1.
Nautilus
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The nautilus is a pelagic marine mollusc of the cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus, though it more specifically refers to species Nautilus pompilius, the name chambered nautilus is also used for any species of the Nautilidae. All are protected under CITES Appendix II, having survived relatively unchanged for millions of years, nautiluses represent the only living members of the subclass nautiloidea, and are often considered living fossils. Each nautilus tentacle is composed of a long, soft, flexible cirrus and is retractable into a corresponding hardened sheath, nautiluses typically have more tentacles than other cephalopods — up to ninety. Nautilus tentacles differ from those of other cephalopods, lacking pads, the tentacles stick to prey by virtue of their ridged surface. Attempts to take an object already seized by a nautilus may tear away the creatures tentacles, the main tentacles emerge from sheaths which cohere into a single firm fleshy mass. Two pairs of tentacles are separate from the other 90-ish, the pre-ocular and post-ocular, situated before and these are more evidently grooved, with more pronounced ridges. They are extensively ciliated and serve an olfactory purpose, the radula is wide and distinctively has nine teeth. The mouth consists of a beak made up of two interlocking jaws capable of ripping the animals food— mostly crustaceans— from the rocks to which they are attached. The crop is the largest portion of the tract, and is highly extensible. From the crop, food passes to the small muscular stomach for crushing, like all cephalopods, the blood of the nautilus contains hemocyanin, which is blue in its oxygenated state. There are two pairs of gills which are the remnants of the ancestral metamerism to be visible in extant cephalopods. The one exception to this is the vena cava, a large vein running along the underside of the crop into which nearly all other vessels containing deoxygenated blood empty. All blood passes through one of the four sets of filtering organs upon leaving the vena cava, blood waste is emptied through a series of corresponding pores into the pallial cavity. From this ring extend all of the forward to the mouth, tentacles, and funnel, laterally to the eyes and rhinophores. Nautiluses also tend to have rather short memory spans, and the ring is not protected by any form of brain case. Nautiluses are the sole living cephalopods whose bony body structure is externalized as a shell, the animal can withdraw completely into its shell and close the opening with a leathery hood formed from two specially folded tentacles. The shell is coiled, aragonitic, nacreous and pressure resistant, the nautilus shell is composed of two layers, a matte white outer layer, and a striking white iridescent inner layer
2.
Seashell
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A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer created by an animal that lives in the sea. The shell is part of the body of the animal, empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the parts have been eaten by another animal or have rotted out. The term seashell usually refers to the exoskeleton of an invertebrate, most shells that are found on beaches are the shells of marine mollusks, partly because many of these shells endure better than other seashells. Apart from mollusk shells, other shells that can be found on beaches are those of barnacles, horseshoe crabs, marine annelid worms in the family Serpulidae create shells which are tubes made of calcium carbonate that are cemented onto other surfaces. The shells of sea urchins are called tests, and the shells of crabs. While most seashells are external, some cephalopods have internal shells, Seashells have been used by humans for many different purposes throughout history and pre-history. However, seashells are not the kind of shells, in various habitats, there are shells from freshwater animals such as freshwater mussels and freshwater snails. When the word refers only to the shells of marine mollusks. The study of the entire molluscan animal is known as malacology, Seashells are commonly found in beach drift, which is natural detritus deposited along strandlines on beaches by the waves and the tides. Shells are very often washed up onto an empty and clean. Empty seashells are often picked up by beachcombers, however, the majority of seashells which are offered for sale commercially have been collected alive and then killed and cleaned, specifically for the commercial trade. This type of large-scale exploitation can sometimes have a negative impact on local ecosystems. The word seashell is often used to only the shell of a marine mollusk. These shells are often the most commonly encountered, both in the wild, and for sale as decorative objects. Marine species of gastropods and bivalves are more numerous land and freshwater species. The shells of species also often have more sculpture and more color. Although there are a number of species of shelled mollusks that are large, there are vast numbers of extremely small species too
3.
Mollusc shell
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Not all shelled molluscs live in the sea, many live on the land and in freshwater. Within some species of molluscs, there is often a degree of variation in the exact shape, pattern, ornamentation. A mollusc shell is formed, repaired and maintained by a part of the called the mantle. Any injuries to or abnormal conditions of the mantle are reflected in the shape and form. When the animal encounters harsh conditions that limit its food supply, or otherwise cause it to become dormant for a while, when conditions improve again and the mantle resumes its task, a growth line is produced. The mantle edge secretes a shell which has two components, the shell formation requires certain biological machinery. This caps off the space, which is bounded on its other surfaces by the existing shell. The accumulation of ions is driven by ion pumps packed within the calcifying epithelium, the organic matrix forms the scaffold that directs crystallization, and the deposition and rate of crystals is also controlled by hormones produced by the mollusc. Nucleation is endoepithelial in Neopilina and Nautilus, but exoepithelial in the bivalves, the formation of the shell involves a number of genes and transcription factors. On the whole, the factors and signalling genes are deeply conserved. Engrailed serves to demark the edge of the field, dpp controls the shape of the shell. In gastropod embryos, Hox1 is expressed where the shell is being accreted, perlucin operates in association with Perlustrin, a smaller relative of lustrin A, a protein responsible for the elasticity of organic layers that makes nacre so resistant to cracking. Lustrin A bears remarkable structural similarity to the involved in mineralization in diatoms – even though diatoms use silica, not calcite. The shell at another first giant clam, the characterizations of the second elasticity sheels. The second responsibles id makes by commons however no association has been observed between Hox genes and cephalopod shell formation, a wide range of enzymes are expressed during the formation of the shell, including carbonic anhydrase, alkaline phosphatase, and DOPA-oxidase /peroxidase. The shell-secreting area is differentiated very early in embryonic development, an area of the ectoderm thickens, then invaginates to become a shell gland. The gland subsequently evaginates in molluscs that produce an external shell, a wide range of enzymes are expressed during the formation of the shell, including carbonic anhydrase, alkaline phosphatase, and DOPA-oxidase /peroxidase. The form of the shell is constrained by the organisms ecology
4.
Bivalve shell
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A bivalve shell is part of the body, the exoskeleton or shell, of a bivalve mollusk. In life, the shell of this class of mollusks is composed of two hinged parts or valves, bivalves are very common in essentially all aquatic locales, including saltwater, brackish water, and freshwater. The shells of bivalves commonly wash up on beaches and along the edges of lakes, rivers, bivalves by definition possess two shells or valves, a right valve and a left valve, that are joined by a ligament. The two valves usually articulate with one another using structures known as teeth which are situated along the hinge line, if symmetrical front-to-back, the valves are said to be equilateral, and are otherwise considered inequilateral. This exoskeleton serves not only for muscle attachment, but also for protection from predators, the shell has several layers, and is typically made of calcium carbonate precipitated out into an organic matrix. It is secreted by a part of the body known as the mantle. The bivalve shell is composed of two calcareous valves, the mantle, a thin membrane surrounding the body, secretes the shell valves, ligament, and hinge teeth. The mantle lobes secrete the valves, and the mantle crest creates the other parts, the mantle itself is attached to the shell by numerous small mantle retractor muscles, which are arranged in a narrow line along the length of the interior of the shell. The adductor muscles are what allow the bivalve to close the shell tightly, in some bivalves the mantle edges fuse to form siphons, which take in and expel water during suspension feeding. Species which live buried in sediment usually have long siphons, and when the needs to close its shell. This feature of the anatomy of a bivalve is clearly indicated on the interior of the shell surface as a pallial sinus. The outermost layer of the shell is known as the periostracum and is composed of an organic substance. This sometimes forms a yellowish or brownish skin on the outside of the shell, the periostracum may start to peel off of a shell when the shell is allowed to dry out for long periods. The shell is added to, and increases in size, in two ways - by increments added to the edge of the shell, and by a gradual thickening throughout the animals life. The two shell valves are held together at the animals dorsum by the ligament, which is composed of the tensilium and resilium, in life the ligament opens the shell, and the adductor muscle or muscles close the shell. When a bivalve dies, its adductor muscle relax and the resilium pushes the valves open, in many species of cemented bivalves, the lower valve is more deeply cupped than the upper valve, which tends to be rather flat. In some groups of cemented bivalves the lower or cemented valve is the left valve, the oldest point of a bivalve shell is called the beak, and the raised area around it is known as the umbo. The hinge area is the dorsum or back of the shell, the lower, curved margin is the ventral side
5.
Chiton
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Chitons /ˈkaɪtənz/ are marine molluscs of varying size in the class Polyplacophora, formerly known as Amphineura. About 940 extant and 430 fossil species are recognized and they are also sometimes known as sea cradles or coat-of-mail shells, or more formally as loricates, polyplacophorans, and occasionally as polyplacophores. Chitons have a shell composed of eight separate plates or valves. These plates overlap slightly at the front and back edges, the shell plates are encircled by a skirt known as a girdle. Chitons live worldwide, from cold waters through to the tropics and they live on hard surfaces, such as on or under rocks, or in rock crevices. Some species live high in the intertidal zone and are exposed to the air. Most species inhabit intertidal or subtidal zones, and do not extend beyond the photic zone, chitons are exclusively and fully marine. All chitons bear a protective shell that is divided into eight articulating aragonite valves embedded in the tough muscular girdle that surrounds the chitons body. Compared with the single or two-piece shells of molluscs, this arrangement allows chitons to roll into a protective ball when dislodged. In some species the valves are reduced or covered by the girdle tissue, the valves are variously colored, patterned, smooth, or sculptured. The most anterior plate is crescent-shaped, and is known as the cephalic plate, the most posterior plate is known as the anal plate The inner layer of each of the six intermediate plates is produced anteriorly as an articulating flange, called the articulamentum. This inner layer may also be produced laterally in the form of notched insertion plates and these function as an attachment of the valve plates to the soft body. A similar series of insertion plates may be attached to the anterior border of the cephalic plate or the convex posterior border of the anal plate. The sculpture of the valves is one of the taxonomic characteristics, after a chiton dies, the individual valves which make up the eight-part shell come apart because the girdle is no longer holding them together, and then the plates sometimes wash up in beach drift. The individual shell plates from a chiton are known as butterfly shells due to their shape. The protein component of the scales and sclerites is minuscule in comparison with other biomineralized structures and this implies that polysaccharides make up the bulk of the matrix. The girdle spines often bear length-parallel striations, the wide form of girdle ornament suggests it serves a secondary role, chitons can survive perfectly well without them. Camouflage or defence are two likely functions, spicules are secreted by cells that do not express engrailed, but these cells are surrounded by engrailed-expressing cells
6.
Gastropod shell
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The gastropod shell is part of the body of a gastropod or snail, a kind of mollusk or mollusc. The shell is a skeleton or exoskeleton, which may serve for muscle attachment, but also for protection from predators, mechanical damage, dehydration. Some gastropods appear shell-less but may have a remnant within the mantle, some snails also possess an operculum that seals the opening of the shell, known as the aperture, which provides further protection. The study of shells is known as conchology. The biological study of gastropods, and other molluscs in general, is malacology, Shell morphology terms vary by species group. An excellent source for terminology of the shell is How to Know the Eastern Land Snails by John B. Burch now freely available at the Hathi Trust Digital Library, the gastropod shell has three major layers secreted by the mantle. The calcareous central layer, the ostracum, is made of calcium carbonate precipitated into an organic matrix known as conchiolin. The outermost layer is the periostracum which is resistant to abrasion, gastropod shell morphology is usually quite constant among individuals of a species. Controlling variables are, The rate of growth per revolution around the coiling axis, high rates give wide-mouthed forms such as the abalone, low rates give highly coiled forms such as Turritella or some of the Planorbidae. The shape of the curve, roughly equivalent to the shape of the aperture. It may be round, for instance in the shell, elongate as in the cone shell or have an irregular shape with a siphonal canal extension. The rate of translation of the curve along the axis of coiling, controlling how high-spired the resulting shell becomes. This may range from zero, a flat shell, to nearly the diameter of the aperture. Ontologic growth changes as the animal reaches adulthood, good examples are the flaring lip of the adult conch and the inward-coiled lip of the cowry. Some of these factors can be modelled mathematically and programs exist to generate extremely realistic images, early work by David Raup on the analog computer also revealed many possible combinations that were never adopted by any actual gastropod. Some shell shapes are more often in certain environments, though there are many exceptions. High-spired and highly sculptured forms become more common in water environments
7.
Tusk shell
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Shells of species within this class range from about 0.5 to 15 cm in length. Members of the order Dentaliida tend to be larger than those of the order Gadilida. These molluscs live in soft substrates offshore, molecular data suggest that the scaphopods are a sister group to the cephalopods, although higher-level molluscan phylogeny remains somewhat unresolved. The morphological shape of the body makes it difficult to orient it satisfactorily. As a result, researchers have disagreed as to which direction is anterior/ posterior. According to Shimek and Steiner, he apex of the shell and mantle are anatomically dorsal, consequently, the concave side of the shell and viscera are anatomically dorsal. The convex side has to be divided into ventral and dorsally posterior portions. Functionally, as in cephalopods, the aperture with the foot is anterior, the apical area posterior, the concave side dorsal. The shells of the members of the Gadilida are usually glassy-smooth in addition to being quite narrow and this along with other structures of their anatomy allows them to move with surprising speed through loose sediment to escape potential bottom-dwelling predators. The Dentalids, on the hand, tend to have strongly ribbed. When they sense vibrations anywhere around them, their response is to freeze. This makes them harder to detect by animals such as ratfish which can sense the electrical signals given off by the most minute muscle movement, the mantle of a scaphopod is entirely within the shell. The foot extends from the end of the shell, and is used to burrow through the substrate. The scaphopod positions itself head down in the substrate, with the end of the shell projecting upward. This end seldom appears above the level of the substrate, however, most adult scaphopods live their lives entirely buried within the substrate. Water enters the cavity through the apical aperture, and is wafted along the body surface by cilia. There are no gills, the surface of the mantle cavity absorbs oxygen from the water. Unlike most other molluscs, there is no flow of water with a separate exhalant stream
8.
Conchology
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Conchology is the study of mollusc shells. Conchology is one aspect of malacology, the study of molluscs, however, malacology is the study of molluscs as whole organisms and it includes the study of land and freshwater mollusc shells as well as seashells and extends to the study of a gastropods operculum. Conchology is now seen as an archaic study, because relying on only one aspect of an organisms morphology can be misleading. However, a shell often gives at least some insight into molluscan taxonomy, even in current museum collections it is common for the dry material to greatly exceed the amount of material that is preserved whole in alcohol. Conchologists mainly deal with four orders, the gastropods, bivalves, Polyplacophora. Cephalopods only have internal shells, with the exception of the Nautiloidea. Some groups, such as the sea slug nudibranchs, have lost their shells altogether, the terms shell collector and conchologist can be regarded as two distinct categories. Not all shell collectors are conchologists, some are concerned with the aesthetic value of shells instead of their scientific study. It is also true that not all conchologists are shell collectors, there is some debate in the conchological community, with some people regarding all shell collectors as conchologists. Molluscs have probably been used by primates as a food long before humans evolved. Shell collecting, the precursor of conchology, probably goes back as far as there have been living near beaches. Stone Age seashell necklaces have been found, sometimes in areas far from the ocean, Shell jewellery is found at almost all archaeological sites, including at ancient Aztec ruins, digs in ancient China, and the Indus Valley. During the Renaissance people began taking interest in objects of beauty to put in cabinets of curiosities. Because of their attractiveness, variety, durability and ubiquity, shells became a part of these collections. Towards the end of the 17th century, people looking at shells with scientific interest. Martin Lister in 1685–1692 published Historia Conchyliorum, which was the first comprehensive conchological text, george Rumpf, or Rumphius, published the first mollusc taxonomy. He suggested single shelled ones, snails or whelks, and two-shelled ones, many of Rumpfs terms were adopted by Carl Linnaeus. Rumpf continued to do important scientific work after he went blind, the study of zoology, including conchology, was revolutionized by Swedish naturalist Carl Linnaeus and his system of binomial nomenclature
9.
Valve (mollusc)
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Valve is an anatomical term applied to the shell of those molluscs that have a shell. This exceptional family is known as the bivalved gastropods. Gastropods in general are sometimes called univalves, because in those that have a shell, the valves of chitons are eight dorsal, articulated shell plates, which are frequently coloured and sculpted. After death the girdle that holds the plates together disintegrates and the plates separate, thus individual plates can be found washed up in beach drift, as shown in the image at the top of this article. Bivalve molluscs have a shell which is composed of two separate but articulating parts, each one of these two parts is known as a valve. The two valves are known as the valve and the left valve, these are labeled with respect to the anterior end of the bivalve. In many, but not all, bivalves, the two valves are more or less symmetrical and thus look like mirror images of one another, the great majority of shelled gastropods or snails have a shell in one part, hence the older name univalve. The gastropod operculum, when present, even when it is composed mostly of carbonate, is not considered to be a valve. In contrast, species within one family of sea snails. These two parts very closely resemble the two valves of a bivalve and this group of species are often referred to as bivalved gastropods. These are sacoglossans in several genera including Julia, Berthelinia, Midorigai, Edenttellina, Tamanovalva and these bivalve gastropods were for a long time known only from fossils and dead material. Because of this, they had described as being somewhat atypical bivalves. It was not until living individuals were found in the late 20th century that it was understood that these are in very unusual gastropods
10.
Brachiopod
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Brachiopods, phylum Brachiopoda, are a group of lophotrochozoan animals that have hard valves on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the end, while the front can be opened for feeding or closed for protection. Two major groups are recognized, articulate and inarticulate, the word brachiopod is formed from the Ancient Greek words βραχίων and πούς. They are often known as shells, since the curved shells of the class Terebratulida look rather like pottery oil-lamps. Lifespans range from three to thirty years. Ripe gametes float from the gonads into the coelom and then exit into the mantle cavity. The larvae of inarticulate brachiopods are miniature adults, with lophophores that enable the larvae to feed, traditionally, brachiopods have been regarded as members of, or as a sister group to, the deuterostomes, a superphylum that includes chordates and echinoderms. Lineages of brachiopods that have both fossil and extant taxa appeared in the early Cambrian, Ordovician, and Carboniferous periods, other lineages have arisen and then become extinct, sometimes during severe mass extinctions. Brachiopod fossils have been useful indicators of climate changes during the Paleozoic, however, after the Permian–Triassic extinction event, brachiopods recovered only a third of their former diversity. A study in 2007 concluded the brachiopods were especially vulnerable to the Permian–Triassic extinction, as they built calcareous hard parts and had low metabolic rates, Brachiopods live only in the sea, and most species avoid locations with strong currents or waves. The larvae of articulate species settle in quickly and form dense populations in well-defined areas while the larvae of inarticulate species swim for up to a month and have wide ranges, Brachiopods now live mainly in cold water and low light. Fish and crustaceans seem to find brachiopod flesh distasteful and seldom attack them, among brachiopods, only the lingulids have been fished commercially, on a very small scale. One brachiopod species may be a measure of environmental conditions around an oil terminal being built in Russia on the shore of the Sea of Japan, modern brachiopods range from 1 to 100 millimetres long, and most species are about 10 to 30 millimetres. The largest brachiopods known – Gigantoproductus and Titanaria, reaching 30 to 38 centimetres in width – occurred in the part of the Lower Carboniferous. Each has two valves which cover the dorsal and ventral surface of the animal, unlike bivalve molluscs whose shells cover the lateral surfaces, the valves are termed brachial and pedicle. The brachial valve bears on its inner surface the brachia from which the phylum gets its name, the pedicle valve has on its inner surface the attachment to the stalk-like pedicle by which most brachiopods attach themselves to the substrate. The pedicle valve is larger than the brachial. In most articulate brachiopod species, both valves are convex, the surfaces often bearing growth lines and/or other ornamentation, however, inarticulate lingulids, which burrow into the seabed, have valves that are smoother, flatter and of similar size and shape
11.
Crustacean
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Crustaceans form a large, diverse arthropod taxon which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill, woodlice and barnacles. In other words, some crustaceans are more related to insects. The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm, to the Japanese spider crab with a leg span of up to 3.8 m, like other arthropods, crustaceans have an exoskeleton, which they moult to grow. Most crustaceans are free-living aquatic animals, but some are terrestrial, some are parasitic, the group has an extensive fossil record, reaching back to the Cambrian, and includes living fossils such as Triops cancriformis, which has existed apparently unchanged since the Triassic period. More than 10 million tons of crustaceans are produced by fishery or farming for human consumption, krill and copepods are not as widely fished, but may be the animals with the greatest biomass on the planet, and form a vital part of the food chain. The scientific study of crustaceans is known as carcinology, and a scientist who works in carcinology is a carcinologist, the body of a crustacean is composed of segments, which are grouped into three regions, the cephalon or head, the thorax, and the pleon or abdomen. The head and thorax may be fused together to form a cephalothorax, the crustacean body is protected by the hard exoskeleton, which must be moulted for the animal to grow. The shell around each somite can be divided into a dorsal tergum, ventral sternum, various parts of the exoskeleton may be fused together. The abdomen bears pleopods, and ends in a telson, which bears the anus, the number and variety of appendages in different crustaceans may be partly responsible for the groups success. It is unclear whether the condition is a derived state which evolved in crustaceans. Trilobites, for instance, also possessed biramous appendages, the main body cavity is an open circulatory system, where blood is pumped into the haemocoel by a heart located near the dorsum. Malacostraca have haemocyanin as the pigment, while copepods, ostracods, barnacles. The alimentary canal consists of a tube that often has a gizzard-like gastric mill for grinding food and a pair of digestive glands that absorb food. Structures that function as kidneys are located near the antennae, a brain exists in the form of ganglia close to the antennae, and a collection of major ganglia is found below the gut. In many decapods, the first pair of pleopods are specialised in the male for sperm transfer, many terrestrial crustaceans mate seasonally and return to the sea to release the eggs. Others, such as woodlice, lay their eggs on land, in most decapods, the females retain the eggs until they hatch into free-swimming larvae. Marine crustaceans are as ubiquitous in the oceans as insects are on land, some branchiurans are able to withstand rapid changes of salinity and will also switch hosts from marine to non-marine species. Krill are the layer and the most important part of the food chain in Antarctic animal communities
12.
Horseshoe crab
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Horseshoe crabs are marine arthropods of the family Limulidae and order Xiphosura or Xiphosurida. They are invertebrates meaning that they lack a spine, horseshoe crabs live primarily in and around shallow ocean waters on soft sandy or muddy bottoms. They occasionally come onto shore to mate and they are commonly used as bait and in fertilizer. In recent years, a decline in the population has occurred as a consequence of coastal destruction in Japan. Tetrodotoxin may be present in the roe of species inhabiting the waters of Thailand, because of their origin 450 million years ago, horseshoe crabs are considered living fossils. They belong to a separate subphylum, Chelicerata, and are related to arachnids. The earliest horseshoe crab fossils are found in strata from the late Ordovician period, the latter become functional just before the embryo hatches. Also, a pair of eyes is located near the mouth. The horseshoe crab has 5 additional eyes on top of its shell, the mouth is located in the center of the legs, whose bases are referred to as gnathobases and have the same function as jaws and help grind up food. The horseshoe crab has five pairs of legs for walking, swimming, the long, straight, rigid tail can be used to flip the animal over if turned upside down, so a horseshoe crab with a broken tail is susceptible to desiccation or predation. Behind its legs, the crab has book gills, which exchange respiratory gases. As in other arthropods, a true endoskeleton is absent, and they are more often found on the ocean floor searching for worms and molluscs, which are their main food. They may also feed on crustaceans and even small fish, females are larger than males, C. rotundicauda is the size of a human hand, while L. polyphemus can be up to 60 cm long. The juveniles grow about 33% larger with every molt until reaching adult size, during the breeding season, horseshoe crabs migrate to shallow coastal waters. A male selects a female and clings to her back, often, several males surround the female and all fertilize together which makes it easy to spot and count females as they are the large center carapace surrounded by 3-5 smaller ones. The female digs a hole in the sand and lays her eggs while the male fertilize them, the female can lay between 60,000 and 120,000 eggs in batches of a few thousand at a time. The eggs take about two weeks to hatch, shore birds eat many of them before they hatch, the larvae molt six times during the first year. Raising horseshoe crabs in captivity has proven to be difficult, some evidence indicates mating takes place only in the presence of the sand or mud in which the horseshoe crabs eggs were hatched
13.
Sea urchin
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Sea urchins or urchins, archaically called sea hedgehogs, are small, spiny, globular animals that, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. About 950 species of echinoids inhabit all oceans from the intertidal to 5,000 metres deep, the shell, or test, of sea urchins is round and spiny, typically from 3 to 10 cm across. Common colors include black and dull shades of green, olive, brown, purple, blue, Sea urchins move slowly, feeding primarily on algae. Sea otters, starfish, wolf eels, triggerfish, and other predators hunt and their roe is a delicacy in many cuisines. The name urchin is an old word for hedgehog, which sea urchins resemble, Sea urchins are members of the phylum Echinodermata, which also includes sea stars, sea cucumbers, brittle stars, and crinoids. Like other echinoderms, they have five-fold symmetry and move by means of hundreds of tiny, transparent, the symmetry is not obvious in the living animal, but is easily visible in the dried test. The irregular sea urchins are an infra-class inside the Euechinoidea, called Irregularia, irregular echinoids include, flattened sand dollars, sea biscuits, and heart urchins. Together with sea cucumbers, they make up the subphylum Echinozoa, Sea cucumbers and the irregular echinoids have secondarily evolved diverse shapes. Urchins typically range in size from 6 to 12 cm, although the largest species can reach up to 36 cm, like other echinoderms, sea urchin early larvae have bilateral symmetry, but they develop five-fold symmetry as they mature. This is most apparent in the sea urchins, which have roughly spherical bodies with five equally sized parts radiating out from their central axes. Several sea urchins, however, including the sand dollars, are oval in shape, with front and rear ends. In these urchins, the surface of the body is slightly domed. This irregular body form has evolved to allow the animals to burrow through sand or other soft materials, Sea urchins tube feet arise from the five ambulacral grooves. Tube feet are moved by a vascular system, which works through hydraulic pressure, allowing the sea urchin to pump water into and out of the tube feet. The lower half of a sea urchins body is referred to as the surface, because it contains the mouth. The internal organs are enclosed in a shell or test composed of fused plates of calcium carbonate covered by a thin dermis and epidermis. The test is rigid, and divides into five ambulacral grooves separated by five interambulacral areas, each of these areas consists of two rows of plates, so the sea urchin test includes 20 rows of plates in total. The plates are covered in rounded tubercles, to which the spines are attached, the inner surface of the test is lined by peritoneum
14.
Composite material
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The individual components remain separate and distinct within the finished structure. The new material may be preferred for reasons, common examples include materials which are stronger, lighter. More recently, researchers have begun to actively include sensing, actuation, computation and communication into composites. The most advanced examples perform routinely on spacecraft and aircraft in demanding environments, the earliest man-made composite materials were straw and mud combined to form bricks for building construction. Ancient brick-making was documented by Egyptian tomb paintings, wattle and daub is one of the oldest man-made composite materials, at over 6000 years old. Concrete is also a material, and is used more than any other man-made material in the world. As of 2006, about 7.5 billion cubic metres of concrete are made each year—more than one metre for every person on Earth. 2181–2055 BC and was used for death masks Cob Mud Bricks, concrete was described by Vitruvius, writing around 25 BC in his Ten Books on Architecture, distinguished types of aggregate appropriate for the preparation of lime mortars. For structural mortars, he recommended pozzolana, which were volcanic sands from the beds of Pozzuoli brownish-yellow-gray in colour near Naples. Natural cement-stones, after burning, produced cements used in concretes from post-Roman times into the 20th century, the glass fiber is relatively strong and stiff, whereas the polymer is ductile. Thus the resulting fiberglass is relatively stiff, strong, flexible, concrete is the most common artificial composite material of all and typically consists of loose stones held with a matrix of cement. Concrete is a material, and will not compress or shatter even under quite a large compressive force. However, concrete cannot survive tensile loading, therefore, to give concrete the ability to resist being stretched, steel bars, which can resist high stretching forces, are often added to concrete to form reinforced concrete. Fibre-reinforced polymers or FRPs include carbon-fiber-reinforced polymer or CFRP, and glass-reinforced plastic or GRP, if classified by matrix then there are thermoplastic composites, short fiber thermoplastics, long fibre thermoplastics or long fibre-reinforced thermoplastics. There are numerous thermoset composites, including paper composite panels, many advanced thermoset polymer matrix systems usually incorporate aramid fibre and carbon fibre in an epoxy resin matrix. Shape memory polymer composites are high-performance composites, formulated using fibre or fabric reinforcement and they can also be reheated and reshaped repeatedly without losing their material properties. These composites are ideal for such as lightweight, rigid, deployable structures, rapid manufacturing. Although high strain composites exhibit many similarities to shape memory polymers, Composites can also use metal fibres reinforcing other metals, as in metal matrix composites or ceramic matrix composites, which includes bone, cermet and concrete
15.
Mollusca
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The molluscs compose the large phylum Mollusca of invertebrate animals. Around 85,000 extant species of molluscs are recognized, molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats and they are highly diverse, not just in size and in anatomical structure, but also in behaviour and in habitat. The phylum is divided into 9 or 10 taxonomic classes. The gastropods are by far the most numerous molluscs in terms of classified species, the three most universal features defining modern molluscs are a mantle with a significant cavity used for breathing and excretion, the presence of a radula, and the structure of the nervous system. Other than these things, molluscs express great morphological diversity, so many textbooks base their descriptions on an ancestral mollusc. This has a single, limpet-like shell on top, which is made of proteins and chitin reinforced with calcium carbonate, the underside of the animal consists of a single muscular foot. Although molluscs are coelomates, the coelom tends to be small, the main body cavity is a hemocoel through which blood circulates, their circulatory systems are mainly open. The generalized mollusc has two paired nerve cords, or three in bivalves, the brain, in species that have one, encircles the esophagus. Most molluscs have eyes, and all have sensors to detect chemicals, vibrations, the simplest type of molluscan reproductive system relies on external fertilization, but more complex variations occur. All produce eggs, from which may emerge trochophore larvae, more complex veliger larvae, good evidence exists for the appearance of gastropods, cephalopods and bivalves in the Cambrian period 541 to 485.4 million years ago. Molluscs have, for centuries, also been the source of important luxury goods, notably pearls, mother of pearl, Tyrian purple dye and their shells have also been used as money in some preindustrial societies. Mollusc species can also represent hazards or pests for human activities, the bite of the blue-ringed octopus is often fatal, and that of Octopus apollyon causes inflammation that can last for over a month. Stings from a few species of large tropical cone shells can also kill, schistosomiasis is transmitted to humans via water snail hosts, and affects about 200 million people. Snails and slugs can also be serious pests, and accidental or deliberate introduction of some snail species into new environments has seriously damaged some ecosystems. The words mollusc and mollusk are both derived from the French mollusque, which originated from the Latin molluscus, from mollis, molluscus was itself an adaptation of Aristotles τα μαλακά, the soft things, which he applied to cuttlefish. The scientific study of molluscs is accordingly called malacology, as it is now known these groups have no relation to molluscs, and very little to one another, the name Molluscoida has been abandoned. The most universal features of the structure of molluscs are a mantle with a significant cavity used for breathing and excretion
16.
Pearl
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A pearl is a hard object produced within the soft tissue of a living shelled mollusk or another animal, such as a conulariid. Just like the shell of a clam, a pearl is composed of calcium carbonate. in minute crystalline form, the ideal pearl is perfectly round and smooth, but many other shapes, known as baroque pearls, can occur. The finest quality natural pearls have been valued as gemstones. Because of this, pearl has become a metaphor for something rare, fine, the most valuable pearls occur spontaneously in the wild, but are extremely rare. These wild pearls are referred to as natural pearls, cultured or farmed pearls from pearl oysters and freshwater mussels make up the majority of those currently sold. Imitation pearls are widely sold in inexpensive jewelry, but the quality of their iridescence is usually very poor and is easily distinguished from that of genuine pearls. Pearls have been harvested and cultivated primarily for use in jewelry and they have also been crushed and used in cosmetics, medicines and paint formulations. Whether wild or cultured, gem-quality pearls are almost always nacreous and iridescent, however, almost all species of shelled mollusks are capable of producing pearls of lesser shine or less spherical shape. The English word pearl comes from the French perle, originally from the Latin perna meaning leg, nacreous pearls, the best-known and most commercially significant, are primarily produced by two groups of molluskan bivalves or clams. A nacreous pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the shell, natural pearls, formed without human intervention, are very rare. Cultured pearls are formed in pearl farms, using human intervention as well as natural processes, saltwater pearls can grow in several species of marine pearl oysters in the family Pteriidae. Freshwater pearls grow within certain species of mussels in the order Unionida. The unique luster of pearls depends upon the reflection, refraction, the thinner and more numerous the layers in the pearl, the finer the luster. The iridescence that pearls display is caused by the overlapping of successive layers, in addition, pearls can be dyed yellow, green, blue, brown, pink, purple, or black. The very best pearls have a metallic mirror-like luster, because pearls are made primarily of calcium carbonate, they can be dissolved in vinegar. Calcium carbonate is susceptible to even a weak acid solution because the crystals of calcium carbonate react with the acid in the vinegar to form calcium acetate. Freshwater and saltwater pearls may sometimes look quite similar, but they come from different sources, Freshwater pearls form in various species of freshwater mussels, family Unionidae, which live in lakes, rivers, ponds and other bodies of fresh water. These freshwater pearl mussels occur not only in hotter climates, most freshwater cultured pearls sold today come from China
17.
Iridescence
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Iridescence is the phenomenon of certain surfaces that appear to gradually change colour as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, butterfly wings and sea shells and it is often created by structural coloration. The word iridescence is derived in part from the Greek word ἶρις îris, meaning rainbow, Iris in turn derives from the goddess Iris of Greek mythology, who is the personification of the rainbow and acted as a messenger of the gods. Goniochromism is derived from the Greek words gonia, meaning angle, iridescence is an optical phenomenon of surfaces in which hue changes with the angle of observation and the angle of illumination. It is often caused by reflections from two or more semi-transparent surfaces in which phase shift and interference of the reflections modulates the incidental light. The thickness of the layers of the material determines the interference pattern, iridescence is also found in plants, animals and many other items. The range of colours of natural iridescent objects can be narrow, iridescence can also be created by diffraction. This is found in items like CDs, DVDs, or cloud iridescence, in the case of diffraction, the entire rainbow of colours will typically be observed as the viewing angle changes. In biology, this type of results from the formation of diffraction gratings on the surface. In biological uses, colours produced other than with pigments or dyes are called structural coloration and it was later found that iridescence in the peacock is due to a complex photonic crystal. The feathers of birds such as kingfishers, Birds-of-paradise, hummingbirds, parrots, starlings, grackles, ducks, the lateral line on the Neon tetra is also iridescent. A single iridescent species of gecko, Cnemaspis kolhapurensis, was identified in India in 2009, the tapetum lucidum, present in the eyes of many vertebrates, is also iridescent. Many groups of plants have developed iridescence as an adaptation to use light in dark environments such as the lower levels of tropical forests. Nanocellulose is sometimes iridescent, as are films of gasoline and some other hydrocarbons. Iridescent products in the cosmetic and clothing industries are often referred as being holographic
18.
Bivalvia
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Bivalves as a group have no head and they lack some usual molluscan organs like the radula and the odontophore. They include the clams, oysters, cockles, mussels, scallops, the gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment where they are safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces, some bivalves, such as the scallops and file shells, can swim. The shipworms bore into wood, clay, or stone and live inside these substances, the shell of a bivalve is composed of calcium carbonate, and consists of two, usually similar, parts called valves. These are joined together along one edge by a ligament that, usually in conjunction with interlocking teeth on each of the valves. This arrangement allows the shell to be opened and closed without the two halves detaching, the shell is typically bilaterally symmetrical, with the hinge lying in the sagittal plane. Adult shell sizes of bivalves vary from fractions of a millimetre to over a metre in length, Bivalves have long been a part of the diet of coastal and riparian human populations. Oysters were cultured in ponds by the Romans, and mariculture has more become a important source of bivalves for food. Modern knowledge of molluscan reproductive cycles has led to the development of hatcheries, a better understanding of the potential hazards of eating raw or undercooked shellfish has led to improved storage and processing. Pearl oysters are the most common source of natural pearls, the shells of bivalves are used in craftwork, and the manufacture of jewellery and buttons. Bivalves have also used in the biocontrol of pollution. Bivalves appear in the record first in the early Cambrian more than 500 million years ago. The total number of living species is about 9,200 and these species are placed within 1,260 genera and 106 families. Marine bivalves represent about 8,000 species, combined in four subclasses and 99 families with 1,100 genera, the largest recent marine families are the Veneridae, with more than 680 species and the Tellinidae and Lucinidae, each with over 500 species. The freshwater bivalves include seven families, the largest of which are the Unionidae, the taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. More recently, the class was known as Pelecypoda, meaning axe-foot, the name bivalve is derived from the Latin bis, meaning two, and valvae, meaning leaves of a door. Bivalves vary greatly in overall shape, some, such as the cockles, have shells that are nearly globular, cockles can jump by bending and straightening their foot
19.
Gastropoda
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The Gastropoda or gastropods, more commonly known as snails and slugs, are a large taxonomic class within the phylum Mollusca. The class Gastropoda includes snails and slugs of all kinds and all sizes from microscopic to large, there are many thousands of species of sea snails and sea slugs, as well as freshwater snails, freshwater limpets, land snails and land slugs. The class Gastropoda contains a vast total of named species, second only to the insects in overall number, the fossil history of this class goes back to the Late Cambrian. There are 611 families of known, of which 202 are extinct. Gastropoda are a part of the phylum Mollusca, and are the most highly diversified class in the phylum, with 65,000 to 80,000 living snail. The anatomy, behavior, feeding, and reproductive adaptations of gastropods vary significantly from one clade or group to another, therefore, it is difficult to state many generalities for all gastropods. The class Gastropoda has an extraordinary diversification of habitats and those gastropods without a shell, and those with only a very reduced or internal shell, are usually known as slugs, those with a shell into which they cannot withdraw are termed limpets. In a number of families of species, such as all the various limpets, the shell is coiled only in the larval stage, in the scientific literature, gastropods were described under gasteropodes by Georges Cuvier in 1795. Cuvier chose gastropod by derivation from the Ancient Greek words γαστήρ stomach, the earlier name univalve means one valve or shell, in contrast to bivalve applied to mollusks such as clams and meaning that those animals possess two valves or shells. At all taxonomic levels, gastropods are second only to the insects in terms of their diversity, Gastropods have the greatest numbers of named mollusc species. However, estimates of the number of gastropod species vary widely. The number of species can be ascertained from estimates of the number of described species of Mollusca with accepted names. But an estimate of the number of Mollusca, including undescribed species, is about 240,000 species. The estimate of 85,000 molluscs includes 24,000 described species of terrestrial gastropods, different estimates for aquatic gastropods give about 30,000 species of marine gastropods, and about 5,000 species of freshwater and brackish gastropods. The total number of living species of snails is about 4,000. There are 444 recently extinct species of gastropods,18 species that are now extinct in the wild and 69 possibly extinct species, the number of prehistoric species of gastropods is at least 15,000 species. Some of the familiar and better-known gastropods are terrestrial gastropods and some live in freshwater. Gastropods have a distribution from the near Arctic and Antarctic zones to the tropics
20.
Cephalopod
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A cephalopod is any member of the molluscan class Cephalopoda. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, fishermen sometimes call them inkfish, referring to their common ability to squirt ink. The study of cephalopods is a branch of known as teuthology. Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids, the class now contains two, only distantly related, extant subclasses, Coleoidea, which includes octopuses, squid, and cuttlefish, and Nautiloidea, represented by Nautilus and Allonautilus. In the Coleoidea, the shell has been internalized or is absent, whereas in the Nautiloidea. About 800 living species of cephalopods have been identified, two important extinct taxa are the Ammonoidea and Belemnoidea. There are over 800 extant species of cephalopod, although new species continue to be described, an estimated 11,000 extinct taxa have been described, although the soft-bodied nature of cephalopods means they are not easily fossilised. Cephalopods are found in all the oceans of Earth, none of them can tolerate freshwater, but the brief squid, Lolliguncula brevis, found in Chesapeake Bay, is a notable partial exception in that it tolerates brackish water. Cephalopods are thought to be unable to live in due to multiple biochemical constraints. Cephalopods occupy most of the depth of the ocean, from the plain to the sea surface. Their diversity is greatest near the equator and decreases towards the poles, Cephalopods are widely regarded as the most intelligent of the invertebrates, and have well developed senses and large brains. The nervous system of cephalopods is the most complex of the invertebrates, the brain is protected in a cartilaginous cranium. Cephalopods have also known to climb out of their aquaria, maneuver a distance of the lab floor, enter another aquarium to feed on the crabs. Cephalopods are social creatures, when isolated from their own kind, some cephalopods are able to fly through the air for distances of up to 50 m. While cephalopods are not particularly aerodynamic, they achieve these impressive ranges by jet-propulsion, the animals spread their fins and tentacles to form wings and actively control lift force with body posture. Cephalopods have advanced vision, can detect gravity with statocysts, and have a variety of sense organs. Octopuses use their arms to explore their environment and can use them for depth perception, most cephalopods rely on vision to detect predators and prey, and to communicate with one another. Consequently, cephalopod vision is acute, training experiments have shown that the octopus can distinguish the brightness, size, shape
21.
Porcelain
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Porcelain /ˈpɔːrsəlᵻn, ˈpɔːrslᵻn/ is a ceramic material made by heating materials, generally including kaolin, in a kiln to temperatures between 1,200 and 1,400 °C. Porcelain was first developed in China around 2,000 years ago, then spread to other East Asian countries, and finally Europe. It combines well with both glazes and paint, and can be modelled very well, allowing a range of decorative treatments in tablewares, vessels. It also has uses in technology and industry. The European name, porcelain in English, come from the old Italian porcellana because of its resemblance to the translucent surface of the shell, Porcelain is also referred to as china or fine china in some English-speaking countries, as it was first seen in imports from China. Porcelain has been described as being completely vitrified, hard, impermeable, white or artificially coloured, translucent, however, the term porcelain lacks a universal definition and has been applied in a very unsystematic fashion to substances of diverse kinds which have only certain surface-qualities in common. Terms such as porcellaneous or near-porcelain may be used in such cases, a high proportion of modern porcelain is made of the variant bone china. Kaolin is the material from which porcelain is made, even though clay minerals might account for only a small proportion of the whole. The word paste is an old term for both the unfired and fired material, a more common terminology these days for the unfired material is body, for example, when buying materials a potter might order an amount of porcelain body from a vendor. The composition of porcelain is highly variable, but the mineral kaolinite is often a raw material. Other raw materials can include feldspar, ball clay, glass, bone ash, steatite, quartz, petuntse, the clays used are often described as being long or short, depending on their plasticity. Long clays are cohesive and have high plasticity, short clays are cohesive and have lower plasticity. Clays used for porcelain are generally of lower plasticity and are shorter than many other pottery clays and they wet very quickly, meaning that small changes in the content of water can produce large changes in workability. Thus, the range of content within which these clays can be worked is very narrow. The following section provides information on the methods used to form, decorate, finish, glaze. Many types of glaze, such as the iron-containing glaze used on the wares of Longquan, were designed specifically for their striking effects on porcelain. Porcelain wares may be decorated under the glaze using pigments that include cobalt and copper or over the glaze using coloured enamels. Like many earlier wares, modern porcelains are often biscuit-fired at around 1,000 °C, coated with glaze, another early method is once-fired where the glaze is applied to the unfired body and the two fired together in a single operation
22.
Conch
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Conch is a common name that is applied to a number of different medium to large-sized sea snails or their shells. The term generally applies to large snails whose shell has a high spire, in North America, a conch is often identified as a queen conch, found off the coast of Florida. Queen conches are valued for fish bait, and are known as seafood. The group of conchs that are referred to as true conchs are marine gastropod molluscs in the family Strombidae, specifically in the genus Strombus. For example, see Lobatus gigas, the conch, and Laevistrombus canarium. Many other species are often called conch, but are not at all closely related to the family Strombidae, including Melongena species. Species commonly referred to as conchs also include the sacred chank or more correctly shankha shell, the English word conch is attested in Middle English, coming from Latin concha, which in turn comes from Greek konchē ultimately from PIE root *konkho-, cognate with Sanskrit śaṅkha. The meat of conchs is eaten raw in salads, or cooked, as in burgers, chowders, fritters, all parts of the conch meat are edible. In The Bahamas, conch is served in fritter form, or as a raw. In the West Indies, local people eat conch in soups, stews, restaurants all over the islands serve this particular meat. In the Dominican Republic, Grenada, and Haiti, conch is commonly eaten in curries or in a spicy soup and it is locally referred to as lambi. In The Turks and Caicos Islands, the Annual Conch Festival is held in November each year, local restaurateurs compete for the best and most original conch dishes, that are then judged by international chefs. Free sampling of the dishes follows the judging, along with those festivities, other competitions, events, and music performances occur well into the evening. In Puerto Rico, conch is served as a ceviche, often called ensalada de carrucho, consisting of raw conch marinated in lime juice, olive oil, vinegar, garlic, green peppers and it is also used to fill empanadas. In East Asian cuisines, this seafood is often cut into thin slices, Conch shells can be used as wind instruments. They are prepared by cutting a hole in the spire of the shell near the apex, sometimes a mouthpiece is used, but some shell trumpets are blown without one. Many different kinds of mollusks can produce pearls, pearls from the queen conch, L. gigas, are rare and have been collectors items since Victorian times. In some gemological texts, non-nacreous gastropod pearls used to be referred to as calcareous concretions because they were porcellaneous, rather than nacreous, although non-nacreous, the surface of fine conch pearls has a unique and attractive appearance of its own
23.
Pinctada
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Pinctada is a genus of saltwater oysters, marine bivalve molluscs in the family Pteriidae, the pearl oysters. These oysters have an inner shell layer composed of nacre. Pearl oysters are not closely related to either the edible oysters of family Ostreidae or the pearl mussels of the families Unionidae and Margaritiferidae. P. margaritifera and P. maxima are used for culturing South Sea and they are cultured widely primarily in the central and eastern Indo-Pacific. A pearl oyster can be seen on the side of the 1. All species within the genus produce pearls, attempts have been made to harvest pearls commercially from many Pinctada species. Pearls are also obtained in commercial quantities from some species of the related winged oyster genus Pteria. Pearls are also produced from freshwater mussel species unrelated to pearl oysters and these freshwater species include Hyriopsis cumingii, Hyriopsis schlegelii, and a hybrid of the two species. At danger from the demand for pearls, the typical lifespan of a pearl oyster is usually around 3 years to 14 years. Pinctada maxima are seeded at about 2 years of age and take 2 years to develop a pearl. They can be reseeded up to 3 or 4 times, akoya pearls are harvested after about 9 to 16 months. He analyzed historical records and used information about the biology of these and other species to explain its rapid disappearance
24.
Freshwater pearl mussel
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The freshwater pearl mussel, scientific name Margaritifera margaritifera, is an endangered species of freshwater mussel, an aquatic bivalve mollusc in the family Margaritiferidae. Although the name freshwater pearl mussel is often used for species, other freshwater mussel species can also create pearls. The interior of the shell of Margaritifera margaritifera has thick nacre and this species is capable of making fine-quality pearls, and was historically exploited in the search for pearls from wild sources. Zyuganov have been confirmed by the Finnish malacologists and gained general acceptance and this subspecies is mentioned in annexes II and V of Habitats Directive as Margaritifera durrovensis. The freshwater pearl mussel is one of the invertebrates in existence. The oldest known specimen in Europe was caught in 1993 in Estonia when it was 134 years old, like all bivalve molluscs, the freshwater pearl mussel has a shell consisting of two parts that are hinged together, which can be closed to protect the animals soft body within. The shell is large, heavy and elongated, typically yellowish-brown in colour when young and becoming darker with age, older parts of the shell often appear corroded, an identifying feature of this mussel species. The inner surface of the shell is white, sometimes tinged with attractive iridescent colours. The native distribution of species is Holarctic. The freshwater pearl mussel can be found on both sides of the Atlantic, from the Arctic and temperate regions of western Russia, through Europe to northeastern North America, belgium Czech Republic - critically endangered. In Bohemia, probably extinct in Moravia. Listed in Decree for implementation, No, 395/1992 Sb. as Critically Threatened species. Its Conservation status in 2004-2006 is bad in report for European commission in accordance with Habitats Directive, denmark Estonia Fennoscandia - vulnerable in Finland and Norway, endangered in Sweden. Very rare in southern Finland, more common in the north, widespread but not common in Norway, Norway is considered to host a large proportion of the European stock. Also in Kola Peninsula and Karelia, listed as strictly protected species in annex 1 in Bundesartenschutzverordnung. More than half the worlds recruiting population exists in Scotland with populations in more than 50 rivers, mainly in the Highlands, although illegal harvesting has seriously affected their survival. 75% of sites surveyed in 2010 had suffered significant and lasting damage and in response the police. This species has been protected in the United Kingdom under the Wildlife and Countryside Act 1981 since 1998
25.
Haliotis
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Haliotis, common name abalone, pāua, or ormer, is the only genus in the family Haliotidae. This genus once contained six subgenera and these subgenera have become alternate representations of Haliotis. The genus consists of small to large, edible, herbivorous sea snails. The number of species recognized worldwide ranges between 30 and 130, with over 230 species-level taxa described, the most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies. The shells of abalones have a low, open, spiral structure, the shell of abalones is convex, rounded to oval shape, and may be highly arched or very flattened. The shell of the majority of species is ear-shaped, presenting a small, flat spire, the last whorl, known as the body whorl, is auriform, meaning that the shell resembles an ear, giving rise to the common name ear shell. Haliotis asinina has a different shape, as it is more elongated and distended. The shell of Haliotis cracherodii cracherodii is also unusual as it has a form, is imperforate, shows an exserted spire. A mantle cleft in the shell impresses a groove in the shell, in which are the row of holes and these holes are respiratory apertures for venting water from the gills and for releasing sperm and eggs into the water column. They make up what is known as the selenizone which forms as the shell grows and this series of eight to 38 holes is near the anterior margin. Only a small number are generally open, the older holes are gradually sealed up as the shell grows and new holes form. Therefore, the number of tremata is not characteristic for the species, each species has a number of open holes, between four and 10, in the selenizone. This number is not fixed and can vary within a species, the aperture of the shell is very wide and nacreous. The exterior of the shell is striated and dull, the color of the shell is very variable from species to species, which may reflect the animals diet. The iridescent nacre that lines the inside of the shell varies in color from white, to pink, red and green-red, to deep blue. The side-lobes are also fimbriated and cirrated, the rounded foot is very large. The radula has small teeth, and the lateral teeth are single. About 70 uncini are present, with denticulated hooks, the first four very large, the soft body is coiled around the columellar muscle, and its insertion, instead of being on the columella, is on the middle of the inner wall of the shell
26.
Trochidae
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The Trochidae, common name top-snails or top-shells, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda. This family is known as the top-snails because in many species the shell resembles a toy spinning top. The animal is similar in form to the Turbinidae. The top snails are characterized by primitive traits, a heart with two atria. They have retained only one kidney and the second osphradium has been lost in the course of evolution, the mantle cavity contains a single gill. Along the side of the foot are three or more pairs of sensory epipodial tentacles, the head has a short, broad rostrum. The intertentacular lobes are simple or digitated, separate or united across the front, the jaws are developed or absent. The rhachidian teeth are present and well-developed. The lateral teeth generally number 5 on each side, sometimes more numerous, the marginal teeth are narrow and very numerous. The length of a shell varies between 5 mm and 130 mm. There is also a variation in the shape of the shell. This goes from low auriform with an aperture to the long. The shape may also be subglobose, turbinate or helicoid and their height may vary between 3 mm and 152 mm. The shell contains only a few whorls and these have a highly variable exterior, ranging from smooth or glossy to sculptured. They have a brown, entirely corneous, circular, multispiral operculum which fits the aperture snugly, the operculum is formed of numerous gradually increasing whorls with a central nucleus. The aperture may be entire, tetragonal or rounded and has no reflected lip, the peristome is generally not continuous. These shells are brightly colored and adorned with darker bands. The Trochidae differ from the Turbinidae in having a corneous, never calcareous, operculum, most species in the family live either in the intertidal zone or in the shallow subtidal zone, but some live in deeper water
27.
Turbinidae
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Turbinidae, the turban snails, are a family of small to large marine gastropod molluscs in the superfamily Trochoidea. Turbinidae have a strong, thick calcareous operculum readily distinguishing them from the somewhat similar Trochidae or top snails and this strong operculum serves as a passive defensive structure against predators that try to enter by way of the aperture or that would break the shell at the outer lip. The common name turban snail presumably refers to the similarity in appearance to a turban. However, the scientific name Turbinidae is based on the genus name Turbo, which is Latin for spinning top, the word turbine has a similar derivation. Previously they were classified in the subclass Prosobranchia, in the order Archaeogastropoda in the superfamily Trochacea, trochaecea is now a synonym for the superfamily Trochoidea. However, this is an ancient group of gastropods, probably originating in the Permian period 298 to 250 million years ago. They have typical primitive characters like the interior of the shell. Turbinidae belongs to superfamily Turbinoidea according to the taxonomy of the Gastropoda by Bouchet & Rocroi, angariidae was elevated to family level, Colloniinae was elevated to family Colloniidae within Phasianelloidea, Margaritinae was moved to Turbinidae from Trochidae. This family consists of five following subfamilies according to Williams et al, the family has a large distribution, from the tropics to the polar regions, but most of the species live in tropical and subtropical shallow waters. Sowerby I,1838, synonym of Norrisia Bayle,1880 † Tylastralium Sacco,1896, synonym of Bolma Risso,1826 Valvatella Gray,1857, synonym of Margarites Gray,1847 Marshall, B. A.1988. Skeneidae, Vitrinellidae and Orbitestellidae associated with biogenic substrata from bathyal depths off New Zealand, journal of Natural History 22, 949-1004. A classification of the living Mollusca, molecular systematics of Vetigastropoda, Trochidae, Turbinidae and Trochoidea redefined. Seashells of New South Wales, Turbinidae Seashells of New South Wales, Skeneinae
28.
Structural coloration
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Structural coloration is the production of colour by microscopically structured surfaces fine enough to interfere with visible light, sometimes in combination with pigments. For example, peacock feathers are pigmented brown, but their microscopic structure makes them also reflect blue, turquoise, and green light. Structural coloration was first observed by English scientists Robert Hooke and Isaac Newton, Young described iridescence as the result of interference between reflections from two or more surfaces of thin films, combined with refraction as light enters and leaves such films. The geometry then determines that at certain angles, the light reflected from both surfaces interferes constructively, while at other angles, the light interferes destructively, different colours therefore appear at different angles. Some cuts of meat also show structural coloration due to the exposure of the arrangement of the muscular fibres. Many of these photonic mechanisms correspond to elaborate structures visible by electron microscopy, in plants, brilliant colours are produced by structures within cells. In his 1704 book Opticks, Isaac Newton described the mechanism of the other than the brown pigment of peacock tail feathers. Thomas Young extended Newtons particle theory of light by showing that light could behave as a wave. He showed in 1803 that light could diffract from sharp edges or slits, Colours of the latter kind are often spoken of as structural colours, they are caused by the structure of the coloured surfaces. The metallic lustre of the feathers of birds, such as the humming birds, is due to the presence of excessively fine striae upon the surface of the feathers. Structural coloration is caused by interference effects rather than by pigments, Colours are produced when a material is scored with fine parallel lines, formed of one or more parallel thin layers, or otherwise composed of microstructures on the scale of the colours wavelength. Structural coloration is responsible for the blues and greens of the feathers of birds, as well as many butterfly wings. These are often iridescent, as in peacock feathers and nacreous shells such as of pearl oysters and this is because the reflected colour depends on the viewing angle, which in turn governs the apparent spacing of the structures responsible. Structural colours can be combined with pigment colours, peacock feathers are pigmented brown with melanin, iridescence, as explained by Thomas Young in 1803, is created when extremely thin films reflect part of the light falling on them from their top surfaces. The rest of the light goes through the films, and a part of it is reflected from their bottom surfaces. The two sets of reflected waves travel back upwards in the same direction, when the waves are one or more whole wavelength apart – in other words at certain specific angles, they add, giving a strong reflection. At other angles and phase differences, they can subtract, giving weak reflections, the thin film therefore selectively reflects just one wavelength – a pure colour – at any given angle, but other wavelengths – different colours – at different angles. So, as a structure like a butterflys wing or birds feather moves
29.
Aragonite
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Aragonite is a carbonate mineral, one of the two most common, naturally occurring, crystal forms of calcium carbonate, CaCO3. It is formed by biological and physical processes, including precipitation from marine, aragonites crystal lattice differs from that of calcite, resulting in a different crystal shape, an orthorhombic crystal system with acicular crystal. Repeated twinning results in pseudo-hexagonal forms, Aragonite may be columnar or fibrous, occasionally in branching stalactitic forms called flos-ferri from their association with the ores at the Carinthian iron mines. The type location for aragonite is Molina de Aragón,25 km from Aragon for which it was named in 1797, an aragonite cave, the Ochtinská Aragonite Cave, is situated in Slovakia. In the US, aragonite in the form of stalactites and cave flowers is known from Carlsbad Caverns, massive deposits of oolitic aragonite sand are found on the seabed in the Bahamas. Aragonite is the high pressure polymorph of calcium carbonate, as such, it occurs in high pressure metamorphic rocks such as those formed at subduction zones. Aragonite forms naturally in almost all mollusk shells, and as the calcareous endoskeleton of warm-, because the mineral deposition in mollusk shells is strongly biologically controlled, some crystal forms are distinctively different from those of inorganic aragonite. In some mollusks, the shell is aragonite, in others. The nacreous layer of the fossil shells of some extinct ammonites forms an iridescent material called ammolite. Aragonite also forms in the ocean and in caves as inorganic precipitates called marine cements and speleothems, Aragonite is not uncommon in serpentinites where high Mg in pore solutions apparently inhibits calcite growth and promotes aragonite precipitation. Aragonite is metastable at the low pressures near the Earths surface and is commonly replaced by calcite in fossils. Aragonite older than the Carboniferous is essentially unknown and it can also be synthesized by adding a calcium chloride solution to a sodium carbonate solution at temperatures above 60 °C or in water-ethanol mixtures at ambient temperatures. Aragonite is thermodynamically unstable at temperature and pressure, and tends to alter to calcite on scales of 107 to 108 years. The mineral vaterite, also known as μ-CaCO3, is another phase of calcium carbonate that is metastable at ambient conditions typical of Earths surface, in aquaria, aragonite is considered essential for the replication of reef conditions. Aragonite provides the necessary for much sea life and also keeps the pH of the water close to its natural level. Aragonite has been tested for the removal of pollutants like zinc, cobalt. Aragonite sea Ikaite, CaCO3·6H2O Monohydrocalcite, CaCO3·H2O Nacre, otherwise known as Mother-of-Pearl Oolitic aragonite sand The Ochtinska aragonite cave Kosovo Caves Aragonite Formations
30.
Calcium carbonate
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Calcium carbonate is a chemical compound with the formula CaCO3. It is a substance found in rocks as the minerals calcite and aragonite and is the main component of pearls and the shells of marine organisms, snails. Calcium carbonate is the ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It is medicinally used as a supplement or as an antacid. Calcium carbonate shares the properties of other carbonates. CaCO3 + CO2 + H2O → Ca2 This reaction is important in the erosion of rock, forming caverns. An unusual form of calcium carbonate is the hexahydrate, ikaite, ikaite is stable only below 6 °C. The vast majority of calcium used in industry is extracted by mining or quarrying. Pure calcium carbonate, can be produced from a quarried source. Alternatively, calcium carbonate is prepared from calcium oxide, other forms can be prepared, the denser, orthorhombic λ-CaCO3 and μ-CaCO3, occurring as the mineral vaterite. The aragonite form can be prepared by precipitation at temperatures above 85 °C, calcite contains calcium atoms coordinated by 6 oxygen atoms, in aragonite they are coordinated by 9 oxygen atoms. The vaterite structure is not fully understood, magnesium carbonate MgCO3 has the calcite structure, whereas strontium and barium carbonate adopt the aragonite structure, reflecting their larger ionic radii. Calcite, aragonite and vaterite are pure calcium carbonate minerals, industrially important source rocks which are predominantly calcium carbonate include limestone, chalk, marble and travertine. Eggshells, snail shells and most seashells are predominantly calcium carbonate, oyster shells have enjoyed recent recognition as a source of dietary calcium, but are also a practical industrial source. While not practical as a source, dark green vegetables such as broccoli. Beyond Earth, strong evidence suggests the presence of Calcium carbonate on Mars, signs of Calcium Carbonate have been detected at more than one location. This provides some evidence for the past presence of liquid water, Carbonate is found frequently in geologic settings and constitute an enormous carbon reservoir. Calcium carbonate occurs as aragonite, calcite and dolomite, the carbonate minerals form the rock types, limestone, chalk, marble, travertine, tufa, and others
31.
Elasticity (physics)
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In physics, elasticity is the ability of a body to resist a distorting influence or deforming force and to return to its original size and shape when that influence or force is removed. Solid objects will deform when adequate forces are applied on them, if the material is elastic, the object will return to its initial shape and size when these forces are removed. The physical reasons for elastic behavior can be different for different materials. In metals, the atomic lattice changes size and shape when forces are applied, when forces are removed, the lattice goes back to the original lower energy state. For rubbers and other polymers, elasticity is caused by the stretching of polymer chains when forces are applied, perfect elasticity is an approximation of the real world. The most elastic body in modern science found is Quartz fibre which is not even a perfect elastic body, so perfect elastic body is an ideal concept only. Most materials which possess elasticity in practice remain purely elastic only up to very small deformations. In engineering, the amount of elasticity of a material is determined by two types of material parameter, the first type of material parameter is called a modulus, which measures the amount of force per unit area needed to achieve a given amount of deformation. The SI unit of modulus is the pascal, a higher modulus typically indicates that the material is harder to deform. The second type of measures the elastic limit, the maximum stress that can arise in a material before the onset of permanent deformation. Its SI unit is also pascal, when describing the relative elasticities of two materials, both the modulus and the elastic limit have to be considered. Rubbers typically have a low modulus and tend to stretch a lot, of two rubber materials with the same elastic limit, the one with a lower modulus will appear to be more elastic, which is however not correct. When an elastic material is deformed due to a force, it experiences internal resistance to the deformation. The various moduli apply to different kinds of deformation, for instance, Youngs modulus applies to extension/compression of a body, whereas the shear modulus applies to its shear. The elasticity of materials is described by a curve, which shows the relation between stress and strain. The curve is nonlinear, but it can be approximated as linear for sufficiently small deformations. For even higher stresses, materials exhibit behavior, that is, they deform irreversibly. Elasticity is not exhibited only by solids, non-Newtonian fluids, such as viscoelastic fluids, in response to a small, rapidly applied and removed strain, these fluids may deform and then return to their original shape. Under larger strains, or strains applied for longer periods of time, because the elasticity of a material is described in terms of a stress-strain relation, it is essential that the terms stress and strain be defined without ambiguity
32.
Chitin
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Chitin n is a long-chain polymer of an N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world. The structure of chitin is comparable to the cellulose, forming crystalline nanofibrils or whiskers. In terms of function, it may be compared to the protein keratin, chitin has proved versatile for several medicinal, industrial and biotechnological purposes. The English word chitin comes from the French word chitine, which first appeared in 1821 and derived from the Greek word χιτών, a similar word, chiton, refers to a marine animal with a protective shell. The structure of chitin was solved by Albert Hofmann in 1929, chitin is a modified polysaccharide that contains nitrogen, it is synthesized from units of N-acetyl-D-glucosamine. Therefore, chitin may be described as cellulose with one group on each monomer replaced with an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers, giving the chitin-polymer matrix increased strength, in its pure, unmodified form, chitin is translucent, pliable, resilient, and quite tough. Combined with calcium carbonate, as in the shells of crustaceans and molluscs and this composite material is much harder and stiffer than pure chitin, and is tougher and less brittle than pure calcium carbonate. Another difference between pure and composite forms can be seen by comparing the body wall of a caterpillar to the stiff. The elaborate chitin gyroid construction in butterfly wings creates a model of optical devices having potential for innovations in biomimicry, scarab beetles in the genus Cyphochilus also utilize chitin to form extremely thin scales that diffusely reflect white light. These scales are networks of randomly ordered filaments of chitin with diameters on the scale of hundreds of nanometres, the multiple scattering of light is thought to play a role in the unusual whiteness of the scales. In addition, some wasps, such as Protopolybia chartergoides, orally secrete material containing predominantly chitin to reinforce the outer nest envelopes. Chitosan is produced commercially by deacetylation of chitin, chitosan is soluble in water, chitin producing organisms like protozoa, fungi, arthropods, and nematodes are often pathogens in other species. Keratinocytes in skin can also react to chitin or chitin fragments, according to in vitro studies, chitin is sensed by receptors, such as FIBCD1, KLRB1, REG3G, Toll-like receptor 2, CLEC7A, and mannose receptors. Plants also have receptors that can cause a response to chitin, namely chitin elicitor receptor kinase 1, the first chitin receptor was cloned in 2006. When the receptors are activated by chitin, genes related to plant defense are expressed, and jasmonate hormones are activated, commensal fungi that have ways to interact with the host immune response that as of 2016 were not well understood. Some pathogens produce chitin-binding proteins that mask the chitin they shed from these receptors, zymoseptoria tritici is an example of a fungal pathogen that has such blocking proteins, it is a major pest in wheat crops. Chitin was probably present in the exoskeletons of Cambrian arthropods such as trilobites, the oldest preserved chitin dates to the Oligocene, about 25 million years ago, consisting of a scorpion encased in amber
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Silk
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Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by insect larvae to form cocoons. The best-known silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity, Silk is produced by several insects, but generally only the silk of moth caterpillars has been used for textile manufacturing. There has been research into other types of silk, which differ at the molecular level. Silk is mainly produced by the larvae of insects undergoing complete metamorphosis, Silk production also occurs in Hymenoptera, silverfish, mayflies, thrips, leafhoppers, beetles, lacewings, fleas, flies, and midges. Other types of arthropod produce silk, most notably various arachnids such as spiders, the word silk comes from Old English sioloc, from Greek σηρικός serikos, silken, ultimately from an Asian source. Several kinds of silk, which are produced by caterpillars other than the mulberry silkworm, have been known and used in China, South Asia. However, the scale of production was far smaller than for cultivated silks. Thus, the way to obtain silk suitable for spinning into textiles in areas where commercial silks are not cultivated was by tedious. Commercial silks originate from reared silkworm pupae, which are bred to produce a silk thread with no mineral on the surface. The pupae are killed by either dipping them in boiling water before the adult moths emerge or by piercing them with a needle. These factors all contribute to the ability of the cocoon to be unravelled as one continuous thread. Wild silks also tend to be difficult to dye than silk from the cultivated silkworm. Genetic modification of domesticated silkworms is used to facilitate the production of more types of silk. Silk fabric was first developed in ancient China, the earliest example of silk fabric is from 3630 BC, and it was used as wrapping for the body of a child from a Yangshao culture site in Qingtaicun at Xingyang, Henan. Legend gives credit for developing silk to a Chinese empress, Leizu, because of its texture and lustre, silk rapidly became a popular luxury fabric in the many areas accessible to Chinese merchants. Silk was in demand, and became a staple of pre-industrial international trade. In July 2007, archaeologists discovered intricately woven and dyed silk textiles in a tomb in Jiangxi province, Silk is described in a chapter on mulberry planting by Si Shengzhi of the Western Han
34.
Protein
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Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, a linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide, short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides, or sometimes oligopeptides. The individual amino acid residues are bonded together by peptide bonds, the sequence of amino acid residues in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the code specifies 20 standard amino acids, however. Sometimes proteins have non-peptide groups attached, which can be called prosthetic groups or cofactors, proteins can also work together to achieve a particular function, and they often associate to form stable protein complexes. Once formed, proteins only exist for a period of time and are then degraded and recycled by the cells machinery through the process of protein turnover. A proteins lifespan is measured in terms of its half-life and covers a wide range and they can exist for minutes or years with an average lifespan of 1–2 days in mammalian cells. Abnormal and or misfolded proteins are degraded more rapidly due to being targeted for destruction or due to being unstable. Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms, many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. In animals, proteins are needed in the diet to provide the essential amino acids that cannot be synthesized, digestion breaks the proteins down for use in the metabolism. Methods commonly used to study structure and function include immunohistochemistry, site-directed mutagenesis, X-ray crystallography, nuclear magnetic resonance. Most proteins consist of linear polymers built from series of up to 20 different L-α-amino acids, all proteinogenic amino acids possess common structural features, including an α-carbon to which an amino group, a carboxyl group, and a variable side chain are bonded. Only proline differs from this structure as it contains an unusual ring to the N-end amine group. The amino acids in a chain are linked by peptide bonds. Once linked in the chain, an individual amino acid is called a residue, and the linked series of carbon, nitrogen. The peptide bond has two forms that contribute some double-bond character and inhibit rotation around its axis, so that the alpha carbons are roughly coplanar
35.
Young's modulus
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Youngs modulus, also known as the elastic modulus, is a measure of the stiffness of a solid material. It is a property of linear elastic solid materials. It defines the relationship between stress and strain in a material, Youngs modulus is named after the 19th-century British scientist Thomas Young. The term modulus is the diminutive of the Latin term modus which means measure, a solid material will deform when a load is applied to it. If it returns to its shape after the load is removed. In the range where the ratio between load and deformation remains constant, the curve is linear. Not many materials are linear and elastic beyond a small amount of deformation, although such a material cannot exist, a material with a very high Youngs modulus can be approximated as rigid. g. The technical definition is, the ratio of the stress along an axis to the strain along that axis in the range of stress in which Hookes law holds, Youngs modulus is the ratio of stress to strain, and so Youngs modulus has units of pressure. Its SI unit is therefore the pascal, the practical units used are megapascals or gigapascals. In United States customary units, it is expressed as pounds per square inch, the abbreviation ksi refers to kips per square inch. A kip is an Imperial unit of force and is equal to 1000 pounds-force, the Youngs modulus enables the calculation of the change in the dimension of a bar made of an isotropic elastic material under tensile or compressive loads. For instance, it predicts how much a material sample extends under tension or shortens under compression, the Youngs modulus directly applies to cases of uniaxial stress, that is tensile or compressive stress in one direction and no stress in the other directions. Youngs modulus is used in order to predict the deflection that will occur in a statically determinate beam when a load is applied at a point in between the beams supports. Other elastic calculations usually require the use of one additional property, such as the shear modulus. Any two of these parameters are sufficient to fully describe elasticity in an isotropic material, Youngs modulus represents the factor of proportionality in Hookes law, which relates the stress and the strain. However, Hookes law is valid under the assumption of an elastic. If the range over which Hookes law is valid is large compared to the typical stress that one expects to apply to the material. Otherwise the material is said to be non-linear, steel, carbon fiber and glass among others are usually considered linear materials, while other materials such as rubber and soils are non-linear
36.
Pascal (unit)
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The pascal is the SI derived unit of pressure used to quantify internal pressure, stress, Youngs modulus and ultimate tensile strength. It is defined as one newton per square meter and it is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal which is equal to one millibar, the unit of measurement called standard atmosphere is defined as 101,325 Pa and approximates to the average pressure at sea-level at the latitude 45° N. Meteorological reports typically state atmospheric pressure in hectopascals, the unit is named after Blaise Pascal, noted for his contributions to hydrodynamics and hydrostatics, and experiments with a barometer. The name pascal was adopted for the SI unit newton per square metre by the 14th General Conference on Weights, one pascal is the pressure exerted by a force of magnitude one newton perpendicularly upon an area of one square metre. The unit of measurement called atmosphere or standard atmosphere is 101325 Pa and this value is often used as a reference pressure and specified as such in some national and international standards, such as ISO2787, ISO2533 and ISO5024. In contrast, IUPAC recommends the use of 100 kPa as a standard pressure when reporting the properties of substances, geophysicists use the gigapascal in measuring or calculating tectonic stresses and pressures within the Earth. Medical elastography measures tissue stiffness non-invasively with ultrasound or magnetic resonance imaging, in materials science and engineering, the pascal measures the stiffness, tensile strength and compressive strength of materials. In engineering use, because the pascal represents a small quantity. The pascal is also equivalent to the SI unit of energy density and this applies not only to the thermodynamics of pressurised gases, but also to the energy density of electric, magnetic, and gravitational fields. In measurements of sound pressure, or loudness of sound, one pascal is equal to 94 decibels SPL, the quietest sound a human can hear, known as the threshold of hearing, is 0 dB SPL, or 20 µPa. The airtightness of buildings is measured at 50 Pa, the units of atmospheric pressure commonly used in meteorology were formerly the bar, which was close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure pressures in hectopascals unit, exceptions include Canada and Portugal, which use kilopascals. In many other fields of science, the SI is preferred, many countries also use the millibar or hectopascal to give aviation altimeter settings. In practically all fields, the kilopascal is used instead. Centimetre of water Metric prefix Orders of magnitude Pascals law
37.
Silicon
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Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a metallic luster. It is a member of group 14 in the table, along with carbon above it and germanium, tin, lead. It is not very reactive, although more reactive than germanium, Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earths crust. It is most widely distributed in dusts, sands, planetoids, over 90% of the Earths crust is composed of silicate minerals, making silicon the second most abundant element in the Earths crust after oxygen. Most silicon is used commercially without being separated, and often with little processing of the natural minerals, such use includes industrial construction with clays, silica sand, and stone. Silicate is used in Portland cement for mortar and stucco, and mixed with sand and gravel to make concrete for walkways, foundations. Silicates are used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass, Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics. Elemental silicon also has an impact on the modern world economy. Most free silicon is used in the refining, aluminium-casting. Silicon is the basis of the widely used synthetic polymers called silicones, Silicon is an essential element in biology, although only tiny traces are required by animals. However, various sea sponges and microorganisms, such as diatoms and radiolaria, silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa, horsetails and many grasses. Silicon is a solid at room temperature, with a point of 1,414 °C. Like water, it has a density in a liquid state than in a solid state and it expands when it freezes. With a relatively high conductivity of 149 W·m−1·K−1, silicon conducts heat well. In its crystalline form, pure silicon has a gray color, like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a cubic crystal structure with a lattice spacing of 0.5430710 nm. The outer electron orbital of silicon, like that of carbon, has four valence electrons, the 1s, 2s, 2p and 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six
38.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
39.
Interference (wave propagation)
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In physics, interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves or matter waves. If a crest of a wave meets a crest of wave of the same frequency at the same point. If a crest of one wave meets a trough of another wave, constructive interference occurs when the phase difference between the waves is an even multiple of π, whereas destructive interference occurs when the difference is an odd multiple of π. If the difference between the phases is intermediate between two extremes, then the magnitude of the displacement of the summed waves lies between the minimum and maximum values. Consider, for example, what happens when two identical stones are dropped into a pool of water at different locations. Each stone generates a circular wave propagating outwards from the point where the stone was dropped, when the two waves overlap, the net displacement at a particular point is the sum of the displacements of the individual waves. At some points, these will be in phase, and will produce a maximum displacement, in other places, the waves will be in anti-phase, and there will be no net displacement at these points. Thus, parts of the surface will be stationary—these are seen in the figure above, prime examples of light interference are the famous Double-slit experiment, laser speckle, optical thin layers and films and interferometers. Dark areas in the slit are not available to the photons. Thin films also behave in a quantum manner, the above can be demonstrated in one dimension by deriving the formula for the sum of two waves. Suppose a second wave of the frequency and amplitude but with a different phase is also traveling to the right W2 = A cos where ϕ is the phase difference between the waves in radians. Constructive interference, If the phase difference is a multiple of pi. Interference is essentially a redistribution process. The energy which is lost at the interference is regained at the constructive interference. One wave is travelling horizontally, and the other is travelling downwards at an angle θ to the first wave, assuming that the two waves are in phase at the point B, then the relative phase changes along the x-axis. Constructive interference occurs when the waves are in phase, and destructive interference when they are half a cycle out of phase. Thus, a fringe pattern is produced, where the separation of the maxima is d f = λ sin θ
40.
Monoplacophora
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Monoplacophora, meaning bearing one plate, is a polyphyletic superclass of molluscs with a cap-like shell now living at the bottom of the deep sea. Extant representatives were not recognized as such until 1952, previously they were only from the fossil record. Although the shell of many monoplacophorans is limpet-like in shape, they are not gastropods and are not closely related to gastropods, the inclusion of the gastropod-like Bellerophontoidea within the group is also contentious. One attempt to resolve this confusion was to out the predominantly coiled helcionelloids from the traditional, cap-like tergomyans. Monoplacophorans are univalved, limpet-shaped, and are untorted and they have a pseudometamerism of bilaterally symmetrical repeated organs and muscles. The extant members of the class live only in the ocean at depths below 180 metres. Cambrian forms predominately lived in shallow seas, whereas later Paleozoic forms are commonly found in deeper waters with soft. The repeated organs include from three to six pair of gills located in a line along each side of the foot. The tip or point of their low shells points forward rather than towards the back, the shell ranges from 3mm to 37mm in diameter depending on species. The mouth is located within the animals undeveloped head in front of its large foot and contains a radula. They also have a stomach with a single crystalline style though no gastric shield. The intestines are long and make between four and six loops before reaching the posteriorly-positioned anus, the sexes are separate with any given animal having two pair of either ovaries or testes connected to either the third or fourth pair of kidneys. One genus, Micropilina, has apparently been recorded as brooding young in the oviduct and pallial groove. In 2006 a molecular study on Laevipilina antarctica suggested that extant Monoplacophora and Polyplacophora form a clade with the researched Neopilina closest to the chitons. The two classes in this new clade, with the proposed name Serialia, all show a number of serially repeated gills. However, some dispute this view and do not necessarily see modern Monoplacophora as related to their fossil ancestors. The concept of Serialia is supported by molecular studies. This is plausible, modern monoplacophorans are not closely related to vent-dwelling representatives from the Silurian, cambrian monoplacophoran Knightoconus antarcticus is thought to be an ancestor to the cephalopods
41.
Epitaxy
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Epitaxy refers to the deposition of a crystalline overlayer on a crystalline substrate. The overlayer is called a film or epitaxial layer. The term epitaxy comes from the Greek roots epi, meaning above and it can be translated as arranging upon. For most technological applications, it is desired that the material form a crystalline overlayer that has one well-defined orientation with respect to the substrate crystal structure. Epitaxial films may be grown from gaseous or liquid precursors, because the substrate acts as a seed crystal, the deposited film may lock into one or more crystallographic orientations with respect to the substrate crystal. If the overlayer either forms a random orientation with respect to the substrate or does not form an ordered overlayer, if an epitaxial film is deposited on a substrate of the same composition, the process is called homoepitaxy, otherwise it is called heteroepitaxy. Homoepitaxy is a kind of epitaxy performed with only one material and this technology is used to grow a film which is more pure than the substrate and to fabricate layers having different doping levels. In academic literature, homoepitaxy is often abbreviated to homoepi, heteroepitaxy is a kind of epitaxy performed with materials that are different from each other. In heteroepitaxy, a crystalline film grows on a substrate or film of a different material. This technology is used to grow crystalline films of materials for which crystals cannot otherwise be obtained. Examples include silicon on sapphire, gallium nitride on sapphire, aluminium gallium indium phosphide on gallium arsenide or diamond or iridium. Heterotopotaxy is a similar to heteroepitaxy except that thin film growth is not limited to two-dimensional growth. Pendeo-epitaxy is a process in which the film is growing vertically and laterally at the same time. Epitaxy is used in nanotechnology and in semiconductor fabrication, indeed, epitaxy is the only affordable method of high quality crystal growth for many semiconductor materials. In surface science, epitaxy is used to create and study monolayer and multilayer films of adsorbed organic molecules on single crystalline surfaces, adsorbed molecules form ordered structures on atomically flat terraces of single crystalline surfaces and can directly be observed via scanning tunnelling microscopy. Molecular-beam and liquid-phase epitaxy are also used, mainly for compound semiconductors, solid-phase epitaxy is used primarily for crystal-damage healing. Growth rates above 2 micrometres per minute produce polycrystalline silicon, an additional etching reaction competes with the deposition reaction, SiCl4 + Si ↔ 2SiCl2 Silicon VPE may also use silane, dichlorosilane, and trichlorosilane source gases. VPE is sometimes classified by the chemistry of the gases, such as hydride VPE
42.
Nautiloid
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Nautiloids are a large and diverse group of marine cephalopods belonging to the subclass Nautiloidea that began in the Late Cambrian and are represented today by the living Nautilus and Allonautilus. Nautiloids flourished during the early Paleozoic era, where they constituted the main predatory animals, some 2,500 species of fossil nautiloids are known, but only a handful of species survive to the present day. Nautiloids are among the group of known as cephalopods, an advanced class of mollusks which also includes ammonoids, belemnites and modern coleoids such as octopus. Other mollusks include gastropods, scaphopods and bivalves, traditionally, the most common classification of the cephalopods has been a four-fold division, into the Orthoceratoids, nautiloids, ammonoids, and coleoids. This article is about nautiloids in that sense, sometimes called Nautiloidea sensu lato. Cladistically speaking, nautiloids are a paraphyletic assemblage united by shared primitive features not found in derived cephalopods. In other words, they are a group that is thought to have given rise to Orthoceratoids, ammonoids and coleoids. Both ammonoids and coleoids have traditionally assumed to have descended from bactritids. The ammonoids are extinct cousins of the nautiloids that evolved early in the Devonian period, some workers apply the name Nautiloidea to a more exclusive group, called Nautiloidea sensu stricto. This taxon consists only of those orders that are related to the modern nautilus. The membership assigned varies somewhat from author to author, but usually includes Tarphycerida, Oncocerida, the septa between the chambers of the phragmocone are formed during growth spurts of the animal. At that time the rear of the mantle secretes a new septum adding another chamber while the forward part adds onto the shell. The body of the animal, its viscera, continues to occupy the last chamber of the shell – the living chamber, the septa are perforated by the siphuncle, which runs through each of the internal chambers of the shell. Surrounding the fleshy tube of the siphuncle are structures made of aragonite, septal necks, some of the earlier nautiloids deposited calcium carbonate in the empty chambers or within the siphuncle, a process which may have been connected with controlling buoyancy. The nature of the siphuncle and its position within the shell are important in classifying nautiloids, sutures are visible as a series of narrow wavy lines on the surface of the shell, and they appear where each septum contacts the wall of the outer shell. The sutures of the nautiloids are simple in shape, being either straight or slightly curved and this is different from the zigzag sutures of the goniatites and the highly complex sutures of the ammonites. It is not usually found in less than 100 meters deep. Nautili are free swimming animals that possess a head with two simple eyes and arms
43.
Oklahoma
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Oklahoma is a state located in the South Central United States. Oklahoma is the 20th-most extensive and the 28th-most populous of the 50 United States, the states name is derived from the Choctaw words okla and humma, meaning red people. The name was settled upon statehood, Oklahoma Territory and Indian Territory were merged, on November 16,1907, Oklahoma became the 46th state to enter the union. Its residents are known as Oklahomans, or informally Okies, and its capital, a major producer of natural gas, oil, and agricultural products, Oklahoma relies on an economic base of aviation, energy, telecommunications, and biotechnology. In 2007, it had one of the economies in the United States, ranking among the top states in per capita income growth. Oklahoma City and Tulsa serve as Oklahomas primary economic anchors, with nearly two-thirds of Oklahomans living within their metropolitan statistical areas. With small mountain ranges, prairie, mesas, and eastern forests, most of Oklahoma lies in the Great Plains, Cross Timbers, interior Highlands—a region especially prone to severe weather. The name Oklahoma comes from the Choctaw phrase okla humma, literally meaning red people, equivalent to the English word Indian, okla humma was a phrase in the Choctaw language used to describe Native American people as a whole. Oklahoma later became the de facto name for Oklahoma Territory, and it was approved in 1890. Oklahoma is the 20th-largest state in the United States, covering an area of 69,898 square miles and it is one of six states on the Frontier Strip and lies partly in the Great Plains near the geographical center of the 48 contiguous states. It is bounded on the east by Arkansas and Missouri, on the north by Kansas, on the northwest by Colorado, on the far west by New Mexico, much of its border with Texas lies along the Southern Oklahoma Aulacogen, a failed continental rift. The geologic figure defines the placement of the Red River, the Oklahoma panhandles Western edge is out of alignment with its Texas border. The Oklahoma/New Mexico border is actually 2.1 to 2.2 miles east of the Texas line, the border between Texas and New Mexico was set first as a result of a survey by Spain in 1819. It was then set along the 103rd Meridian, in the 1890s, when Oklahoma was formally surveyed using more accurate surveying equipment and techniques, it was discovered the Texas line was not set along the 103rd Meridian. Surveying techniques were not as accurate in 1819, and the actual 103rd Meridian was approximately 2.2 miles to the east and it was much easier to leave the mistake than for Texas to cede land to New Mexico to correct the surveying error. The placement of the Oklahoma/New Mexico border represents the true 103rd Meridian, cimarron County in Oklahomas panhandle is the only county in the United States that touches four other states, New Mexico, Texas, Colorado and Kansas. Its highest and lowest points follow this trend, with its highest peak, Black Mesa, at 4,973 feet above sea level, situated near its far northwest corner in the Oklahoma Panhandle. The states lowest point is on the Little River near its far southeastern boundary near the town of Idabel, Oklahoma, which dips to 289 feet above sea level
44.
Pennsylvanian (geology)
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The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly 323.2 million years ago to 298.9 million years ago Ma. As with most other units, the rock beds that define the Pennsylvanian are well identified. The Pennsylvanian is named after the U. S. state of Pennsylvania, the division between Pennsylvanian and Mississippian comes from North American stratigraphy. In Europe, the Mississippian and Pennsylvanian are one continuous sequence of lowland continental deposits and are grouped together as the Carboniferous Period. The current internationally used geologic timescale of the ICS gives the Mississippian and Pennsylvanian the rank of subperiods, all modern classes of fungi have been found in rocks of Pennsylvanian age. Amphibians were diverse and common, some were several meters long as adults, the collapse of the rainforest ecology in the mid Pennsylvanian removed many amphibian species that did not survive as well in the cooler, drier conditions. Reptiles, however, prospered due to specific key adaptations, one of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed for the further exploitation of the land by certain tetrapods. These included the earliest sauropsid reptiles, and the earliest known synapsid, small lizard-like animals quickly gave rise to many descendants. Reptiles underwent an evolutionary radiation, in response to the drier climate that followed the rainforest collapse. The Pennsylvanian has been variously subdivided, the Missourian or Monongahela corresponds to the rest of the Kasimovian. The Desmoinesian or Allegheny corresponds to the half of the Moscovian. The Atokan or upper Pottsville corresponds to the half of the Moscovian. The Morrowan corresponds to the Bashkirian, in the European subdivision, the Carboniferous is divided into two epochs, Dinantian and Silesian. The Silesian starts earlier than the Pennsylvanian and is divided in three ages, Namurian Westphalian Stephanian, the Late Carboniferous a Time of Great Coal Swamps, Paleomap project. World map from this time period, the Carboniferous -354 to 290 Million Years Ago, University of California Museum of Paleontology. Information on stratigraphies, localities, tectonics, and life, the Pennsylvanian Epoch of the Carboniferous Period,318 to 299 Mya, Paleos. com US Geological Survey comparison of time scales
45.
Epithelium
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Epithelial is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of blood vessels and organs throughout the body, there are three principal shapes of epithelial cell, squamous, columnar, and cuboidal. All glands are made up of epithelial cells, functions of epithelial cells include secretion, selective absorption, protection, transcellular transport, and sensing. Epithelial layers contain no blood vessels, so they must receive nourishment via diffusion of substances from the connective tissue. Cell junctions are well-employed in epithelial tissues, in general, epithelial tissues are classified by the number of their layers and by the shape and function of the cells. The three principal shapes associated with epithelial cells are—squamous, cuboidal and columnar, squamous epithelium has cells that are wider than their height. Cuboidal epithelium has cells whose height and width are approximately the same, columnar epithelium has cells taller than they are wide. However, when taller simple columnar epithelial cells are viewed in cross section showing several nuclei appearing at different heights and this kind of epithelium is therefore described as pseudostratified columnar epithelium. Transitional epithelium has cells that can change from squamous to cuboidal, Simple epithelium is a single layer of cells with every cell in direct contact with the basement membrane that separates it from the underlying connective tissue. In general, it is found where absorption and filtration occur, the thinness of the epithelial barrier facilitates these processes. In general, simple epithelial tissues are classified by the shape of their cells, the four major classes of simple epithelium are, simple squamous, simple cuboidal, simple columnar, pseudostratified. Simple squamous, which is found lining areas where passive diffusion of gases occur, E. g. skin, walls of capillaries, linings of the pericardial, pleural, and peritoneal cavities, as well as the linings of the alveoli of the lungs. Simple cuboidal, these cells may have secretory, absorptive, or excretory functions, examples include small collecting ducts of kidney, pancreas and salivary gland. Simple columnar, cells can be secretory, absorptive, or excretory, Simple columnar epithelium can be ciliated or non-ciliated, ciliated columnar is found in the reproductive tract. Non-ciliated epithelium can also possess microvilli, pseudostratified columnar epithelium, can be ciliated or non-ciliated. The ciliated type is called respiratory epithelium as it is almost exclusively confined to the larger respiratory airways of the nasal cavity, trachea. Stratified epithelium differs from simple epithelium in that it is multilayered and it is therefore found where body linings have to withstand mechanical or chemical insult such that layers can be abraded and lost without exposing subepithelial layers. Cells flatten as the layers become more apical, though in their most basal layers the cells can be squamous, stratified epithelia can have the following specializations, The basic cell types are squamous, cuboidal, and columnar classed by their shape
. PMID 26631940.
