The pupil is the necessary formation of the organs of vision. Without pupils, it makes no sense to have eyes, because it is through these holes that light passes into the eye and enters the retina, which consists of numerous light and color receptors.
A variety of pupil shapes
Nature created holes for the passage of light of various shapes. In each species of organisms, the pupil has exactly the form that is most beneficial to the animal in terms of survival.
So, in humans, the pupils have a round shape. The fact is that we need a review in all directions equally. The round pupil is characteristic of hunters and gatherers.
Cats have a vertical pupil. Because when hunting, they need to determine the distance to the target of the attack most accurately in order to calculate the strength of the jump. The vertical pupil helps with this. However, in tigers, lions and all other large feline pupils, pupils are round, like in humans. Only small cats have vertical holes. Apparently, with a higher body height, the vertical shape of the pupil does not help.
Who has a rectangular pupil? Too many mammals have this form.
In the dark, the hole becomes square. Which mammals have a rectangular pupil? Almost all ungulates. The fact is that herbivorous mammals need a wide view of the terrain to survive. The rectangular pupil allows you to increase visibility to 340 degrees. Moreover, ungulates usually graze in herds. Many eyes constantly look around the area. What is also interesting is that the goat’s eyes, for example, can rotate 50 degrees to keep the pupil horizontal while moving the head. By tilting the head to the grass, that is, eating, the goat keeps the horizontal of the rectangular hole.
Giraffe pupil
In the school course on tests, this question may come across: who has a rectangular pupil? Giraffe or octopus? This question is tricked. I should think. People may know that goats have rectangular pupils. Based on this, we conclude that the giraffe, which is also ungulate, has eye openings that are rectangular. But his pupils are rather oval. Horses have the same. In low light, their pupil becomes large and round.
Pupil of the cephalopod
Who has a rectangular pupil? The octopus. The hole in his eye is strictly rectangular in shape.
Who else has a rectangular pupil? At the mongooses. Apparently, also to increase the view of the area.
To some cephalopods, nature has given intricate forms of pupils. In cuttlefish, they are sickle-shaped or in the form of the Latin letter "S".
Pupils of amphibians and reptiles
In geckos, the pupil in the constricted state has the form of beads strung on a string.
A variety of forms of eye openings and amphibians differ. Our frogs have horizontal pupils. And the garlic has a vertical orientation, like a cat. On this basis, it is easily distinguished by all young zoologists. There are amphibians with diamond-shaped pupils. This feature also helps to expand the review of vision in all directions.
The origin of the forms of the pupils
Consider the example of ungulates. Those with a rectangular pupil in the distant past had round eye openings. But the constant bright sun made the muscles narrow the openings of the pupils. Ungulates need to take care of their eyes in order to maintain good vision in low night light. In such mammals, muscles responsible for horizontal contraction of the pupil are currently developed. It is this form that allows you to most widely examine the territory without turning your head. With muscle relaxation, which occurs with fear or a decrease in illumination, the pupils expand. This increases the flow of light to the retina.
Thus, having analyzed many animals, scientists came to the conclusion that the shape of the pupils depends on the ecological specialization of the species. Hunters and gatherers have a round pupil. In ungulates, it is rectangular. And for hunters from an ambush, a pupil of a vertical shape is better suited.