eye
Quick Summary
The eyeball is a complex, spheroidal structure housing the sense receptors for vision, functioning much like a camera. It contains the retina, a light-sensitive layer of nerve tissue, and structures that focus light onto it. The tough outer shell, the sclera, protects the eye and anchors the muscles that move it. Light enters through the transparent cornea, which, along with the aqueous humor, provides the eye's primary focusing power.12
Inside, the iris controls the amount of light entering through the pupil, and the lens further refines focus. The eyeball is filled with vitreous humor, a gel-like substance maintaining its shape. The retina, an extension of the brain, converts light into chemical energy, initiating nerve impulses sent to the brain via the optic nerve. The retina contains rods for low-light vision and cones for detailed color perception.34
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- induction
ā¦is the development of the eye lens from epidermis under influence of the eye cup, which grows toward the skin from the brain. As the eye cup comes into contact with any neighbouring epidermis, it transforms that particular region into a lens. The exact nature of the stimulus for lensā¦
Read Moreā¦is the development of the eye lens from epidermis under influence of the eye cup, which grows toward the skin from the brain. As the eye cup comes into contact with any neighbouring epidermis, it transforms that particular region into a lens. The exact nature of the stimulus for lensā¦
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animal developmentThe eyeAs has been pointed out, the rudiments of the eyes develop from optic vesicles, each of which remains connected to the brain by an eye stalk, which later serves as the pathway for the optic nerve. The optic vesicles extend laterally until they reachā¦
Read MoreAs has been pointed out, the rudiments of the eyes develop from optic vesicles, each of which remains connected to the brain by an eye stalk, which later serves as the pathway for the optic nerve. The optic vesicles extend laterally until they reachā¦
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amphibianCommon featuresThe eye of the modern amphibian (or lissamphibian) has a lid, associated glands, and ducts. It also has muscles that allow its accommodation within or on top of the head, depth perception, and true colour vision. These adaptations are regarded as the first evolutionary improvements inā¦
Read MoreThe eye of the modern amphibian (or lissamphibian) has a lid, associated glands, and ducts. It also has muscles that allow its accommodation within or on top of the head, depth perception, and true colour vision. These adaptations are regarded as the first evolutionary improvements inā¦
Read More- CaudataNervous system and sense organs
The eyes, usually large and well developed, are reduced and nearly lost in some cave-dwelling species. Vision is especially important in terrestrial foraging, because the projection of the tongue is guided visually. Certain parts of the inner ear are large and well developed. Hearing mechanisms ofā¦
Read MoreThe eyes, usually large and well developed, are reduced and nearly lost in some cave-dwelling species. Vision is especially important in terrestrial foraging, because the projection of the tongue is guided visually. Certain parts of the inner ear are large and well developed. Hearing mechanisms ofā¦
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falconiformVision, hearing, and smellThe eyes move little in their sockets. To see behind itself, therefore, a falconiform must rotate its head. Forward vision is binocular through 35ā50Ā° of arc. The proverbially high resolving power of hawksā eyes depends partly on a large image being focused on the retina andā¦
Read MoreThe eyes move little in their sockets. To see behind itself, therefore, a falconiform must rotate its head. Forward vision is binocular through 35ā50Ā° of arc. The proverbially high resolving power of hawksā eyes depends partly on a large image being focused on the retina andā¦
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owlForm and functionā¦to accommodate the exceptionally large eyes. The eyes are elongated forward, and each is encased in a tube made up of joined bony elements. Virtually immobile, the eye is rigidly encased. Remarkable flexibility of the neck compensates for the fixed position of the eyes; an owl can turn its headā¦
Read Moreā¦to accommodate the exceptionally large eyes. The eyes are elongated forward, and each is encased in a tube made up of joined bony elements. Virtually immobile, the eye is rigidly encased. Remarkable flexibility of the neck compensates for the fixed position of the eyes; an owl can turn its headā¦
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pollinationBirdsā¦the sensitivity of the birdās eye is greatest in the middle and red part of the spectrum. This is sometimes ascribed to the presence in the retina of orange-red drops of oil, which together may act as a light filter.
Read Moreā¦the sensitivity of the birdās eye is greatest in the middle and red part of the spectrum. This is sometimes ascribed to the presence in the retina of orange-red drops of oil, which together may act as a light filter.
Read More- branchiopodThe nervous system
ā¦conspicuous sense organs are the eyes. In the anostracans the eyes are on movable stalks, while in the notostracans the paired eyes lie close together on top of the head. In the other living branchiopods the eyes join together to form a single more or less spherical eye in theā¦
Read Moreā¦conspicuous sense organs are the eyes. In the anostracans the eyes are on movable stalks, while in the notostracans the paired eyes lie close together on top of the head. In the other living branchiopods the eyes join together to form a single more or less spherical eye in theā¦
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reptileSightIn general construction the eyes of reptiles are like those of other vertebrates. Accommodation for near vision in all living reptiles except snakes is accomplished by pressure being exerted on the lens by the surrounding muscular ring (ciliary body), which thus makes the lens more spherical. In snakes theā¦
Read MoreIn general construction the eyes of reptiles are like those of other vertebrates. Accommodation for near vision in all living reptiles except snakes is accomplished by pressure being exerted on the lens by the surrounding muscular ring (ciliary body), which thus makes the lens more spherical. In snakes theā¦
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snakeSkull and sense organsThe eye of the snake is lidless and covered by a transparent cap of epidermis, which is shed with the rest of the skin at each molt. Animals active during the day usually have round pupils, while the nocturnal species have a vertical or slit pupilā¦
Read MoreThe eye of the snake is lidless and covered by a transparent cap of epidermis, which is shed with the rest of the skin at each molt. Animals active during the day usually have round pupils, while the nocturnal species have a vertical or slit pupilā¦
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crocodileForm and functionā¦many nocturnal animals, crocodiles have eyes with vertical, slit-shaped pupils; these narrow in bright light and widen in darkness, thus controlling the amount of light that enters. On the back wall of the eye, the tapetum lucidum reflects incoming light, thus utilizing the small amount of light available at nightā¦
Read Moreā¦many nocturnal animals, crocodiles have eyes with vertical, slit-shaped pupils; these narrow in bright light and widen in darkness, thus controlling the amount of light that enters. On the back wall of the eye, the tapetum lucidum reflects incoming light, thus utilizing the small amount of light available at nightā¦
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muscleJawed fishesā¦is the set of six eye muscles derived from the three pre-otic somites (those anterior to the ear region of the embryo). The rectus muscles move the eyes about the longitudinal axis of the body, that is, superiorly (upward) or inferiorly (downward), or about a vertical axis, in other words,ā¦
Read Moreā¦is the set of six eye muscles derived from the three pre-otic somites (those anterior to the ear region of the embryo). The rectus muscles move the eyes about the longitudinal axis of the body, that is, superiorly (upward) or inferiorly (downward), or about a vertical axis, in other words,ā¦
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arachnidNervous system and sense organsThe number of simple eyes found on the carapace varies. Scorpions, for example, may have as many as five pairs of simple eyes on the sides of the carapace in addition to a median pair, while daddy longlegs have only median eyes, and many cryptic or cave-dwelling species haveā¦
Read MoreThe number of simple eyes found on the carapace varies. Scorpions, for example, may have as many as five pairs of simple eyes on the sides of the carapace in addition to a median pair, while daddy longlegs have only median eyes, and many cryptic or cave-dwelling species haveā¦
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How Many Eyes Does a Spider Have?eyes, although some species may have fewer. The number and arrangement of eyes can be a distinguishing feature among different spider families. For example, the jumping spiders of family Salticidae have incredible eyesight and can perceive the full spectrum of color and discern fine details.ā¦
Read Moreeyes, although some species may have fewer. The number and arrangement of eyes can be a distinguishing feature among different spider families. For example, the jumping spiders of family Salticidae have incredible eyesight and can perceive the full spectrum of color and discern fine details.ā¦
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scorpionInternal featuresTheir eyes cannot form sharp images, but their central eyes are among the most sensitive to light in the animal kingdom. Evidently they can navigate at night by using shadows cast by starlight. Lateral eyes (ocelli) sense only changes in light intensity and are used toā¦
Read MoreTheir eyes cannot form sharp images, but their central eyes are among the most sensitive to light in the animal kingdom. Evidently they can navigate at night by using shadows cast by starlight. Lateral eyes (ocelli) sense only changes in light intensity and are used toā¦
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spiderNervous system and sensesThe simple eyes of spiders, which number eight or less, consist of two groups, the main or direct eyes (called the anterior medians) and the secondary eyes, which include anterior laterals, posterior laterals, and posterior medians. Structures called rhabdoms, which receive light rays, face the lenses inā¦
Read MoreThe simple eyes of spiders, which number eight or less, consist of two groups, the main or direct eyes (called the anterior medians) and the secondary eyes, which include anterior laterals, posterior laterals, and posterior medians. Structures called rhabdoms, which receive light rays, face the lenses inā¦
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apterygoteHeadThe diplurans lack eyes and sense organs, while the Zygentoma have simple lateral eyes and are hypognathous. Archaeognatha have both large compound eyes and ocelli. Monurans had large compound eyes. Mouthparts are important taxonomically in primitive wingless hexapods. Movable mouthparts are generally recognized as walking limbs that wereā¦
Read MoreThe diplurans lack eyes and sense organs, while the Zygentoma have simple lateral eyes and are hypognathous. Archaeognatha have both large compound eyes and ocelli. Monurans had large compound eyes. Mouthparts are important taxonomically in primitive wingless hexapods. Movable mouthparts are generally recognized as walking limbs that wereā¦
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OdonataBasic structureā¦vision, and the large compound eyes, acutely responsive to movement and form, play an important role in capturing food and interacting with other individuals. In most dragonflies (suborder Anisoptera) the compound eyes meet at the top of the head and can consist of 30,000 individual optical units, or ommatidia. Theirā¦
Read Moreā¦vision, and the large compound eyes, acutely responsive to movement and form, play an important role in capturing food and interacting with other individuals. In most dragonflies (suborder Anisoptera) the compound eyes meet at the top of the head and can consist of 30,000 individual optical units, or ommatidia. Theirā¦
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DipteraEyesThe eyes of flies often occupy most of the surface of the head, especially in males, where the eyes may meet in the middle line (holoptic). In female flies, with few exceptions, the eyes do not meet (dichoptic). In some families, notably robber fliesā¦
Read MoreThe eyes of flies often occupy most of the surface of the head, especially in males, where the eyes may meet in the middle line (holoptic). In female flies, with few exceptions, the eyes do not meet (dichoptic). In some families, notably robber fliesā¦
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HymenopteraExternal structureThe compound eyes (i.e., consisting of many mosaic-like facets) are large. There are usually three ocelli, or simple eyes, arranged in a triangle on the top of the head. The antennae vary greatly in form. Rarely are they shorter than the head is wide. Usually they areā¦
Read MoreThe compound eyes (i.e., consisting of many mosaic-like facets) are large. There are usually three ocelli, or simple eyes, arranged in a triangle on the top of the head. The antennae vary greatly in form. Rarely are they shorter than the head is wide. Usually they areā¦
Read More- HymenopteraOptical
ā¦has been demonstrated that the eye of the bee is sensitive to ultraviolet radiation but is blind to red light. White flowers, which only partially reflect ultraviolet as a rule, appear colored to a bee. Certain color combinations, while invisible to the human eye, are not only visible but alsoā¦
Read Moreā¦has been demonstrated that the eye of the bee is sensitive to ultraviolet radiation but is blind to red light. White flowers, which only partially reflect ultraviolet as a rule, appear colored to a bee. Certain color combinations, while invisible to the human eye, are not only visible but alsoā¦
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homopteranHeadā¦a pair of large compound eyes, but in certain male scale insects three pairs of eyes are present. Simple eyes or ocelli usually occur on the head and probably function as organs of light perception. Cicadas normally have three, while other homopterans have two or none. Vision is variable amongā¦
Read Moreā¦a pair of large compound eyes, but in certain male scale insects three pairs of eyes are present. Simple eyes or ocelli usually occur on the head and probably function as organs of light perception. Cicadas normally have three, while other homopterans have two or none. Vision is variable amongā¦
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batSensesIn fact, the eyes in the Microchiroptera are small and have not been well studied. Among the Megachiroptera the eyes are large, but vision has been studied in detail only in flying foxes. These bats are able to make visual discriminations at lower light levels than humans can.ā¦
Read MoreIn fact, the eyes in the Microchiroptera are small and have not been well studied. Among the Megachiroptera the eyes are large, but vision has been studied in detail only in flying foxes. These bats are able to make visual discriminations at lower light levels than humans can.ā¦
Read More- batSenses
In folklore, bats have been considered to be blind. In fact, the eyes in the Microchiroptera are small and have not been well studied. Among the Megachiroptera the eyes are large, but vision has been studied in detail only in flying foxes. These batsā¦
Read MoreIn folklore, bats have been considered to be blind. In fact, the eyes in the Microchiroptera are small and have not been well studied. Among the Megachiroptera the eyes are large, but vision has been studied in detail only in flying foxes. These batsā¦
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felineForm and functionTheir large eyes are especially adapted for seeing at night. The retina has a layer of guanine called the tapetum lucidum, which reflects light and causes the eyes to shine at night when illuminated. Cats have good senses of sight and hearing, but their sense of smellā¦
Read MoreTheir large eyes are especially adapted for seeing at night. The retina has a layer of guanine called the tapetum lucidum, which reflects light and causes the eyes to shine at night when illuminated. Cats have good senses of sight and hearing, but their sense of smellā¦
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horseSensesThe extremely large eyes placed far back on the elongated head admirably suit the horse for its chief mode of defense: flight. Its long neck and high-set eyes, which register a much wider range than do the eyes of a human being, enable the horse to discern aā¦
Read MoreThe extremely large eyes placed far back on the elongated head admirably suit the horse for its chief mode of defense: flight. Its long neck and high-set eyes, which register a much wider range than do the eyes of a human being, enable the horse to discern aā¦
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insectivoreNatural historyVision is poor; eyes are small, degenerate, or covered with skin in solenodons, shrews, moles, and golden moles. Although the eyes are larger in hedgehogs, the moonrat, gymnures, and tenrecs, they are still smaller than in other orders of living mammals. Hearing is acute. Insectivores vocalize by hissesā¦
Read MoreVision is poor; eyes are small, degenerate, or covered with skin in solenodons, shrews, moles, and golden moles. Although the eyes are larger in hedgehogs, the moonrat, gymnures, and tenrecs, they are still smaller than in other orders of living mammals. Hearing is acute. Insectivores vocalize by hissesā¦
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sound receptionEcholocation in other mammalsā¦when submerged, and apparently their eyes remain fairly serviceable when their heads are out of water. Dolphins can be trained to strike targets or leap over obstacles held several feet above the surface of the water. For many tasks, however, they use echolocation very effectively, such as when catching fishā¦
Read Moreā¦when submerged, and apparently their eyes remain fairly serviceable when their heads are out of water. Dolphins can be trained to strike targets or leap over obstacles held several feet above the surface of the water. For many tasks, however, they use echolocation very effectively, such as when catching fishā¦
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tarsierā¦information from the large goggling eyes, the animalās most striking feature. The size of the eyes and visual cortex is probably made necessary by the absence of a reflective layer (tapetum) that the eyes of most other nocturnal mammals possess. The tarsier is also unusual in having especially long ankleā¦
Read Moreā¦information from the large goggling eyes, the animalās most striking feature. The size of the eyes and visual cortex is probably made necessary by the absence of a reflective layer (tapetum) that the eyes of most other nocturnal mammals possess. The tarsier is also unusual in having especially long ankleā¦
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cephalopodForm and functionā¦organs of the cephalopods are eyes, rhinophores (olfactory organs), statocysts (organs of equilibrium), and tactile organs. In Nautilus the eyes are open pits without lenses. In the Coleoidea the eyes are complex and approach those of some lower vertebrates in efficiency.
Read Moreā¦organs of the cephalopods are eyes, rhinophores (olfactory organs), statocysts (organs of equilibrium), and tactile organs. In Nautilus the eyes are open pits without lenses. In the Coleoidea the eyes are complex and approach those of some lower vertebrates in efficiency.
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nervous systemComplex mollusksThe eyes of cephalopods are especially well developed and bear close resemblance to the vertebrate eye. The eye fits into a socket of cartilaginous plates separate from the cartilages that protect the brain, and external muscles permit its movement. A transparent cornea covers the surface andā¦
Read MoreThe eyes of cephalopods are especially well developed and bear close resemblance to the vertebrate eye. The eye fits into a socket of cartilaginous plates separate from the cartilages that protect the brain, and external muscles permit its movement. A transparent cornea covers the surface andā¦
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giant squidNatural historyThe eye diameter of the giant squid, which measures up to 27 cm (10.6 inches), is among the largest of all living animals; it is second only to that of the colossal squid. Such large eyes are thought to have given the giant squid and theā¦
Read MoreThe eye diameter of the giant squid, which measures up to 27 cm (10.6 inches), is among the largest of all living animals; it is second only to that of the colossal squid. Such large eyes are thought to have given the giant squid and theā¦
Read More- nervous systemSimple mollusks
ā¦the scallop, for example, the eyes are set in a row. They are well developed and consist of a cornea, a lens, and a retina, in which the photoreceptor cells are not placed superficially (an arrangement much like that in the vertebrate retina).
Read Moreā¦the scallop, for example, the eyes are set in a row. They are well developed and consist of a cornea, a lens, and a retina, in which the photoreceptor cells are not placed superficially (an arrangement much like that in the vertebrate retina).
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- movement perceptionVisual cues to movement
The eye is by far the most effective organ for sensing movement. Some animals are especially sensitive to visual stimuli that move in specific ways. For instance, electrical patterns from the eye of a frog show that some elements in the organ respond only when theā¦
Read MoreThe eye is by far the most effective organ for sensing movement. Some animals are especially sensitive to visual stimuli that move in specific ways. For instance, electrical patterns from the eye of a frog show that some elements in the organ respond only when theā¦
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photoreceptionEvolution of eyesThe soft-bodied animals that inhabited the worldās seas before the Cambrian explosion (about 541 million years ago) undoubtedly had eyes, probably similar to the pigment-pit eyes of flatworms today. However, there is no fossil evidence to support the presence of eyes in the
Read MoreThe soft-bodied animals that inhabited the worldās seas before the Cambrian explosion (about 541 million years ago) undoubtedly had eyes, probably similar to the pigment-pit eyes of flatworms today. However, there is no fossil evidence to support the presence of eyes in the
Read More- photoreceptionDiversity of eyes
The eyes of animals are diverse not only in size and shape but also in the ways in which they function. For example, the eyes of fish from the deep sea often show variations on the basic spherical design of the eye. In theseā¦
Read MoreThe eyes of animals are diverse not only in size and shape but also in the ways in which they function. For example, the eyes of fish from the deep sea often show variations on the basic spherical design of the eye. In theseā¦
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