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Author
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Topic: Evolution of complexity/information
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Hangdawg13
Member (Idle past 780 days) Posts: 1189 From: Texas Joined: 05-30-2004
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Message 121 of 254 (125038)
07-16-2004 2:30 PM
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Reply to: Message 119 by NosyNed
07-16-2004 2:17 PM
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Re: Partial?
Thank you for your reply.
There are extant organisms with "partial" eyes, circulatory systems and (less clearly ) metamorphosis. So these can all work in a variety of forms some of which may appear to be "partial" but work adequately for the environment in which they find themselves. Ok, but what natural selection factor would drive an insect to mutate so that it forms a larvae that has no reproductive ability and then puts itself in the very precarious position of turning itself into soup for somedays before adult forms? And what do you mean by "partial" eyes? And what natural selection factor would cause other structures around the light sensitive cells to form improving the ability to evaluate light? This message has been edited by Hangdawg13, 07-16-2004 01:33 PM
| This message is a reply to: | | | Message 119 by NosyNed, posted 07-16-2004 2:17 PM | | NosyNed has replied |
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Asgara
Member (Idle past 2332 days) Posts: 1783 From: Wisconsin, USA Joined: 05-10-2003
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Re: Partial?
I don't think it is a matter of "natural selection factors" causing anything. A mutation happens that improves the ability to evaluate light and natural selection is what says.."Ah, that's a little better"
Asgara "Embrace the pain, spank your inner moppet, whatever....but get over it" http://asgarasworld.bravepages.comhttp://perditionsgate.bravepages.com
| This message is a reply to: | | | Message 121 by Hangdawg13, posted 07-16-2004 2:30 PM | | Hangdawg13 has not replied |
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NosyNed
Member Posts: 9004 From: Canada Joined: 04-04-2003
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Re: Partial?
Ok, but what natural selection factor would drive an insect to mutate so that it forms a larvae that has no reproductive ability and then puts itself in the very precarious position of turning itself into soup for somedays before adult forms? I don't know. However, specialization can be an advantage. In this case we have a very specialized eating machine and a very specialized reproductive machine. They take the cost of the metamorphosis to be very good at both things.
And what do you mean by "partial" eyes? What do you mean by "partial" eyes? I've said that in one sense no eye is "parital". That is they all do a "good enough" job. And I've said that in another sense all eyes are "partial". That is they are imperfect. What I'm suggesting in this case is that if we take mammalian eyes (as an example) there are eyes that lack pretty much any or all of the parts of the mammalian eye. No lens, no iris, no eyeball at all, no movement muscles etc. There are also eyes with various of these parts in combination. If we take the mammalian eye as "complete" then these might be all called "partial". About the only thing that is constant, of course, if the ability to sense light.
And what natural selection factor would cause other structures around the light sensitive cells to form improving the ability to evaluate light? Natural selection doesn't to the "forming" it keeps things which form during reproduction. IF the environment gives an advantage to an "improvement" then NS keeps it. We've already seen how mutations can give rise to a lot of changes bigger than the difference between various existing eyes. That is, all the small steps are still there in living animals. This message has been edited by NosyNed, 07-16-2004 01:40 PM
| This message is a reply to: | | | Message 121 by Hangdawg13, posted 07-16-2004 2:30 PM | | Hangdawg13 has not replied |
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jar
Member (Idle past 423 days) Posts: 34026 From: Texas!! Joined: 04-20-2004
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Re: Partial?
Let me try to address a point for you. You said
Ok, but what natural selection factor would drive and
And what natural selection factor would cause other structures around the light sensitive cells to form improving the ability to evaluate light?
but that's not exactly what happens. Change does not seem to be driven. Instead, change happens. Sometimes those changes help a critter, but not always. The critter never had sight as a goal. Rather, a critter was born that could sense light (most likely during the Cambrian Period). That gave it an advantage over its blind prey. One other thing. Most such systems appear to have been independently developed by many different critters. That is why we see so many different solutions to something like sight. There is everything from simple light sensitive cells to complex eyes. It is not a case of a great idea coming along and then being passed on to other creatures. While we do see some improvement in a particular subset of critters, we also see examples of different and unique independent evolution using totally different mechanisms. Just look at the variety of solutions to flight or legs or digestion or hearing or grasping.
Aslan is not a Tame Lion
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Loudmouth
Inactive Member
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quote:
A very interesting statement. So info would be gained during weak selection and whether or not this new info makes any sense is determined by strong selection which removes the non-sensical info.
Info is always gained at all times through random mutations regardless of the selective pressure. I simply stated that weak selection cold POSSIBLY allow the accumulation of detrimental mutations. If there is strong selection then the detrimental mutations are much more likely to disappear. Hope that makes sense.
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So in a no pressure situation adaptability is gained, but overall complexity or function is lost.
In a no pressure situation there is nothing to adapt to. Multiple functions would appear, but since there is no selective pressure the only traits selected against are those that prevent reproduction.
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So in a no pressure situation adaptability is gained, but overall complexity or function is lost.
Adaptability would be gained but complexity may or may not be gained (using the subjective measure of complexity). A strong selective force for quick generation times may result in a simpler genome that is easier to duplicate in a short amount of time, therefore limiting complexity. A strong selective force for small size may result in a small genome, such as is seen with bacteriophages. Functions may be lost, complexity may be lost, but an organism that is better adapted to it's environment is what results from strong selective pressures.
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I think jar said something about they weren't ever partially functional, but always served a purpose. How is this true of systems like metamorphosis or the eyeball or the circulatory system?
Let's look at dogs. Say we come back in 30 million years and find that dogs now have super sensitive ears, an opposable thumb, and a tail with a spike on the end of it. Would we then claim that the dogs we see today are half-evolved? Would we say that their ears are partially evolved? Of course not. Each living organism is fully evolved, and each fossil species was fully evolved at the time of its death. Using the eyeball, organisms with a photosensitive patch on their dorsal surface outcompete organisms without sight in their environment. Each change in the eye gives another advantage over the competition. What good is half an eye? A lot of good for quite a few organisms.
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haha... you see! A Christian fundy isn't necessarily so bad and closed-minded just because of what he believes.
I don't judge fundies by their beliefs, only by their willingness to understand the theory of evolution. For some reason, a lot of fundies refuse to learn what the TOE states, and instead rely on the strawmen that creationist sites promulgate. If I want to learn about christianity I talk to a pastor, I don't go down the local athiest club and learn about it from them. I only expect the same from other people, for them to go to the source and understand the opposite viewpoint before they claim that it is false. This is also known as being intellectually honest.
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Loudmouth
Inactive Member
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Re: Partial?
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Ok, but what natural selection factor would drive an insect to mutate so that it forms a larvae that has no reproductive ability and then puts itself in the very precarious position of turning itself into soup for somedays before adult forms?
Hence, insects lay hundreds of eggs with the expectation that only 10% or fewer are going to make it to adulthood. Crocodiles, for instance, lay a clutch of 50 eggs or more. Perhap only 4 or 5 of those young will survive to reproduce. There are many strategies for ensuring the species continues, and not all of the strategies are like those of mammals or even humans.
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And what do you mean by "partial" eyes?
Take the planaria (picture below). All this worm has is a photosensitive patches on its dorsal surface. It allows the worm to stay out of direct sunlight and to avoid predation. It doens't require a lens or cupped retina. A very simple eye suffices for it's niche and lifestyle.
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And what natural selection factor would cause other structures around the light sensitive cells to form improving the ability to evaluate light?
That is a good question. Obviously, predatory niches rely on recognition of prey species. Therefore, small improvements of the eye would allow for greater success in gathering food. Fish, for example, are great at recognizing floating insects (fly fishing is great fun). Small improvements allow for greater reproductive success, and therefore the new improvements become part of the population. This message has been edited by Loudmouth, 07-16-2004 02:08 PM This message has been edited by Loudmouth, 07-16-2004 03:58 PM
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crashfrog
Member (Idle past 1496 days) Posts: 19762 From: Silver Spring, MD Joined: 03-20-2003
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Ok, but what natural selection factor would drive an insect to mutate so that it forms a larvae that has no reproductive ability and then puts itself in the very precarious position of turning itself into soup for somedays before adult forms? It eliminates competition for resources between adult and juvenile conspecifics by creating separate niches for adult and juvenile stages. For the competitive insect world it works great which is why metamorphosis is so common in the insect world.
And what natural selection factor would cause other structures around the light sensitive cells to form improving the ability to evaluate light? I would presume that the advantages of better eyesight would be so varied and useful as to be obvious. Are you telling me you can't see any advantage whatsoever in seeing farther, in more light conditions, and with better clarity? Just ask a camera salesman. This message has been edited by crashfrog, 07-16-2004 03:42 PM
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Loudmouth
Inactive Member
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Re: Directionless Direction
quote:
So did fungi evolve FROM bacteria or from something else? If so, what? I guess I'm asking where and how did the Eu's split from the Pro's and what selection factor drove this change, and how much new information is necessary for this change to occur?
Sorry about the confusion, it's all my fault. Somehow I totally screwed up the order of uni- to multi-. Must be the excitement of the upcoming weekend (golf on saturday  ). Eukaryotes developed from bacteria. Mitochondria and chloroplasts within these eukaryotic cells are theorized to be captured bacteria. The development of eukaryotes seems to be dependent on this bacterial capture, as well as compartmentalization of chemical reactions that take place in a cell. So, we see the development of a nucleus, golgi apparati, endoplasmic reticulum, etc. In bacteria, the process of DNA duplication, metabolism, and protein production all occur in the same medium but these processes are done within compartments in the eukaroytic cell. The transition between a "simpler" bacterial cell and "complex" eukaroytic cell is quite hazy simply because the inner workings of single cells do not fossilize. However, the result of the transition was a larger cell that was capable of engulfing bacterial cells, hence the constant warfare between fungi and bacteria. Plants were able to move onto land, they no longer had to rely on an aquatic mileu for osmotic regulation. So, plants moved onto land where algae couldn't go and fungi ate the smaller bacteria. This is one possible pathway. I am not really "up" on the latest research on eukaryotic evolution, but there is an interesting article I have been meaning to get around to:
BMC Evol Biol. 2004 Jan 28;4(1):2. Related Articles, Links A molecular timescale of eukaryote evolution and the rise of complex multicellular life. Hedges SB, Blair JE, Venturi ML, Shoe JL. NASA Astrobiology Institute and Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA. sbh1@psu.edu BACKGROUND: The pattern and timing of the rise in complex multicellular life during Earth's history has not been established. Great disparity persists between the pattern suggested by the fossil record and that estimated by molecular clocks, especially for plants, animals, fungi, and the deepest branches of the eukaryote tree. Here, we used all available protein sequence data and molecular clock methods to place constraints on the increase in complexity through time. RESULTS: Our phylogenetic analyses revealed that (i) animals are more closely related to fungi than to plants, (ii) red algae are closer to plants than to animals or fungi, (iii) choanoflagellates are closer to animals than to fungi or plants, (iv) diplomonads, euglenozoans, and alveolates each are basal to plants+animals+fungi, and (v) diplomonads are basal to other eukaryotes (including alveolates and euglenozoans). Divergence times were estimated from global and local clock methods using 20-188 proteins per node, with data treated separately (multigene) and concatenated (supergene). Different time estimation methods yielded similar results (within 5%): vertebrate-arthropod (964 million years ago, Ma), Cnidaria-Bilateria (1,298 Ma), Porifera-Eumetozoa (1,351 Ma), Pyrenomycetes-Plectomycetes (551 Ma), Candida-Saccharomyces (723 Ma), Hemiascomycetes-filamentous Ascomycota (982 Ma), Basidiomycota-Ascomycota (968 Ma), Mucorales-Basidiomycota (947 Ma), Fungi-Animalia (1,513 Ma), mosses-vascular plants (707 Ma), Chlorophyta-Tracheophyta (968 Ma), Rhodophyta-Chlorophyta+Embryophyta (1,428 Ma), Plantae-Animalia (1,609 Ma), Alveolata-plants+animals+fungi (1,973 Ma), Euglenozoa-plants+animals+fungi (1,961 Ma), and Giardia-plants+animals+fungi (2,309 Ma). By extrapolation, mitochondria arose approximately 2300-1800 Ma and plastids arose 1600-1500 Ma. Estimates of the maximum number of cell types of common ancestors, combined with divergence times, showed an increase from two cell types at 2500 Ma to approximately 10 types at 1500 Ma and 50 cell types at approximately 1000 Ma. CONCLUSIONS: The results suggest that oxygen levels in the environment, and the ability of eukaryotes to extract energy from oxygen, as well as produce oxygen, were key factors in the rise of complex multicellular life. Mitochondria and organisms with more than 2-3 cell types appeared soon after the initial increase in oxygen levels at 2300 Ma. The addition of plastids at 1500 Ma, allowing eukaryotes to produce oxygen, preceded the major rise in complexity. You can read the complete paper here. This message has been edited by Loudmouth, 07-16-2004 04:23 PM
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Ooook!
Member (Idle past 5844 days) Posts: 340 From: London, UK Joined: 09-29-2003
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Hello, Blimey! I spend a day away from my keyboard and the whole thread careers away from me - ho hum. The statement in your post I wanted to deal with was related to the mechanism of natural selection and has already been well fielded by a number of other people, so I won't labour over it again. I suppose I could summarise it though by saying: If mutations that cause this subjective increase in complexity (ie 'better' lifeforms) can occur, and a reasonable explaination for why they would be an advantage can be suggested I see no problem with the progression from bacteria to humans. One thing that I would suggest (if you weren't doing it on this thread already) is to take a look at all of the steps on the pathway and ask - "Now how would that give it an advantage?". When doing this of course you should take into consideration the likely selective pressures at the time the change took place (if bacteria nowadays for example were to turn multicellular they would have to compete with quite a few really quite well adapted organisms). One possible stumbling block for this I can see is supposedly IC systems - but that, as you point out, is another thread. As an aside: I see your talking about the transition from prokaryotes to eukaryotes with Loudmouth, and are asking whether there is any fossil evidence. As LM quite rightly points out, internal components of cells don't fossilise - but there is other evidence that the organelles (the separate compartments) of eukaryotes were once bacteria in their own right. Mitochondria and chloroplasts contain their own genome, and their own protein sythesis machinary - and their DNA sequence shows that they are related to existing bacteria. Apologies to Loudmouth if this has already been mentioned.
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Hangdawg13
Member (Idle past 780 days) Posts: 1189 From: Texas Joined: 05-30-2004
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Message 130 of 254 (125138)
07-16-2004 9:42 PM
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Reply to: Message 124 by jar
07-16-2004 2:57 PM
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Re: Partial?
Thank you for your reply. Alright. I had several replies to my questions about what factors would drive an evolution of specific systems such as eyes and metamorphosis. I will try to address everyone's replies to this. Everyone seems to be saying that natural selection singles out an advantage and makes it more common. THIS I understand. It is more advantageous to have better eyesight, so those with mutations causing better eyesight should, in the right environment, evolve better eyes. What I don't understand is the mechanics of how it gets there. In other words, how would a lens form? A layer of cells over an area of light sensitive cells offers absolutely no advantage in seeing light better until it evolves translucentness, a definate shape, and supporting fluid or structure to keep the lense the right distance away from cells. An arperture is also extremely complex, and I cannot imagine any way it could evolve in small steps. Unless there is some specific evidence to show how this happens, perhaps you all might understand my viewpoint better when I say it takes a little imagination to get it to work. Also, with the metamorphosis. Crashfrog said that metamorphosis allows adults and larvae to have a different food supply which helps the insects out. This makes perfect sense. What doesn't make perfect sense to me (and correct me if I'm wrong) is how the system of metamorphosis evolves by small steps because I can't imagine any possible way that it could happen by small steps. Unless there is some evidence to show us how metamorphosis evolved (and if there is please tell me about it), again it seems to me that HOW is left up to the imagination and scientists simply assume that it happened by natural selection because, well, how else is it going to happen?
| This message is a reply to: | | | Message 124 by jar, posted 07-16-2004 2:57 PM | | jar has replied |
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jar
Member (Idle past 423 days) Posts: 34026 From: Texas!! Joined: 04-20-2004
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Re: Partial?
A layer of cells over an area of light sensitive cells offers absolutely no advantage in seeing light better until it evolves translucentness, a definate shape, and supporting fluid or structure to keep the lense the right distance away from cells. But initially it might not be a lens. It might a covering to keep dirt out. Or maybe it reflects colors diferently and so is useful in mating rituals. A lot of what is seen in evolution are Rube Goldberg solutions. Some part that is used for one function gradually takes on some other function. It ain't neat or even efficient. The eye, primate at least, is a good example. It's a lousy design, all wrong. But it's good enough.
Aslan is not a Tame Lion
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Hangdawg13
Member (Idle past 780 days) Posts: 1189 From: Texas Joined: 05-30-2004
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Message 132 of 254 (125144)
07-16-2004 10:08 PM
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Reply to: Message 125 by Loudmouth
07-16-2004 2:58 PM
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Info is always gained at all times through random mutations regardless of the selective pressure. I think I may have come to agree with this. Unless I learn about a way that a loss of genetic material occurs. BTW don't certain kinds of radiation have the ability to destroy genes?
In a no pressure situation there is nothing to adapt to. Multiple functions would appear, but since there is no selective pressure the only traits selected against are those that prevent reproduction. To put my summary in a simple model: A land of giants evolves so that there exist giants, normal people, and midgets. Everyone eats off the ground and lives outside so there are no problems. In this situation adaptability and information (assuming a mutation caused the change) have increased. The land is invaded by tables and chairs causing all the midgets to die out. The land is then hit again by ceilings and doorways causing all the giants to die out. Now we are left with average people. The environmental pressure removed adaptablity and information in the form of the midget gene, but the people that are left have one gene more than the giants had so they carry more info.
[qs] Each living organism is fully evolved, and each fossil species was fully evolved at the time of its death. /qs I get your point. But as I said in the other post, I don't get the mechanics of how certain things did evolve, and I don't think I ever can unless I see evidence of how it evolved. Otherwise I am forced to use my imagination.
I only expect the same from other people, for them to go to the source and understand the opposite viewpoint before they claim that it is false. This is also known as being intellectually honest. Dittos. However, when people start pontificating, I have the tendency to pontificate right back. I really enjoy this kind of question and answer conversation much better though.
| This message is a reply to: | | | Message 125 by Loudmouth, posted 07-16-2004 2:58 PM | | Loudmouth has replied |
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crashfrog
Member (Idle past 1496 days) Posts: 19762 From: Silver Spring, MD Joined: 03-20-2003
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A layer of cells over an area of light sensitive cells offers absolutely no advantage in seeing light better until it evolves translucentness, The lens of the eye is a bubble of fluid held between two thin, clear membranes. But a simple pinhole surrounded by a muscular iris does very well, too. (Surely the construction of a simple pinhole camera is something you're familiar with.)
Unless there is some specific evidence to show how this happens, perhaps you all might understand my viewpoint better when I say it takes a little imagination to get it to work. The natural world provides us with the evidence - for every step on the path to human-like eyes, there's an organism that uses that step for eyes even now. All you have to do is look at the animal kingdom to see the steps of eye evolution.
What doesn't make perfect sense to me (and correct me if I'm wrong) is how the system of metamorphosis evolves by small steps because I can't imagine any possible way that it could happen by small steps. Why? It's simply the recycling of cellular machinery employed by every organism on the path from gamete to adult. There's nothing that happens in an insect's metamorphosis that doesn't happen to literally every living thing, at one part of its life.
again it seems to me that HOW is left up to the imagination and scientists simply assume that it happened by natural selection because, well, how else is it going to happen? I wouldn't say the "how" is left up to the imagination; rather, it's left up to the hundreds of thousands of biologists laboring in their field in laboratories and universities all over the world. What did you think biologists did all day? Go over stuff they already knew?
| This message is a reply to: | | | Message 130 by Hangdawg13, posted 07-16-2004 9:42 PM | | Hangdawg13 has not replied |
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crashfrog
Member (Idle past 1496 days) Posts: 19762 From: Silver Spring, MD Joined: 03-20-2003
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I don't get the mechanics of how certain things did evolve, and I don't think I ever can unless I see evidence of how it evolved. You might want to consider a degree in the biological sciences. You could help us answer some of these questions.
| This message is a reply to: | | | Message 132 by Hangdawg13, posted 07-16-2004 10:08 PM | | Hangdawg13 has not replied |
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Yaro
Member (Idle past 6525 days) Posts: 1797 Joined: 07-12-2003
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Re: Partial?
What I don't understand is the mechanics of how it gets there. In other words, how would a lens form? A layer of cells over an area of light sensitive cells offers absolutely no advantage in seeing light better until it evolves translucentness, a definate shape, and supporting fluid or structure to keep the lense the right distance away from cells. Ok, so we got a critt with a sensitive light sensor and it has a thin layer of protective tissue over it. This is generation A which leads to generation B1 and B2. B1, has varied slightly so that the thin layer of cells has become pigmented makeing it harder for the light spot to detect light. B2 has a variation that has the skin become more transucent, by having less pigment and thinner tissue. B1 gets eaten more, B2 gets eaten less on the bassis of sight alone. Eventually B1 gets eaten to the point of extinxion, but B2 is alive and well cuz it can actually see its predators. A few generations later, say generation D1, the skin has not only become more resiliant, but has developed a thin layer of fluid between it and the eye, mainly because the old layer of thin skin didnt offer as much protection and could be wounded easely. So a protective layer of fluid formed, since we already know from B1 that dark skin dosn't work over the eye, the thiker skin evolved so that it would be see-thrugh. And so on and so on, over millions of years.
An arperture is also extremely complex, and I cannot imagine any way it could evolve in small steps. Its not that complex, have you ever seen a pinhole camera? It's basicaly a hole in a box, you can vary the hole size to create an aperture. Very simple, infact some animals have eyes like this. Like the Nautillus.
Unless there is some specific evidence to show how this happens, perhaps you all might understand my viewpoint better when I say it takes a little imagination to get it to work. Evolution: Library: Evolution of the Eye Its got a video and everything. Its pretty cool.
| This message is a reply to: | | | Message 130 by Hangdawg13, posted 07-16-2004 9:42 PM | | Hangdawg13 has not replied |
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