Why animals see in the dark, and we are no? And why cats are burning?
Twilight vision in people is very good, but now we will talk about animals that see where for a person – dark-dirty.
Recall the device of a digital camera – the technical analog of the vertebrate. So, the analogue of glass lenses lens in the eye is a transparent cornea and a lens. Analogue of iris diaphragm – Rainbow shell. Analogue of a matrix consisting of pixels – retina, or retine, composed of photosensitive cells.
And now we take the lens. Photographers know that one of its most important characteristics is a light – a coefficient connecting the energy of light streams: emanating from a photographed object and falling on the matrix of the camera. The signing lens is able to collect and pass through itself more light, which allows you to take pictures with relatively weak lighting, without resorting to long exposures. Lens lens directly depends on the disclosure of the diaphragm. Also with the eye. Enough to remember huge pupils of cats in a huge room.
Another parameter defining the lens light is its focal length. What it is less, the more threw. In nature, this uses many twilight animals, but on all some deep-water fish went on. Their eyes, equipped with a very convex cornea and large, as a convex lens, can catch even the weakest rays of light, but at the same time such fish are mining.
Now let’s talk about the matrix and the retina. To spend a photo session with a lack of illumination, a camera with a particularly sensitive matrix will be required. The same in animals with twilight or night activity. Their eyes work not quite like a person. People and animals with activity in the bright time of the day directly opposite the pupil is the yellow spot – the accumulation of special photosensitive cells responsible for color vision. These cells are known as columns. Retina eye contains three types of colums. The first react only to the red rays, the second – on the yellow, third – on blue. So it creates a motley mosaic, from which the brain then collects a wonderful picture with all halftones. By the way, about the same work and the matrix camera containing red, green and blue elements.
At twilight zverushek macular there or it is weakly expressed. Conversely pupil is accumulation of photosensitive cells, which are dominated not cones and rods, which react to any quantum of light regardless of its wavelength. Consequently, the wand is not suitable for color vision, but it is useful for working in low light conditions. That’s because the cones perceive quanta of only one segment of the optical range – one of the three. A stick – all three. So theoretically Wand sensitive cones are about three times!
In addition, the nature of life hacking invented that allow multiple agencies to enhance the sensitivity of the twilight of animals.
First, the concentration of visual pigment rhodopsin them many times more than the daily brothers. Therefore, the probability of capture of photons impinging on the retina of the eye, too, more.
Secondly, in the twilight of animals sticks do not work as a single pixel, and combined into powerful battery. If the quantum of light will make one stick to react, it will provoke a reaction of the neighbors, who also will be sent to the momentum in the visual center owner. This is because the signal sent by one cell is too weak to draw the attention of the owner. And that’s not a friendly volley proignoriruesh.
Finally, in the third. Everyone knows how to burn in the night eyes of cats and other animals Twilight. This is due to the fact that behind the retina they are tapetum – a kind of mirror, composed of guanine crystals. Its meaning is as follows. Most of the light rays passes through the retina, without stopping and without causing reaction of photosensitive cells. Without tapetum they had swallowed deeper lying tissues and their energy is dissipated as heat. Tapetum, these rays are reflected, and they penetrate the retina in the reverse direction to give another chance to cause a reaction of the photosensitive cells. Those light rays, which again had no luck, and make the animal’s eyes to burn, causing an involuntary thrill us.
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