1.
Halteres (ancient Greece)
–
This article concerns an ancient sports object. For halteres in insect anatomy, see Halteres, Halteres were a type of dumbbells used in Ancient Greece. In ancient Greek sports, halteres were used as lifting weights, and also as weights in their version of the long jump, Halteres were held in both hands to allow an athlete to jump a greater distance, they may have been dropped after the first or second jump. Halteres were made of stone or metal, and weighed between 2 and 9 kg, writing in Nature, biophysicist Alberto E. Minetti calculates that halteres added about 17 cm to a 3 m long jump
2.
Fly
–
True flies are insects of the order Diptera, the name being derived from the Greek di = two, and ptera = wings. Insects of this use only a single pair of wings to fly. Diptera is an order containing an estimated 1,000,000 species including horse-flies, crane flies, hoverflies and others. Flies have a head, with a pair of large compound eyes. Their wing arrangement gives them great manoeuvrability in flight, and claws, Flies undergo complete metamorphosis, the eggs are laid on the larval food-source and the larvae, which lack true limbs, develop in a protected environment, often inside their source of their food. The pupa is a capsule from which the adult emerges when ready to do so. Diptera is one of the insect orders and are of considerable ecological. Flies are important pollinators, second only to the bees and their Hymenopteran relatives, Flies may have been among the evolutionarily earliest pollinators responsible for early plant pollination. Flies can be annoyances especially in parts of the world where they can occur in large numbers. Larger flies such as flies and screwworms cause significant economic harm to cattle. Blowfly larvae, known as gentles, and other larvae, known more generally as maggots, are used as fishing bait. They are also used in medicine in debridement to clean wounds, dipterans are endopterygotes, insects that undergo radical metamorphosis. They belong to the Mecopterida, alongside the Mecoptera, Siphonaptera, Lepidoptera and Trichoptera, the possession of a single pair of wings distinguishes most true flies from other insects with fly in their names. However, some true flies such as Hippoboscidae have become secondarily wingless and this cladogram represents the current consensus view. The first true dipterans known are from the Middle Triassic, and they became widespread during the Middle, modern flowering plants did not appear until the Cretaceous, so the original dipterans must have had a different source of nutrition other than nectar. The basal clades in the Diptera include the Deuterophlebiidae and the enigmatic Nymphomyiidae, three episodes of evolutionary radiation are thought to have occurred based on the fossil record. Many new species of lower Diptera developed in the Triassic, about 220 million years ago, many lower Brachycera appeared in the Jurassic, some 180 million years ago. A third radiation took place among the Schizophora at the start of the Paleogene,66 million years ago, the phylogenetic position of Diptera has been controversial
3.
Crane fly
–
Crane fly is a common name referring to any member of the insect family Tipulidae, of the order Diptera, true flies in the superfamily Tipuloidea. Cylindrotominae, Limoniinae, and Pediciinae have been ranked as subfamilies of Tipulidae by most authors, in the most recent classifications, only Pediciidae is now ranked as a separate family, due to considerations of paraphyly. In colloquial speech crane flies are known as daddy longlegs. The larvae of flies are known commonly as leatherjackets. Crane flies are worldwide, though individual species usually have limited ranges. They are most diverse in the tropics, and are common in northern latitudes. The Tipulidae is one of the largest groups of flies, including over 15,000 species and subspecies in 525 genera and subgenera, most crane flies were described by the entomologist Charles Paul Alexander, a fly specialist, in over 1000 research publications. The adult crane fly, resembling an oversized mosquito, has a body and stilt-like legs that are deciduous. The wingspan is generally about 1.0 to 6.5 cm, the antennae have up to 39 segments. It is also characterized by a V-shaped suture on the back of the thorax, the rostrum is long, in some species it is as long as the head and thorax together. For terms see Morphology of Diptera Tipulidae are large to medium-sized flies with elongated legs, wings and their colour is yellow, brown or grey. The rostrum is short to very short with a point called the nasus. The apical segment of the palpi is flagelliform and much longer than the subapical segment. These are whorled, serrate, or ctenidial, there is a distinct V-shaped suture between the mesonotal prescutum and scutum. The wings are monochromatic, longitudinally striped or marbled, in females the wings are sometimes rudimentary. The sub-costal vein joins through Sc2 with the vein, Sc1 is at most a short stump. There are four, rarely three branches of the radial vein merging into the alar margin, the discoidal wing cell is usually present. The wing has two anal veins, sternite 9 of the male genitalia has, with few exceptions, two pairs of appendages
4.
Divergent evolution
–
Divergent evolution is the accumulation of differences between groups, leading to the formation of new species. The term can also be applied in molecular biology characteristics, such as to proteins that derive from two or more homologous genes, both orthologous genes and paralogous genes can be said to display divergent evolution. Because of the latter, it is possible for divergent evolution to occur between two genes within a species, similarities between species that have diverged is due to their common origin, so such similarities are homologies. In contrast, convergent evolution arises when an adaptation has arisen independently, creating structures such as the wings of birds. Divergent evolution similarly split the lineage from chimpanzees. Darwins finches provide an example of divergent evolution, where some 15 species diverged from a single species of finch that arrived on the Galapagos islands. The divergent evolution of wolves and domesticated dogs from an ancestor, perhaps the grey wolf. Recent studies of the mitochondrial DNA of wolves and of domesticated dogs have found great divergence while also supporting the hypothesis that dogs descend from wolves. Speciation, the divergence of one species into two or more descendant species, occurs when a part of the species is separated from the population by a reproductive barrier. In allopatric and peripatric speciation, the barrier is the result of a physical barrier. Once separated, the species begins to adapt to their new environment via genetic drift, after many generations and continual evolution, the populations become unable to interbreed with one another. Adaptive radiation Cladistics Devolution Molecular evolution
5.
Homology (biology)
–
In biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different taxa. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor, examples include the legs of a centipede, the maxillary palp and labial palp of an insect, and the spinous processes of successive vertebrae in a vertebral column. Sequence homology between protein or DNA sequences is defined in terms of shared ancestry. Two segments of DNA can have shared ancestry because of either an event or a duplication event. Homology among proteins or DNA is inferred from their sequence similarity, significant similarity is strong evidence that two sequences are related by divergent evolution from a common ancestor. Alignments of multiple sequences are used to discover the homologous regions, the word homology, coined in about 1656, derives from the Greek ὁμόλογος homologos from ὁμός homos same and λόγος logos relation. Homology is the relationship between biological structures or sequences that are derived from a common ancestor, for example, many insects possess two pairs of flying wings. In beetles, the first pair of wings has evolved into a pair of hard wing covers, the same major forearm bones are found in fossils of lobe-finned fish such as Eusthenopteron. The opposite of homologous organs are analogous organs which do similar jobs in two taxa that were not present in their last common ancestor but rather evolved separately. For example, the wings of insects and birds evolved independently in widely separated groups, similarly, the wings of a sycamore maple seed and the wings of a bird are analogous but not homologous, as they develop from quite different structures. A structure can be homologous at one level, but only analogous at another, for example, in the pterosaurs, the wing involves both the forelimb and the hindlimb. Analogy is called homoplasy in cladistics, and convergent or parallel evolution in evolutionary biology, specialised terms are used in taxonomic research. Primary homology is that initially conjectured by a researcher based on similar structure or anatomical connections, secondary homology is implied by parsimony analysis, where a character that only occurs once on a tree is taken to be homologous. As implied in this definition, many cladists consider homology to be synonymous with synapomorphy, homologies provide the fundamental basis for all biological classification, although some may be highly counter-intuitive. The homologies between these have been discovered by comparing genes in evolutionary developmental biology, among insects, the stinger of the female honey bee is a modified ovipositor, homologous with ovipositors in other insects such as the Orthoptera, Hemiptera, and those Hymenoptera without stingers. The three small bones in the ear of mammals including humans, the malleus, incus. The malleus and incus develop in the embryo from structures that form jaw bones in lizards, both lines of evidence show that these bones are homologous, sharing a common ancestor. Among the many homologies in mammal reproductive systems, ovaries and testicles are homologous, in many plants, defensive or storage structures are made by modifications of the development of primary leaves, stems, and roots
6.
Insect wing
–
Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third segments. The wings are strengthened by a number of veins, which often have cross-connections that form closed cells in the membrane. Physically, some insects move their flight muscles directly, others indirectly, in insects with direct flight, the wing muscles directly attached to the wing base, so that a small downward movement of the wing base lifts the wing itself upward. Those insects with indirect flight have muscles that attach to and deform the thorax, the wings are present in only one sex in some groups such as velvet ants and Strepsiptera, or are selectively lost in workers of social insects such as ants and termites. Rarely, the female is winged but the male not, as in fig wasps, in some cases, wings are produced only at particular times in the life cycle, such as in the dispersal phase of aphids. Wing structure and colouration often vary with morphs, such as in the aphids, migratory phases of locusts, how and why insect wings evolved is not well understood. Each of the consists of a thin membrane supported by a system of veins. Within each of the major veins there is a nerve and a trachea, as the wing develops, the dorsal and ventral integumental layers become closely apposed over most of their area forming the wing membrane. The remaining areas form channels, the veins, in which the nerves. The cuticle surrounding the veins becomes thickened and more heavily sclerotized to provide strength, two types of hair may occur on the wings, microtrichia, which are small and irregularly scattered, and macrotrichia, which are larger, socketed, and may be restricted to veins. The scales of Lepidoptera and Trichoptera are highly modified macrotrichia, in some very small insects, the venation may be greatly reduced. In Chalcidoidea, for instance, only the subcosta and part of the radius are present, large numbers of cross-veins are present in some insects, and they may form a reticulum as in the wings of Odonata and at the base of the forewings of Tettigonioidea and Acridoidea. The archedictyon is the given to a hypothetical scheme of wing venation proposed for the very first winged insect. It is based on a combination of speculation and fossil data, since all winged insects are believed to have evolved from a common ancestor, the archediction represents the template that has been modified by natural selection for 200 million years. According to current dogma, the archedictyon contained 6–8 longitudinal veins, the trachea of the costal vein is perhaps a branch of the subcostal trachea. Located after the costa is the vein, the subcosta. The base of the subcosta is associated with the end of the neck of the first axillary
7.
Coriolis force
–
In physics, the Coriolis force is an inertial force that acts on objects that are in motion relative to a rotating reference frame. In a reference frame with clockwise rotation, the acts to the left of the motion of the object. In one with anticlockwise rotation, the acts to the right. Early in the 20th century, the term Coriolis force began to be used in connection with meteorology, deflection of an object due to the Coriolis force is called the Coriolis effect. Newtons laws of motion describe the motion of an object in a frame of reference. When Newtons laws are transformed to a frame of reference. Both forces are proportional to the mass of the object, the Coriolis force is proportional to the rotation rate and the centrifugal force is proportional to its square. The Coriolis force acts in a perpendicular to the rotation axis. The centrifugal force acts outwards in the direction and is proportional to the distance of the body from the axis of the rotating frame. These additional forces are termed inertial forces, fictitious forces or pseudo forces and they allow the application of Newtons laws to a rotating system. They are correction factors that do not exist in a non-accelerating or inertial reference frame, a commonly encountered rotating reference frame is the Earth. The Coriolis effect is caused by the rotation of the Earth, such motions are constrained by the surface of the Earth, so only the horizontal component of the Coriolis force is generally important. This force causes moving objects on the surface of the Earth to be deflected to the right in the Northern Hemisphere, the horizontal deflection effect is greater near the poles, since the effective rotation rate about a local vertical axis is largest there, and smallest at the equator. This effect is responsible for the rotation of large cyclones, riccioli, Grimaldi, and Dechales all described the effect as part of an argument against the heliocentric system of Copernicus. In other words, they argued that the Earths rotation should create the effect, the effect was described in the tidal equations of Pierre-Simon Laplace in 1778. Gaspard-Gustave Coriolis published a paper in 1835 on the yield of machines with rotating parts. That paper considered the forces that are detected in a rotating frame of reference. Coriolis divided these forces into two categories
8.
Acrobatics
–
Acrobatics is the performance of extraordinary feats of balance, agility, and motor coordination. It can be found in many of the arts, sports events. Although acrobatics is most commonly associated with human performance, it may also apply to other types of performance. Acrobatic traditions are found in cultures, and there is evidence that the earliest such traditions occurred thousands of years ago. For example, Minoan art from c.2000 BC contains depictions of acrobatic feats on the backs of bulls, ancient Greeks and Romans practiced acrobatics, and the noble court displays of the European Middle Ages would often include acrobatic performances that included juggling. In China, acrobatics have been a part of the culture since the Western Han Dynasty, acrobatics were part of village harvest festivals. Acrobatics continues to be an important part of modern Chinese variety art, though the term initially applied to tightrope walking, in the 19th century, a form of performance art including circus acts began to use the term as well. In the late 19th century, tumbling and other acrobatic and gymnastic activities became competitive sport in Europe, acrobatics has often served as a subject for fine art. An aerialist is an acrobat who performs in the air, on a suspended apparatus such as a trapeze, rope, cloud swing, aerial cradle, aerial pole, aerial silk, acrobatic gymnastics Contortion List of acrobatic activities
9.
Strepsiptera
–
The Strepsiptera are an endopterygote order of insects with nine extant families making up about 600 species. Males of the Strepsiptera have wings, legs, eyes, and antennae, many of their mouthparts are modified into sensory structures. Adult males are very short-lived, usually surviving less than five hours, females, in all families except the Mengenillidae, are not known to leave their hosts and are neotenic in form, lacking wings, legs, and eyes. Virgin females release a pheromone which the use to locate them. In the Stylopidia, the anterior region protrudes out of the host body and the male mates by rupturing the females brood canal opening. Sperm passes through the opening in a process termed hypodermic insemination, the offspring consume their mother from the inside in a process known as hemocelous viviparity. Each female thus produces many thousands of larvae that emerge from the brood opening on the head. These larvae have legs, and actively search out new hosts and their hosts include members of the orders Zygentoma, Orthoptera, Blattodea, Mantodea, Heteroptera, Hymenoptera, and Diptera. In the strepsipteran family Myrmecolacidae, the males parasitize ants, while the females parasitize Orthoptera, Strepsiptera eggs hatch inside the female, and the planidium larvae can move around freely within the females haemocoel, which is unique to these animals. The female has a canal that communicates with the outside world. The larvae are active, as they only have a limited amount of time to find a host before they exhaust their food reserves. These first-instar larvae have stemmata, and once they latch onto a host, they enter it by secreting enzymes that soften the cuticle, some species have been reported to enter the eggs of hosts. Larvae of Stichotrema dallatorreanurn Hofeneder from Papua New Guinea were found to enter their orthopteran hosts tarsus, once inside the host, they undergo hypermetamorphosis and become a less mobile, legless larval form. They induce the host to produce a bag-like structure inside which they feed and this structure, made from host tissue, protects them from the immune defences of the host. Larvae go through four instars, and in each moult separation of the older cuticle occurs. Male larvae produce pupae after the last moult, but females directly become neotenous adults, the colour and shape of the hosts abdomen may be changed and the host usually becomes sterile. The parasites then undergo pupation to become adults, adult males emerge from the host bodies, while females stay inside. Females may occupy up to 90% of the volume of their hosts
10.
Gyroscope
–
A gyroscope is a spinning wheel or disc in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum, because of this, gyroscopes are useful for measuring or maintaining orientation. Due to their precision, gyroscopes are used in gyrotheodolites to maintain direction in tunnel mining. Gyroscopes can be used to construct gyrocompasses, which complement or replace magnetic compasses, a gyroscope is a wheel mounted in two or three gimbals, which are a pivoted supports that allow the rotation of the wheel about a single axis. In the case of a gyroscope with two gimbals, the gimbal, which is the gyroscope frame, is mounted so as to pivot about an axis in its own plane determined by the support. This outer gimbal possesses one degree of freedom and its axis possesses none. The inner gimbal is mounted in the frame so as to pivot about an axis in its own plane that is always perpendicular to the pivotal axis of the gyroscope frame. This inner gimbal has two degrees of rotational freedom, the axle of the spinning wheel defines the spin axis. The rotor is constrained to spin about an axis, which is perpendicular to the axis of the inner gimbal. So the rotor possesses three degrees of freedom and its axis possesses two. The wheel responds to a force applied to the axis by a reaction force to the output axis. The behaviour of a gyroscope can be most easily appreciated by consideration of the front wheel of a bicycle. If the wheel is leaned away from the vertical so that the top of the moves to the left. In other words, rotation on one axis of the turning wheel produces rotation of the third axis, a gyroscope flywheel will roll or resist about the output axis depending upon whether the output gimbals are of a free or fixed configuration. Examples of some free-output-gimbal devices would be the attitude reference gyroscopes used to sense or measure the pitch, roll, the centre of gravity of the rotor can be in a fixed position. Some gyroscopes have mechanical equivalents substituted for one or more of the elements, for example, the spinning rotor may be suspended in a fluid, instead of being pivotally mounted in gimbals. In some special cases, the outer gimbal may be omitted so that the rotor has two degrees of freedom. Essentially, a gyroscope is a top combined with a pair of gimbals, Tops were invented in many different civilizations, including classical Greece, Rome, and China
11.
Rotation
–
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object always rotates around a line called a rotation axis. If the axis passes through the center of mass, the body is said to rotate upon itself. A rotation about a point, e. g. the Earth about the Sun, is called a revolution or orbital revolution. The axis is called a pole, mathematically, a rotation is a rigid body movement which, unlike a translation, keeps a point fixed. This definition applies to rotations within both two and three dimensions All rigid body movements are rotations, translations, or combinations of the two, a rotation is simply a progressive radial orientation to a common point. That common point lies within the axis of that motion, the axis is 90 degrees perpendicular to the plane of the motion. If the axis of the rotation lies external of the body in question then the body is said to orbit, there is no fundamental difference between a “rotation” and an “orbit” and or spin. The key distinction is simply where the axis of the rotation lies and this distinction can be demonstrated for both “rigid” and “non rigid” bodies. If a rotation around a point or axis is followed by a rotation around the same point/axis. The reverse of a rotation is also a rotation, thus, the rotations around a point/axis form a group. However, a rotation around a point or axis and a rotation around a different point/axis may result in something other than a rotation, Rotations around the x, y and z axes are called principal rotations. Rotation around any axis can be performed by taking a rotation around the x axis, followed by a rotation around the y axis and that is to say, any spatial rotation can be decomposed into a combination of principal rotations. In flight dynamics, the rotations are known as yaw, pitch. This terminology is used in computer graphics. In astronomy, rotation is an observed phenomenon. Stars, planets and similar bodies all spin around on their axes, the rotation rate of planets in the solar system was first measured by tracking visual features. Stellar rotation is measured through Doppler shift or by tracking active surface features and this rotation induces a centrifugal acceleration in the reference frame of the Earth which slightly counteracts the effect of gravity the closer one is to the equator
12.
William Derham
–
William Derham FRS was an English clergyman, natural theologian and natural philosopher. He produced the earliest, reasonably accurate estimate of the speed of sound, William Derham was the son of Thomas Derham. He was born at Stoulton, in Worcestershire, England and he was educated at Blockley, Gloucestershire and at Trinity College, Oxford from 1675 to 1679. He was ordained on 29 May 1681, in 1682, he became vicar of Wargrave, Berkshire and from 1689 to 1735 he was Rector at Upminster, Essex. While at Upminster, in 1716 he became a Canon of Windsor, the parish registers of Upminster record his burial at St. Laurences in 1735. However, the site of his grave is unknown and, in accordance with his wishes. In 1696, he published his Artificial Clockmaker, which went through several editions, the best known of his subsequent works are Physico-Theology, published in 1713, Astro-Theology,1714, and Christo-Theology,1730. All three of these books are teleological arguments for the being and attributes of God, and were used by William Paley nearly a century later, however, these books also include quantities of original scientific observations. For example, Physico-Theology contains his recognition of natural variation within species and it also includes one of the earliest theoretical descriptions of a marine chronometer, accompanied by a discussion of the use of vacuum seals to reduce inaccuracies in the operation of timepieces. Similarly, Astro-Theology includes several newly identified nebulae and his 16-feet long telescope was at the top of the tower of St Laurences Church, where the necessary doors are still in place. On 3 February 1703, Derham was elected Fellow of the Royal Society and he was Boyle lecturer in 1711–1712. His last known work, entitled A Defence of the Churchs Right in Leasehold Estates, but besides the works published in his own name, Derham contributed a variety of papers to the Transactions of the Royal Society. He edited the correspondence and wrote a biography of John Ray, whose physico-theology tradition he continued and he edited Eleazar Albins Natural History, and published some of the manuscripts of the scientist Robert Hooke. His meteorological observations at Upminster are amongst the earliest series in England, in 1709 Derham published a more accurate measure of the speed of sound, at 1,072 Parisian feet per second. Measurements were made of gunshots from a number of local landmarks, the distance was known by triangulation, and thus the speed that the sound had travelled was calculated
13.
Hot air balloon
–
A hot air balloon is a lighter than air aircraft consisting of a bag, called an envelope, which contains heated air. Suspended beneath is a gondola or wicker basket, which carries passengers, the heated air inside the envelope makes it buoyant since it has a lower density than the colder air outside the envelope. As with all aircraft, hot air balloons cannot fly beyond the atmosphere, unlike gas balloons, the envelope does not have to be sealed at the bottom, since the air near the bottom of the envelope is at the same pressure as the surrounding air. In modern sport balloons the envelope is made from nylon fabric. The hot air balloon is the first successful human-carrying flight technology, the first hot-air balloon flown in the Americas was launched from the Walnut Street Jail in Philadelphia on January 9,1793 by the French aeronaut Jean Pierre Blanchard. Hot air balloons that can be propelled through the air rather than simply drifting with the wind are known as thermal airships, early unmanned hot air balloons were used in China. Zhuge Liang of the Shu Han kingdom, during the Three Kingdoms era and these lanterns are known as Kongming lanterns. Later that same day, Pilatre de Rozier became the human to ascend into the air, reaching an altitude of 26 m. The first free flight with passengers was made a few weeks later. King Louis XVI had originally decreed that condemned criminals would be the first pilots, the first military use of a hot air balloon happened in 1794 during the battle of Fleurus, when the French used the balloon lEntreprenant for observation. Modern hot air balloons, with a heat source, were developed by Ed Yost, beginning during the 1950s, his work resulted in his first successful flight. The first modern hot air balloon to be made in the United Kingdom was the Bristol Belle, presently, hot air balloons are used primarily for recreation. Hot air balloons are able to fly to extremely high altitudes, on November 26,2005 Vijaypat Singhania set the world altitude record for highest hot air balloon flight, reaching 21,027 m. He took off from downtown Mumbai, India, and landed 240 km south in Panchale, the previous record of 19,811 m had been set by Per Lindstrand on June 6,1988, in Plano, Texas. With a volume of 74 thousand cubic meters, the envelope was the largest ever built for a hot air craft. Designed to fly in the jet streams, the Pacific Flyer recorded the fastest ground speed for a manned balloon at 245 mph. The longest duration record was set by Swiss psychiatrist Bertrand Piccard, Auguste Piccards grandson and it was the first nonstop trip around the world by balloon. The balloon left Château-dOex, Switzerland, on March 1,1999, the two men exceeded distance, endurance, and time records, traveling 19 days,21 hours, and 55 minutes
14.
Insecta
–
Insects are a class of hexapod invertebrates within the arthropod phylum that have a chitinous exoskeleton, a three-part body, three pairs of jointed legs, compound eyes and one pair of antennae. They are the most diverse group of animals on the planet, including more than a million described species, the number of extant species is estimated at between six and ten million, and potentially represent over 90% of the differing animal life forms on Earth. Insects may be found in all environments, although only a small number of species reside in the oceans. The life cycles of insects vary but most hatch from eggs, insect growth is constrained by the inelastic exoskeleton and development involves a series of molts. The immature stages can differ from the adults in structure, habit and habitat, Insects that undergo 3-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages. The higher level relationship of the Hexapoda is unclear, fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm. The most diverse insect groups appear to have coevolved with flowering plants, adult insects typically move about by walking, flying or sometimes swimming. As it allows for rapid yet stable movement, many insects adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles, Insects are the only invertebrates to have evolved flight. Many insects spend at least part of their lives under water, with adaptations that include gills. Some species, such as water striders, are capable of walking on the surface of water, Insects are mostly solitary, but some, such as certain bees, ants and termites, are social and live in large, well-organized colonies. Some insects, such as earwigs, show maternal care, guarding their eggs, Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over great distances, other species communicate with sounds, crickets stridulate, or rub their wings together, to attract a mate and repel other males. Lampyridae in the beetle order communicate with light, humans regard certain insects as pests, and attempt to control them using insecticides and a host of other techniques. Some insects damage crops by feeding on sap, leaves or fruits, a few parasitic species are pathogenic. Some insects perform complex ecological roles, blow-flies, for example, help consume carrion, Many other insects are considered ecologically beneficial as predators and a few provide direct economic benefit. Silkworms and bees have been used extensively by humans for the production of silk and honey, in some cultures, people eat the larvae or adults of certain insects. Insect first appears documented in English in 1601 in Hollands translation of Pliny, translations of Aristotles term also form the usual word for insect in Welsh, Serbo-Croatian, Russian, etc. The evolutionary relationship of insects to other animal groups remains unclear, in the Pancrustacea theory, insects, together with Entognatha, Remipedia, and Cephalocarida, make up a natural clade labeled Miracrustacea
15.
Lepidoptera
–
The Lepidoptera is an order of insects that includes moths and butterflies. 180,000 species of Lepidoptera are described, in 126 families and 46 superfamilies and it is one of the most widespread and widely recognizable insect orders in the world. The term was coined by Linnaeus in 1735 and is derived from Ancient Greek λεπίδος, the Lepidoptera show many variations of the basic body structure that have evolved to gain advantages in lifestyle and distribution. Recent estimates suggest the order may have more species than earlier thought, and is among the four most speciose orders, along with the Hymenoptera, Diptera, and Coleoptera. Lepidopteran species are characterized by more than three derived features, some of the most apparent being the scales covering their bodies and wings, the scales are modified, flattened hairs, and give butterflies and moths their extraordinary variety of colors and patterns. Almost all species have some form of wings, except for a few that have reduced wings or are wingless. Like most other insects, butterflies and moths are holometabolous, meaning they undergo complete metamorphosis, mating and the laying of eggs are carried out by adults, normally near or on host plants for the larvae. As they grow, these change in appearance, going through a series of stages called instars. Once fully matured, the larva develops into a pupa A few butterflies and many species spin a silk case or cocoon prior to pupating, while others do not. A butterfly pupa, called a chrysalis, has a hard skin, once the pupa has completed its metamorphosis, a sexually mature adult emerges. Accordingly, this is the most recognized and popular of insect orders with many involved in the observation, study, collection, rearing of. A person who collects or studies this order is referred to as a lepidopterist, in many species, the female may produce from 200 to 600 eggs, while in others, the number may approach 30,000 eggs in one day. The caterpillars hatching from eggs can cause damage to large quantities of crops. Many moth and butterfly species are of economic interest by virtue of their role as pollinators, the word Lepidoptera comes from the Latin word for scaly wing, from the Ancient Greek λεπίς meaning scale and πτερόν meaning wing. The origins of the common names butterfly and moth are varied, the English word butterfly is from Old English buttorfleoge, with many variations in spelling. Other than that, the origin is unknown, although it could be derived from the yellow color of many species wings suggesting the color of butter. The species of Heterocera are commonly called moths, the origins of the English word moth are more clear, deriving from the Old English moððe from Common Germanic. The Lepidoptera are among the most successful groups of insects, among the most northern dwelling species of butterflies and moths is the Arctic Apollo, which is found in the Arctic Circle in northeastern Yakutia, at an altitude of 1500 m above sea level
16.
Parasitism
–
In biology/ecology, parasitism is a non-mutual relationship between species, where one species, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred primarily to organisms visible to the naked eye, Parasites can be microparasites, which are typically smaller, such as protozoa, viruses, and bacteria. Examples of parasites include the plants mistletoe and cuscuta, and animals such as hookworms, unlike predators, parasites typically do not kill their host, are generally much smaller than their host, and will often live in or on their host for an extended period. Both are special cases of consumer-resource interactions, Parasites show a high degree of specialization, and reproduce at a faster rate than their hosts. Classic examples of parasitism include interactions between vertebrate hosts and tapeworms, flukes, the Plasmodium species, and fleas, parasitism differs from the parasitoid relationship in that parasitoids generally kill their hosts. Parasites reduce host biological fitness by general or specialized pathology, such as parasitic castration and impairment of secondary sex characteristics, Parasites increase their own fitness by exploiting hosts for resources necessary for their survival, e. g. food, water, heat, habitat, and transmission. Although parasitism applies unambiguously to many cases, it is part of a continuum of types of interactions between species, rather than an exclusive category, in many cases, it is difficult to demonstrate harm to the host. In others, there may be no apparent specialization on the part of the parasite, coined in English in 1611, the word parasitism comes from the Greek παρά + σιτισμός feeding, fattening. Parasites are classified based on their interactions with their hosts and on their life cycles, an obligate parasite is totally dependent on the host to complete its life cycle, while a facultative parasite is not. A direct parasite has one host while an indirect parasite has multiple hosts. For indirect parasites, there always be a definitive host. Parasites that live on the outside of the host, either on the skin or the outgrowths of the skin, are called ectoparasites and those that live inside the host are called endoparasites. Endoparasites can exist in one of two forms, intercellular parasites or intracellular parasites, intracellular parasites, such as protozoa, bacteria or viruses, tend to rely on a third organism, which is generally known as the carrier or vector. The vector does the job of transmitting them to the host, an example of this interaction is the transmission of malaria, caused by a protozoan of the genus Plasmodium, to humans by the bite of an anopheline mosquito. Those parasites living in a position, being half-ectoparasites and half-endoparasites, are called mesoparasites. An epiparasite is one that feeds on another parasite and this relationship is also sometimes referred to as hyperparasitism, exemplified by a protozoan living in the digestive tract of a flea living on a dog. Social parasites take advantage of interactions between members of social organisms such as ants, termites, and bumblebees, an extreme example of social parasitism is the ant species of Tetramorium inquilinum of the Alps, which spend their whole lives on the back of Tetramorium host ants. With tiny and deprecated bodies they have evolved for one single task, if they fall off, they most likely would not have the strength to climb back on top of another ant, and eventually they will die
17.
Thorax
–
The thorax or chest is a part of the anatomy of humans and various other animals located between the neck and the abdomen. The thorax includes the thoracic cavity and the thoracic wall and it contains organs including the heart, lungs, and thymus gland, as well as muscles and various other internal structures. Many diseases may affect the chest, and one of the most common symptoms is chest pain, in humans and other hominids, the thorax is the chest region of the body between the neck and the abdomen, along with its internal organs and other contents. It is mostly protected and supported by the rib cage, spine, arteries and veins are also contained –, bones. The area exposed by open-necked shirts, the V of the chest is sometimes the location of a skin disease polymorphous light eruption. In the human body, the region of the thorax between the neck and diaphragm in the front of the body is called the chest, the corresponding area in an animal can also be referred to as the chest. The shape of the chest does not correspond to part of the thoracic skeleton that encloses the heart. All the breadth of the shoulders is due to the girdle, and contains the axillae. Level with this line the second ribs join the sternum, at the lower part of the sternum, where the seventh or last true ribs join it, the ensiform cartilage begins, and above this there is often a depression known as the pit of the stomach. The bones of the thorax, called the thoracic skeleton is a component of the axial skeleton and it consists of the ribs and sternum. The ribs of the thorax are numbered in ascending order from 1-12. 11 &12 are known as floating ribs because they have no anterior attachment point in particular the cartilage attached to the sternum, as 1-7 are, whereas ribs 8-10 are termed false ribs as their costal cartilage articulates with the rib aboves costal cartilage. The anatomy of the chest can also be described through the use of anatomical landmarks, the female nipple is surrounded for half an inch by a more or less pigmented disc, the areola. The apex of a heart is in the fifth left intercostal space. Different types of diseases or conditions that affect the chest include pleurisy, flail chest, atelectasis, and these conditions can be hereditary or caused by birth defects or trauma. Any condition that lowers the ability to breathe deeply or to cough is considered a chest disease or condition. Injury to the chest results in up to ¼ of all due to trauma in the United States. The major pathophysiologies encountered in blunt chest trauma involve derangements in the flow of air, blood, sepsis due to leakage of alimentary tract contents, as in esophageal perforations, also must be considered. Blunt trauma commonly results in chest wall injuries, the pain associated with these injuries can make breathing difficult, and this may compromise ventilation
18.
Host (biology)
–
In biology, a host is an organism that harbors a parasitic, a mutual, or a commensal symbiont, typically providing nourishment and shelter. Examples include animals playing host to parasitic worms, cells harbouring a parasitic virus, more specifically in botany, a host plant supplies food resources and acts as a substrate for commensalist insects or other fauna. Guest is the term used for parasites, mutualists and commensals. The host range of a parasite is the collection of hosts that an organism can utilize as a partner, in the case of human parasites, the host range influences the epidemiology of the parasitism or disease. For instance, the production of antigenic shifts in Influenza A virus can result from pigs being infected with the virus from different hosts. This co-infection provides an opportunity for mixing of the viral genes between existing strains, thereby producing a new viral strain
19.
Antenna (biology)
–
Antennae, sometimes referred to as feelers, are paired appendages used for sensing in arthropods. Antennae are connected to the first one or two segments of the arthropod head and they vary widely in form, but are always made of one or more jointed segments. While they are sensory organs, the exact nature of what they sense. Functions may variously include sensing touch, air motion, heat, vibration, antennae are sometimes modified for other purposes, such as mating, brooding, swimming, and even anchoring the arthropod to a substrate. Larval arthropods have antennae that differ from those of the adult, many crustaceans, for example, have free-swimming larval forms that use their antennae for swimming. Except the chelicerates and proturans, which have none, all non-crustacean arthropods have a pair of antennae. Crustaceans bear two pairs of antennae, the pair attached to the first segment of the head are called primary antennae or antennules. This pair is generally uniramous, but is biramous in crabs and lobsters, the pair attached to the second segment are called secondary antennae or simply antennae. The second antennae are biramous, but many species later evolved uniramous pairs. The second antennae may be reduced, apparently absent, or modified to such an extent that they no longer resemble antennae. The subdivisions of crustacean antennae have many names, including flagellomeres, annuli, articles, the terminal ends of crustacean antennae have two major categorizations, segmented and flagellate. An antenna is considered segmented if each of the annuli is separate from those around it and has individual muscle attachments. Flagellate antennae, on the hand, have muscle attachments only around the base. There are several notable uses of antennae in crustaceans. Many crustaceans have a larval stage called a nauplius, which is characterized by its use of antennae for swimming. Barnacles, a highly modified crustacean, use their antennae to attach to rocks, insects evolved from prehistoric crustaceans, and they have secondary antennae like crustaceans, but not primary antennae. Antennae are the primary olfactory sensors of insects and are accordingly well-equipped with a variety of sensilla. Paired, mobile, and segmented, they are located between the eyes on the forehead, embryologically, they represent the appendages of the second head segment
20.
Hox gene
–
Hox genes are a group of related genes that control the body plan of an embryo along the cranio-caudal axis. After the embryonic segments have formed, the Hox proteins determine the type of segment structures that form on a given segment. Hox proteins thus confer segmental identity, but do not form the segments themselves. An analogy for the Hox genes can be made to the role of a director that calls which scene the actors should carry out next. If the play director calls the scenes in the wrong order, similarly, mutations in the Hox genes can result in body parts and limbs in the wrong place along the body. Like a play director, the Hox genes do not act in the play or participate in limb formation themselves, the protein product of each Hox gene is a transcription factor. Each Hox gene contains a well-conserved DNA sequence known as the homeobox, Hox genes are thus a subset of the homeobox transcription factor genes. The products of Hox genes are Hox proteins, the same Hox protein can act as a repressor at one gene and an activator at another. The ability of Hox proteins to bind DNA is conferred by a part of the referred to as the homeodomain. The homeodomain is a 60-amino-acid-long DNA-binding domain and this amino acid sequence folds into a helix-turn-helix motif that is stabilized by a third helix. In addition, homeodomains of individual Hox proteins usually exhibit greater similarity to homeodomains in other species than to proteins encoded by adjacent genes within their own Hox cluster. The functional conservation of Hox proteins can be demonstrated by the fact that a fly can function well with a chicken Hox protein in place of its own. So, despite having a last common ancestor that lived over 670 million years ago, Drosophila melanogaster is an important model for understanding body plan generation and evolution. The general principles of Hox gene function and logic elucidated in flies will apply to all bilaterian organisms, Drosophila, like all insects, has eight Hox genes. These are clustered into two complexes, both of which are located on chromosome 3, the Antennapedia complex consists of five genes, labial, proboscipedia, deformed, sex combs reduced, and Antennapedia. The Bithorax complex, named after the Ultrabithorax gene, consists of the three genes, Ultrabithorax, abdominal-A and abdominal-B. The lab gene is the most anteriorly expressed gene and it is expressed in the head, primarily in the intercalary segment, and also in the midgut. Loss of function of lab results in the failure of the Drosophila embryo to internalize the mouth, failure of head involution disrupts or deletes the salivary glands and pharynx
21.
Arthropod
–
An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods form the phylum Arthropoda, which includes the insects, arachnids, myriapods, arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages, the rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Their versatility has enabled them to become the most species-rich members of all guilds in most environments. They have over a million described species, making up more than 80% of all described living species, some of which. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab, arthropods primary internal cavity is a hemocoel, which accommodates their internal organs, and through which their haemolymph – analogue of blood – circulates, they have open circulatory systems. Like their exteriors, the organs of arthropods are generally built of repeated segments. Their nervous system is ladder-like, with paired ventral nerve cords running through all segments and their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong, arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many setae that project through their cuticles. Aquatic species use internal or external fertilization. Almost all arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother, arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form. The level of care for hatchlings varies from nonexistent to the prolonged care provided by scorpions. The evolutionary ancestry of arthropods dates back to the Cambrian period, the group is generally regarded as monophyletic, and many analyses support the placement of arthropods with cycloneuralians in a superphylum Ecdysozoa. Overall however, the relationships of Metazoa are not yet well resolved. Likewise, the relationships between various groups are still actively debated. Arthropods contribute to the food supply both directly as food, and more importantly indirectly as pollinators of crops. Some species are known to spread disease to humans, livestock. The word arthropod comes from the Greek ἄρθρον árthron, joint, and πούς pous, i. e. foot or leg, arthropods are invertebrates with segmented bodies and jointed limbs
22.
Vertebra
–
The basic configuration of a vertebra varies, the large part is the body, and the central part is the centrum. The upper and lower surfaces of the vertebra body give attachment to the intervertebral discs, the posterior part of a vertebra forms a vertebral arch, in eleven parts, consisting of two pedicles, two laminae, and seven processes. The laminae give attachment to the ligamenta flava, there are vertebral notches formed from the shape of the pedicles, which form the intervertebral foramina when the vertebrae articulate. These foramina are the entry and exit conducts for the spinal nerves, the body of the vertebra and the vertebral arch form the vertebral foramen, the larger, central opening that accommodates the spinal canal, which encloses and protects the spinal cord. Vertebrae articulate with other to give strength and flexibility to the spinal column. Structurally, vertebrae are essentially alike across the species, with the greatest difference seen between an aquatic animal and other vertebrate animals. As such, vertebrates take their name from the vertebrae that compose the vertebral column, each vertebra is an irregular bone. The size of the vertebrae varies according to placement in the column, spinal loading, posture. Along the length of the spine the vertebrae change to different needs related to stress. Every vertebra has a body, which consists of a large anterior middle portion called the centrum, the body is composed of cancellous bone, which is the spongy type of osseous tissue, whose micro-anatomy has been specifically studied within the pedicle bones. This cancellous bone is in turn, covered by a coating of cortical bone. The vertebral arch and processes have thicker coverings of cortical bone, the upper and lower surfaces of the body of the vertebra are flattened and rough in order to give attachment to the intervertebral discs. These surfaces are the vertebral endplates which are in contact with the intervertebral discs. The endplates are formed from a layer of the cancellous bone of the vertebral body. The endplates function to contain the adjacent discs, to spread the applied loads. They also act as an interface for the exchange of water. The vertebral arch is formed by pedicles and laminae, two pedicles extend from the sides of the vertebral body to join the body to the arch. The pedicles are short thick processes that extend, one each side, posteriorly, from the junctions of the posteriolateral surfaces of the centrum
23.
Metamorphosis
–
Metamorphosis is iodothyronine-induced and an ancestral feature of all chordates. Some insects, fishes, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, animals that go through metamorphosis are called metamorphoses. Animals can be divided into species that undergo metamorphosis, incomplete metamorphosis. Scientific usage of the term is technically precise, and it is not applied to general aspects of cell growth, the word metamorphosis derives from Greek μεταμόρφωσις, transformation, transforming, from μετα-, change and μορφή, form. Metamorphosis is iodothyronine-induced and a feature of all chordates. In insects growth and metamorphosis are controlled by hormones synthesized by endocrine glands near the front of the body, neurosecretory cells in an insects brain secrete a hormone, the prothoracicotropic hormone that activates prothoracic glands, which secrete a second hormone, usually ecdysone, that induces ecdysis. PTTH also stimulates the corpora allata, an organ, to produce juvenile hormone. Experiments on firebugs have shown how juvenile hormone can affect the number of nymph instar stages in hemimetabolous insects, All three categories can be found in the diversity of insects, including no metamorphosis, incomplete or partial metamorphosis, and complete metamorphosis. In hemimetabolous insects, immature stages are called nymphs, development proceeds in repeated stages of growth and ecdysis, these stages are called instars. The juvenile forms closely resemble adults, but are smaller and lack features such as wings. The size and morphological differences between nymphs in different instars are small, often just differences in proportions and the number of segments, in later instars. In holometabolous insects, immature stages are called larvae, and differ markedly from adults, insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa, and finally emerge as adults. The earliest insect forms showed direct development, and the evolution of metamorphosis in insects is thought to have fuelled their dramatic radiation, some early ametabolous true insects are still present today, such as bristletails and silverfish. Hemimetabolous insects include cockroaches, grasshoppers, dragonflies, and true bugs, phylogenetically, all insects in the Pterygota undergo a marked change in form, texture and physical appearance from immature stage to adult. According to research from 2008, adult Manduca sexta is able to retain behavior learned as a caterpillar, many observations have indicated that programmed cell death plays a considerable role during physiological processes of multicellular organisms, particularly during embryogenesis and metamorphosis. Sequence illustrating complete metamorphosis in the white butterfly, Pieris rapae In typical amphibian development, eggs are laid in water. Frogs, toads, and newts all hatch from the eggs as larvae with external gills, afterwards, newt larvae start a predatory lifestyle, while tadpoles mostly scrape food off surfaces with their horny tooth ridges. Metamorphosis in amphibians is regulated by thyroxin concentration in the blood, which stimulates metamorphosis, and prolactin, specific events are dependent on threshold values for different tissues
24.
Phenotype
–
A phenotype is the composite of an organisms observable characteristics or traits, such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior. A phenotype results from the expression of a genetic code, its genotype, as well as the influence of environmental factors. When two or more clearly different phenotypes exist in the population of a species, the species is called polymorphic. A well-documented polymorphism is Labrador Retriever coloring, while the color depends on many genes, it is clearly seen in the environment as yellow, black. This genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organisms heredity and what that heredity produces, the distinction is similar to that proposed by August Weismann, who distinguished between germ plasm and somatic cells. The term phenotype has sometimes incorrectly used as a shorthand for phenotypic difference from wild type. Despite its seemingly straightforward definition, the concept of the phenotype has hidden subtleties and it may seem that anything dependent on the genotype is a phenotype, including molecules such as RNA and proteins. It may seem that this goes beyond the intentions of the concept with its focus on the organism in itself. Either way, the term phenotype includes traits or characteristics that can be visible by some technical procedure. A notable extension to this idea is the presence of molecules or metabolites that are generated by organisms from chemical reactions of enzymes. Another extension adds behavior to the phenotype, since behaviors are also observable characteristics, behavioral phenotypes include cognitive, personality, and behavioral patterns. Some behavioral phenotypes may characterize psychiatric disorders or syndromes, phenotypic variation is a fundamental prerequisite for evolution by natural selection. It is the organism as a whole that contributes to the next generation. Without phenotypic variation, there would be no evolution by natural selection, the plant Hieracium umbellatum is found growing in two different habitats in Sweden. These habitats alternate along the coast of Sweden and the habitat that the seeds of Hieracium umbellatum land in, the concept of phenotype can be extended to variations below the level of the gene that affect an organisms fitness. For example, silent mutations that do not change the amino acid sequence of a gene may change the frequency of guanine-cytosine base pairs. The term extended phenotype refers to the idea that a phenotype is not restricted to biological processes, the concept generalized by Richard Dawkins explains that phenotype includes all the influence a gene has on the environment and other organisms. ”There are three types of extended phenotypes. The first describes an organism using architectural constructions to modify their environment for living, the most common example given by Dawkins is the beaver
25.
Insect flight
–
Insects are the only group of invertebrates that have evolved wings and flight. Two insect groups, the dragonflies and the mayflies, have flight muscles attached directly to the wings, other insects have the flight muscles attached to the thorax, making it oscillate and indirectly causing the wings to beat. Some very small insects make use not of steady-state aerodynamics but of the Weis-Fogh clap and fling mechanism, many insects can hover, maintaining height and controlling their position. Some insects such as moths have the forewings coupled to the hindwings so these can work in unison, insects first flew in the Carboniferous, some 350 million years ago. Wings may have evolved from appendages on the sides of existing limbs, which already had nerves, joints and these may initially have been used for sailing on water, or to slow the rate of descent when gliding. Dragonflies and damselflies have fore and hind wings similar in shape, each operates independently, which gives a degree of fine control and mobility in terms of the abruptness with which they can change direction and speed, not seen in other flying insects. This is not surprising, given that odonates are all aerial predators, other than the two orders with direct flight muscles, all other living winged insects fly using a different mechanism, involving indirect flight muscles. There are also exceptions to be found among the more advanced Neoptera, a set of dorsal longitudinal muscles compress the thorax from front to back, causing the dorsal surface of the thorax to bow upward, making the wings flip down. A set of tergosternal muscles pull the notum downward again, causing the wings to flip upward, in a few groups, the downstroke is accomplished solely through the elastic recoil of the thorax when the tergosternal muscles are relaxed. This specialized form of muscle is termed asynchronous flight muscle, the overall effect is that many higher Neoptera can beat their wings much faster than insects with direct flight muscles. There are two basic models of insect flight, creating a leading edge vortex, and using clap. Most insects use a method that creates a leading edge vortex. These flapping wings move through two basic half-strokes, the downstroke starts up and back and is plunged downward and forward. Then the wing is flipped over so that the leading edge is pointed backward. The upstroke then pushes the wing upward and backward, then the wing is flipped again and another downstroke can occur. The frequency range in insects with synchronous flight muscles typically is 5 to 200 hertz, in those with asynchronous flight muscles, wing beat frequency may exceed 1000 Hz. When the insect is hovering, the two take the same amount of time. A slower downstroke, however, provides thrust, identification of major forces is critical to understanding insect flight
26.
Forceps
–
Forceps are a handheld, hinged instrument used for grasping and holding objects. Forceps are used when fingers are too large to small objects or when many objects need to be held at one time while the hands are used to perform a task. The term forceps is used almost exclusively within the medical field, outside medicine, people usually refer to forceps as tweezers, tongs, pliers, clips or clamps. Forceps can be used as both the singular and plural form of the word, also, it is not referred to as a pair as one refers to a pair of scissors. Etymologically, the word derives from the Latin forca, meaning a snare or trap, mechanically, forceps employ the principle of the lever to grasp and apply pressure. Surgical forceps are commonly made of carbon steel, which ensures they can withstand repeated sterilization in high-temperature autoclaves. Lower quality steel is used in forceps made for other uses, some forceps, intended to be used once and then discarded, are made of plastic. The invention of surgical forceps is attributed to Stephen Hales, there are two basic types of forceps, non-locking and locking, though these two types come in dozens of specialized forms for various uses. Non-locking forceps also come in two forms, hinged at one end, away from the grasping end and hinged in the middle. Locking forceps are almost always hinged in the middle, though some place the hinge very close to the grasping end. Locking forceps use various means to lock the grasping surfaces in a position to facilitate manipulation or to independently clamp. Thumb forceps are commonly held between the thumb and two or three fingers of one hand, with the top end resting on the first dorsal interosseous muscle at the base of the thumb, spring tension at one end holds the grasping ends apart until pressure is applied. This allows one to quickly and easily grasp small objects or tissue to move and release it or to grasp, thumb forceps can have smooth tips, cross-hatched tips or serrated tips. Common arrangements of teeth are 1×2, 7×7 and 9×9, serrated forceps are used on tissue, counter-intuitively, teeth will damage tissue less than a smooth surface because one can grasp with less overall pressure. Smooth or cross-hatched forceps are used to move dressings, remove sutures, locking forceps, sometimes called clamps, are used to grasp and hold objects or tissue. When they are used to compress an artery to forestall bleeding they are called hemostats, another form of locking forceps is the needle holder, used to guide a suturing needle through tissue. Many locking forceps use finger loops to facilitate handling, the finger loops are usually grasped by the thumb and middle or ring fingers, while the index finger helps guide the instrument. The most common locking mechanism is a series of interlocking teeth located near the finger loops, as the forceps are closed, the teeth engage and keep the instruments grasping surfaces from separating
27.
Phase (waves)
–
Phase is the position of a point in time on a waveform cycle. A complete cycle is defined as the interval required for the waveform to return to its initial value. The graphic to the right shows how one cycle constitutes 360° of phase, the graphic also shows how phase is sometimes expressed in radians, where one radian of phase equals approximately 57. 3°. Phase can also be an expression of relative displacement between two corresponding features of two waveforms having the same frequency, in sinusoidal functions or in waves phase has two different, but closely related, meanings. One is the angle of a sinusoidal function at its origin and is sometimes called phase offset or phase difference. Another usage is the fraction of the cycle that has elapsed relative to the origin. Phase shift is any change that occurs in the phase of one quantity and this symbol, φ is sometimes referred to as a phase shift or phase offset because it represents a shift from zero phase. For infinitely long sinusoids, a change in φ is the same as a shift in time, if x is delayed by 14 of its cycle, it becomes, x = A ⋅ cos = A ⋅ cos whose phase is now φ − π2. It has been shifted by π2 radians, Phase difference is the difference, expressed in degrees or time, between two waves having the same frequency and referenced to the same point in time. Two oscillators that have the frequency and no phase difference are said to be in phase. Two oscillators that have the frequency and different phases have a phase difference. The amount by which such oscillators are out of phase with each other can be expressed in degrees from 0° to 360°, if the phase difference is 180 degrees, then the two oscillators are said to be in antiphase. If two interacting waves meet at a point where they are in antiphase, then interference will occur. It is common for waves of electromagnetic, acoustic or other energy to become superposed in their transmission medium, when that happens, the phase difference determines whether they reinforce or weaken each other. Complete cancellation is possible for waves with equal amplitudes, time is sometimes used to express position within the cycle of an oscillation. A phase difference is analogous to two athletes running around a track at the same speed and direction but starting at different positions on the track. They pass a point at different instants in time, but the time difference between them is a constant - same for every pass since they are at the same speed and in the same direction. If they were at different speeds, the difference is undefined
28.
Cuticle
–
A cuticle /ˈkjuːtɪkəl/, or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of cuticle are non-homologous, differing in their origin, structure, function, in human anatomy, cuticle refers to several structures. In zoology, the cuticle or cuticula is a multi-layered structure outside the epidermis of many invertebrates, notably roundworms and arthropods. The main structural components of the cuticle are proteins, highly cross-linked collagens and specialised insoluble proteins known as cuticlins, together with glycoproteins. The rigidity is a function of the types of proteins and the quantity of chitin, the more acidic the protein is, the softer the cuticle. It is believed that the cells and hemocytes produce protein and also monitors the timing. Often, in the cuticle of arthropods, structural coloration-producing nanostructures are observed, in botany, plant cuticles are protective, hydrophobic, waxy coverings produced by the epidermal cells of leaves, young shoots and all other aerial plant organs. Cuticles minimize water loss and effectively reduce pathogen entry due to their waxy secretion, the main structural components of plant cuticles are the unique polymers cutin and/or cutan, impregnated with wax. The cuticles of plants function as permeability barriers for water and water-soluble materials, the cuticle both prevents plant surfaces from becoming wet and helps to prevent plants from drying out. Xerophytic plants such as cactus have very thick cuticles to help them survive in their arid climates, plants that live in range of seas spray also may have thicker cuticles that protect them from the toxic effects of salt. Some plants, particularly adapted to life in damp or aquatic environments, have an extreme resistance to wetting. A well-known example is the Sacred Lotus and this adaptation is not purely the physical and chemical effect of a waxy coating, however, it depends largely on the microscopic shape of the surface. The effect is to reduce wetting of the surface substantially, structural coloration is also observed in the cuticles of plants (see, as an example, the so-called marble berry, Pollia condensata. Cuticle is one used for the outer layer of tissue of a mushrooms basidiocarp. The alternative term pileipellis, Latin for skin of a cap might be technically preferable and it is the part removed in peeling mushrooms. On the other hand, some terminology in mycology makes finer distinctions. Be that as it may, the pileipellis is distinct from the trama, the fleshy tissue of a mushroom or similar fruiting body, and also from the spore-bearing tissue layer
29.
Transmission (mechanics)
–
A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term refers simply to the gearbox that uses gears and gear trains to provide speed. In British English, the term refers to the whole drivetrain, including clutch, gearbox, prop shaft, differential. In American English, however, the term more specifically to the gearbox alone. The most common use is in vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a high rotational speed, which is inappropriate for starting, stopping. The transmission reduces the engine speed to the slower wheel speed. Transmissions are also used on bicycles, fixed machines. Often, a transmission has multiple gear ratios with the ability to switch between them as speed varies and this switching may be done manually or automatically. Directional control may also be provided, single-ratio transmissions also exist, which simply change the speed and torque of motor output. The output of the transmission is transmitted via the driveshaft to one or more differentials, while a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds as it changes the direction of rotation. Conventional gear/belt transmissions are not the mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation, automatic transmissions use a valve body to shift gears using fluid pressures in conjunction with an ecm. Early transmissions included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, in support of pumping, milling, most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft. This means that the shaft of a gearbox rotates at a slower rate than the input shaft. A gearbox can be set up to do the opposite and provide an increase in speed with a reduction of torque. Some of the simplest gearboxes merely change the rotational direction of power transmission. Many typical automobile transmissions include the ability to select one of several gear ratios, in this case, most of the gear ratios are used to slow down the output speed of the engine and increase torque
30.
Clutch
–
A clutch is a mechanical device which engages and disengages power transmission especially from driving shaft to driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts, in these devices, one shaft is typically attached to an engine or other power unit while the other shaft provides output power for work. While typically the motions involved are rotary, linear clutches are also possible, in a torque-controlled drill, for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so they may be locked together and spin at the speed, locked together but spinning at different speeds, or unlocked. This type of clutch has protruding circular edge and a hole for them that engages and disengages during operation and this type is less effective since human foot or hand power on clutching reaches about 10 KN or 1,000 kg. The vast majority of clutches ultimately rely on frictional forces for their operation, the purpose of friction clutches is to connect a moving member to another that is moving at a different speed or stationary, often to synchronize the speeds, and/or to transmit power. Usually, as little slippage as possible between the two members is desired, various materials have been used for the disc-friction facings, including asbestos in the past. Modern clutches typically use an organic resin with copper wire facing or a ceramic material. Ceramic materials are used in heavy applications such as racing or heavy-duty hauling, though the harder ceramic materials increase flywheel. In the case of wet clutches, composite materials are very common. Since these wet clutches typically use an oil bath or flow-through cooling method for keeping the disc pack lubricated and cooled, friction-disc clutches generally are classified as push type or pull type depending on the location of the pressure plate fulcrum points. In a pull-type clutch, the action of pressing the pedal pulls the release bearing, pulling on the spring and disengaging the vehicle drive. The opposite is true with a type, the release bearing is pushed into the clutch disengaging the vehicle drive. In this instance, the bearing can be known as a thrust bearing. A clutch damper is a device that softens the response of the clutch engagement/disengagement, in automotive applications, this is often provided by a mechanism in the clutch disc centres. In addition to the damped disc centres, which reduce driveline vibration and these weaker springs are compressed solely by the radial vibrations of an idling engine. They are fully compressed and no longer in use once the main damper springs take up drive, mercedes truck examples, A clamp load of 33 kN is normal for a single plate 430. The 400 Twin application offers a clamp load of a mere 23 kN, bursts speeds are typically around 5,000 rpm with the weakest point being the facing rivet
31.
Brachycera
–
The Brachycera are a suborder of the order Diptera. It is a major suborder consisting of around 120 families and their most distinguishing characteristic is reduced antenna segmentation. A summary of the main characteristics is, Antenna size is reduced. The maxillary palp has two segments or fewer, the back portions of the larval head capsule extend into the prothorax. Two distinct parts make up of the larval mandible, the epandrium and hypandrium of the genitalia are separated in males. No premandible is present on the surface of the labrum. The configuration of the CuA2 and A1 wing veins is distinct, brachyceran flies can also be distinguished through behavior. Many of the species are predators or scavengers, additionally, most recent classifications no longer use the Linnaean ranks for taxa, and this creates its own set of problems. Larger brachycera Media related to Brachycera at Wikimedia Commons Data related to Brachycera at Wikispecies The Tree of Life Web Project, Brachycera Brachycera images
32.
Nematocera
–
The Nematocera are a suborder of elongated flies with thin, segmented antennae and mostly aquatic larvae, consisting of the mosquitoes, crane flies, gnats, black flies, and midges. Nematocera are typically characterized by filamentous, multisegmented antennae which may be plumose in some males, examples of the Nematocera include the mosquitoes, crane flies and black flies. Many of the families, are called gnats, while others are called midges. The larvae are aquatic and have distinct heads with mouthparts that may be modified for filter feeding. The bodies and legs of the adults are usually elongate, many species form mating swarms of males, and in some of these, competition for females is extreme. Although many species have an association with water, even within a single family there may be a trend toward semiaquatic
33.
Phylogenetics
–
In biology, phylogenetics /ˌfaɪloʊdʒəˈnɛtɪks, -lə-/ is the study of the evolutionary history and relationships among individuals or groups of organisms. These relationships are discovered through phylogenetic inference methods that evaluate observed heritable traits, the result of these analyses is a phylogeny – a diagrammatic hypothesis about the history of the evolutionary relationships of a group of organisms. The tips of a tree can be living organisms or fossils. Phylogenetic analyses have become central to understanding biodiversity, evolution, ecology, taxonomy is the classification, identification and naming of organisms. It is usually richly informed by phylogenetics, but remains a methodologically and logically distinct discipline, usual methods of phylogenetic inference involve computational approaches implementing the optimality criteria and methods of parsimony, maximum likelihood, and MCMC-based Bayesian inference. All these depend upon an implicit or explicit mathematical model describing the evolution of characters observed, prior to 1990, phylogenetic inferences were generally presented as narrative scenarios. Such methods are often ambiguous and lack explicit criteria for evaluating alternative hypotheses, the term phylogeny derives from the German Phylogenie, introduced by Haeckel in 1866, and the Darwinian approach to classification became known as the phyletic approach. During the late 19th century, Ernst Haeckels recapitulation theory, or biogenetic fundamental law, was widely accepted, but this theory has long been rejected. O. See, Huerta-Cepas, Jaime, Dopazo, Joaquín, Gabaldón, ETE, A python Environment for Tree Exploration. PhylomeDB, A public database hosting thousands of gene phylogenies ranging many different species, See, Huerta-Cepas, J. Capella-Gutierrez, S. Pryszcz, L. P. Denisov, I. Kormes, D. Marcet-Houben, M. Gabaldón, T. PhylomeDB v3.0, An expanding repository of genome-wide collections of trees, alignments, lents, N. H. Cifuentes, O. E. Carpi, A. Teaching the Process of Molecular Phylogeny and Systematics, A Multi-Part Inquiry-Based Exercise
34.
Calliphoridae
–
The Calliphoridae are a family of insects in the order Diptera, with 1,100 known species. The maggot larvae, often used as fishing bait, are known as gentles, the family is known to be polyphyletic, but much remains disputed regarding proper treatment of the constituent taxa, some of which are occasionally accorded family status. The name blow fly comes from an older English term for meat that had laid on it. The first known association of the blow with flies appears in the plays of William Shakespeare, Loves Labours Lost, The Tempest. Calliphoridae adults are commonly shiny with metallic colouring, often blue, green, or black thoraces. The arista are plumose the entire length, and the antennal segment is distinctly grooved. Members of Calliphoridae have branched Rs 2 veins, frontal sutures are present, the characteristics and arrangement of hairlike bristles are used to tell the difference between members of this family. All blow flies have bristles located on the meron, having two notopleural bristles and a hindmost posthumeral bristle located lateral to presutural bristle are characteristics to look for when identifying this family. The thorax has the dorsal suture across the middle, along with well-defined posterior calli. The postscutellum is absent or weakly developed, the costa is unbroken and the subcosta is apparent on the insect. Most species of blow flies studied thus far are anautogenous, a female requires an amount of protein to develop mature eggs within her ovaries. The current theory is that females visit carrion both for protein and egg laying, but this remains to be proven. Blow fly eggs, usually yellowish or white in color, are about 1.5 mm x 0.4 mm, and, when laid, look like rice balls. While the female blow fly typically lays 150–200 eggs per batch, she is usually iteroparous, the sex ratio of blow fly eggs is usually 50,50, but one exception is females from two species of the genus Chrysomya, which are either arrhenogenic or thelygenic. Hatching from an egg to the first larval stage takes about eight hours to one day, larvae have three stages of development, each stage is separated by a molting event. The instars are separable by examining the posterior spiracles, or openings to the breathing system, the larvae use proteolytic enzymes in their excreta to break down proteins on the livestock or corpse on which they are feeding. Blow flies are poikilothermic – the rate at which they grow and develop is highly dependent on temperature, under room temperature, the black blow fly Phormia regina can change from egg to pupa in 150–266 hours. When the third stage is complete, it will leave the corpse and burrow into the ground to pupate
35.
Hoverfly
–
Hoverflies, sometimes called flower flies, or syrphid flies, make up the insect family Syrphidae. As their common name suggests, they are seen hovering or nectaring at flowers. In some species, the larvae are saprotrophs, eating decaying plant and animal matter in the soil or in ponds, in other species, the larvae are insectivores and prey on aphids, thrips, and other plant-sucking insects. Some adult syrphid flies are important pollinators, about 6,000 species in 200 genera have been described. Hoverflies are common throughout the world and can be found on all continents except Antarctica, Hoverflies are harmless to most other animals, despite their mimicry of more dangerous wasps and bees, which wards off predators. The size of hoverflies varies depending on the species, some, like members of the genus Baccha, are small, elongated, and slender, while others, like members of Criorhina, are large, hairy, and yellow and black. As members of the Diptera, all hoverflies have a functional pair of wings. They are brightly colored, with spots, stripes, and bands of yellow or brown covering their bodies, due to this coloring, they are often mistaken for wasps or bees, they exhibit Batesian mimicry. With a few exceptions, hoverflies are distinguished from other flies by a spurious vein, adults feed mainly on nectar and pollen. They also hover around flowers, lending to their common name and this is beneficial to gardens, as aphids destroy crops, and hoverfly maggots are often used in biological control. Certain species, such as Lampetia equestris or Eumerus tuberculatus, are responsible for pollination, an example of a well-known hoverfly maggot is the rat-tailed maggot, of the drone fly, Eristalis tenax. It has a siphon at its rear end, giving it its name. The species lives in stagnant water, such as sewage and lagoons, the maggots also have a commercial use, and are sometimes sold for ice fishing. On occasion, hoverfly larvae have been known to cause myiasis in humans. This occurs when the larvae are accidentally ingested on food or from other sources, myiasis causes discomfort, pain, or itching, however, hoverflies do not normally prey upon humans and cases of myiasis from hoverflies are very rare. Hoverflies are a family found in most biomes, except deserts, tundra at extremely high latitudes. About 6,000 species and 200 genera are in the family, while some hoverfly larvae are aquatic and are often found in stagnant water, those of species which prey upon aphids and other plant pests are usually terrestrial, residing on leaves. Adults are often found near flowers, their food source being nectar
36.
Mechanoreceptor
–
A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. Normally there are four types in glabrous mammalian skin, lamellar corpuscles, tactile corpuscles, Merkel nerve endings. Invertebrate mechanoreceptors include campaniform sensilla and slit sensilla, among others, the third-order neurons then send the signal to the somatosensory cortex. More recent work has expanded the role of the cutaneous mechanoreceptors for feedback in fine motor control, in glabrous skin, there are four principal types of mechanoreceptors, each shaped according to its function. The tactile corpuscles respond to touch, and adapt rapidly to changes in texture. The bulbous corpuscles detect tension deep in the skin and fascia, the Merkel nerve endings detect sustained pressure. The lamellar corpuscles in the skin and fascia detect rapid vibrations, receptors in hair follicles sense when a hair changes position. Indeed, the most sensitive mechanoreceptors in humans are the cells in the cochlea of the inner ear. Mechanosensory free nerve endings detect touch, pressure, and stretching, baroreceptors are a type of mechanoreceptor sensory neuron that is excited by stretch of the blood vessel. Cutaneous mechanoreceptors respond to stimuli that result from physical interaction, including pressure. They are located in the skin, like other cutaneous receptors and they are all innervated by Aβ fibers, except the mechanorecepting free nerve endings, which are innervated by Aδ fibers. Cutaneous mechanoreceptors can be categorized by morphology, by kind of sensation they perceive. Furthermore, each has a different receptive field, the Slowly Adapting type 1 mechanoreceptor, with the Merkel corpuscle end-organ, underlies the perception of form and roughness on the skin. They have small receptive fields and produce sustained responses to static stimulation and they also produce sustained responses to static stimulation, but have large receptive fields. The Rapidly Adapting or Meissner corpuscle end-organ mechanoreceptor underlies the perception of flutter and they have small receptive fields and produce transient responses to the onset and offset of stimulation. The Pacinian corpuscle or Vater-Pacinian corpuscles or Lamellar corpuscles underlie the perception of high frequency vibration and they also produce transient responses, but have large receptive fields. Cutaneous mechanoreceptors can also be separated into categories based on their rates of adaptation, when a mechanoreceptor receives a stimulus, it begins to fire impulses or action potentials at an elevated frequency. The cell, however, will adapt to a constant or static stimulus
37.
Action potential
–
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of cells, called excitable cells, which include neurons, muscle cells. In other types of cells, their function is to activate intracellular processes. In muscle cells, for example, a potential is the first step in the chain of events leading to contraction. In beta cells of the pancreas, they provoke release of insulin, action potentials in neurons are also known as nerve impulses or spikes, and the temporal sequence of action potentials generated by a neuron is called its spike train. A neuron that emits an action potential is often said to fire, action potentials are generated by special types of voltage-gated ion channels embedded in a cells plasma membrane. When the channels open they allow a flow of sodium ions, which changes the electrochemical gradient. This then causes more channels to open, producing an electric current across the cell membrane. The process proceeds explosively until all of the ion channels are open. The rapid influx of ions causes the polarity of the plasma membrane to reverse. As the sodium channels close, sodium ions can no longer enter the neuron, potassium channels are then activated, and there is an outward current of potassium ions, returning the electrochemical gradient to the resting state. After an action potential has occurred, there is a transient negative shift, in animal cells, there are two primary types of action potentials. One type is generated by voltage-gated sodium channels, the other by voltage-gated calcium channels, sodium-based action potentials usually last for under one millisecond, whereas calcium-based action potentials may last for 100 milliseconds or longer. In some types of neurons, slow calcium spikes provide the force for a long burst of rapidly emitted sodium spikes. In cardiac muscle cells, on the hand, an initial fast sodium spike provides a primer to provoke the rapid onset of a calcium spike. Nearly all cell membranes in animals, plants and fungi maintain a voltage difference between the exterior and interior of the cell, called the membrane potential. A typical voltage across a cell membrane is –70 mV. In most types of cells the membrane potential usually stays fairly constant, some types of cells, however, are electrically active in the sense that their voltages fluctuate over time
38.
Halteres
–
In dipterous insects, halteres are minute dumbbell-shaped organs that have been modified from hindwings to provide a means of encoding body rotations during flight. Halteres are rapidly oscillated simultaneously with the wings, allowing them to experience forces resulting from body rotations, if the body of the insect rotates about one of its three axes, the rotation exerts a force on the vibrating halteres – this is known as the Coriolis effect. Halteres act as a balance and guidance system by providing feedback to the wing-steering muscles. This is what allows flies to perform their fast acrobatic maneuvers, the majority of insects have two pairs of wings. What makes flies unique is that they possess only one set of lift-generating wings, the only difference is that strepsipterans have adapted their forewings into halteres, whereas dipterans have adapted their hindwings into halteres. This unique structure which detects rotations/perturbations during flight has never described in nature elsewhere. Halteres are able to sense small deviations in body position using the properties of moving mass. Now, instead of the following a linear path, they begin to follow a curved path. The larger the perturbation they experience, the farther the halteres move from their original linear path, during these periods, the haltere is no longer moving in only two directions, but four. When this occurs, tiny bell-shaped structures at the base of the haltere experience strain as the haltere stalk bends in their direction, the nervous system can then transform the bending of these hairs into electrical signals, which the fly interprets as body rotation information. The fly uses this information to make corrections to its position, further details explaining the dynamics and physiology of halteres are described below. Halteres may also be useful for other behaviors, certain species of flies have been observed to oscillate their halteres while walking in addition to oscillating them during flight. In these individuals, halteres could thus be detecting sensory information during walking behavior as well, when the halteres are removed, these insects perform more poorly at certain walking challenges. However, how information is processed and used during walking remains, with few exceptions. Specific examples of what has been found are described below, Halteres were first documented by William Derham in 1714. He discovered that flies were unable to remain airborne when their halteres were surgically removed and this result was initially attributed to the halteres ability to sense and maintain equilibrium. In 1917 v. Buddenbrock asserted that something else was responsible for the loss of flight ability. He claimed that the halteres should instead be considered stimulation organs, in other words, that the activity of the halteres energized the wing muscular system, so that they acted as an on/off switch for flight
39.
Afferent nerve fiber
–
In the peripheral nervous system, an afferent nerve fiber is the axon of a sensory neuron. It is a long process extending far from the cell body that carries an action potential from the sensory neuron toward the central nervous system. Bundles of these form a nerve known as an afferent nerve. The opposite direction of activity is efferent conduction. The efferent nerve fiber is the axon of a motor neuron, bundles of these axons form a motor nerve, or efferent nerve. In the nervous system there is a loop system of sensation, decision. This process is carried out through the activity of neurons, interneurons. A touch or painful stimulus, for example, creates a sensation in the brain only after information about the stimulus travels there via afferent nerve pathways, Afferent neurons are pseudounipolar neurons that have a single long axon with a short central and a long peripheral branch. These cells do not have dendrites and they have a smooth and rounded cell body. Just outside the spinal cord, thousands of afferent neuronal cell bodies are aggregated in a swelling in the dorsal root known as the root ganglion. Afferent neurons somas are located in the ganglia of the nervous system. The majority of these are unipolar neurons in that they have a single axon leaving the body and is sent towards the sensory organ. All of the axons in the root, which contains afferent nerve fibers, are used in the transduction of somatosensory information. Somatosensory receptors include senses such as pain, touch, temperature, itch, all of these sensations travel along the same general pathway towards the brain, from the dorsal root ganglion they travel to the spinal cord. From the spinal cord to the medulla, which leads to the medial lemniscus of the midbrain. From here it travels to the somatosensory cortex of the parietal lobe. Types of afferent fibers include the general somatic, the visceral, the special somatic. Afferent is derived from Latin participle afferentem, meaning carrying into, ad and ex give an easy mnemonic device for remembering the relationship between afferent and efferent, afferent connection arrives and an efferent connection exits
40.
Neuropil
–
For example, the neocortex and olfactory bulb both contain neuropil. White matter, which is composed of axons and glial cells, is generally not considered to be a part of the neuropil. Neuropil comes from the Greek, neuro, meaning tendon, sinew, nerve and pilos, the terms origin can be traced back to the late 19th century. Neuropil has been found in the regions, outer neocortex layer, barrel cortex, inner plexiform layer and outer plexiform layer, posterior pituitary. These are all found in humans, with the exception of the barrel cortex, however, the degree of similarity depends upon the composition of neuropil being compared. Comparing the concentrations can determine whether or not proportions of different postsynaptic elements contacted a particular axonal pathway, relative concentrations could signify a reflection of different postsynaptic elements in the neuropil or show that axons sought out and formed synapses only with specific postsynaptic elements. Since neuropils have a role in the nervous system, it is difficult to define a certain overarching function for all neuropils. For instance, the olfactory glomeruli function as sorts of way-stations for the information flowing from the receptor neurons to the olfactory cortex. The inner plexiform layer of the retina is a more complex. The bipolar cells post-synaptic to either rods or cones are either depolarized or hyperpolarized depending on whether the cells have sign-inverting synapses or a sign-conserving synapses. Neurons are necessary for all connections made in the brain, researchers at Cold Spring Harbor Laboratory formulated the optimal balance of the four variables and calculated the optimal ratio of axon plus dendrite volume to total volume of grey matter. The formula predicted an optimal brain with 3/5 of its volume occupied by neuropil, experimental evidence taken from three mouse brains agrees with this result. The fraction of wire is 0.59 ±0.036 for layer IV of visual cortex,0.62 ±0.055 for layer Ib of piriform cortex, and 0.54 ±0.035 for the stratum radiatum of hippocampal field CA1. The overall average is 0.585 ±0.043, the deterioration of the neuropil in this cortex has been proposed as the cause of schizophrenia. Alzheimers is a disease that is hypothesized to result from the loss of dendritic spines and/or deformation of these spines in the patients frontal and temporal cortices. This malfunction presents itself in the form of filaments that tangle together in the neuropil. Interestingly, this phenomenon seems to occur in the elderly as well. A significant non-human area of neuropil is the barrel cortex found in mammals with whiskers, Neuropil have been hypothesized to be a key factor in differentiating human cognitive capacity from that of other animals
41.
Sensory neuron
–
Sensory neurons also known as afferent neurons are neurons that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction, the cell bodies of the sensory neurons are located in the dorsal ganglia of the spinal cord. This sensory information travels along afferent nerve fibers in an afferent or sensory nerve, the stimulus can come from extoreceptors outside the body, for example light and sound, or from interoreceptors inside the body, for example blood pressure or the sense of body position. Different types of neurons have different sensory receptors that respond to different kinds of stimuli. The sensory neurons involved in smell are called olfactory receptor neurons and these receptor neurons contain receptors, called olfactory receptors, that are activated by the odor molecules in the air. The perception of odor molecules is called a scent. Similarly to olfactory receptor neurons, taste receptors in taste buds interact with chemicals in food to produce an action potential, photoreceptor cells are capable of phototransduction, a process which converts light into electrical signals. These signals are refined and controlled by the interactions with other types of neurons in the retina, the five basic classes of neurons within the retina are photoreceptor cells, bipolar cells, ganglion cells, horizontal cells, and amacrine cells. The basic circuitry of the retina incorporates a three-neuron chain consisting of the photoreceptor, bipolar cell, the first action potential occurs in the retinal ganglion cell. This pathway is the most direct way for transmitting information to the brain. There are three types of photoreceptors, Cones are photoreceptors that respond significantly to color. In humans the three different types of cones correspond with a response to short wavelength, medium wavelength. Rods are photoreceptors that are sensitive to the intensity of light. The concentrations and ratio of rods to cones is strongly correlated with whether an animal is diurnal or nocturnal, in humans, rods outnumber cones by approximately 20,1, while in nocturnal animals, such as the tawny owl, the ratio is closer to 1000,1. Retinal ganglion cells are involved in the sympathetic response, of the ~1.3 million ganglion cells present in the retina, 1-2% are believed to be photosensitive. Glaucoma – loss of retinal cells which causes some loss of vision to blindness. Diabetic retinopathy – poor blood sugar due to diabetes damages the tiny blood vessels in the retina. The auditory system is responsible for converting pressure waves generated by vibrating air molecules or sound into signals that can be interpreted by the brain and this mechanoelectrical transduction is mediated with hair cells within the ear
. PMID 10382224.