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Author
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Topic: Evolution of Eyes
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Lyston
Member (Idle past 5847 days) Posts: 64 From: Anon Joined: 02-27-2008
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Message 1 of 52 (459481)
03-07-2008 10:05 PM
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As suggested by several people, I am starting a new thread for the Evolution of Eyes. To get the ball rolling, a pamphlet that I have says:
The Trilobite Eye.
Millions of Trilobites exist in ancient Cambrian rock. These Trilobites have eyes that are as complex as any eyes that exist today. This fossil fact (and thousands others) falsifies the Theory of Evolution by complex systems appearing suddenly without any transitions. Although it exaggerates with the "thousands others", I think the eye thing might hold some truth to it. I looked up Trilobites on Wikipedia, and while I skimmed through most of it, I read the part about eyes. The eyes of the organism is very similar to the Ophiocoma Wendtii's eyes, something that exists today. Cambrian, I believe, is the oldest fossil layer with signs of complex organisms. The eyes are complex organs and found in ancient times. So I'm making this thread to discuss the evolution of such eyes (and others later). So, let's continue, shall we? Edited by Lyston, : For the Admin
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Admin
Director Posts: 13017 From: EvC Forum Joined: 06-14-2002 Member Rating: 1.9
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Message 2 of 52 (459511)
03-08-2008 8:46 AM
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Reply to: Message 1 by Lyston
03-07-2008 10:05 PM
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Excellent introduction. If you remove this portion:
Lyston writes: (of course, as pointed out before, I have very limited scientific knowledge and am here for understanding). Then I'll promote this.
| -- | Percy | | | EvC Forum Director |
| This message is a reply to: | | | Message 1 by Lyston, posted 03-07-2008 10:05 PM | | Lyston has replied |
| Replies to this message: | | | Message 3 by Lyston, posted 03-08-2008 3:39 PM | | Admin has not replied |
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Lyston
Member (Idle past 5847 days) Posts: 64 From: Anon Joined: 02-27-2008
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Message 3 of 52 (459560)
03-08-2008 3:39 PM
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Reply to: Message 2 by Admin
03-08-2008 8:46 AM
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Fixed.
| This message is a reply to: | | | Message 2 by Admin, posted 03-08-2008 8:46 AM | | Admin has not replied |
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Admin
Director Posts: 13017 From: EvC Forum Joined: 06-14-2002 Member Rating: 1.9
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Message 4 of 52 (459562)
03-08-2008 3:59 PM
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Thread moved here from the Proposed New Topics forum.
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RAZD
Member (Idle past 1426 days) Posts: 20714 From: the other end of the sidewalk Joined: 03-14-2004
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Message 5 of 52 (459569)
03-08-2008 4:28 PM
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Reply to: Message 1 by Lyston
03-07-2008 10:05 PM
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Cambrian, I believe, is the oldest fossil layer with signs of complex organisms. Nope. Google "pre-cambrian fossils" Just a moment...Ediacara Hills, Australia Canada, Ukraine and Australia all have pre-cambrian fossils. The oldest fossils are of cyano-bacteria, simple organisms without eyes.
The eyes of the organism is very similar to the Ophiocoma Wendtii's eyes, something that exists today.
The eyes are complex organs and found in ancient times. So I'm making this thread to discuss the evolution of such eyes (and others later). Eyes may be hard to detect\identify in some fossils -- if they are soft parts, for instance. Eyes have also evolved or re-evolved several times, as shown by the different types of eyes and different arrangements of the basic elements. Is a light-sensitive patch of skin on a flat worm an eye? Enjoy.
we are limited in our ability to understand
by our ability to understand
RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ...
to share.
• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
| This message is a reply to: | | | Message 1 by Lyston, posted 03-07-2008 10:05 PM | | Lyston has replied |
| Replies to this message: | | | Message 6 by molbiogirl, posted 03-08-2008 4:42 PM | | RAZD has seen this message but not replied | | | Message 10 by Lyston, posted 03-08-2008 4:52 PM | | RAZD has replied |
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molbiogirl
Member (Idle past 2663 days) Posts: 1909 From: MO Joined: 06-06-2007
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Message 6 of 52 (459571)
03-08-2008 4:42 PM
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Reply to: Message 5 by RAZD
03-08-2008 4:28 PM
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I'd just like to add that Pharyngula has a brief, very easy to read post on the evolution of the eye (in which he addresses the independent evolution of the eye in several different species). Eyeing the Evolutionary Past http://www.seedmagazine.com/...ing_the_evolutionary_past.php Here's a taste:
While eyes are common in larger animal species, about a third of all animal phyla lack eyes altogether; sea urchins do not bother with them, nor do many worms. Another third have eyes that look rudimentary to us; spots and patches and pits that can sense whether it's night or day or whether a shadow is passing overhead, but that do not form any kind of image. The final third have true image-forming eyes that can capture a picture of what's going on around them and pass that on to some kind of brain or nerve net. The phyla that have true eyes are a diverse subset of the multicellular animals, including jellyfish and sea anemones, molluscs, annelid worms, onychophora (velvet worms), arthropods, and us chordates, which is a strange distribution. It's as if eyes popped up in scattered lineages interspersed with groups that lack them. For a long time, one of the hypotheses to explain all these eyes was that they evolved independently, multiple times within the animal kingdom. ABE: Dawkins has a nice eye evo article, too.
"Speaking as a physicist, I cannot believe that there has been enough time for an organ as complicated as the eye to have evolved from nothing. Do you really think there has been enough time?" (An argument that stems) from the Argument from Personal Incredulity. ... I have usually fallen back on the sheer magnitude of geological time. It now appears that the shattering enormity of geological time is a steam hammer to crack a peanut. A recent study by a pair of Swedish scientists, Dan Nilson and Susanne Pelger, suggests that a ludicrously small fraction of that time would have been plenty. When one says "the" eye, by the way, one implicitly means the vertebrate eye, but serviceable image-forming eyes have evolved between 40 and 60 times, independently from scratch, in many different invertebrate groups. Among these 40-plus independent evolutions, at least nine distinct design principles have been discovered, including pinhole eyes, two kinds of camera-lens eyes, curved-reflector ("satellite dish") eyes, and several kinds of compound eyes. Nilsson and Pelger have concentrated on camera eyes with lenses, such as are well developed in vertebrates and octopuses. The first was: is there a smooth gradient of change, from flat skin to full camera eye, such that every intermediate is an improvement? ... Second, how long would the necessary quantity of evolutionary change take? But even with these conservative assumptions, the time taken to evolve a fish eye from fiat skin was minuscule: fewer than 400,000 generations. For the kinds of small animals we are talking about, we can assume one generation per year, so it seems that it would take less than half a million years to evolve a good camera eye. Page not found – Marcus du Sautoy There's your answer, Lys. Less than half a million years. Edited by molbiogirl, : No reason given.
| This message is a reply to: | | | Message 5 by RAZD, posted 03-08-2008 4:28 PM | | RAZD has seen this message but not replied |
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molbiogirl
Member (Idle past 2663 days) Posts: 1909 From: MO Joined: 06-06-2007
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Message 7 of 52 (459573)
03-08-2008 4:44 PM
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Reply to: Message 1 by Lyston
03-07-2008 10:05 PM
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The eyes of the organism is very similar to the Ophiocoma Wendtii's eyes, something that exists today. I get a distinct whiff of "If it exists today ("unchanged" from its ancient cousin), then doesn't that disprove evolution?" off of this quote. Is that your intent?
| This message is a reply to: | | | Message 1 by Lyston, posted 03-07-2008 10:05 PM | | Lyston has replied |
| Replies to this message: | | | Message 8 by Lyston, posted 03-08-2008 4:49 PM | | molbiogirl has replied |
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Lyston
Member (Idle past 5847 days) Posts: 64 From: Anon Joined: 02-27-2008
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Message 8 of 52 (459574)
03-08-2008 4:49 PM
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Reply to: Message 7 by molbiogirl
03-08-2008 4:44 PM
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I get a distinct whiff of "If it exists today ("unchanged" from its ancient cousin), then doesn't that disprove evolution?" off of this quote. Is that your intent?
Close, but no. More of, from what I understand from the pamphlet "That was pretty complex for back then, seeing as organisms still have such a structure."
| This message is a reply to: | | | Message 7 by molbiogirl, posted 03-08-2008 4:44 PM | | molbiogirl has replied |
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molbiogirl
Member (Idle past 2663 days) Posts: 1909 From: MO Joined: 06-06-2007
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Message 9 of 52 (459575)
03-08-2008 4:51 PM
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Reply to: Message 1 by Lyston
03-07-2008 10:05 PM
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Here's a handy pic (from wiki) that shows the various stages of the evolution of the eye.
| This message is a reply to: | | | Message 1 by Lyston, posted 03-07-2008 10:05 PM | | Lyston has replied |
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Lyston
Member (Idle past 5847 days) Posts: 64 From: Anon Joined: 02-27-2008
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Message 10 of 52 (459577)
03-08-2008 4:52 PM
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Reply to: Message 5 by RAZD
03-08-2008 4:28 PM
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The oldest fossils are of cyano-bacteria, simple organisms without eyes.
Hence the "Complex organisms" part, not "simple organisms".
| This message is a reply to: | | | Message 5 by RAZD, posted 03-08-2008 4:28 PM | | RAZD has replied |
| Replies to this message: | | | Message 15 by RAZD, posted 03-08-2008 8:01 PM | | Lyston has replied |
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Lyston
Member (Idle past 5847 days) Posts: 64 From: Anon Joined: 02-27-2008
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Message 11 of 52 (459578)
03-08-2008 4:53 PM
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Reply to: Message 9 by molbiogirl
03-08-2008 4:51 PM
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Yeah, I saw that before making this thread. I'm curious about the transition between "c" and "d" on that.
| This message is a reply to: | | | Message 9 by molbiogirl, posted 03-08-2008 4:51 PM | | molbiogirl has replied |
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molbiogirl
Member (Idle past 2663 days) Posts: 1909 From: MO Joined: 06-06-2007
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Message 12 of 52 (459579)
03-08-2008 4:59 PM
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Reply to: Message 8 by Lyston
03-08-2008 4:49 PM
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More of, from what I understand from the pamphlet "That was pretty complex for back then, seeing as organisms still have such a structure." The fact that eyes are a highly conserved feature is unremarkable. Evolutionarily conserved features are common. Oh so very common. Furthermore, the eye of the brittlestar ( Ophiocoma wendtii) is nothing like the eye of the trilobite.
It turns out the dorsal side of the brittle star is covered with microscopic lenses embedded in its skeleton, making the entire back of the creature into a compound eye. http://www.biomechanics.bio.uci.edu/...ittlestar/brittle.htm
Although they were not the first animals with eyes, trilobites developed one of the first sophisticated visual systems in the animal kingdom. The majority of trilobites bore a pair of compound eyes (made up of many lensed units). They typically occupied the outer edges of the fixigena (fixed cheeks) on either side of the glabella, adjacent to the facial sutures. At least one suborder of trilobites, the Agnostina, are thought to be primarily eyeless. None have ever been found with eyes. In contrast, a few secondarily eyeless species (in which a clear evolutionary trend toward reduced eye size with eventual disappearence of eyes altogether) have developed within several groups, even those known for large, well-developed eyes (e.g., Phacopina). The Trilobite Eye Edited by molbiogirl, : No reason given.
| This message is a reply to: | | | Message 8 by Lyston, posted 03-08-2008 4:49 PM | | Lyston has replied |
| Replies to this message: | | | Message 19 by Lyston, posted 03-11-2008 7:56 PM | | molbiogirl has replied |
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molbiogirl
Member (Idle past 2663 days) Posts: 1909 From: MO Joined: 06-06-2007
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Message 13 of 52 (459580)
03-08-2008 5:01 PM
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Reply to: Message 11 by Lyston
03-08-2008 4:53 PM
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Yeah, I saw that before making this thread. I'm curious about the transition between "c" and "d" on that. The explanation in the wiki article suggested earlier covers that aspect of eye evolution. Evolution of the eye - Wikipedia
| This message is a reply to: | | | Message 11 by Lyston, posted 03-08-2008 4:53 PM | | Lyston has not replied |
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Granny Magda
Member Posts: 2462 From: UK Joined: 11-12-2007 Member Rating: 3.8
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Message 14 of 52 (459595)
03-08-2008 7:04 PM
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Reply to: Message 8 by Lyston
03-08-2008 4:49 PM
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Ancient Complexity
Close, but no. More of, from what I understand from the pamphlet "That was pretty complex for back then, seeing as organisms still have such a structure." But this objection makes no sense. The complexity of the trilobite eyes was a great advance for its time, but the fact that similar structures still exist is irrelevant. As has been noted above, cyanobacteria are extremely ancient, yet cyanobacteria still exist today, much as they did millions of years ago. Trilobites happen to be pretty much the first animals with complex eyes of which we have a good fossil record. Precambrian fossils do exist, and although the record is fairly poor, it is constantly improving. The point I am trying to get across here is that whilst our understanding of the transitions between late-Precambrian to early-Cambrian is imperfect, this doesn't really pose a problem for the theory of evolution. It only poses a problem if you want to have a full natural history of the changes between one species and another. It would be nice to have a full record of every intermediate stage of trilobite eye development, but we don't have that. In truth, we don't need it, because we have so many other examples of fossils that show clear evidence of evolution. To clarify, natural history describes what changes in took place in the history of life (to the best of our ability), whilst evolution describes the process of change itself. Just because we have there are imperfections in our knowledge of natural history, this in no way invalidates the ToE. To do that you would have to point to something that contradicted the ToE.
Mutate and Survive
| This message is a reply to: | | | Message 8 by Lyston, posted 03-08-2008 4:49 PM | | Lyston has not replied |
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RAZD
Member (Idle past 1426 days) Posts: 20714 From: the other end of the sidewalk Joined: 03-14-2004
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Message 15 of 52 (459609)
03-08-2008 8:01 PM
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Reply to: Message 10 by Lyston
03-08-2008 4:52 PM
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okaaaaay, we need simple steps? We have evidence of a lot of life before the cambrian, starting with simple bacteria and proceeding to ediacarians, some with eyes. One line replies to non-essential parts of the post just demonstrate a reluctance to deal with information, particularly information that contradicts your position. Anything to say about the rest of Message 5?
Cambrian, I believe, is the oldest fossil layer with signs of complex organisms. Nope. Google "pre-cambrian fossils" Just a moment...Ediacara Hills, Australia Canada, Ukraine and Australia all have pre-cambrian fossils. The oldest fossils are of cyano-bacteria, simple organisms without eyes.
The eyes of the organism is very similar to the Ophiocoma Wendtii's eyes, something that exists today.
The eyes are complex organs and found in ancient times. So I'm making this thread to discuss the evolution of such eyes (and others later). Eyes may be hard to detect\identify in some fossils -- if they are soft parts, for instance. Eyes have also evolved or re-evolved several times, as shown by the different types of eyes and different arrangements of the basic elements. Is a light-sensitive patch of skin on a flat worm an eye? Enjoy. How "complex" is a patch of light sensitive skin? Enjoy.
we are limited in our ability to understand
by our ability to understand
RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ...
to share.
• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
| This message is a reply to: | | | Message 10 by Lyston, posted 03-08-2008 4:52 PM | | Lyston has replied |
| Replies to this message: | | | Message 22 by Lyston, posted 03-11-2008 8:22 PM | | RAZD has replied |
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