Posted: 11/25/2006 11:08:57 PM EDT
|
Really how in the hell did eye sight happen? Im getting a headache thinking about it. I mean with out sight how would an animal even know of light and vision? How in the hell did it decide one day to start evolving eye sight? |
That don't make a whole lot of sense to me on how vision would come about, maybe explain a little more, my understanding of ocular would mean some type of vision. I ain't no smarty pants scientist, so laymen terms. |
Good question. I just looked it up and found this concerning eye evolution... www.wehi.edu.au/resources/vce_biol_science/articles/finkel3.html After reading most of it, it's still pretty much an unknown. Some interesting ideas though. |
Some chemicals are light sensitive. Some cells had inter/intra-cellular signalling altered by the presence of light. Some animals that noticed and took advantage of this new 'sense' were better able to avoid predators or were better able to find food/water/shelter/prey than others, and were therefore more successful at reproducing. Etc. etc. etc. |
|
How did any sense evolve? It’s a good question, but it doesn’t have a really simple answer. I’ll try to put forth one that makes sense to me based on what I’ve been taught and what makes some logical sense. I've kept things as short as I really can, but its late and I'm inclined to ramble. Forgive me. To use your terms, how did any animal first ‘decide’ to evolve the ability to smell? To hear? Simply put, very slowly. Sight probably first started developed in earnest in the sea. 'Creatures' which probably resembled masses of cells more then what we would consider animals were once the height of evolution once. Really they were just a mass of independent cells that had developed a complex sort of symbioses. Anyways, light plays an important role in the sea, particularly sunlight. Being able to tell which way is up in water is a whole lot easier when you can see the sunlight on the surface, and food tends to grow in light. So being able to sense light is a pretty advantageous thing. So you have an attribute that would prove enormously advantageous to an organism. Light sensing isn't a terribly complex thing in terms of biochemistry (relatively- nothing about biochem is simple); even plants grow towards light, exhibiting a very slow, very simple form of 'sight'. Very slowly, some cells probably started to get better at producing certain chemicals when they where receiving light. When the rest of the organism detects these chemicals, it ‘knows’ it is oriented towards light, and away from the light when the chemical is diminished. So you have a very simple but effective chemical loop, made possible by some cells that happen to be photosensitive. The organisms with these cells are more successful, and both the number of photosensitive cells and the number of organisms with them increases. So the first form of sight probably wasn't really anything more then the ability to detect light from dark, and even then it was in the absence of a brain. Sort of like some jelly fish. In fact, jellyfish can sense light from dark, and some ‘advanced’ jelly fish even have rudimentary eyes that can detect shapes blocking light (like fish between it and the surface). This kind of vision is analogous to what I’ve been talking about- there are levels of vision. Complex vision is a progression of that principle. It is massively more complex, but the way that it came to be isn't. It's difficult, maybe impossible, to fully comprehend the timescale involved, but over hundreds of millions of years it happened. Very very small steps lead to increasing complexity and refinement. Factor in billions of steps and random mutation, and something like an eye is inevitable, given a need for it. Saying that the human eye could not function with out every component present, and thus evolution is not possible, is just flat out wrong. Besides examples of eyes in nature that lack features of more complex eyes like ours, there are eyes that are better then ours. Our own eyes show defects, like a blind spot caused by the optic nerve taking up space on the retina, that an octopus does not (the octopus having a different evolutionary path that stressed the need for excellent eyesight). Evolution is all about adaptation to better fill a niche. It’s very, very, very slow process that takes very small steps but results in astonishing complexity. People always talk about how evolution can't occur, because life is so complex it must require some sort of intelligence. I say that the intelligence is apparent, and it is nature its self. It is a phenomenally stupid intelligence but it acts relentlessly with virtually no time limit. Computers to, are limited intelligences but operate on such a different timescale that they can do amazingly complex things. You have to divorce your self from the 100 year time frame that our lives impose on our thinking. When viewed over millions of years, things aren't so hard to believe. -Local |
Yep. |
We evolved to have vision... Because, how else do you expect us to enjoy watching porn? We needed eyesight for that. How about teeth? The front teeth are thin and allow us to scrape and slice things. I have no idea what kind of effect it might have on speech, but doubt it is enough for thinner teeth. The ones on the sides are thick, and become more-so towards the jaw joint. These teeth allow us to crush things, and it makes sense to have them closer to the jaw joint to allow better use of our strength. Our 'fangs' allow us to tear things, such as meat. We have very versatile teeth... It's very common, with variances here and there depending on the species. |
|
Interesting topic. Coincidentally, I watched a show on pre-dinosaur evolution last night. Vision first appeared in a species of fish about 300-400 million years ago. It's eyes were nothing like what we have today. Try to image two globes in pillars sticking out of the top of a fish's head. It had numerous lens all around the 'globes'. Sight was used to avoid predators and catch prey as one would assume. |
Wow! That explains everything!! |