Do fish sleep? Detailed answer

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Do fish sleep? Detailed answer

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Do fish sleep?

Can you sleep with your eyes open? No, you definitely need to close your eyelids in order to fall asleep. Therefore, fish do not sleep the way we do. They don't have eyelids that they can lower. But with the onset of darkness, the fish also rest. Some of them even lie on their side. There is some similarity between the eyes of fish and humans. But there are also differences due to the fact that a person lives in the air, and a fish lives in the water.

Like humans, fish have an iris that surrounds the pupil. In most fish, the pupil does not change its size. This means that it does not narrow in bright light and does not expand in the dark in the same way that it does in the human eye. Therefore, the fish cannot stand bright light, it can go blind from it. The fish cannot reduce the amount of light passing through the pupil, as we do. Although there are some fish whose pupils can narrow.

By the way, fish don't have tears because they don't have lacrimal glands. Their eyes are moist from the environment. Most fish have eyes on either side of their head. Each eye of the fish sees the image from only one side. Therefore, fish have a large field of view on both sides, much larger than a human. They can see in front of them, behind them, above and below. And right in front of the nose, the fish can focus both eyes on one object.

Experiments have proven that some fish can distinguish colors. They can distinguish between red and green, probably blue and yellow. But few species of fish have been studied. Therefore, it cannot be concluded that all fish distinguish colors. There are big differences between fish species.

Author: Likum A.

Random interesting fact from the Great Encyclopedia:

What rule, derived by Leonardo, obeys the trunk and branches of trees?

Leonardo da Vinci derived the rule that the square of the diameter of a tree trunk is equal to the sum of the squares of the diameters of the branches, taken at a common fixed height. Later studies confirmed it with only one difference - the degree in the formula is not necessarily equal to 2, but lies in the range from 1,8 to 2,3. Traditionally it was believed that this pattern is due to the fact that a tree with such a structure has an optimal mechanism for supplying branches with nutrients. However, in 2010, the American physicist Christoph Elloy found a simpler mechanical explanation for the phenomenon: if we consider a tree as a fractal, then Leonardo's law minimizes the likelihood of breaking branches under the influence of wind.

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