Vision is vital for most living organisms. It helps to properly orientate and respond to the environment. It is the eyes that transmit about 90 percent of the information to the brain. But the structure and placement of the eyes of different representatives of the living world is different.
What vision happens
The following types of vision are distinguished:
- panoramic (monocular);
- stereoscopic (binocular).
With monocular vision, the surrounding world is perceived, as a rule, with one eye. This type of vision is typical mainly for birds and herbivores. This feature allows you to notice and respond to imminent danger in time.
Stereoscopic vision is inferior to panoramic less visibility. But it has a number of advantages, one of which is a three-dimensional image.
Distinctive features of stereoscopic vision
Stereoscopic vision is the ability to see the world with two eyes. In other words, the overall picture is made up of the fusion of pictures entering the brain from each eye at the same time.
Using this type of vision, you can correctly evaluate not only the distance to the visible object, but also its approximate size and shape.
In addition, stereoscopic vision has another significant advantage - the ability to see through objects. So, if you place, for example, a fountain pen in an upright position and look alternately with each eye, then a certain area in both the first and second cases will be closed. But if you look with two eyes at the same time, then the pen ceases to be an obstacle. But such an ability to “look through objects” loses its strength, provided that the width of such an object is greater than the distance between the eyes.
The peculiarity of this type of vision in various representatives of the globe is presented below.
Features of the structure of the eyes in insects
Their vision has a unique structure. The eyes of insects resemble a mosaic (for example, the eyes of a wasp). Moreover, the number of these mosaics (facets) for different representatives of this representative of the living world differs and ranges from 6 to 30,000. Each facet perceives only part of the information, but in total they provide a complete picture of the world.
And insects perceive the color scheme differently than people. For example, the red flower that a person sees is perceived by the eyes of a wasp as black.
Birds
Stereoscopic vision in birds is the exception rather than the rule. The fact is that in most birds the eyes are located on the sides, which provides a wider viewing angle.
This type of vision is inherent mainly to birds of prey. This helps them correctly calculate the distance to the moving prey.
But visibility in birds is much less than, for example, in humans. If a person is able to see at 150 °, then birds are only from 10 ° (sparrows and bullfinches) to 60 ° (owls and goats).
But do not rush, claiming that feathered representatives of the living world are deprived of the ability to fully see. Not at all. The fact is that they have other unique features.
For example, owls have eyes closer to their beaks. Moreover, as already noted, their viewing angle is only 60 °. Therefore, owls are able to see only what is directly in front of them, and not the situation from the side and back. These birds have another distinctive feature - their eyes are fixed. But at the same time they are endowed with another unique ability. Owing to the structure of their
skeleton, owls are able to turn their heads 270 °.
Fish
As is known, in the vast majority of fish species, eyes are located on both sides of the head. They are characterized by monocular vision. The exception is predatory fish, especially hammerhead sharks. For many centuries, people have been interested in the question of why this fish has such a head shape. A possible clue was found by American scientists. They put forward the version that the hammer fish sees a three-dimensional image, i.e. she is endowed with stereoscopic vision.
To confirm their theory, scientists conducted an experiment. For this purpose, sensors were placed on the heads of several species of sharks, with the help of which the activity of the fish brain was measured under the influence of bright light. Then the subjects were placed in an aquarium. As a result of this experiment, it became known that the hammer fish is endowed with stereoscopic vision. Moreover, the accuracy of determining the distance to the object the more accurate, the greater the distance between the eyes of this species of shark.
In addition, it became known that the eyes of the hammerfish rotate, which allows it to fully see the surrounding environment. This gives her a significant advantage over other predators.
Animals
Animals, depending on the type and habitat, are endowed with both monocular and stereoscopic vision. For example, herbivores who live in open spaces, to preserve their lives and quickly respond to imminent danger, should see as much space around them as possible. Therefore, they are endowed with monocular vision.
Stereoscopic vision in animals is characteristic of predators and inhabitants of forests and jungles. First, it helps to correctly calculate the distance to your victim. The second such vision allows you to better focus your eyes among many obstacles.
So, for example, this type of vision helps wolves with a long pursuit of prey. Cats - with a lightning attack. By the way, in cats, thanks to parallel visual axes, the viewing angle reaches 120 °. But some dog breeds have developed both monocular and stereoscopic vision. Their eyes are located on the sides. Therefore, to view the subject at a great distance, they use frontal stereoscopic vision. And for a review of nearby objects, dogs are forced to turn their heads.
Inhabitants of the tops of trees (primates, squirrels, etc.) stereoscopic vision helps in the search for food and in calculating the trajectory of the jump.
People
Stereoscopic vision in humans is not developed from the very birth. At birth, babies cannot focus their eyes on a specific subject. Binocular vision in them begins to form only at 2 months of life. However, in full, children begin to orientate themselves in space only when they begin to crawl and walk.
Despite the apparent identity, the human eyes are different. One of them is the leader, the other is the slave. For recognition, it is enough to conduct an experiment. Position the sheet with a small hole at a distance of about 30 cm and look through it at a distant object. Then alternately do the same, covering either the left or the right eye. The position of the head should remain constant. The eye for which the image does not change position will be the leading one. Such a definition is important for photographers, videographers, hunters and some other professions.
The role of binocular vision for humans
This type of vision arose in humans, as in some other representatives of the living world, as a result of evolution.
Of course, modern people do not need to hunt for prey. But at the same time, stereoscopic vision plays a significant role in their life. It is especially important for athletes. So, without an accurate calculation of the distance, biathletes will not hit the target, and gymnasts will not be able to perform on a log.
This type of vision is very important for professions that require an instant reaction (drivers, hunters, pilots).
And in everyday life one cannot do without stereoscopic vision. For example, it is quite difficult, seeing with one eye, to thread a thread into the eye of a needle. Partial loss of vision is very dangerous for humans. Seeing with only one eye, he will not be able to correctly orientate in space. And the multifaceted world will turn into a flat image.
Obviously, stereoscopic vision is the result of evolution. And only the chosen ones are endowed with it.