Evolution Of The Eye
The evolution of the eye is the origin and development with diversification by natural selection over geological time of organs of photosensitivity and vision in living organisms. Many scientists have found the evolution of the eye attractive to study because the eye distinctively exemplifies an analogous organ found in many animal forms. Simple light eye evolution is the distinction between different types of photoreceptor cells. Salvini-Plawen and Mayr (1977) noted a remarkable diversity of photoreceptor cell morphology across the animal kingdom, and suggested that photoreceptors evolved independently numerous times." – Land, M.F. and Nilsson, D.-E., ''Animal Eyes''(2-nd ed.), Oxford University Press, Oxford (2012), p. 7. Diverse eyes are known from the Burgess shale of the Middle Cambrian, and from the slightly older Emu Bay Shale. Eyes vary in their visual acuity, the range of wavelengths they can detect, their sensitivity in no light, their ability to detect motion or to ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Diagram Of Eye Evolution
A diagram is a symbolic representation of information using visualization techniques. Diagrams have been used since prehistoric times on walls of caves, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three-dimensional visualization which is then projected onto a two-dimensional surface. The word ''graph'' is sometimes used as a synonym for diagram. Overview The term "diagram" in its commonly used sense can have a general or specific meaning: * ''visual information device'' : Like the term "illustration", "diagram" is used as a collective term standing for the whole class of technical genres, including graphs, technical drawings and tables. * ''specific kind of visual display'' : This is the genre that shows qualitative data with shapes that are connected by lines, arrows, or other visual links. In science the term is used in both ways. For example, Anderson (1997) stated more generally: "diagrams are pictorial, yet abstract, representatio ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Compound Eye
A compound eye is a Eye, visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidium, ommatidia, which are tiny independent photoreception units that consist of a cornea, lens (anatomy), lens, and photoreceptor cells which distinguish brightness and color. The image perceived by this arthropod eye is a combination of inputs from the numerous ommatidia, which are oriented to point in slightly different directions. Compared with single-aperture eyes, compound eyes have poor image resolution; however, they possess a very large view angle and the ability to detect fast movement and, in some cases, the Polarization (waves), polarization of light. Because a compound eye is made up of a collection of ommatidia, each with its own lens, light will enter each ommatidium instead of using a single entrance point. The individual light receptors behind each lens are then turned on and off due to a series of changes in the light intensity during mov ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Bilateria
Bilateria () is a large clade of animals characterised by bilateral symmetry during embryonic development. This means their body plans are laid around a longitudinal axis with a front (or "head") and a rear (or "tail") end, as well as a left–right–symmetrical belly ( ventral) and back ( dorsal) surface. Nearly all bilaterians maintain a bilaterally symmetrical body as adults; the most notable exception is the echinoderms, which have pentaradial symmetry as adults, but bilateral symmetry as embryos. With few exceptions, bilaterian embryos are triploblastic, having three germ layers: endoderm, mesoderm and ectoderm, and have complete digestive tracts with a separate mouth and anus. Some bilaterians lack body cavities, while others have a primary body cavity derived from the blastocoel, or a secondary cavity, the coelom. Cephalization is a characteristic feature among most bilaterians, where the sense organs and central nerve ganglia become concentrated at th ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Urbilaterian
The urbilaterian (from German ur- 'original') is the hypothetical last common ancestor of the bilaterian clade, i.e., all animals having a bilateral symmetry. Appearance Its appearance is a matter of debate, for no representative has been (or may or may not ever be) identified in the fossil record. Two reconstructed urbilaterian morphologies can be considered: first, the less complex ancestral form forming the common ancestor to Xenacoelomorpha and Nephrozoa; and second, the more complex (coelomate) urbilaterian ancestral to both protostomes and deuterostomes, sometimes referred to as the "urnephrozoan". Since most protostomes and deuterostomes share features — e.g. nephridia (and the derived kidneys), through guts, blood vessels and nerve ganglia— that are useful only in relatively large (macroscopic) organisms, their common ancestor ought also to have been macroscopic. However, such large animals should have left traces in the sediment in which they moved, and evidenc ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Opsin
Animal opsins are G-protein-coupled receptors and a group of proteins made light-sensitive via a chromophore, typically retinal. When bound to retinal, opsins become retinylidene proteins, but are usually still called opsins regardless. Most prominently, they are found in photoreceptor cells of the retina. Five classical groups of opsins are involved in Visual perception, vision, mediating the conversion of a photon of light into an electrochemical signal, the first step in the Visual phototransduction, visual transduction cascade. Another opsin found in the mammalian retina, melanopsin, is involved in circadian rhythms and Pupillary light reflex, pupillary reflex but not in vision. Humans have in total nine opsins. Beside vision and light perception, opsins may also sense temperature, sound, or chemicals. Structure and function Animal opsins detect light and are the molecules that allow us to see. Opsins are G-protein-coupled receptors (GPCRs), which are chemoreceptors and hav ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Exaptation
Exaptation or co-option is a shift in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another. Exaptations are common in both anatomy and behaviour. Bird feathers are a classic example. Initially they may have evolved for temperature regulation, but later were adapted for flight. When feathers were first used to aid in flight, that was an exaptive use. They have since then been shaped by natural selection to improve flight, so in their current state they are best regarded as adaptations for flight. So it is with many structures that initially took on a function as an exaptation: once molded for a new function, they become further adapted for that function. Interest in exaptation relates to both the process and products of evolution: the process that creates complex traits and the products (functions, anatomical structures, biochemicals, etc.) that may be imperfectly developed ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Crystallin
In anatomy, a crystallin is a water-soluble structural protein found in the lens and the cornea of the eye accounting for the transparency of the structure. It has also been identified in other places such as the heart, and in aggressive breast cancer tumors. The physical origins of eye lens transparency and its relationship to cataract are an active area of research. Since it has been shown that lens injury may promote nerve regeneration, crystallin has been an area of neural research. So far, it has been demonstrated that crystallin β b2 (crybb2) may be a neurite-promoting factor. Function The main function of crystallins at least in the lens of the eye is probably to increase the refractive index while not obstructing light. However, this is not their only function. It has become clear that crystallins may have several metabolic and regulatory functions, both within the lens and in other parts of the body. More proteins containing βγ-crystallin domains have now been char ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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David Berlinski
David Berlinski (born 1942) is an American mathematician and philosopher. He has written books about mathematics and the history of science as well as fiction. An opponent of evolution, he is a senior fellow of the Discovery Institute's Center for Science and Culture, an organization that promotes the pseudoscience, pseudoscientific idea of intelligent design. Berlinski professes to be a skepticism, skeptic about evolution, but he disavows belief in intelligent design. Early life and education David Berlinski was born in the United States in 1942 to German-born Jews, Jewish refugees who had emigrated to New York City in order to flee from France, where the Vichy France, Vichy government was Collaboration with Nazi Germany and Fascist Italy, collaborating with Nazi Germany. His father was composer Herman Berlinski and his mother was musician Sina Berlinski (née Goldfein), who was a pianist, Piano pedagogy, piano teacher and Vocal coach, voice coach. Both of his parents were bor ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Proceedings Of The Royal Society B
''Proceedings of the Royal Society'' is the main research journal of the Royal Society. The journal began in 1831 and was split into two series in 1905: * Series A: for papers in physical sciences and mathematics. * Series B: for papers in life sciences. Many landmark scientific discoveries are published in the Proceedings, making it one of the most important science journals in history. The journal contains several articles written by prominent scientists such as Paul Dirac, Werner Heisenberg, Ernest Rutherford, Erwin Schrödinger, William Lawrence Bragg, Lord Kelvin, J.J. Thomson, James Clerk Maxwell, Dorothy Hodgkin and Stephen Hawking. In 2004, the Royal Society began '' The Journal of the Royal Society Interface'' for papers at the interface of physical sciences and life sciences. History The journal began in 1831 as a compilation of abstracts of papers in the ''Philosophical Transactions of the Royal Society'', the older Royal Society publication, that began in 1665. ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Generation Time
In population biology and demography Demography () is the statistical study of human populations: their size, composition (e.g., ethnic group, age), and how they change through the interplay of fertility (births), mortality (deaths), and migration. Demographic analysis examine ..., generation time is the average time between two consecutive generations in the lineages of a population. In human populations, generation time typically has ranged from 20 to 30 years, with wide variation based on gender and society. Historians sometimes use this to date events, by converting generations into years to obtain rough estimates of time. Definitions and corresponding formulas The existing definitions of generation time fall into two categories: those that treat generation time as a renewal time of the population, and those that focus on the distance between individuals of one generation and the next. Below are the three most commonly used definitions: Time for a population to gro ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Red Queen Hypothesis
The Red Queen's hypothesis is a hypothesis in evolutionary biology proposed in 1973, that species must constantly adapt, evolve, and proliferate in order to survive while pitted against ever-evolving opposing species. The hypothesis was intended to explain the constant (age-independent) extinction probability as observed in the paleontological record caused by co-evolution between competing species; however, it has also been suggested that the Red Queen hypothesis explains the advantage of sexual reproduction (as opposed to asexual reproduction) at the level of individuals,Bell, G. (1982). The Masterpiece Of Nature: The Evolution and Genetics of Sexuality. University of California Press, Berkeley, 378 pp. and the positive correlation between speciation and extinction rates in most higher taxa. Origin In 1973, Leigh Van Valen proposed the hypothesis as an "explanatory tangent" to explain the "law of extinction" known as "Van Valen's law", which states that the probability of ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Andrew Parker (zoologist)
Andrew Parker (born 1967) (PhD Macquarie University) is a zoologist who has worked on biomimetics. He worked at the Natural History Museum in London, and from 1990 to 1999 he was a Royal Society University Research Fellow and is a research associate of the Australian Museum and University of Sydney and from 1999 until 2005 he worked at the University of Oxford. Parker is a visiting research fellow at Green Templeton College where he is head of a research team into photonic structures and eyes. "Light Switch Theory" and popular science books In his 2003 book ''In the Blink of an Eye'', Parker proposes that the Cambrian Explosion, as the sudden diversification in animal fossil forms at the start of the Cambrian Period, was due to the development of the vision faculty and the consequent intensification of predation. He calls this the "Light Switch Theory." In particular he concludes that predation with vision led to the development of hard body parts, explaining why the fossil rec ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |