Why and how did eyes evolve, if an organism did not have eyes in the first place?

Question

If the earlist organisms did not have eyes in the first place, and it did not "know" that there was an evironment to "look" at, how and why did it evolve eyes?

Answer 1

Orgqanisms that were not able to react to their environment didnt last long. Other evolved rudimentary senses: like a sense of feel. Different kinds of 'feel' then mutated over time. Feeling heat. Feeling sun. Feeling light. And the sense of feeling light was so useful, it continued to evolved more and more in detail. Until it is now what we call 'seeing'.

Answer 2

There is no why in evolution. No organism decides to evolve. Those that develop beneficial traits proliferate, those that do not are squeezed into tighter ecological niches by more numerous compeditors.

The ability to sense your environment is more than enough of a payoff to explain how the traits became commonplace. Navigation and orientation, predator evasion.

Photoreceptor organs occur in some single celled organisms. Multicellular organisms just reactivated the coding for sub cellular photo receptors and wired the specialized cells into their nervous systems. (Yes that's a teleological oversimplification, the genes were reactivated by mutation) Nerve cells seem to be almost the default setting for cellular differentiations, so that doesn't require any involved changes, just mutations that inactivate the specializing in cells between the core and the photoreceptor patches.

You might be interested to learn that the vertebrate eye is badly 'designed'. The light reaching the photo receptors has to pass through the capillaries that feed the cells and the nerve endings that connect all the cells to the optic nerve before actually hitting any cells that trigger the electrical signals we process into vision. Essentially we see the world through the obstruction of our eyes' plumbing and wiring.

Cephalopods (squids octopi) don't have this problem. Their photoreceptor's have a clear unobstructed view of the pupil. All their eyes' plumbing and wiring is behind the retina, not in the front like ours.

Answer 3

If you read this paper, they estimate that it takes a few hundred thousand years for an eye to develop - and as it says, this is the pessimistic estimate...
Light detectors proved to be of such a big advantage that even plants have them. Think about where energy comes from for photosyntesis and the speed of chemical reactions in dependence of temperature...
A lot of organism have very simple photodetectors. Some are a single cell which just sees if there is any light, the next step is that the cell has some pigment beside it which allows it directionality. Look on the website below for more info about eye evolution as well. By now the evolution of the eye is not the miracle any more, the steps are decently well understood.

Answer 4

Interestingly Trilobites have complex eyes and there is a raging debate whether they are Huygens;s corrected optics or if they were lenses like bifocals.

Trilobites are among the supposedly first eyes and as complex as they come. Like all animal types they appear abruptly in the fossil record fully formed

you could say... gee they needed to see preditors... but there were supposedly no trilobite predators and the theory unravels

In reality trilobites were probably bottom dwellers and during the catastrophic flood of Noah would be among the first animals to be buried and end up fossilized at the lowest layers. some e animals would hydrologically sorted at other layers and some more suited to survives and escape longer than others an appear rather at other layers.

As faras as sight and light, interestingly we have the only planet with a thick atmosphere that allows much light in for eyes. One living on Venus or a Gas planet would not know of sun moon or stars... the things which make for the complexity of sight and life make for the world to be a wonderful place of exploration, to give glory to the creator.

Answer 5

There are in other organisms a variety of other light sensing organs of varying complexity. If you line them up in order of complexity, you can easily see how each feature of the eye might have evolved. No doubt, it took a very long time. I wish I could find an online source that shows all of the pictures, but the best I can do is an old college biology text.

Answer 6

it quite is an elementary challenge from uninformed skeptics of evolution. Biologists use the variety of much less complicated easy comfortable structures that exist in living species in the present day to hypothesize the particularly some evolutionary stages eyes might have long undergone. this is how some scientists think of a few eyes might have developed: the straightforward easy-comfortable spot on the floor of a few ancestral creature gave it some tiny survival earnings, possibly permitting it to keep away from a predator. Random adjustments then created a melancholy interior the sunshine-comfortable patch, a deepening pit that made "imaginative and prescient" slightly sharper. on the same time, the pit's establishing progressively narrowed, so easy entered with the aid of a small aperture, like a pinhole digicam. each replace had to confer a survival earnings, no matter how average. finally, the sunshine-comfortable spot developed right into a retina, the layer of cells and pigment at the back of the human eye. over the years a lens formed on the front of the attention. it would desire to have arisen as a double-layered sparkling tissue containing increasing quantities of liquid that gave it the convex curvature of the human eye. in fact, eyes resembling each degree in this sequence have been recent in latest living species. The life of this variety of much less complicated easy-comfortable structures helps scientists' hypotheses approximately how complicated eyes like ours might desire to evolve. the 1st animals with something equivalent to a watch lived approximately 550 million years in the past. And, in accordance to one scientist's calculations, purely 364,000 years might have been mandatory for a digicam-like eye to conform from a easy-comfortable patch. Oh- FWIW, human infrequently have the appropriate eyes of all of the animals.

Answer 7

There are a number of organisms with light sensitive "proto-eyes." These are light sensitive regions sometimes on the head, sometimes on the back. They can't really "see" anything, but they can note the presence or absence of light.

If you are a water-living animal, these photo-sensitive regions would be VERY useful to survival. If the light is suddenly blocked out, you know it's time to engage in flight or fight responses.

Photo-sensitive neurons are a slight variant of heat sensitive neurons, so the jump wouldn't be that large. Then you'd get groupings of them and/or versions more or less sensitive to specific wavelengths. The eye structure would be the last thing to evolve to enhance and protect those neurons.

Answer 8

Maybe they do have 'eyes' we just cant recognise it.
Look at it from an other perspective.

If you took a bit of paper and started cutting it in half, and then cutting every bit of paper in half, and continued to do this. everysingle bit of paper getting cut in half then eventually that paper will no longer exist, because we cant see it and it has long since been a bit of paper but if it was brought together again with all the bits you cant see then it would become a bit of paper again.

Maybe an organism has something so small that cannot be identified as an eye but can develop into an eye like we have in the same way all the small miniscule bits of paper can be brought together to make a sheet of paper.

Answer 9

I think they evolved from a colonial algae called volvox C. which came from a single celled algae called Chlamydomonas reinhardtii. Chlamy has both the light harvesting material needed and flagella, which eyes need for a connecting cilium.
For the people with the intelligent design, why don't you read a book about evolution and get a little different view.

Answer 10

Given how relatively transparent our atmosphere is to "visible" radiation, it is hardly remarkable that we "see" light.
Consider a very primitive organism without eyes, like a paramecium. Now, that little protozoan, even though "blind" still avoids heat that can kill it. This is not "intelligence," but "reflex." It moves away from heat, which is infrared radiation.
Consider next the plants that rely on some wavelengths of radiation to grow. They sense light and move towards it (well, the actually move away from dark), even though they have no "eyes" to "see."
Since animals need to be able to sense their environment in order to achieve food, shelter, safety, they "chose" to develop sensitivity to a common form of information transmission in their environment - light.
Initially, that ability to sense light was very basic - light versus dark, shadow verses sunlight. Oysters and clams have this sort of sense ability. But those primitives that could discriminate more information from this radiation had an evolutionary advantage. They were literally "sighted" in a world of the blind. And they thrived and multiplied, transmitting their superior sense abilities to their offspring.
Eyes are merely the best we have, the result of this being a relatively light planet. It is a fairly limited sense, and costly in terms of bodily energy.
Consider the reverse as a proof of this. In competitive environments where sight is NOT an advantage (like in caves), the animals will quickly evolve to lose their eyes, leading to blind versions of shrimps, crabs, scorpions, fish and other cave-dwelling critters. They get along better by not wasting the energy to grow eyes that do not give them an advantage in seeking food,shelter,safety.
What would be interesting would be to see what senses creatures would develop on planets where there were other abundant energy sources (heat, wind, gravity ... who knows?) but little light. Might they not develop extremely discriminating awareness of air pressure, or sound waves, or mass?
Thanks for the interesting question! I hope I have given you an idea of how eyes came to be.
Be seeing you!