Wednesday, November 22, 2017

The Eyes Have it

Do you ever think about your eyes?
To truly appreciate your eyes, the functioning of your eyes, you have to realize that your normal, healthy eyes are automatically triangulating your spacial relation continuously. That, in addition to detecting detail in even extremely low levels of light, distinguishing over ten million distinct colors, observing the smallest discrete motion, adapting to changes in visible light through changes in the pupil, automatic adaptation to light quality, focusing during movement from close objects to distant objects, continual focus with both rapid and slow object movement, observing three dimensions, and recognizing subtle patterns.

Our eyes are exquisitely amazing and complicated organs. *

The evolution of sight is also truly amazing.

Our complex eyes began long ago with a few cells that were capable of sensing light. These specialized cells detected light and that light was then detected by the brain. Most resources that I found date early sight and early photoreceptive cells at about 700 million years ago. Followed by greater and greater organ development: lenses, fluid-filled sac, optic nerve, etc. 

Following that, the fossil record begins to show all kind of differences in specialization of species. Those with exceedingly excellent night vision or distance vision, light waves that are completely invisible to human beings, under water sight, heck, even under water and above water vision at the same time. Some creatures with one eye and some with more than two eyes.  Some creatures still have incredibly simple optical systems while many creatures have exquisitely complex systems for detecting the visible.

And all of this got me to thinking about something.

About how the evolution of sight went on to create further evolution of species. With sight comes the need to hide better, to hunt better, to breed better, to feed better, placement of the eyes. As the various species develop, so does their need to camouflage or stand out: all bits of evolution spurred by the development of sight. 

Also, I'm wondering just how many times those initial photosensitive cells had to happen before something really took off and started a species or two to create more and more complex photoreceptivity. How many times did the process have to start over again as one species faded out, taking the advanced sight cells with them. These processes over millions of years just boggles my brain.

Did you know that there are existing organisms today with only the basic photoreceptor cells? The euglena has a photoreceptive spot that allows it to locate light. That's all it does and the spot allows the euglena to move towards light for better opportunities for photosynthesis.

In fact, the entire range of complexity of sight is traceable in organisms on the planet today, from the simplest of photoreceptive spots all of the way up to the most complex eyes in any organism, the mantis shrimp. Dude, there is so much to learn about sight.

I visited my father-in-law the other day for an eye exam because, yes, he's an eye doctor. 😊  I'm very fortunate because with all of my many questions about eyes he had all of the answers and, furthermore, is even more of a nerd than I am. So we had a fabulous talk as he checked out my vision.

 * The internet has many great websites that look at the process of the evolution of sight. 
      Please look at several sights for greater appreciation!

iscovery consists not in seeking new landscapes, but in having new eyes. Marcel Proust
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The real voyage of discovery consists not in seeking new landscapes, but in having new eyes. Marcel Proust
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