Animals and Light
Indeed, all fascinating stuff! Good choice of content from a vast field and well chosen images.
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The basic principle of the eye is that light-sensitive cells send visual signals via nerve cells to the brain, where they are interpreted as images.
The first eyes are thought to be little more than light-sensitive cell clusters, used by primitive sea animals to tell light (up) from dark (down). When cells could detect light more accurately, they could be used to see things like other animals. However, smooth patches of cells give poor, blurred images, so they evolved to sit in depressions to increase image quality. This meant that few photoreceptor cells are exposed, giving a narrow field of view. Lenses then evolved which could bend the light towards the edges of the eye cavity. The eye then became detached almost entirely from its socket and became movable, as it is today in most mammals.
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However, some animals - mainly arthropods- evolved a separate solution to the barriers of patches of photosensitive cells - the compound eye. They are made up of many eye facets, each with its own lens and optic nerve strand. This can give a very large field of view - almost 360° in dragonflies.
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An interesting example of further evolution of the eye is in the 'four eyed fish'. It spends much of its time looking out of the water, but it always needs to be able to see under the water, too. Water diffracts light so that eyes used to air cannot focus, so the eyes started to split. They now have one pair that can focus in air and one for water.
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It's absolutely amazing that an electromagnetic field changing direction 4X1014 times in one second and traveling at 299 792 458 m / s can hit a photosensitive cell, be translated into a nervous electrical impulse which is sent to the brain and be translated as the colour red.

Some facts about eyes:
There are about 12 million photoreceptors in the human eye.
There are six muscles controling the eye's movement.
The iris can control the amount of light entering the eye.
The pupil dilates in dark conditions and in response to strong emotions such as fear.
The iris is unique to each person and can be used like a fingerpint.
Visual Trickery
Sometimes the brain can be confused into thinking still images are moving. Have a look at these...
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Top 10 Optical Illusions on Internet - Fun Stuff! | Top 10 Lists |
Top 10 Optical Illusions on Internet - Fun Stuff! | Top 10 Lists |