[_ Old Earth _] The Eye: Darwin's Dilemma

[Barbarian]

Barbarian observes:
Cutting and pasting things you know nothing about, is a continuous source of embarrassment for you, and a source of amusement for the rest of us. Just saying...

You're 'just saying' nonsense. Here's Parker (from wiki). Go argue with him:

Andrew Parker (born 1967) (Ph.D. Macquarie University) is a visiting member of the University of Oxford Department of Zoology since 1999. He is a Royal Society University Research Fellow, an Ernest Cook Research Fellow, and a Research Associate of the Australian Museum and University of Sydney. He was characterised by The Times as "one of the three most important young scientists in the world for his work in investigating and answering the great riddle of the Cambrian explosion."[1] Since 2003 he has lived in Oxfordshire, in the United Kingdom.
Can you match that?

I can top it.

Reality tops anyone's opinion. Sorry. He's just wrong about this. Notice that the nautilus has an eye with no lens, and yet has a retina on which images are formed.

Surprise.

Barbarian observes:
In fact, there is a continuous range of eyes from a simple light-sensitive tissue in a depression, to a fully functional nautilus eye. And there are organisms with a simple light-sensitive tissue in a cupped depression, capable of forming an image. Want to learn about it?

Not really.

Not surprising. But the few intermediates in the picture I showed you gives you some understanding how it works.

Can you account for how the compound eye arose in the Cambrian? NO question begging, please, and do answer the question.

Turns out, there's a lot of information on that, although it's almost certain that compound eyes arose in the Precambrian.

PNAS
Proceedings of the National Academy of Sciences of the United States of America

Molecular phylogenetic evidence for the independent evolutionary origin of an arthropod compound eye

Todd H. Oakley and
Clifford W. Cunningham

Abstract

Eyes often take a central role in discussions of evolution, with debate focused on how often such complex organs might have evolved. One such debate is whether arthropod compound eyes are the product of single or multiple origins. Here we use molecular phylogeny to address this long-standing debate and find results favoring the multiple-origins hypothesis. Our analyses of DNA sequences encoding rRNA unequivocally indicate that myodocopids—the only Ostracoda (Crustacea) with compound eyes—are nested phylogenetically within several groups that lack compound eyes. With our well-supported phylogeny, standard maximum likelihood (ML) character reconstruction methods significantly reconstruct ancestral ostracods as lacking compound eyes. We also introduce a likelihood sensitivity analysis, and show that the single-origin hypothesis is not significantly favored unless we assume a highly asymmetric model of evolution (one favoring eye loss more than 30:1 over gain). These results illustrate exactly why arthropod compound eye evolution has remained controversial, because one of two seemingly very unlikely evolutionary histories must be true. Either compound eyes with detailed similarities evolved multiple times in different arthropod groups or compound eyes have been lost in a seemingly inordinate number of arthropod lineages.


Barbarian observes:
I would think that an organ capable of forming a optical image could be nothing but an eye, unless you want to redefine "eye" to mean only organs with lenses.

You can think what you like. You need to provide, in this instance at least, some evidence as to how the compound eye arose in the Cambrian, and why it has remained virtually unchanged till today in, for example, the dragonflies.

See above. Molecular biology shows us a rather surprising number of clues as to the evolution of those eyes. And there are arthropod classes like the chelicerates, which generally lack them, having only ocelli and other simple eyes. Nevertheless, jumping spiders have evolved eyes that can see almost as well as we can; I had one on a plant in my house to which I sometimes brought an insect for it to stalk. It became visibly excited at my approach, having associated me with the arrival of lunch.

Have fun.

As always. As you see, the lack of detail in fossilized eyes is not a problem; we have other avenues of investigation to determine how they came about. Genetics adds to the data. It turns out that insects have a duplicated set of HOX genes, one that codes for compounded eyes.

http://books.google.com/books?id=OP...Q6AEwAA#v=onepage&q=compound eyes HOX&f=false

 

[Asyncritus]

Barbarian observes:
Cutting and pasting things you know nothing about, is a continuous source of embarrassment for you, and a source of amusement for the rest of us. Just saying...

The amount of critical ability you display is practically non-existent, and you continue tp parade nonsense as fact. Here is the lack of critical ability on display in full flower:

Did you think about this silly diagram before you posted it? Are you invoking some kind of black magic in assuming that this series is any indication of reality?

Just look at the differences between diagrams 3 and 4. Just look.

Nautilus has no lens, merely a 'water filled cavity'.

Suddenly, with no reason behind it, no logical process whatsoever, a 'lens' appears in Murex. And you obligingly swallow the nonsense.

How can a lens appear from a 'water filled cavity'? Think, man, think. It is impossible for the one to 'evolve' into the other. Water does not become protein. Water knows nothing about the refractive indices involved. Neither, for that matter does either Nautilus or Murex.

So assuming that the lens is functional and not merely decorative, can you account for how the different systems may have originated?

Now with great suddenness, you cast the octopus eye into the picture.

Lo and behold, the miserable Murex lens, has become cornea, iris, vitreous humour and all else.

How did all that happen, I ask?

Oh well, mutation and natural selection, you say. Please, engage brain before swallowing such garbage - you might get some nasty things down your throat.


Reality tops anyone's opinion. Sorry. He's just wrong about this. Notice that the nautilus has an eye with no lens, and yet has a retina on which images are formed.

Barbarian observes:

In fact, there is a continuous range of eyes from a simple light-sensitive tissue in a depression, to a fully functional nautilus eye. And there are organisms with a simple light-sensitive tissue in a cupped depression, capable of forming an image. Want to learn about it?

See above. Produce some explanations, not fancies.

Turns out, there's a lot of information on that, although it's almost certain that compound eyes arose in the Precambrian.

Turns out that you're guessing again.

Let me help you to see that.

Let's suppose that compound eyes, the most advanced on the planet, arose in the PreCambrian - or maybe in the granite basement layer. For that matter, why not in the magma below?

Question: HOW did they arise in the preCambrian? Fill in the blanks below:

Guess 1:

Guess 2:

Guess 3:

Before I go on to read this potential junk, can I ask you if YOU've read it?

Have you noted the frequency of the guesswork in the article?

Does the fact that there is a considerable amount of guesswork not give you pause for thought?

Or is it the old thing: ah, here's an article. Problem solved reflex in your neural circuitry swinging into play? No?

Let me have a look, and highlight the guesswork in red.

Abstract

Eyes often take a central role in discussions of evolution, with debate focused on how often such complex organs might have evolved.

One such debate is whether arthropod compound eyes are the product of single or multiple origins. Here we use molecular phylogeny to address this long-standing debate and find results favoring the multiple-origins hypothesis.

Our analyses of DNA sequences encoding rRNA unequivocally indicate that myodocopids—the only Ostracoda (Crustacea) with compound eyes—are nested phylogenetically within several groups that lack compound eyes. With our well-supported phylogeny, :toofunny standard maximum likelihood (ML) character reconstruction methods significantly reconstruct ancestral ostracods as lacking compound eyes. We also introduce a likelihood sensitivity analysis, and show that the single-origin hypothesis is not significantly favored unless we assume a highly asymmetric model of evolution (one favoring eye loss more than 30:1 over gain). These results illustrate exactly why arthropod compound eye evolution has remained controversial, because one of two seemingly very unlikely [heh heh heh! :biglol You don't say!!!] evolutionary histories must be true. Either compound eyes with detailed similarities evolved multiple times :toofunny in different arthropod groups or compound eyes have been lost in a seemingly inordinate number of arthropod lineages :toofunny.

In other words, big words notwithstanding, WE DUNNO.:toofunny

See above. Molecular biology shows us a rather surprising number of clues as to the evolution of those eyes. And there are arthropod classes like the chelicerates, which generally lack them, having only ocelli and other simple eyes. Nevertheless, jumping spiders have evolved eyes [question begging rampant!] that can see almost as well as we can; I had one on a plant in my house to which I sometimes brought an insect for it to stalk. It became visibly excited at my approach, having associated me with the arrival of lunch.

None of which has the slightest bearing on HOW THE TRILOBITE GOT ITS EYE IN THAT 'MAGICAL MILLION YEARS'.

You do see that, don't you?

As always. As you see, the lack of detail in fossilized eyes is not a problem; we have other avenues of investigation to determine how they came about. Genetics adds to the data. It turns out that insects have a duplicated set of HOX genes, one that codes for compounded eyes.

Yeah. So where did the HOX genes come from? Let me guess... mut... nah. You're not that daft.

 

[Barbarian]

Did you think about this silly diagram before you posted it? Are you invoking some kind of black magic in assuming that this series is any indication of reality?

Calm yourself. It's merely an illustration of how gradually a complex eye can form.

Just look at the differences between diagrams 3 and 4. Just look.

Nautilus has no lens, merely a 'water filled cavity'.

Suddenly, with no reason behind it, no logical process whatsoever, a 'lens' appears in Murex.

Notice that the evolution of the lens is gradual as well.

How can a lens appear from a 'water filled cavity'?

The evidence from embryology and cell biology is that the thin formed over the pit split into two layers, with liquid in between. Not much of a change, and something that happens to tissues in other cases.

It is impossible for the one to 'evolve' into the other.

Surprise. And the tissue doesn't have to "know" anything. But a higher refractive index helps focus an image.

Now with great suddenness, you cast the octopus eye into the picture.

And we see a bit of a change. The tissue over the eye has become thinner and more transparent. And some dermal muscles have adapted to open and close the aperature of the eye.

How did all that happen, I ask?

Turns out that even a small improvement in usability has a large selective value.

Barbarian observes:
Reality tops anyone's opinion. Sorry. He's just wrong about this. Notice that the nautilus has an eye with no lens, and yet has a retina on which images are formed.

See above. Produce some explanations, not fancies.

It's a fact. The nautulis has an eye that produces images and yet it has no lens. Your guy is just wrong.

Would you like to see the evidence again?

Barbarian observes:
Turns out, there's a lot of information on that, although it's almost certain that compound eyes arose in the Precambrian.

Turns out that you're guessing again.

Nope. There is fossil evidence for that.

Let's suppose that compound eyes, the most advanced on the planet, arose in the PreCambrian - or maybe in the granite basement layer. For that matter, why not in the magma below?

Fossils don't form in igneous rock. Only sedimentary. I thought you knew.

HOW did they arise in the preCambrian?

Genetically, the evidence indicates dark pigmented spots were the first light-sensitive organs.

http://www.sciencedirect.com/science/article/pii/S0959438800001148

Barbarian observes:
See above. Molecular biology shows us a rather surprising number of clues as to the evolution of those eyes. And there are arthropod classes like the chelicerates, which generally lack them, having only ocelli and other simple eyes. Nevertheless, jumping spiders have evolved eyes [question begging rampant!] that can see almost as well as we can; I had one on a plant in my house to which I sometimes brought an insect for it to stalk. It became visibly excited at my approach, having associated me with the arrival of lunch.

None of which has the slightest bearing on HOW THE TRILOBITE GOT ITS EYE IN THAT 'MAGICAL MILLION YEARS'.

Actually, it's important information, since the evidence shows the genetic path to eyes is the same in all arthropods.

You do see that, don't you?

Funny you should mention "see."

Yeah. So where did the HOX genes come from? Let me guess... mut... nah. You're not that daft.

Nature Reviews Genetics 8, 328 (May 2007) | doi:10.1038/nrg2114

How old are Hox genes?

Patrick Goymer

Hox genes and their relatives are involved in several developmental processes in diverse animals, but when did they first arise? The genome sequence of the sponge Amphimedon queenslandica shows that early metazoans possessed several Hox-like genes of the NK family, but Hox genes themselves arose and expanded only after sponges split from other metazoans.