EvC Forum: Evolution of the Eye - Nerves in the air?

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Topic: Evolution of the Eye - Nerves in the air?

RAZD

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Message 5 of 11 (442003)
12-19-2007 4:11 PM

Reply to: Message 1 by Equinox
12-19-2007 1:28 PM

So - I know we have examples of the intermediate stages, both light sensitive cells as well as cups, and so on. Do some of them have the nerves sticking up? Or, are there other ideas about how this arrangement evolved, and from what precursors on the skin?

Either way up the eye develops the top layer(s) need to be transluscent, and thus it is possible to have skin cells, nerves, retina cells for the initial light sensitive spot.

As taz pointed out the octopuses, squids, nautilus all have the retina light cells on the light side and the nerves behind.

It could be a flip of the coin for one or the other, or there could be some slight protection from UV for those venturing on land (or near the surface of the water).

Enjoy.

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RAZD

Member (Idle past 1435 days)

Posts: 20714

From: the other end of the sidewalk

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Message 8 of 11 (442293)
12-20-2007 5:43 PM

Reply to: Message 7 by RickJB
12-20-2007 9:50 AM

I don't quite get that from the article

quote:
Fortunately, we have evidence far better than fossils to show us how eyes may have developed. Not only can we learn a lot about the stages of ocular evolution from the study of how eyes develop in the vertebrate embryo, organisms still living exhibit photoreceptor organs smoothly spanning the structural spectrum from the "eye-spots" of single-celled organisms to eyes even more complex than the human eye.

Rather they are using the evidence from stages recorded by embryonic development for how the eye evolved.

Thanks

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RAZD

Member (Idle past 1435 days)

Posts: 20714

From: the other end of the sidewalk

Joined: 03-14-2004

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Message 11 of 11 (446363)
01-05-2008 9:49 PM

Reply to: Message 10 by tymygy
01-04-2008 4:09 PM

and light sensitive opague couldnt have made eyes..

Ever felt the sun on your arm?

Enjoy

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	Message 10 by tymygy, posted 01-04-2008 4:09 PM		tymygy has not replied

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