Posted on 03/11/2010 12:11:56 PM PST by decimon
(Santa Barbara, Calif.) –– By studying the hydra, a member of an ancient group of sea creatures that is still flourishing, scientists at UC Santa Barbara have made a discovery in understanding the origins of human vision. The finding is published in this week's issue of the Proceedings of the Royal Society B, a British journal of biology.
Hydra are simple animals that, along with jellyfish, belong to the phylum cnidaria. Cnidarians first emerged 600 million years ago.
"We determined which genetic 'gateway,' or ion channel, in the hydra is involved in light sensitivity," said senior author Todd H. Oakley, assistant professor in UCSB's Department of Ecology, Evolution and Marine Biology. "This is the same gateway that is used in human vision."
Oakley explained that there are many genes involved in vision, and that there is an ion channel gene responsible for starting the neural impulse of vision. This gene controls the entrance and exit of ions; i.e., it acts as a gateway.
The gene, called opsin, is present in vision among vertebrate animals, and is responsible for a different way of seeing than that of animals like flies. The vision of insects emerged later than the visual machinery found in hydra and vertebrate animals.
"This work picks up on earlier studies of the hydra in my lab, and continues to challenge the misunderstanding that evolution represents a ladder-like march of progress, with humans at the pinnacle," said Oakley. "Instead, it illustrates how all organisms –– humans included –– are a complex mix of ancient and new characteristics."
###
David Plachetzki, who received his Ph.D. for work done in the Oakley lab, is the first author. Plachetzki is now a postdoctoral fellow at UC Davis. UCSB undergraduate Caitlin R. Fong is the second author of the paper.
|
|
|||
Gods |
The eyes have it. Thanks decimon. Eyebrow to your audacity. :') |
||
|
· Discover · Nat Geographic · Texas AM Anthro News · Yahoo Anthro & Archaeo · Google · · The Archaeology Channel · Excerpt, or Link only? · cgk's list of ping lists · |
|||
Cnicker.
This is preposterous. There is so much complexity in the human eye, that to believe that it arose through a series of mistakes in the DNA is absurd.
We determined which genetic 'gateway,' or ion channel, in the hydra is involved in light sensitivity...This is the same gateway that is used in human vision... there are many genes involved in vision, and that there is an ion channel gene responsible for starting the neural impulse of vision. This gene controls the entrance and exit of ions; i.e., it acts as a gateway...The gene, called opsin, is present in vision among vertebrate animals, and is responsible for a different way of seeing than that of animals like flies.
The fact that there is a specific gene that establishes the ion channel for neural transmission for vision is a scientifically verifiable fact. That this gene is the same in hydra and in vertebrate animals, including humans, is a scientifically verifiable fact.
In order to make "vision" you need three things. 1. a lens. 2. a bundle of light sensitive neurons onto which the lens focuses light, and 3. the visual processing part of the brain to take the neural response to the images focused on the light sensors (the retina) and extract information from that (the visual cortex).
There is nothing remarkable about human vision. I have a sight-hound who sees many things at far greater distance than I do or can. I cannot even see things that he has seen and is straining at the lease to chase.
A fascinating book to read on the subject of how all this transmission has been taking place is: “Endless Forms Most Beautiful: The New Science of Evo Devo” by Sean B. Carroll, 2005
One fascinating experiment involved the eye. They identified three analogous genes, the “eyeless” gene of fruit flys, the “small eye” gene in mice, and the “aniridia” gene in humans. The defective gene causes malformation, shrinking, or absence of eye formation in the subjects. This is a “master” gene for eye development. Without it, eye formation fails, but where active, tissue forms eye structures. Flys and mammals have very different eye structures. However, when the mouse eye tissue was grafted on to legs or wings of the fruit fly, and then “switched on”, guess what developed. Although the tissue was from a mouse, what grew was fly eye tissue. I think that is pretty amazing. I think the whole book is amazing. Hope some of you will read it. It should improve the quality of our evolution arguments greatly.
the fascinating thing is that eyes have been created or evolved in 40 different ways over time. The creator must have been really busy.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.