Evolution of the eye
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Not sure what this means: It is biologically difficult to maintain a transparent layer of cells as sizes, therefore the thicknesses gradually increased. Graft 07:09, 22 June 2006 (UTC)
- Neither am I. The "as sizes" part is particularly baffling. I took the line (and much of the rest of the article's end) from Eye#Evolution of eyes. I think that the last two sections both need some significant cleanup and expansion; I couldn't find as many good sources for them as for the early stages of eye development, and the lens-formation stages are tricky to explain in layman's terms, so I gave up for the time being. -Silence 07:19, 22 June 2006 (UTC)
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- Very nice work, by the way. Graft 13:32, 22 June 2006 (UTC)
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[edit] Evolution of lenses
Completely disagree with the statement "The development of the eye is considered by most experts to be monophyletic". On the contrary, most experts would probably say that it seems to have developed at least 40 times independently. Perhaps the writer means the vertebrate eye.
In response to the request by Silence, I put together the diagram of major stages in the evolution of the eye. However, I'm not 100% happy with one of the diagrams, specifically diagram E, which shows the development of lenses. Some of the diagrams I looked at for reference (specifically this one and this one) appear to state that lenses derived from the cellular humor inside the eye, whereas the article itself states they evolved by "splitting" from the cornea. The diagram is not totally clear in this respect, but I'd like to know which of these is the most accepted. Were the diagrams I referenced out of date? Is there a difference of opinion over how lenses evolved? Did both situations happen in parallel? I'd like to make sure the diagram is as clear and accurate as it can be. I already raised this on Silence's talk page, but decided to throw it open to wider discussion here. ~ Matticus78 12:23, 10 July 2006 (UTC)
[edit] Vision and Intelligent Design
Propose actually citing and quoting a key ID proponent on vision as follows:
Howard Glicksman, M.D. reviews the human body's complex function and its challenges to macroevolution. [1] He extensively reviews the complexity of vision. [2] [3] [4]
Dr. Glicksman challenges macroevolution to explain:
- the extreme complexity and physiological interdependence of many parts of the eyeball
- the absolute necessity of many specific biomolecules reacting in exactly the right order to allow for photoreceptor cells and other neurons to transmit nervous impulses to the brain
- the presence of, not only an eyeball whose size is in the proper order to allow for focusing by the cornea and lens, but also a region in the retina (fovea) that is outfitted with the proper concentration of photoreceptor cells that are connected to the brain in a 1:1:1 fashion to allow for clear vision
- that vision is dependent on a complex array of turned around, upside down, split-up, and overlapping messages, from over two million optic nerve fibers that course their way to the visual cortex causing a neuroexcitatory spatial pattern that is interpreted as sight
- that scientists are blind to how the brain accomplishes the task of vision
[edit] References
- ^ Glicksman, Howard, (2004) Exercise Your Wonder
- ^ Glicksman (2004) Part IV: Vision Part 1–Parts of the Eye October 1, 2004
- ^ Glicksman (2004) Part V: Vision Part 2 –The Retina November 1, 2004
- ^ Glicksman (2004) Part VI: Vision Part 3 – What Does the Brain See? December 1, 2004
DLH 18:05, 13 July 2006 (UTC)
[edit] Delete Undocumented Assertion
Propose deleting the following section as an assertion without support. The reference to Miller does not appear to mention the eye or vision and appears irrelevant.
Although the eye remains a common and popular argument among laypeople, some intelligent design and creationism advocates have abandoned the eye as an example of "irreducible complexity" because of the relatively thorough understanding of its evolutionary origins biologists now have, instead relying more on mollecular and microscopic structures such as the flagella, though recent developments have shed significant light on these structures as well.[5]
DLH 18:09, 13 July 2006 (UTC)
- That sentence, and especially the one immediately following it, seemed to fail a NPOV test. Both sentences discuss evolution vs. ID and creationism, and do not really bring new information to the question of if and how eyes developed through natural selection. It is revealing to see people referred to as "laypeople" of evolution, as if it itself were a religion.
(this is getting pretty tangential, but this is a correct usage of "laypeople" -- see [1] -- and it has nothing to do with religion, except perhaps by distant etymology Montyy0 22:01, 10 December 2006 (UTC))
[edit] Review article in Science
Perhaps you are already familiar with this or it will not be helpful, but I came across a good review article in Science last month: “Casting a Genetic Light on the Evolution of Eyes”. Perhaps those more familiar with this topic might find something useful to add to this article. — Knowledge Seeker দ 03:01, 25 October 2006 (UTC)
[edit] primitive eyes
Unicellular invertebrates?
The earliest predecessor of the eye was a simple patch of photosensitive cells, physically similar to receptor patches for taste and smell, called an "eyespot". Eyespots can only sense ambient brightness: they can distinguish light from dark, but can not distinguish shapes or determine the direction light is coming from. Some organisms covered the spot in transparent skin cells for protection. Eyepatches are found in nearly all major animal groups, and are common among lower invertebrates such as the unicellular euglena. The euglena's eyespot, called a stigma, is located at its anterior end, has a red pigment, and allows the organism to move in response to light, often to assist in photosynthesis.[14][15]
This whole paragraph is a bit of a mess, but I haven't read enough to know how best to fix it. However, since Euglena is unicellular, it is not an invertebrate nor can it have a "patch of photosensitive cells." Also, it is inconsistent in terminology between "eyespot" and "eyepatch," and it's got a very strange voice, i.e. "Some organisms covered the spot in transparent skin cells for protection," rather than, say, "In some animals, the eyespot is covered by transparent skin cells for protection" or something. On a more detailed level, though, there are apparently even phototaxic prokaryotes, so claiming Eugelena as the fundamental precursor appears to be wrong. In overviews in some journals, there appears to be even some debate as to whether the eye arose independently numerous times, and there is a lot of evidence that the opsin proteins were not originally photosensing, and it's hypothesized (but I don't know that it's widely accepted) that prokaryotic rhodopsin evolved in archaea as a primitve form of photosynthesis. [2] and [3] are interesting reading in this area, but the latter needs a Science subscription for the full article.
Montyy0 21:56, 10 December 2006 (UTC)
[edit] Degradation/loss of eyes
Is it worth mentioning the opposite process, where the eyes of an organism are reduced in size, covered over, or disappear completely? The mole is one example given by Darwin. I'm not sure if the opposite process is relevant to the evolution of the eye, but it is enlightening to know the process of eye formation isn't always beneficial to an organism. Richard001 08:35, 27 December 2006 (UTC)
[edit] Paragraph needs context
Despite the precision and complexity of the eye, theoretical analysis of eye evolution, developed by Dan-Erik Nilsson and Susanne Pelger,[5] demonstrated that a primitive optical sense organ could evolve into a complex human-like eye within a reasonable period (less than a million years) simply through small mutations and natural selection.*Pro-intelligent design mathematician David Berlinski[6] criticized these findings, including a criticism that the work contained no computer simulations (something assumed by a number of scientists but disclaimed by the original authors), and criticisms of the scientific establishment in general.[7] The original authors and other scientists subsequently challenged Berlinski's criticisms.
There are a couple of things wrong with this paragraph, not the least that the part in italics is almost information-free, only inferring some dispute, or controversy. David Berlinski has not published in a peer-reviewed journal, and it is misleading to infer a scientific controversy can be made. The criticism regarding a computer simulation is directed toward errors in popular reports of their work, not the original paper. I will replace the above with the following:
In 1802, William Paley claimed that the eye was a miracle of design. Since then, it has often been claimed that the eye is too complex to have evolved in any reasonable time-frame. To examine this claim empirically, Dan-Erik Nilsson and Susanne Pelger demonstrated that a primitive optical sense organ could evolve into a complex human-like eye within a reasonable period (less than a million years) simply through small mutations and natural selection. This paper has not raised any scientific controversy. Pro-intelligent design writer David Berlinski[6] has criticized the findings in the public arena, questioning the basis of the calculations. The original authors and other scientists responded by addressing Berlinski's apparent misunderstandings, including a challenge to submit a paper of his own to a peer-reviewed journal.Trishm 06:58, 3 February 2007 (UTC)
