Аналiз кадрово полiтики





Опубликовано: 09.05.2017.

Аналiз кадрово полiтики

Eyes are organs of the visual system. They provide organisms with visionthe ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and аналiз кадрово полiтики it into electro-chemical impulses in neurons.

In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragmfocuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. The simplest "eyes", such as those in microorganismsdo nothing but detect whether the surroundings are light or darkwhich is sufficient for the entrainment of circadian rhythms.

Complex eyes can distinguish shapes and colours. The visual fields of many organisms, especially predators, involve large areas of binocular vision to improve depth perception. In other organisms, eyes are аналiз кадрово полiтики so as to maximise the field of view, such as in rabbits and horseswhich have monocular vision.

The cone cells for colour and the rod cells for low-light contrasts in the retina detect and convert light into neural signals аналiз кадрово полiтики vision.

The visual signals are then transmitted to аналiз кадрово полiтики brain via the optic nerve.

Аналiз кадрово полiтики

Such eyes are typically roughly spherical, filled with a transparent gel-like substance called the vitreous humourwith a focusing lens and often an iris ; the relaxing or tightening of the muscles around the iris change the size of the pupilthereby regulating the amount of light that enters the eye, [5] and reducing aberrations when there is enough light.

Compound eyes are found among the arthropods and are composed of аналiз кадрово полiтики simple facets which, depending on the details of anatomy, may give either a single pixelated image or multiple images, per eye. аналiз кадрово полiтики

Аналiз кадрово полiтики

Each sensor has its own lens and photosensitive cell s. Compound eyes are very sensitive to motion. Some arthropods, including many Strepsipterahave compound eyes of only a few facets, each with a retina capable of creating an image, creating аналiз кадрово полiтики. With each eye viewing a аналiз кадрово полiтики thing, a fused image from all the eyes is produced in the brain, providing very different, high-resolution images.

They used clear calcite crystals to form the lenses of their eyes. In this, they differ from most other arthropods, which have soft eyes.

Аналiз кадрово полiтики

The number of lenses in such an eye varied, however: In contrast to compound eyes, simple eyes are those that have a single lens.

For example, jumping spiders have a large pair of simple eyes with a narrow field of viewsupported by an array of other, smaller eyes for peripheral vision. Some insect larvaelike caterpillarshave a different type of simple eye stemmata which usually provides only аналiз кадрово полiтики rough image, but as in sawfly larvae can possess resolving powers of 4 degrees of arc, аналiз кадрово полiтики polarization sensitive аналiз кадрово полiтики capable of increasing its absolute sensitivity at night by a factor of 1, or more.

They do have photosensitive cells, but no lens and no other means of projecting an image onto these cells. They can distinguish between light and dark, but no more. This enables snails to keep out of direct sunlight.

In organisms dwelling near deep-sea ventscompound eyes have been secondarily simplified and аналiз кадрово полiтики to spot the infra-red light produced by the hot vents—in this way the bearers can spot hot springs and avoid being boiled alive.

Аналiз кадрово полiтики

There are ten different eye layouts—indeed every technological method of capturing an optical image commonly used by human beings, with the exceptions of zoom and Fresnel lensesoccur in nature. Indeed, any eye type can be adapted for almost any behaviour or аналiз кадрово полiтики. Also, superposition eyes can achieve greater sensitivity than аналiз кадрово полiтики eyesso are better suited to dark-dwelling creatures.

These two groups are not monophyletic; the cnidaria also possess cilliated cells, [11] and some gastropods[12] as well as some annelids possess both. Simple eyes are rather аналiз кадрово полiтики, and аналiз кадрово полiтики eyes have evolved at least seven times in vertebratescephalopodsannelidscrustaceans and cubozoa.

Pit eyes, also known as stemmaare eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eyespot, to allow the organism to deduce the angle of incoming light.

Аналiз кадрово полiтики

Pit vipers have developed pits that function as eyes by sensing thermal infra-red radiation, in addition to their optical wavelength eyes like those of other vertebrates. The resolution аналiз кадрово полiтики pit eyes can be greatly аналiз кадрово полiтики by incorporating a material with a higher refractive index to form a lens, which may greatly reduce the blur radius encountered—hence increasing the resolution obtainable.

A far sharper image can be obtained using materials with a high refractive index, decreasing to the edges; this decreases the focal length and thus allows a sharp image to form on the retina. Heterogeneous eyes have evolved at least nine times: This eye creates an image that is sharp enough that motion of the eye can cause significant аналiз кадрово полiтики. To minimise the effect of eye motion while the animal moves, most such eyes have stabilising eye muscles.

The ocelli of insects bear a simple lens, but their focal point always lies behind the retina; consequently they can never form аналiз кадрово полiтики sharp image.

Ocelli pit-type eyes of arthropods blur the image across the whole retina, and are consequently excellent at responding to rapid changes in light intensity across the whole visual field; this fast response is further accelerated by the large nerve bundles which rush the information аналiз кадрово полiтики the brain. Some marine organisms bear more than one lens; for instance the copepod Pontella has three.

The outer has a parabolic surface, countering the effects of spherical aberration while allowing a sharp image to be formed. Another copepod, Copiliahas two lenses in each eye, arranged like those in a telescope. Multiple lenses are seen in some hunters such as eagles and jumping spiders, which have a refractive cornea discussed next: In the eyes of most mammalsbirdsreptiles, and most other terrestrial vertebrates аналiз кадрово полiтики with spiders and some insect larvae the vitreous fluid has a higher refractive index than the air.

Spherical lenses produce spherical aberration. In refractive corneas, the lens tissue is corrected with inhomogeneous lens material see Luneburg lensor with an aspheric shape.

Thus, animals that have evolved with a wide field-of-view often have eyes that make use аналiз кадрово полiтики an inhomogeneous lens. As mentioned above, a refractive cornea is only useful out of water; in water, there is аналiз кадрово полiтики difference in refractive index between the vitreous fluid and the surrounding water. Hence creatures that have returned to the water — penguins and seals, for example — lose their highly curved cornea and return to lens-based vision.

An alternative solution, borne by some divers, is to have a very strongly focusing cornea. An alternative to a lens is to line the inside of the eye with аналiз кадрово полiтики, and reflect the image to focus at a central point.

Аналiз кадрово полiтики

аналiз кадрово полiтики Many small organisms such as rotiferscopepods and flatworms use such organs, but these are too small to produce usable images. The scallop Pecten has up to millimetre-scale reflector eyes fringing the edge of аналiз кадрово полiтики shell.

It detects moving objects as they pass successive lenses. There is at least one vertebrate, the spookfishwhose eyes include reflective optics for focusing of light. Each of the two eyes of a spookfish collects light from both above and below; the light coming from above is focused by a lens, while that coming from below, by a curved mirror composed of many layers of small reflective plates made of guanine crystals.

A compound eye may consist of thousands of individual photoreceptor units or ommatidia ommatidiumsingular. The image perceived is a combination of inputs from the numerous ommatidia individual "eye units"which are located on a convex surface, thus pointing in slightly different directions.

Compared with simple eyes, compound eyes possess a very large view angle, and can detect fast movement and, in some cases, the polarisation of light. This can only be countered аналiз кадрово полiтики increasing lens size and number. Compound eyes fall into two groups: Apposition eyes are the most common form of eyes, and are presumably the ancestral form of compound eyes.

They are found in all arthropod groups, although they may have evolved more than once within this phylum. They are also possessed by Limulusthe horseshoe crab, and there are suggestions that other chelicerates developed their simple eyes by reduction from a compound starting point.

Apposition eyes work by gathering a number of images, one from each eye, and combining them in the brain, with each eye typically contributing a single point of information. The typical apposition eye has a lens focusing light from one direction аналiз кадрово полiтики the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. The second type is named the superposition eye. The superposition eye is divided into three types; the refracting, the reflecting and the parabolic superposition eye.

The refracting superposition eye has a gap between the lens and the rhabdom, and no аналiз кадрово полiтики wall. Each lens takes light at an angle to its axis and reflects it to the same angle on the other side.

The result is an image at half the radius of аналiз кадрово полiтики eye, which is where the tips of the rhabdoms are. This type of compound eye, for which аналiз кадрово полiтики minimal size exists below which effective superposition cannot occur, [23] is normally found in nocturnal аналiз кадрово полiтики, because it can create images up to times brighter than аналiз кадрово полiтики apposition eyes, though at the cost of reduced resolution.

Long-bodied decapod crustaceans such as shrimpprawnsаналiз кадрово полiтики and lobsters are alone in having reflecting superposition eyes, which also have a transparent gap but use corner mirrors instead аналiз кадрово полiтики lenses.

This eye type functions by refracting light, then using a parabolic mirror to focus the image; it combines features of superposition and apposition eyes. Another kind of compound eye, found in males of Order Strepsipteraemploys a series of simple eyes—eyes having one opening that provides light for an entire image-forming retina.

Because the aperture of an eyelet is larger than the facets of a compound eye, this arrangement allows vision under low light levels. Good fliers such as flies or honey bees, or prey-catching insects such as praying mantis or dragonflieshave specialised zones of ommatidia organised into a fovea area which gives acute vision.

In the acute zone, the eyes are flattened and the facets larger. The flattening allows more ommatidia to receive light from a spot and therefore higher resolution. The black spot that can be seen on the compound eyes of such insects, which always seems to look directly at the observer, is called a pseudopupil.

Аналiз кадрово полiтики

This occurs because the ommatidia which one observes "head-on" along their optical axes absorb the incident lightwhile those to one side reflect it. There are some exceptions from the types mentioned above.

Some insects have a so-called single lens compound eye, a transitional type which аналiз кадрово полiтики something between a superposition аналiз кадрово полiтики of the multi-lens compound eye and the single lens eye found in animals with simple eyes. Then there is the mysid shrimp Dioptromysis paucispinosa. The shrimp has an eye of the refracting superposition type, in the rear behind this in each eye there is a single large facet that is three times in diameter the others in the eye and behind this is an enlarged crystalline cone.

Аналiз кадрово полiтики

This projects an upright image on a specialised retina. The resulting eye is a mixture of a simple eye within a compound eye.

Аналiз кадрово полiтики

Another version is a compound eye often referred to as "pseudofaceted", as seen in Scutigera. The body of Ophiocoma wendtiia type of brittle staris covered with ommatidia, turning its whole skin into a compound eye. The same is true of many chitons. The tube аналiз кадрово полiтики of sea urchins contain photoreceptor proteins, which together act as a compound eye; they lack screening pigments, but can detect the directionality of light by the shadow cast by its opaque body.

The ciliary body is triangular in horizontal section and is аналiз кадрово полiтики by a double layer, the ciliary epithelium. The inner layer is transparent and covers the vitreous body, and is continuous from the neural tissue of the retina. The outer layer is highly pigmented, continuous with the retinal pigment epithelium, and constitutes the cells of the dilator muscle. The vitreous is the transparent, colourless, gelatinous mass that fills the space between the lens of the eye and the retina lining the back of the eye.

Amazingly, аналiз кадрово полiтики so little solid matter, it tautly holds the eye. Photoreception is phylogenetically very old, with various theories of phylogenesis.

This is based upon the shared genetic features of all eyes; аналiз кадрово полiтики is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some million years ago, [31] [32] [33] and the PAX6 gene is considered a key factor in this.



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