Diagram of major stages in the eye's evolution.

The evolution of the eye has been a subject of significant study, as a distinctive example of a homologous organ present in a wide variety of species. The development of the eye is considered by most experts to be monophyletic; that is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some 540 million years ago.^[1][2][3] The majority of the process is believed to have taken only a few million years, as the first predator to gain true imaging would have touched off an "arms race".^{[citation needed]} Prey animals and competing predators alike would be forced to rapidly match or exceed any such capabilities to survive. Hence multiple eye types and subtypes developed in parallel.^{[citation needed]} Image File history File links Diagram_of_eye_evolution. ... Image File history File links Diagram_of_eye_evolution. ... For other uses, see Eye (disambiguation). ... This article is about evolution in biology. ... For other uses, see Eye (disambiguation). ... In biology, homology is any similarity between structures that is due to their shared ancestry. ... In phylogenetics, a group is monophyletic (Greek: of one stem) if all organisms in that group are known to have developed from a common ancestral form, and all descendants of that form are included in the group. ...

Eyes in various animals show adaption to their requirements. For example, birds of prey have much greater visual acuity than humans and some, like diurnal birds of prey, can see ultraviolet light. The different forms of eye in, for example, vertebrates and mollusks are often cited as examples of parallel evolution. As far as the vertebrate/mollusk eye is concerned, intermediate, functioning stages have existed in nature, which is also an illustration of the many varieties and peculiarities of eye construction. In the monophyletic model, these variations are less illustrative of non-vertebrate types such as the arthropod (compound) eye, but as those eyes are simpler to begin with, there are fewer intermediate stages to find. Orders Accipitriformes     Cathartidae     Pandionidae     Accipitridae     Sagittariidae Falconiformes     Falconidae A bird of prey or raptor is a bird that hunts its food, especially one that preys on mammals or other birds. ... A diurnal animal (dÄ«-Å­rnÉ™l) is an animal that is active during the daytime and sleeps during the night. ... Orders Accipitriformes     Cathartidae     Pandionidae     Accipitridae     Sagittariidae Falconiformes     Falconidae A bird of prey or raptor is a bird that hunts its food, especially one that preys on mammals or other birds. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Bee hovering in flight In evolutionary biology, parallel evolution refers to the independent evolution of similar traits in closely related lineages of species, while convergent evolution refers to the appearance of striking similarities among lineages of organisms only very distantly related. ...

History of research

How a complex structure like the projecting eye could have evolved is often said to be a difficult question for the theory of evolution. Charles Darwin famously treated the subject of eye evolution in his Origin of Species: This article is about evolution in biology. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... The 1859 edition of On the Origin of Species First published in 1859, The Origin of Species (full title On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life) by British naturalist Charles Darwin is one of the pivotal...

The human eye, demonstrating the iris.

To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree. Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real.^[4] Image File history File linksMetadata Download high-resolution version (2788x1864, 652 KB) Human eye. ... Image File history File linksMetadata Download high-resolution version (2788x1864, 652 KB) Human eye. ... In anatomy, the iris (plural irises or irides) is the most visible part of the eye of vertebrates, including humans. ... Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light. ... Absurd can refer to: Look up Absurd in Wiktionary, the free dictionary Absurdism is a philosophy born of Existentialism absurdity, with small a, is a form of Surreal humour Theatre of the Absurd is an artform utilizing the philosophy of Absurdism Absurd (band) is a heavy metal band This is...

However, he has a partial explanation, by his own words too brief and imperfect, which nonetheless set the pattern for later research:

In the Articulata we can commence a series with an optic nerve merely coated with pigment, and without any other mechanism; and from this low stage, numerous gradations of structure, branching off in two fundamentally different lines, can be shown to exist, until we reach a moderately high stage of perfection. In certain crustaceans, for instance, there is a double cornea, the inner one divided into facets, within each of which there is a lens-shaped swelling. In other crustaceans the transparent cones which are coated by pigment, and which properly act only by excluding lateral pencils of light, are convex at their upper ends and must act by convergence; and at their lower ends there seems to be an imperfect vitreous substance. With these facts, here far too briefly and imperfectly given, which show that there is much graduated diversity in the eyes of living crustaceans, and bearing in mind how small the number of living animals is in proportion to those which have become extinct, I can see no very great difficulty (not more than in the case of many other structures) in believing that natural selection has converted the simple apparatus of an optic nerve merely coated with pigment and invested by transparent membrane, into an optical instrument as perfect as is possessed by any member of the great Articulate class.

All light-sensitive organs rely on photoreceptor systems employing a family of proteins called opsins, which, by structural and sequence homology can be shown to be of common origin. Indeed, the seven sub-families of opsins existed in the common animal ancestor. Recent genetic discoveries have provided valuable evidence for the common ancestry of the eye, as the PAX6 gene has been recognized as a universal "master control" gene for production of eyes in species ranging from mice to humans to fruit flies.^[5][6][7] A rhodopsin molecule in the cell membrane. ... // Introduction Paired box (Pax) genes are a family of tissue specific transcription factors containing a PAIRED domain and usually a partial or complete homeodomain. ... Binomial name Meigen, 1830[1] Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order of the flies. ...

In 1802, William Paley claimed that the eye was a miracle of design. Since then, it has often been claimed that the eye is too complex to have evolved in any reasonable time-frame. To examine this claim empirically, Dan-Erik Nilsson and Susanne Pelger ^[8] demonstrated that a primitive optical sense organ could evolve into a complex human-like eye within a reasonable period (less than a million years) simply through small mutations and natural selection. Pro-intelligent design writer Dr. David Berlinski^[9] has criticized the findings in the public arena, questioning the basis of the calculations.^[10] The original authors and other scientists responded by addressing Berlinski's concerns, including a challenge to submit a paper of his own to a peer-reviewed journal.^[11][12] William Paley William Paley (July 1743 – May 25, 1805) was an English divine, Christian apologist, utilitarian, and philosopher. ... A miracle, derived from the old Latin word miraculum meaning something wonderful, is a striking interposition of divine intervention by God in the universe by which the ordinary course and operation of Nature is overruled, suspended, or modified. ... All Saints Chapel in the Cathedral Basilica of St. ... For other uses, see Intelligent design (disambiguation). ... David Berlinski (born 1942 in New York City) is an educator and author of popular books on mathematics, and a notable proponent of intelligent design, author of numerous articles on the topic. ...

Stages of eye evolution

Early eyes

The stigma (2) of the euglena is a light-sensitive patch.

The basic light-processing unit of the eye is the photoreceptor, a specialized cell consisting of two molecules in a membrane: the opsin, a light-sensitive protein, surrounding the chromophore, a pigment that distinguishes colors. When a photon is absorbed by the chromophore, a chemical reaction causes the photon's energy to be transduced into electrical energy and relayed to the nervous system. These photoreceptor cells form part of the retina, a thin layer of cells that relays visual information to the brain.^[13] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Hey Euglena is a common Euglenophyte protist, typical of the euglenids, and commonly found in nutrient-rich freshwater, with a few marine species. ... This article is about cellular photoreceptors. ... A rhodopsin molecule in the cell membrane. ... A chromophore is part (or moiety) of a molecule responsible for its color. ... Natural Ultramarine pigment in powdered form. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. ... Human eye cross-sectional view. ... This does not cite any references or sources. ...

It is likely that a key reason eyes specialize in detecting a specific, narrow range of wavelengths on the electromagnetic spectrum—the visible spectrum—is because the earliest species with eyes were aquatic, and only two specific ranges of electromagnetic radiation can travel through water, the most significant of which is visible light. This same light-filtering property of water also influenced the photosensitivity of plants.^[14][15][16] Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... “Visible light” redirects here. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Photosensitivity is the amount to which an object reacts upon receiving photons of light. ...

The earliest predecessor of the eye was a simple patch of photosensitive cells, physically similar to receptor patches for taste and smell, called an "eyespot". Eyespots can only sense ambient brightness: they can distinguish light from dark, but can not distinguish shapes or determine the direction light is coming from. Some organisms covered the spot in transparent skin cells for protection. Eyepatches are found in nearly all major animal groups, and are common among lower invertebrates such as the unicellular euglena. The euglena's eyespot, called a stigma, is located at its anterior end, has a red pigment, and allows the organism to move in response to light, often to assist in photosynthesis.^[17][18] Schematic representation of a Euglena cell with red eyespot (9) Schematic representation of a Chlamydomonas cell with chloroplast eyespot (4) The eyespot apparatus (or stigma) is a photoreceptive organelle found in the flagellate (motile) cells of green algae and other unicellular photosynthetic organisms such as euglenids. ... Invertebrate is an English word that describes any animal without a spinal column. ... Hey Euglena is a common Euglenophyte protist, typical of the euglenids, and commonly found in nutrient-rich freshwater, with a few marine species. ... The leaf is the primary site of photosynthesis in plants. ...

The planarium has "cup" eyespots that can slightly distinguish light direction.

The patch gradually depressed into a cup, which first granted the ability to discriminate brightness in directions, then in finer and finer directions as the pit deepened. While flat eyespots were ineffective at determining the direction of light, as a beam of light would activate the exact same patch of photo-sensitive cells regardless of its direction, the "cup" shape of the pit eyes allowed very limited directional differentiation by changing which cells the lights would hit depending upon its angle. Pit eyes, which had arisen by the Cambrian period, were seen in ancient snails, and are found in some invertebrates living today, such as planaria. Planaria can slightly differentiate the direction and intensity of light because of their cup-shaped, heavily-pigmented retina cells, which shield the light-sensitive cells from exposure in all directions except for the single opening for the light. However, this proto-eye is still much more useful for detecting the absence or presence of light than its direction; this gradually changes as the eye's pit deepens and the number of photoreceptive cells grows, allowing for increasingly precise visual information.^[17] Image File history File linksMetadata Download high resolution version (2116x880, 439 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File linksMetadata Download high resolution version (2116x880, 439 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Planariam (family Planariidae) are common freshwater, non-parasitic flatworms of the phylum Platyhelminthes, class Turbellaria. ... The Cambrian is a major division of the geologic timescale that begins about 542 ± 1. ... The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. ... Planariam (family Planariidae) are common freshwater, non-parasitic flatworms of the phylum Platyhelminthes, class Turbellaria. ... Human eye cross-sectional view. ...

The primitive nautilus eye functions similarly to a pinhole camera.

During the Cambrian explosion, the development of the eye accelerated rapidly, with radical improvements in image-processing and detection of light direction.^[19] As certain organisms benefited from the dramatic advantages given by full-fledged eyes, many other organisms were forced to evolve similarly advanced eyes in order to compete. As a result, the majority of major developments in eyes are thought to have occurred over the span of only a few million years. In the book In the Blink of an Eye, Andrew Parker discusses a theory that the evolution of the eye was the catalyst for the Cambrian Explosion. ^[20] Image File history File linksMetadata Download high resolution version (800x800, 645 KB) // ファイルの概要 オウムガイ 撮影場所 姫路市立水族館 Source Page http://opencage. ... Image File history File linksMetadata Download high resolution version (800x800, 645 KB) // ファイルの概要 オウムガイ 撮影場所 姫路市立水族館 Source Page http://opencage. ... Genera Allonautilus Nautilus Nautilus (from Greek ναυτίλος, sailor) is the common name of any marine creatures of the cephalopod family Nautilidae, the sole family of the suborder Nautilina. ... Principle of a pinhole camera. ... The Cambrian explosion is the geologically kukko sudden appearance in the fossil record of the ancestors of familiar animals, starting about 542 million years ago (Mya). ...

The "pinhole camera" eye was developed as the pit deepened into a cup, then a chamber. By reducing the size of the opening, the organism achieved true imaging, allowing for fine directional sensing and even some shape-sensing. Eyes of this nature are currently found in the nautilus. Lacking a cornea or lens, they provide poor resolution and dim imaging, but are still a major improvement over the early eyespots.^[21] Principle of a pinhole camera. ... Genera Allonautilus Nautilus Nautilus (from Greek ναυτίλος, sailor) is the common name of any marine creatures of the cephalopod family Nautilidae, the sole family of the suborder Nautilina. ...

Overgrowths of transparent cells prevented contamination and parasitic infestation. The chamber contents, now segregated, could slowly specialize into a transparent humour, for optimizations such as colour filtering, higher refractive index, blocking of ultraviolet radiation, or the ability to operate in and out of water. The layer may, in certain classes, be related to the moulting of the organism's shell or skin. The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... For other uses, see Ultraviolet (disambiguation). ... Ecdysis is the molting of the cuticula in arthropods and related groups (Ecdysozoa). ...

Lens formation and diversification

Light from a distant object and a near object being focused by changing the curvature of the lens.

The transparent cells over the pinhole eye's aperture split into two layers, with liquid in between. The liquid originally served as a circulatory fluid for oxygen, nutrients, wastes, and immune functions, allowing greater total thickness and higher mechanical protection. In addition, multiple interfaces between solids and liquids increase optical power, allowing wider viewing angles and greater imaging resolution. Again, the division of layers may have originated with the shedding of skin; intracellular fluid may infill naturally depending on layer depth. Image File history File links Focus_in_an_eye. ... Image File history File links Focus_in_an_eye. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ...

Note that this optical layout has not been found, nor is it expected to be found. Fossilization rarely preserves soft tissues, and even if it did, the new humour would almost certainly close as the remains desiccated, or as sediment overburden forced the layers together, making the fossilized eye resemble the previous layout. For other uses, see Fossil (disambiguation). ...

Compound eye of Antarctic krill.

Vertebrate lenses are composed of adapted epithelial cells which have high concentrations of the protein crystallin. The refractive index gradient which makes the lens useful is caused by the radial shift in crystallin concentration in different parts of the lens, rather than by the specific type of protein: it is not the presence of crystallin, but the relative distribution of it, that renders the lens useful.^[22] Download high resolution version (1574x1505, 252 KB)Antarctic krill Euphausia superba (Photo by Gerd Alberti and Uwe Kils) GFDL goto large resolution File links The following pages link to this file: Scanning electron microscope Antarctic krill User talk:Jimbo Wales Eye Compound eye Image:Krilleyekils. ... Download high resolution version (1574x1505, 252 KB)Antarctic krill Euphausia superba (Photo by Gerd Alberti and Uwe Kils) GFDL goto large resolution File links The following pages link to this file: Scanning electron microscope Antarctic krill User talk:Jimbo Wales Eye Compound eye Image:Krilleyekils. ... Binomial name Euphausia superba Dana, 1850 The Antarctic krill (Euphausia superba ) is a species of krill found in the Antarctic waters of the Southern Ocean. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ... Types of epithelium In biology and medicine, epithelium is a tissue composed of a layer of cells. ... In biology, a crystallin is a water-soluble structural protein in the lens of the eye, which accounts for the transparency of the structure. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... Gradient index optics is the branch of optics covering optical effects produced by a gradual variation of the refractive index of a material. ...

It is biologically difficult to maintain a transparent layer of cells as sizes, therefore the thicknesses, gradually increased. Deposition of transparent, but nonliving, material eased the need for nutrient supply and waste removal. In trilobites, the material was calcite; in humans, the material is crystallin. A gap between tissue layers naturally forms a biconvex shape, which is optically and mechanically ideal for substances of normal refractive index. A biconvex lens confers not only optical resolution, but aperture and low-light ability, as resolution is now decoupled from hole size—which slowly increases again, free from the circulatory constraints. Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. ...

Independently, a transparent layer and a nontransparent layer may split forward from the lens: a separate cornea and iris. (These may happen before or after crystal deposition, or not at all.) Separation of the forward layer again forms a humour, the aqueous humour. This increases refractive power and again eases circulatory problems. Formation of a nontransparent ring allows more blood vessels, more circulation, and larger eye sizes. This flap around the perimeter of the lens also masks optical imperfections, which are more common at lens edges. The need to mask lens imperfections gradually increases with lens curvature and power, overall lens and eye size, and the resolution and aperture needs of the organism, driven by hunting or survival requirements. This type is now functionally identical to the eye of most vertebrates, including humans. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... In anatomy, the iris (plural irises or irides) is the most visible part of the eye of vertebrates, including humans. ... The aqueous humour is a a thick watery substance that is located in the eye. ...

Other developments

The differences and similarities between human (left) and octopus (right) eyes demonstrate both convergent evolution and a distant (pre-Cambrian) shared ancestry.

"Backward" Illumination of Retina

The retina may revert on itself, forming a double layer. The nerves and blood vessels can migrate to the middle, where they do not block light, or form a blind spot on the retina. This type is seen in squids, which live in the dim oceans. In cats, which hunt at night, the retina does not revert. Instead a second, reflective layer (the tapetum) forms behind the retina. Light which is not absorbed by the retina on the first pass may bounce back and be detected. As a predator, the cat simply accommodates blind spots with head and eye motion. Image File history File links Created by Jerry Crimson Mann 07:07, 2 August 2005 (UTC). ... Image File history File links Created by Jerry Crimson Mann 07:07, 2 August 2005 (UTC). ... For other uses, see Octopus (disambiguation). ... In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. ... For other uses, see Blind spot. ... Suborders Myopsina Oegopsina Squids are the large, diverse group of marine mollusks, popular as food in cuisines as widely separated as the Japanese and the Italian. ...

Color vision

The ability to see colors presents distinct selective advantages for species, such as being better able to recognize predators, food and mates. As opsin molecules were subtly fine-tuned to detect different wavelengths of light, at some point, color vision developed when photoreceptor cells developed multiple pigments.^[13] As a chemical instead of mechanical adaptation, this may have occurred at any of the early stages of the eye's evolution, and the capability may have disappeared and reappeared, as organisms became predator or prey. Similarly, night and day vision emerged when receptors differentiated into rods and cones, respectively. For other uses, see Selection (disambiguation). ... Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect or emit. ...

Focusing mechanism

Some species move the lens back and forth, some stretch the lens flatter. Another mechanism regulates focusing chemically and independently of these two, by controlling growth of the eye and maintaining focal length. Note that a focusing method is not a requirement. As photographers know, focal errors increase as f-number decreases. Thus, countless organisms with small eyes are active in direct sunlight and survive with no focus mechanism at all. As a species grows larger, or transitions to dimmer environments, a means of focusing need only appear gradually. A 35mm lens set to f/11, as indicated by the white dot above the f-stop scale on the aperture ring In photography the f-number (focal ratio) expresses the diameter of the diaphragm aperture in terms of the effective focal length of the lens. ...

In creationism and intelligent design

The eye is a famous example of a supposedly "irreducibly complex" structure: due to its many elaborate and interlocking parts, seemingly all dependent upon one another for proper functioning, it is frequently claimed that the eye could not have evolved through gradual, step-by-step, evolutionary improvements guided only by natural selection. For other uses, see Eye (disambiguation). ... Irreducible complexity (IC) is the argument intended to support intelligent design creationism[1] and refute evolution that certain biological systems are too complex to have evolved from simpler, or less complete predecessors, and are at the same time too complex to have arisen naturally through chance mutations. ... This article is about evolution in biology. ... Darwins illustrations of beak variation in the finches of the Galápagos Islands, which hold 13 closely related species that differ most markedly in the shape of their beaks. ...

Michael Behe used the "development of the eye problem" as evidence for intelligent design in his controversial book, Darwin's Black Box, and creationist website Answers in Genesis describes the eye as evolutionary biologists' "greatest challenge as an example of superb 'irreducible complexity' in God's creation".^[23] Michael J. Behe (born January 18, 1952, in Altoona, Pennsylvania) is an American biochemist and intelligent design advocate. ... The Cover of Darwins Black Box Darwins Black Box: The Biochemical Challenge to Evolution is a 1996 book by Michael J. Behe in which he argues that many biochemical systems are irreducibly complex, and thus the result of intelligent design rather than evolutionary processes. ... AiGs logo Answers in Genesis (AiG) is a non-profit Christian apologetics ministry with a particular focus on Young Earth creationism and a literal, or plain,[1] interpretation of the first chapters of Genesis. ... This article discusses the term God in the context of monotheism and henotheism. ... This article is about the biblical text. ...

The argument that the eye could not have evolved is most commonly invoked in questions such as "What good is half an eye?" The assumption is that an incomplete eye would be completely useless for sight, and therefore an eye could never have evolved through the gradual, step-by-step progression required by modern evolutionary theory. However, this claim has been heavily disputed based on the plentiful evidence of suboptimal eyes in nature. Such eyes, despite their shortcomings, tend to be dramatically more useful for organisms than no eyes at all would be: people with visual impairments are generally much more able to function normally than people who are completely blind, and there are millions of species of animals with significantly simpler eyes than humans that nonetheless thrive, and are in many cases much more successful than similar species with still poorer vision.^[21] Thus eyes with decreased functionality, in humans and in numerous other species, still tend to be more beneficial than having no eyes at all.^[24] This article or section does not cite any references or sources. ... Visual impairment is the functional loss of vision. ... This article is about the visual condition. ...

Conversely, the human eye is suboptimal compared to what many would consider to be "lesser animals." Human visual acuity is, in daytime, noticeably less than that of raptors in terms of spatial resolution, and significantly less than various insects in terms of spectral range. At night, visual acuity is less than predators such as raptors and cats, and invertebrate molluscs such as squid and octopuses. The visual champion, however, is currently the mantis shrimp. This invertebrate possesses polarization capability, hyperspectral capability (with three to four times the number of receptors by range as humans, without including interpolation, over a wider spectral range), and triple redundant depth perception from both their eye constructions and their multiple eyestalk motions (both 2D tracking, and axial rotation). The fact that these capabilities are achieved using a compound eye layout is especially notable, and a sign of radically divergent evolution^{[citation needed]}. Thus, the vertebrate layout can be considered half (perhaps even a third or less) of an eye compared to the mantis shrimp form, while still being "good" in many respects. If you are looking for other meanings of the term, refer to Bird of prey (disambiguation). ... Orders Subclass Apterygota Symphypleona - globular springtails Subclass Archaeognatha (jumping bristletails) Subclass Dicondylia Monura - extinct Thysanura (common bristletails) Subclass Pterygota Diaphanopteroidea - extinct Palaeodictyoptera - extinct Megasecoptera - extinct Archodonata - extinct Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Blattodea (cockroaches) Mantodea (mantids) Isoptera (termites) Zoraptera Grylloblattodea Dermaptera (earwigs) Plecoptera (stoneflies) Orthoptera (grasshoppers, crickets... Cats may refer to: Felines, members of the animal family Felidae The domesticated animal, cat The musical, yeah right, I bet that this was really dumb. ... Suborders †Plesioteuthididae (incertae sedis) Myopsina Oegopsina Squid are a large, diverse group of marine cephalopods. ... For other uses, see Octopus (disambiguation). ... Superfamilies and families Bathysquillidoidea Bathysquillidae Indosquillidae Erythrosquilloidea Erythrosquillidae Gonodactyloidea Alainosquillidae Eurysquillidae Gonodactylidae Hemisquillidae Odontodactylidae Protosquillidae Pseudosquillidae Takuidae Lysiosquilloidea Coronididae Heterosquillidae Lysiosquillidae Nannosquillidae Tetrasquillidae Squilloidea Harpiosquillidae Squillidae incertae sedis Parasquillidae Sculdidae Mantis shrimp or stomatopods are marine crustaceans belonging to the order Stomatopoda, one part of the class Malacostraca, the largest... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... Ash plumes on Kamchatka Peninsula, eastern Russia. ... In the mathematical subfield of numerical analysis, interpolation is a method of constructing new data points from a discrete set of known data points. ... Compound eye of a dragonfly Compound eye of Antarctic krill as imaged by an electron microscope A compound eye is a visual organ found in certain arthropods such as insects and crustaceans. ... Divergent evolution occurs when two or more biological characteristics have a common evolutionary origin but have diverged over evolutionary time. ...

Although the eye remains a common and popular example of complexity in arguments against evolution, some intelligent design and creationism advocates have abandoned the eye as an example of "irreducible complexity". As the detail and history of eye evolution have become better understood, its role in these circles has declined and been replaced by molecular and microscopic structures such as the flagellum. However, much as with the eye, research into these smaller-scale structures has also uncovered details of their evolution^[25]. // A flagellum (plural: flagella) is a long, slender projection from the cell body, composed of microtubules and surrounded by the plasma membrane. ... The evolution of flagella is of great interest to biologists because the three known varieties of flagella (eukaryotic, bacterial, and archaebacterial) each represent an extremely sophisticated cellular structure that requires the interaction of many different and finely-tuned systems to function correctly. ...

The eye argument might be said to stem from a "God of the gaps" strategy, or more broadly, the "argument from incredulity" fallacy. The God of the gaps refers to a view of God deriving from a theistic position in which anything that can be explained by human knowledge is not in the domain of God, so the role of God is therefore confined to the gaps in scientific explanations of nature. ... The argument from ignorance, also known as argumentum ad ignorantiam or argument by lack of imagination, is a logical fallacy wherein a claim is made that lack of evidence for one scenario is instead evidence for another scenario, without additional evidence for the other scenario. ... It has been suggested that this article or section be merged into Fallacy. ...

References

For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... Charles Darwins Origin of Species (publ. ... David Berlinski (born 1942 in New York City) is an educator and author of popular books on mathematics, and a notable proponent of intelligent design, author of numerous articles on the topic. ... Clinton Richard Dawkins (born March 26, 1941) is a British ethologist, evolutionary biologist and popular science writer who holds the Charles Simonyi Chair for the Public Understanding of Science at Oxford University. ... Cover illustration by the zoologist Desmond Morris The Blind Watchmaker is a 1986 book by Richard Dawkins in which he presents an explanation of, and argument for, the theory of evolution by means of natural selection. ... AiGs logo Answers in Genesis (AiG) is a non-profit Christian apologetics ministry with a particular focus on Young Earth creationism and a literal, or plain,[1] interpretation of the first chapters of Genesis. ...

External links

• The Evolution of the Eye Video narrated by Richard Dawkins
• The Evolution of the Eye Video about the model proposed by Zoologist Dan-Eric Nilsson