noun and is never capitalised and is usually italicised. species may only have varieties after it, although the specific name may also be double - barreled. the basic unit of biological classification. generally defined as an aggregation of individuals similar in appearance and structure, mating freely and producing young that themselves mate freely and bear fertile offspring. abbreviated to sp. for one species and spp. for two or more species. a group of organisms with a unique set of characteristics ( like beak shape and behaviour ) that distinguishes them from other organisms. if they reproduce, individuals within the same species can produce offspring that can make more offspring. groups of plant or animal organisms that can interbreed and produce fertile offspring. in the taxonomic hierarchy, ' species ' joins with the higher level ' genus ' to give the binomial term ' genus species '. a taxonomic category ranking which is beneath genus. individuals of the same species are genetically, morphologically, and physiologically differentiated from any other population. the specific name is designated by an uncapitalized latin noun or adjective, and it constitutes the second term in a scientific name. group of related organisms or populations capable of interbreeding. a group of organisms capable of interbreeding freely with each other but not with members of other species ( this is a simplified definition ; species concept is much more complex ). - a taxonomic rank below a genus, consisting of similar individuals capable of exchanging genes ( gene ) or interbreeding. creatures that are extremely similar to one another belong to the same species. a group of organisms which are biologically capable of breeding and producing fertile offspring with each other but not with members of other species the fundamental category of biological classification, ranking below the genus and in some species composed of subspecies or varieties ; of various definitions, the most common is the " biological species concept " " species are actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. " numbers of domains present in a variety of selected taxa ( animal, archaea, bacteria, fungi, plants and protozoa ) are shown in annotation pages. all plants and animals are divided into groups with similar characteristics. the basic building block for this division is the species. organisms of the same species can interbreed. species with common characteristics are grouped into a genus ( plural genera ). genera with similar characteristics are grouped into a family. each species is given a scientific name of two words, the genus and species. these names are latin so they can be recognized worldwide. common names


characteristics are grouped into a genus ( plural genera ). genera with similar characteristics are grouped into a family. each species is given a scientific name of two words, the genus and species. these names are latin so they can be recognized worldwide. common names, on the other hand, vary from nation to nation, and even within a nation. examples : species : mallard scientific name : anus platyrhynchos species : northern pintail scientific name : anus acuta both the mallard and pintail are in the same genus anus and are also grouped into the family of ducks, geese, and swans. individual plants bearing certain characters in common. the fundamental and unique category in the classification of all living things, for example, the song sparrow, the bluebird, the monarch butterfly, the azure butterfly, the lion, the tiger, etc. a taxonomic level above genotype. all creatures in a species are similar on a functional and structural level, but not necessarily in all instruction positions on their genome. species can be used to study clouds around an archetype ( quasispecies ) in genome space. a biological classification that combines organisms sharing common characteristics and are able to mate and produce fertile offspring. a subdivision of a genus — second word in a plant ' s botanical name such as rosa moschata — musk rose a population of individuals that are more or less alike, and that breed and produce fertile offspring under natural conditions. one or more animals which closely resemble one another. a group of them together forms a genus. the category of taxonomic classification, ranking below a genus consisting of related organisms capable of interbreeding. organisms that are capable of interbreeding and is designated by a binomial term in latin. the species designation of timber wolf or gray wolf is canis lupus. a group of organisms which resemble each other to a greater degree than members of other groups and which form a reproductively isolated group that will not normally breed with member of another group. similar species are grouped into genera, genera are grouped into families, families into orders, orders into classes, classes into phyla ( for animals ) and divisions ( for plants ), these are grouped into kingdoms. a group of individuals that share certain physical characteristics and are capable of producing fertile offspring. a group of living organisms that can interbreed to produce viable offspring. a category of biological classification ; a class of individuals having common attributes and designated by a common name. " species " is always properly used with the " s " when referring


. a group of living organisms that can interbreed to produce viable offspring. a category of biological classification ; a class of individuals having common attributes and designated by a common name. " species " is always properly used with the " s " when referring to trees or other biological classifications. a biological species is a group of individuals that can actually or theoretically interbreed successfully with one another but not with members of other groups or species. a class of individual organisms having some common characteristics or qualities ; usually similar or alike in appearance ; always able to breed among themselves ; by some defintions unable to breed with members of other species. the following papers by kenneth cumming provide more information : on the changing definition of the term " species " | patterns of speciation | reticulate evolution a group of organisms that is formally recognized as distinct from other groups ; also a taxon of the rank of species, i. e., a category below genus. species is a group of living things that can mate to produce fertile offspring. groups of animals with shared characteristics that can reproduce and produce fertile offspring red - headed and red - bellied woodpeckers are two different species of woodpeckers. one or more populations of interbreeding or potentially interbreeding organisms that are reproductively isolated in nature from all other organisms. populations of individuals capable of interbreeding and producing viable, fertile offspring. the least inclusive taxonomic category commonly used. picture one kind of organism. of sexually reproducing organisms, one or more natural populations in which individuals are interbreeding and are reproductively isolated from other such groups. a population or series of populations whose individuals have the potential to freely breed with one another and that is discontinuous in variation from other populations or series of populations ; a fundamental category of taxonomic classification that ranks below genus. a group containing all the individulas of a particular kind of plant. the basic lower unit of classification. biological species refers to individuals capable of interbreeding. a " kind " of bird, usually referring to a group of interbreeding natural populations which are reproductively isolated from other such groups ; a species represents a unique evolutionary lineage a distinction for a specific type of animals. for example, geese are a species and ducks are a species. there may be many breeds of each species. typically species cannot interbreed successfully, for example a duck and a goose can not produce offspring together. if species can cross the offspring are typically sterile like a mule ( horse x donkey ). the


. there may be many breeds of each species. typically species cannot interbreed successfully, for example a duck and a goose can not produce offspring together. if species can cross the offspring are typically sterile like a mule ( horse x donkey ). the a€œglobal familya€ of a organism, that can breed or reproduce with one another ( a€œglobal familya€ refers to all of the human, rabbits, cats, dogs ; etc ; they all are the same, no matter the color of fur or eyes ; etc. ) ( both singular and plural ) a natural population or group of populations that are reproductively isolated and transmit specific characteristics from parent to offspring. a group of individuals that has similar characteristics and breeds only with another member of the same group group of organisms with common or similar characteristics and capable of inter breeding. a reproductively isolated group of interbreeding organisms. the main category of taxonomic classification into which living organisms are subdivided, comprising a group of similar individuals having a number of correlated characteristics. a group of closely related organisms capable of mating and producing fertile offspring. a group of natural relations that can interbreed. difficult to define rigorously in two or three lines. defined very simply in a phylogenetic context, species are the smallest lineages that are mutually exclusive of other lineages. the internal branches of a phylogeny may be viewed as ancestral species. note, however, that the unit lineages of a gene phylogeny are not species ( see also terminal ). a singular or plural term for a population or series of populations of organisms that are capable of interbreeding freely with each other but not with members of other species. includes a number of cases : endemic species : a species originating in, or belonging to, a particular region. both " endemic " and " indigenous " are preferred over " native. " exotic species : a species introduced accidentally or intentionally to a region beyond its natural range. " exotic " is preferred over " alien, " " foreign " and " non - native. ' subspecies : a subdivision of a species. a population or series of populations occupying a discrete range and differing genetically from other subspecies of the same species. taxa ) richness : a biological index of river health, species ( taxa ) richness is the number of species or taxa present in a biological sample. a group of similar animals that are isolated reproductively and produce viable offspring. they may include on or more subspecies. all of the organisms that are capable of interbreeding with


richness is the number of species or taxa present in a biological sample. a group of similar animals that are isolated reproductively and produce viable offspring. they may include on or more subspecies. all of the organisms that are capable of interbreeding with each other under natural conditions to produce fertile offsprings ( bisexual organisms ) or all of the morphologically and genetically similar descendants of some inferred ancestral individual ( asexual organisms ). the species is the primary or fundamental concept in the understanding of the forms of life. it is the basic unit in classification. species are combined into genera and variations or subordinate forms of these may be distinguished as subspecies, variety and form in descending order of the botanical hierarchy. a basic taxonomic category. members of a species of plants or animals can breed with another member and produce fertile ( capable of reproducing ) offspring. in this way, a species maintains its ‘ separateness ' from other species ; for example, yellowfin tuna and bigeye tuna are two distinct tuna species, whereas the general term ‘ tuna ' includes all tuna species. a type of animal or plant. the species designations of animals under study. the taxanomic category subordinate to a genus. a group of like individuals. the second part of a scientific name identifies a particular species. ( see genus ) species : organisms with similar phenetic and genetic characteristics that can mate and produce viable offspring that can also mate and produce viable offspring. biological _ a small group of organisms formally recognized by the scientific community as distinct from other groups. legal _ refers to joint policy of the usfws and nmfs that considers a species as defined by the esa to include biological species, subspecies, and dpss. ( spee´ shees ) [ l. : kind ] • the basic lower unit of classification, consisting of a population or series of populations of closely related and similar organisms. the more narrowly defined " biological species " consists of individuals capable of interbreeding freely with each other but not with members of other species. taxonomic groups, usually defined by inability to interbreed and produce viable offspring. species are reproductively isolated from each other. genes in one species cannot combine with genes from another species and produce a successfully reproducing vehicle ( individual ). a group of individuals, usually identifiable by a set of distinctive features, with a unique evolutionary history. classically, the members of a species can interbreed only with each other to produce fertile offspring. a class or specific type of organism ; a group of individuals related


, usually identifiable by a set of distinctive features, with a unique evolutionary history. classically, the members of a species can interbreed only with each other to produce fertile offspring. a class or specific type of organism ; a group of individuals related by descent, and able to breed among themselves but not with other animals ( sp ' sh z ) the category of organization for taxonomy below genus, representing animals capable of interbreeding with each other. the scientific name for a species is generally written with the genus in binomial form. example : homo sapiens. the basic unit of linnaean classification ; a taxonomic subdivision of genus represented by plants that can freely interbreed but rarely with other species. in the scientific name sambucus nigra, the genus is sambucus and the species epithet is nigra ; together sambucus nigra constitutes the species a group of animals or plants having common characteristics and able to breed together to produce fertile ( capable of reproducing ) offspring, so that they maintain their ' from other groups. for example, yellowfin tuna and bigeye tuna are two distinct tuna species, whereas general terms like ' and ' each represent groups of species. a taxon comprising one or more populations of individuals capable of interbreeding to produce fertile offspring. seeing, appearance, shape, kind or quality the smallest classification group of organisms. organisms of the same species mate and produce healthy young subdivision of biological classification composed of related organisms that share common characteristics and can interbreed. group within a genus, the members of which share similar characteristics and can breed successfully together. the basic unit of biological classification. this definition is open to very wide interpretation and what one person regards as just another species, may be seen by someone else, to be a totally separate genus or only a form. a group of plants or animals that have certain common features which set them apart from others. the species, an adjective, often refers to a place, the plant ' s characteristics / appearance, or the name of the person credited with discovering it. species is abbreviated sp. or spp. different definitions are available dependent upon the characters being used to define a species. see also biological species concept, morphospecies concept and phylogenetic species concept.... more a group of animals that have the same characteristics a group of organisms capable of interbreeding to produce fertile offspring a group of plants, animals, or microorganisms that have a high degree of similarity and generally can interbreed only among themselves


a group of animals that have the same characteristics a group of organisms capable of interbreeding to produce fertile offspring a group of plants, animals, or microorganisms that have a high degree of similarity and generally can interbreed only among themselves. a group of similar organisms whose members can breed with one another to produce fertile offspring. the second or specific part of the scientific name of a plant organisms in the same genus that have similar characteristics. the subdivision of genus ; the second name in latin nomenclature i. e. acer palmatum. a group of organisms that can interbreed with each other and produce fertile offspring. it is the fundamental unit of biological evolution. a population or series of populations of closely related and similar organisms. the individuals within a species are able to interbreed freely with each other, producing healthy, fertile offspring. members of a species are not able to interbreed successfully with members of other species. ( 1 ) a group of organisms that have a unique set of characteristics ( like body shape and behavior ) that distinguishes them from other organisms. if they reproduce, individuals within the same species can produce fertile offspring. ( 2 ) the basic unit of biological classification. scientists refer to species using both their genus and species name. the house cat, for example, is called felis catus. the taxonomic division of freely interbreeding population of wild or naturally occurring individuals below genus. living things of the same kind that are potentially capable of breeding and producing fertile offspring. theoretically, plants or animals of different species cannot interbreed. however, occasionally this does not hold true. database entry containing a sequence and associated information. not necessarily consistent with a taxonomic species any subspecies of fish, wildlife, or plants, and any distinct population segment of any species or vertebrate fish or wildlife that interbreeds when mature. a group of animals that under normal conditions can have offspring together. in the same or like form or kind. there are many species of finches available today, and many look a lot a like. always know what species of finch you have before attempting to locate a mate. society finches and zebra finches are examples of two different species. pl. a category of classification, ranking below a genus, consisting of closely related organisms capable of interbreeding. an organism belonging to a species is represented by an uncapitalized latin name and a capitalized genus name, as in hyacinthoides non - scripta, the bluebell. all the populations of organisms that are capable


the bsc has interesting implications for the nature of the last universal common ancestor of all life, especially if horizontal genetic transfer was extensive then ( as it is today between the different unicellular " species " of bacteria, archaea, and eukaryotes ). a subdivision of a genus, almost identifcal organisms, a clone a group of interbreeding populations that are more or less reproductively isolated from all other kinds of organisms. division of plants or herbs which contain individuals capable of reproducing with each other. a classification of related organisms that can freely interbreed. a group of similar organisms within the same genus which are usually capable of interbreeding, and are distinctly different from other members of the genus. a group of organisms which normally can interbreed organisms that successfully reproduce among themselves and cannot reproduce successfully with other organisms. a group of similar fish that can freely interbreed. a group of animals or plants that are the same and breed together, eg. the new zealand robin. a single kind of plant or animal ; about 34, 000 species of spiders known so far worldwide in a little over 100 families ; presumably many more species are undiscovered the smallest unit of classification. individuals in a species are assumed to have emanated from a single original genetic source and are sexually compatible with each other. a group of generally related tree species for which similar management practices have been developed. depending on how they were listed under the esa, species is defined as species, subspecies, distinct population segment ( dps ), or evolutionarily significant unit ( esu ). a set of creatures which, in their natural setting, breed among themselves. different types of plants e. g. cocksfoot and ryegrass are different species species generally grouped for marketing convenience and identified with a single commercial name. ( see astm d 1165, standard nomenclature of domestic hardwoods and softwoods, for commercial practice in the united states and canada. ) a group of organisms that are similar in structure and can mate and produce fertile offspring species is a group of living things that breed with each other in nature and produce offspring that can also breed. coyotes can breed together, and the pups can breed when they grow up, so all coyotes are one species. bobcats can ' t breed with coyotes, so they ' re a different species. in nature, living things in the same species usually look pretty much alike. a taxon of the rank of species ; in the hierarchy of biological classification the category below


. bobcats can ' t breed with coyotes, so they ' re a different species. in nature, living things in the same species usually look pretty much alike. a taxon of the rank of species ; in the hierarchy of biological classification the category below genus ; the basic unit of biological classification ; the lowest principal category of zoological classification. organism classification that includes individuals that share the same heredity, are similar in morphology and behaviour, and can produce similar offspring. a subdivion of a genus in the classification of plants. species of plants are distinguished by the characteristics of fruits, flowers, leaves, bark and wood. the basic unit of classification in biology. examples are the bald eagle, the polar bear, the monarch butterfly, and the tawny mole cricket. the word is both singular ( a species ) and plural ( two species ). species are grouped into genera, and genera are grouped into family. the words kind, sort, type, strain, and variety are not part of this classification even though newspaper reporters often use them as if they were. a group of related organisms with common characteristics that are capable of interbreeding. loblolly and virginia pine are examples of two different tree species. a group of biological organisms that interbreed to produce fertile offspring or possess common characteristics derived from a common gene pool. groups of actually or potentially interbreeding natural populations which are reporductively isolated from other such groups the unit of classification for a plant having particular characteristics. in the botanical name of the plant, the species is identified by the second word of the name : for example acer palmatum. one or more populations of freely interbreeding organisms which are reproductively isolated ( for reasons other than geography ) from other closely related populations. a more modern definition might be a chronologically continuous genome which is isolated from other genomes by non - geographical factors. see also subspecies and species complex. the basic unit of linnaean classification ; a taxonomic subdivision of genus represented by plants that can freely interbreed but rarely with other species. in the latin name ulmus americana, the genus is ulmus and the species epithet is americana ; together ulmus americana constitutes the species taxonomic group whose members can interbreed group of animals or plants with common characteristics a taxonomic category subordinate to a genus ( or subgenus ) and superior to a subspecies or variety, composed of individuals possessing common characters distinguishing them from other categories of individuals of the same taxonomic level. in taxonomic nomenclature, species are designated by the genus name followed by a latin or


to a genus ( or subgenus ) and superior to a subspecies or variety, composed of individuals possessing common characters distinguishing them from other categories of individuals of the same taxonomic level. in taxonomic nomenclature, species are designated by the genus name followed by a latin or latinised adjective or noun. in the same or like form or kind. for the purposes of the cwcp, we refer to scientific animal groupings of genus and then a subgroup called " species. " a group of living things that can interact to produce offspring like themselves. tigers do not have lion cubs, and an eagle and owl cannot interact to produce offspring like themselves. is a group of similar organisms with the ability to interbreed and produce fertile offspring. distinct populations of plants or animals that can and do interbreed and produce fertile offspring a species is a fundamental category of taxonomic classification ranking after genus and consisting of organisms capable of interbreeding. a category of closely related and similar organisms. more narrowly defined, a population of individuals capable of interbreeding but not of breeding with members of another species. a group of individuals that interbreed with each other but not with other such groups. there are however many definitions of species. a natural group of plants composed of similar individuals that can produce similar offspring. the basic unit of living things, consisting of a group of individuals which all look more or less alike and which can all breed with each other to produce another generation of similar creatures. many species are subdivided into sub - species. these normally inhabit different areas and they may differ in appearance, but they can still all interbreed. a group of living things that share common biological characteristics plant species are usually variable in the wild and may be split into three botanically recognized but occasionally overlapping subdivisions ; the subspecies ( subsp. ), the variety ( var. ) and the form ( forma, f. ). biological classification comprising related organisms that share common characteristics and are capable of interbreeding. type of plant genetically different from others. taxonomic division that generally refers to a group of animals which are similar in structure and descent and are able to breed among themselves. a population or group of potentially interbreeding populations that is reproductively isolated from other such populations or groups. a separate and integral reproductive community. ( eldrege ) a group of plants with very similar characteristics ; and, a plant originally found in the wild and not the result of hybridisation or plant breeding by horticulturalists a group of related organisms having common characteristics and capable of interbreeding. loblolly and


group of plants with very similar characteristics ; and, a plant originally found in the wild and not the result of hybridisation or plant breeding by horticulturalists a group of related organisms having common characteristics and capable of interbreeding. loblolly and virginia pine are common tree species that can interbreed. a group of grasses with similar form and / or reproductive mechanisms ; the basic unit of biological classification. a distinct kind of plant. a fundamental biological classification, comprising a subdivision of a genus and consisting of a number of plants or animals all of which have a high degree of similarity, can generally interbreed only among themselves, and show persistent differences from members of allied species. an established classification into which similar individuals in the plant or animal kingdom are placed. a species is described as a morphologically distinctive and genetically isolated natural population. a particular type of plant, animal, or other organism. species differ from one another in at least one characteristic, and generally do not interbreed. in biology, species is a category that ' s part of the scientific system for grouping together related plants, animals and other organisms ( kingdom, phylum, class, order, family, genus, species ). used to refer to individual gems that have distinct characteristics which may be defined and verified. a group of animals or plants that share similiar characteristics such as can reproduce. individuals that are grouped together by having common characteristics and that are capable of interbreeding a group of organisms different fro... basic classification unit of plants comprised of individuals that are recognized as distinct from other species, and which can freely interbreed among themselves. a set of individuals sharing distinctive characteristics likely to produce common, fertile descendents. the notion of species is used in its broadest sense here and refers not only to species proper but also to subspecies, isolated geographic populations, strains and varieties, whether plant or animal. a genetically distinctive group of natural populations that share a common gene pool that are reproductively isolated from all other such groups. a group of closely related individuals that have the potential to reproduce with each other ; a unit of classification. a " species " is generally accepted as a group of individuals that look the same and can breed with each other but not usually with individuals of another species. " species " is the the lowest level of plant classification. this is part of the science called " taxonomy ". scientists refer to living things by a combined " genus " and " species " name, using latin terms. for example, people are called " homo sap


is the the lowest level of plant classification. this is part of the science called " taxonomy ". scientists refer to living things by a combined " genus " and " species " name, using latin terms. for example, people are called " homo sapiens ". a white pine would be called " pinus strobus ". a scientist anywhere in the world can look up information about any living organism by knowing the latin or scientific name. the genus name is always capitalized. the species name is usually not capitalized. incidentally, the word " specie " is incorrect. " species " is the correct singular and plural form of the word. [ to return to previous page, click your browser ' s back button then scroll through the page to your last location in biology a species generally taken to be either the lowest level of taxonomic classification or a group of interbreeding individuals that are reproductively isolated from other organisms. a species in biology is not a " kind " in plato ' s sense of the word. this is the scientific, taxonomic name of a living thing. in plant classification, a group of plants with common characteristics that can cross - breed with one another. a group of organisms that mate freely in nature and can produce viable offspring populations whose individuals freely breed with one another and vary only slightly from one another. the basic category of biological classification consisting of similar organisms that are capable of mating and reproduction is one of the most specific of several levels of classification for a plant. they are ranked in levels from largest to smallest groupings first by kingdom, then by phylum, class, order, family, genus, and species. the name of a category that is part of the scientific classification of all organisms. the category species is located in the classification system after kingdom, phylum, class, order, family and genus. humans, for example, belong to the species sapiens and are identified by the scientific name homo ( genus ) sapiens ( species ). a group of closely related organisms that are capable of interbreeding and are reproductively isolated from other groups of organisms ( in other words, they can breed among themselves and not with others ) ; the basic unit of biological classification. major subdivision of a genus of plants. a biological classification composed of related plant individuals. the type of wood, such as spruce or fir. each species has different characteristics as well as strengths and weaknesses. a group of organisms that can interbreed under natural conditions to produce fertile offspring a group of organisms consisting of similar individuals capable of


. the type of wood, such as spruce or fir. each species has different characteristics as well as strengths and weaknesses. a group of organisms that can interbreed under natural conditions to produce fertile offspring a group of organisms consisting of similar individuals capable of exchanging genes or interbreeding. see also " classification. " ( n ) a group of animals or plants within a genus differing only in minor details form the others, and able to breed with each other but not with other groups an internationally established botanical classification of trees. a genetically distinct group, consisting of related individuals that resemble each other in appearance and behavior, and can breed among themselves but not, with some exceptions, with other species 1. in biological classifications, it is the lowest and most basic unit of the linnaean taxonomic hierarchy ( although it is also divisible into subspecies ), and one of the two required titles of a binomial name. in nature, a species is a group of organisms that breed only amongst themselves and produce offspring that are also capable of reproducing. 2. in chemistry, a group of constituents or molecules, that share major chemical similarities. for example, hg0 and hg + 2, or co and co2. abbreviated to spp. ( singular = sp. ). a group of individuals which interbreed with each other, but generally not with other species. a fundamental category of taxonomic classification, ranking below a genus. a group of related organisms which are capable of interbreeding. in classification, a species is a group of closely related organisms that can reproduce. a group of similar species forms a genus. in the scientific name of an organism, the second name is its species ( for example, people are homo sapiens - our species is sapiens ). the biological species concept is the most widely accepted method for categorizing living species, especially for vertebrates. it defines a species as members of populations that actually or potentially interbreed in nature, not according to similarity of appearance. although appearance is helpful in identifying species, it does not define a biological species. a single, distinct class of living creature with features that distinguish it from others. a group of plants or animals that are of the same type or origin a group of interbreeding individuals, not interbreeding with another such group, being a taxonomic unit including two names in binomial nomenclature, the generic name and specific epithet, similar and related species being grouped into a genus. from the latin, species, " particular kind. "


not interbreeding with another such group, being a taxonomic unit including two names in binomial nomenclature, the generic name and specific epithet, similar and related species being grouped into a genus. from the latin, species, " particular kind. " related strains of a plant that occur naturally. a group of organisms that are biologically capable of exchanging genes with each other but are incapable of exchanging genes with other such groups. n : the boundaries of this taxonomic level ( the most precise in the hierarchical system of binomial nomenclature ) are hotly debated among scientists and there is little real consensus about where to draw the lines between species, subspecies, morphs, races, variants, etc. in general, a species is a group of organisms that resemble one another in appearance, general behavior, ecological niche, chemical makeup and processes, and genetic structure. organisms that reproduce sexually are classified as members of the same species only if they can actually or potentially interbreed with one another and produce fertile offspring. it should be noted that some ( though quite few ) taxonomists believe the species level of classification is frequently invalid and these scientists only recognize classifications down to the level of genus ( again, these taxonomists represent a very small minority view ). fundamental unit of biological taxonomy. generally spoken, two individuals belong to the same species if they can produce fertile offspring the basic category of biological classification, displaying a high degree of mutual similarity determined by a consensus of informed opinion ; a subcategory of genus. ( 16 ) group of closely related individuals, resembling one another in certain inherited characteristics. in biology, a species is one of the basic units of biodiversity. species is the smallest group of classification. a species generally consists of all the individual organisms of a natural population which are able to interbreed, generally sharing similar appearance, characteristics and genetics due to having relatively recent common ancestors. species ( used as a noun ) in metaphysics are defined by their genus ( genos ) and differentia ( diaphora ). the species film series is the group of films that take place in the species universe.


1. to disable with alarm or apprehensions ; to depress the spirits or courage of ; to deprive or firmness and energy through fear ; to daunt ; to appall ; to terrify. " be not afraid, neither be thou dismayed. " ( josh. i. 9 ) " what words be these? what fears do you dismay? " ( fairfax ) 2. to render lifeless ; to subdue ; to disquiet. " do not dismay yourself for this. " ( spenser ) synonyms : to terrify, fright, affright, frighten, appall, daunt, dishearthen, dispirit, discourage, deject, depress. to dismay, daunt, appall. dismay denotes a state of deep and gloomy apprehension. to daunt supposes something more sudden and startling. to appall is the strongest term, implying a sense of terror which overwhelms the faculties. " so flies a herd of beeves, that hear, dismayed, the lions roaring through the midnight shade. " ( pope ) " jove got such heroes as my sire, whose soul no fear could daunt, nor earth nor hell control. " ( pope ) " now the last ruin the whole host appalls ; now greece has trembled in her wooden walls. " ( pope ) origin : oe. desmaien, dismaien, of. esmaier ; pref. es - ( l. ex ) + ohg. magan to be strong or able ; akin to e. may. in english the pref. es - was changed to dis - ( l. dis - ). see may. ( 01 mar 1998 ) | bookmark with : | | word visualiser | | go and visit our forums |


common case and bracelet materials frequently asked questions is my bracelet scratch - proof or scratch - resistant? how do magnetic fields affect my watch? how do i get my watch appraised for insurance purposes? what is a " swiss " watch? do i need to wind my automatic ( self - winding ) watch? a mechanical movement that is wound through the motion of the wearer ' s arm during normal daily arm movement ; sufficient activity is required to build up a power reserve. also known as a " self - winding " watch. the part of the watch that secures the watch to the wrist. the two common types of bands are strap ( i. e. leather ) and bracelet. the rim which secures the crystal in place on the watch case and may be set with diamonds or other stones. bezels may also be rings which are graduated to track elapsed time, as in a diver ' s watch. some bezels are rotating and can be turned to perform different types of timekeeping. the ornament, often a dome - shaped or faceted precious stone such as a ruby or emerald used to accent the winding crown. also, the raised dome - shaped markers used to indicate the hours on some watch dials. the windows or subdials on the dial of a watch that display the day, date, month and / or year. also known as graphite fiber, carbon fiber consists of extremely thin fibers, predominantly of carbon atoms, bonded together in microscopic crystals. the vertical alignment of the crystals gives carbon fiber its unique texture, and makes it incredibly strong. often combined with a polymer, carbon fiber watch cases and dials are exceptionally tough. the metal housing that contains the internal workings of the watch ( the movement, dial and hands ). high - tech ceramic, an extremely hard material containing titanium carbide, is valued by watchmakers for its lightweight and exceptional scratch - resistance. high - polished ceramic timepieces are smooth - to - the - touch, ultra lightweight and durable. a watch that includes a stop watch feature : a timer that can be started and stopped to time an event. a timepiece that has met very high standards of accuracy, tested and certified by the c. o. s. c. ( an official watch institute in switzerland ). each chronometer comes with an individual certificate of precision. the tiny knob on the winding stem used to move the hands to set the time on the watch, and to wind a watch with a manual movement. the transparent " glass " which


). each chronometer comes with an individual certificate of precision. the tiny knob on the winding stem used to move the hands to set the time on the watch, and to wind a watch with a manual movement. the transparent " glass " which protects the dial of the watch. there are three common types of crystals : acrylic, mineral and sapphire. a sapphire crystal is the most expensive, scratch - resistant and durable type of crystal. a buckle or clasp with a two or three piece inner element that folds onto itself securing the two ends of a strap or bracelet. this type fastener allows the wearer to slip on or remove the watch from their wrist with ease. also known as the watch " face. " it gives a watch its beauty and character, based on the material from which it is crafted and the style of the numerals, markers, texture and other details that define it. a sport watch built to withstand underwater pressure, often worn by scuba divers. among other features, these watches are typically equipped with a screw - down crown that creates a strong seal to prevent water from penetrating the case. must be water resistant to 20 atm ( the pressure equivalent of being 200m or 660 feet under water ) to be classified as a diver ’ s watch. a rotating bezel which can be used to indicate the hour in a second time zone, distinct from the time indicated by the hands on the dial. a rubber or plastic ring that is used to seal the watch case against dust, moisture and water. typically used on in conjunction with the crown, crystal and metal case. a type of design in which thin lines are engraved in a crossed or interlaced pattern to create a decorative textural effect on the dial of the watch. another name for a manual wind mechanical movement. see " mechanical movement ". a small synthetic sapphire or ruby placed at various points in a mechanical or quartz watch movement which have been drilled, chamfered and polished to serve as bearings for watch gears reducing friction of mechanical parts to a minimum. growing in popularity, k1 mineral is a type of watch crystal that is more shatter - resistant than sapphire crystal, and more scratch - resistant than regular mineral crystal. extensions from either end of the case that hold the pin used to fasten the strap or bracelet to the case. watch hands coated with a substance, such as tritium and superluminova, that makes them glow in the dark. they are especially common in sports models for better visibility underwater. a type of mechanical movement, also


or bracelet to the case. watch hands coated with a substance, such as tritium and superluminova, that makes them glow in the dark. they are especially common in sports models for better visibility underwater. a type of mechanical movement, also known as a " hand - winding " movement, in which the mainspring of the movement must be wound by hand daily, using the crown. see " mechanical movement ". a watch movement comprised of a series of turning cog wheels and jewels, expertly calibrated by hand. a mechanical movement may be : automatic, also known as " self - winding " ( wound by the motion of the arm during daily wear ) or " manual ", also known as " hand - winding " ( requiring regular / daily winding of the crown by hand ). a function on a watch that can announce the time in hours, quarter - hours, and minutes by means of a push button. an audible chime sounds when the push piece or button is depressed. a window, often half - moon shaped, in a watch dial that shows the current phase of the moon. this distinctive feature is usually seen in combination with other calendar - related features. the iridescent lining of the interior shell of a freshwater mollusk that can be thinly sliced and used to create a watch dial. while mother - of - pearl generally has a milky white luster, it is also available in other natural pearlescent colors such as gray, blue and pink. to ensure your watch ’ s water resistancy, we recommend inspection and maintenance of the case seals and gaskets every 12 - 24 months. this will help keep the watch movement safe from air, dust, and moisture, which over time can get into the watch and affect its ability to function properly. all watch movements will require periodic maintenance. we recommended that a mechanical movement be inspected for possible servicing every 3 to 5 years and quartz movements at each battery change. a calendar feature on a watch that automatically adjusts to account for the different number of days in each month, and for leap years. an aperture or subdial on a mechanical watch, often wedge - shaped, that indicates how much longer the watch will operate before requiring winding. a button that is pressed to operate ( start / stop ) a mechanism. pushers are usually found on chronographs and timepieces with minute strikers and alarms. the letters are an abbreviation for physical vapor deposit, a high - tech vacuum - coating procedure that produces wear - resistant finish. a watch movement


. pushers are usually found on chronographs and timepieces with minute strikers and alarms. the letters are an abbreviation for physical vapor deposit, a high - tech vacuum - coating procedure that produces wear - resistant finish. a watch movement where time is " tuned " to, and measured by, the extremely rapid and consistent vibrations of a quartz crystal. the quartz crystal is powered by a battery. also known as an electronic quartz movement. a device that chimes the time when a button is pushed, or a slide is pulled. see " minute repeater ". a crown that screws down into the case tube making the watch more water resistant. provides the best underwater shock protection ( against rocks, accidental knocks, scrapes, etc. ) to prevent water leakage. to set the time on a watch with a screw - down crown, the crown must first be unscrewed before it can be pulled out to any hand - setting position. a movement that converts mechanical energy generated by the force of gravity and natural movements of the wearer ' s wrist into electrical energy which is stored in an accumulator which powers a quartz movement. another name for an automatic mechanical movement. see " automatic " and " mechanical " movements. to be qualified as " shock resistant ", a watch must have demonstrated the ability to withstand an impact equal to that of being dropped onto a wood floor from a height of three feet during testing. the dial of the watch is " cut out " to allow the inner workings of a watch ' s movement to be seen through the transparent crystal and dial on the front side, or a transparent crystal case back. in a watch with a “ skeletonized ” movement, the rotor, wheels and other moving parts are also painstakingly cut away, creating an elegant transparency all the way through the case. abbreviation stands for " stock keeping unit " ; an identifying number used when taking inventory. same as the watch " model number ". a seconds hand that is mounted in the center of the watch dial ( vs. one positioned in a sub - dial ). a " true " sweep seconds hand is found only on mechanical watches, and has a motion that is undetectable to the human eye. on a quartz watch, the advance of the seconds hand is discernible in tiny step - by - step jumps. a feature found on chronographs consisting of a calibrated scale, usually found around the perimeter of the dial, that can be used to measure the wearer ' s speed of


comes from adding copper color cannot " wear off " ; the gold is an integral part of the material a base metal with a thin layer of gold ( usually 18k to 23k ) applied in a process called electroplating thickness of the gold - plating can range from 2 - 10 microns in depth gives appearance of solid gold at lower price level not solid gold, so plated finish can wear off over time one of the most rare precious metals, it has a rich, white luster. platinum used in jewelry and watches is at least 85 - 95 % pure platinum, with only 5 - 15 % of a base metal one of the strongest and heaviest metals hypoallergenic and tarnish - resistant white, very durable metal stronger and lighter than stainless steel, but softer non - corrosive ; resistant to salt, perspiration, and high temperatures hypoallergenic ; does not contain nickel a metal that is a combination of tungsten and carbon compressed under extreme pressure extremely durable and highly scratch - resistant heavier than stainless steel will not tarnish or rust frequently asked questions a watch may be made of a scratch - resistant material, however no material is truly scratch - proof. therefore, please follow these steps when handling your watch : wrap your watch in a soft cloth prior to placing it on any hard surface. when possible, store your watch in the original box / case. avoid dropping the watch in a drawer or jewelry box, to prevent it from being scratched by coming in contact with other pieces of jewelry. avoid wearing your watch during high - risk activities, for example, when lifting or moving heavy objects or engaging in sports activities. avoid wearing your watch on the same wrist as another piece of jewelry. they could rub against and scratch each other. the exposure of your watch to strong magnetic fields will affect its time keeping and may cause it to stop. a quartz watch will resume working with original accuracy when it is removed from the magnetic field. a mechanical watch may require demagnetization. mgi can provide appraisals for watch brands that we manufacture. please download, complete and return the repair and service request form with your watch to the address below. on the form, indicate, " please appraise my watch for insurance purposes ". after we receive your watch, we will mail you an estimate indicating the cost of the appraisal. 109 state street moonachie, nj 07074 movements made in switzerland, where watchmaking began centuries ago, enjoy a reputation throughout the world today for


the following html text is provided to enhance online readability. many aspects of typography translate only awkwardly to html. please use the page image as the authoritative form to ensure accuracy. rizes some of the more robust findings by listing some phyla from which rrnas were studied to the right and the inferred branching patterns of the rrnas on the left, with the implied appearance of some design elements in metazoan body plans indicated. a few of the design elements require comment. for present purposes, the unqualified terms " hemocoel " and " coelom " refer to fluid - filled spaces usually used as hydrostatic skeletons — the former being developed from the topological position of the blastocoel, the latter being developed within mesoderm. spaces devoted only to serving organs ( commonly as ducts or as buffering against solid tissues ) are termed " organ hemocoels " or ' ' organ coeloms. " " seriation " refers to longitudinal repetition of organs, muscles, or other features but not necessarily in a correlated fashion, while " segmentation " refers to serial repetition with correlation among organ systems. many of the metazoan relationships indicated in figure 4 are quite conventional, such as the sequence of choanoflagellates / poriferans / cnidarians / platyhelminths, the sister - group relationship of platyhelminths with higher metazoans, and the sister - group relationship of protostomes with deuterostomes. less conventional, though hardly shocking, is the sister - group relationship of the arthropods with the unresolved cluster of protostomes, which includes mollusks and annelids. this is a particularly important branching, because it suggests that the last common ancestor of the protostomes was hemocoelic and that the coelom ( s ) of the deuterostomes arose independently of the coelom ( s ) of the protostomes. this branching also suggests that arthropod and annelid segmentation arose independently. the next deeper branching, between protostomes and deuterostomes, suggests that while their last common ancestor was not coelomic and need not have been hemocoelic, it did have a blood - vascular system. other interpretations are possible but they are less parsimonious. late precambrian body plans. the list of phyla on the right of figure 4 indicates the body plans of the living organisms studied but certainly does not indicate the


radiance. future product developments : for more information about our products or to locate a convenient outlet, neem : the ultimate herb, john conrick. originally issued under the auspices of the neem association. updated edition lotus press, twin lakes, wisconsin, 2001. neem, the ultimate herb is the most comprehensive book about neem, the world ' s most amazing plant. this book provides easy - to - understand instructions for using neem along with credible scientific evidence as to its effectiveness. after finishing this book, you will understand and appreciate the amazing qualities found in neem. you will also be able to more intelligently select quality neem products for your own use. neem : a tree for solving global problems, national research council, 1992. national academy press, washington dc. the national research council is made up of members of the national academy of sciences. they undertook to study the incredible potential of the neem tree. this book is the report of their findings. spanning a wide range of practical applications. the studies that are discussed in the book show that neem is one of the most valuable natural resources to solve a wide variety of global issues and concerns. the book contains extensive information including citations, safety tests and resources for follow up. the yoga of herbs : an ayurvedic guide to herbal medicine, frawley and lad. 1986, lotus press, twin lakes, wisconsin. for the first time, here is a detailed explanation and classification of herbs, using the ancient system of ayurveda. more than 270 herbs are listed, with 108 herbs explained in detail. included are many of the most commonly used western herbs with a profound ayurvedic perspective. important chinese and special ayurvedic herbs are introduced. beautiful diagrams and charts, as well as detailed glossaries, appendices and index are included. miracles of neem tree, verma. rasayan pharmacy, new delhi, india, 1988. neem was featured in the doctors prescription for healthy living newsletter during 2001. how to find our products at retail : neemaura naturals products are available at most major natural products stores and online retailers. if you shop at a store that does not carry the item you are seeking, please ask them to carry it as it is available from their distributors in most cases. if you cannot find our products locally, you are welcome to purchase them through our online store. how to find our products wholesale : if you are a retailer interested in selling neemaura ' s products,


a technical analysis by tepco has concluded that fuel in fukushima daiichi unit 1 has mostly melted out of the reactor pressure vessel and into the primary containment vessel. it also concluded that fuel has melted in units 2 & 3, but has mostly remained within the rpvs. - unit 1. tepco now estimates that most of the fuel has drained out of the reactor pressure vessel, via the bottom - mounted control rod tubes or instrumentation penetrations, into the concrete primary containment vessel. it reasons that the unit ' s decay heat before seawater injection ' significantly exceeded ' rpv water and materials ' heat absorption capacity ; it also explains why the rpv temperature has been low from an early stage. based on what tepco calls ' realistic assumptions ', and pcv gas analysis results, tepco estimates that the corium has eroded the 2m - thick pcv floor by about 70cm, but erosion has now assumed to have stopped. - units 2 & 3. lesser amounts of fuel from units 2 & 3 have dropped out of the rpv and into the pcv, because decay heat was less than the total heat absorption capacity of water in the core, and based on evidence from rpv temperature trends after water injection restarted. the study, presented at a japanese government workshop, remains in japanese ; this article is based on an english - language summary provided by tepco. in other news, tepco has explained how it calculates the total amount of radiation currently being emitted by the damaged fukushima daiichi reactors : 60 million bq / hr. at unit 1, the amount released is combined from two numbers : the product of radioactive dust concentration around the top of the reactor building time the assumed amount of steam generation, plus the dust concentration near the equipment hatch, times the air flow rate ( total : 10 million bq / hr ). deducted from that amount is the effectiveness of the exhaust filtration system. at unit 2, the amount is the dust concentration at the blowout panel times the air flow rate. air flow in unit 2 is caused by air from leaks in the truck bay floor and by rising warm vapour from decay heat ( total : 10 million bq / hr ). the calculation method for unit 3 is the same as at unit 1 ( unit 3 total : 40 million bq / hr ). from these figures, tepco concludes that this discharge equates to a personal exposure of 0. 1 msv / yr at the site


is the same as at unit 1 ( unit 3 total : 40 million bq / hr ). from these figures, tepco concludes that this discharge equates to a personal exposure of 0. 1 msv / yr at the site boundary, assuming average climactic conditions, and including external atmospheric exposure, external ground - based exposure and internal exposure through inhalation. in other news, fukushima site director masao yoshida has left his post for medical treatment ( unspecified, but not linked to the crisis ). he is replaced by takeshi takahashi, formerly general manager of tepco ' s nuclear power plant management department. also, tepco has changed the method of nitrogen gas injection in units 1 - 3 so that it can reach the rpv as well as the pcv. all three systems will inject nitrogen into the rpv via the head spray line, in addition to their current nitrogen injection arrangements into the pcv by various means. the unit 1 nitrogen supply will be via a hose attachment point in series to pcv injection via the ac line ; the unit 2 & 3 rpv line will be attached through jigs to test valves on the instrument rack. related articlestrio of vendors submit bids for temelin nuclear plant westinghouse announces cooperation with czech construction firm


optical fibers are circular dielectric wave - guides that can transport optical energy and information. they have a central core surrounded by a concentric cladding with slightly lower ( by ≈ 1 % ) refractive index. fibers are typically made of silica with index - modifying dopants such as geo2. a protective coating of one or two layers of cushioning material ( such as acrylate ) is used to reduce cross talk between adjacent fibers and the loss - increasing microbending that occurs when fibers are pressed against rough surfaces. for greater environmental protection, fibers are commonly incorporated into cables. typical cables have a polyethylene sheath that encases the fiber within a strength member such as steel or kevlar strands. the fiber as a dielectric wave - guide : fiber modes since the core has a higher index of refraction than the cladding, light will be confined to the core if the angular condition for total internal reflectance is met. the fiber geometry and composition determine the discrete set of electromagnetic fields, or fiber modes, which can propagate in the fiber. there are two broad classifications of modes : radiation modes and guided modes. radiation modes carry energy out of the core ; the energy is quickly dissipated. guided modes are confined to the core, and propagate energy along the fiber, transporting information and power. if the fiber core is large enough, it can support many simultaneous guided modes. each guided mode has its own distinct velocity and can be further decomposed into orthogonal linearly polarized components. any field distribution within the fiber can be expressed as a combination of the modes. the two lowest - order guided modes of a circularly symmetrical fiber designated lp01 and lp11 are illustrated in figure 1. when light is launched into a fiber, the modes are excited to varying degrees depending on the conditions of the launch input cone angle, spot size, axial centration and the like. the distribution of energy among the modes evolves with distance as energy is exchanged between them. in particular, energy can be coupled from guided to radiation modes by perturbations such as microbending and twisting of the fiber increasing the attenuation. bandwidth of an optical fiber determines the data rate. the mechanism that limits a fibers bandwidth is known as dispersion. dispersion is the spreading of the optical pulses as they travel down the fiber. the result is that pulses then begin to spread into one another and the symbols become indistinguishable. there are two main categories of dispersion,


dispersion is the spreading of the optical pulses as they travel down the fiber. the result is that pulses then begin to spread into one another and the symbols become indistinguishable. there are two main categories of dispersion, intermodal and intramodal. figure 1alp01 mode distributionfigure 1blp11 mode distributionfigure 1dispersionfigure 2cross section view of optical fiber and single fiber cable. as its name implies, intermodal dispersion is a phenomenon between different modes in an optical fiber. therefore this category of dispersion only applies to mulitmode fiber. since all the different propagating modes have different group velocities, the time it takes each mode to travel a fixed distance is also different. therefore as an optical pulse travels down a multimode fiber, the pulses begin to spread, until they eventually spread into one another. this effect limits both the bandwidth of multimode fiber as well as the distance it can transport data. intramodal dispersion, sometimes called material dispersion, is a result of material properties of optical fiber and applies to both single - mode and multimode fibers. there are two distinct types of intramodal dispersion : chromatic dispersion and polarization - mode dispersion. the index of refraction varies depending upon wavelength. therefore, different wavelengths will travel down an optical fiber at different velocities. this is known as chromatic dispersion. this principle implies that a pulse with a wider fwhm will spread more than a pulse with a narrower fwhm. dispersion limits both the bandwidth and the distance that information can be supported. this is why for long communications links it is desirable to use a laser with a very narrow line width. distributed feedback ( dfb ) lasers are popular for communications because they have a single longitudinal mode with a very narrow line width. polarization mode dispersion ( pmd ) is actually another form of material dispersion. single - mode fiber supports a mode, which consists of two orthogonal polarization modes. ideally, the core of an optical fiber is perfectly circular. however, the fact that in reality, the core is not perfectly circular, and mechanical stresses such as bending introduce birefringency in the fiber, causes one of the orthogonal polarization - modes to travel faster than the other, hence causing dispersion of the optical pulse. light power propagating in a fiber decay


mechanical stresses such as bending introduce birefringency in the fiber, causes one of the orthogonal polarization - modes to travel faster than the other, hence causing dispersion of the optical pulse. light power propagating in a fiber decays exponentially with length due to absorption and scattering losses. attenuation is the single most important factor determining the cost of fiber optic telecommunication systems, as it determines spacing of repeaters needed to maintain acceptable signal levels. in the near infrared and visible regions, the small absorption losses of pure silica are due to tails of absorption bands in the far infrared and ultraviolet. impurities notably water in the form of hydroxyl ions are much more dominant causes of absorption in commercial fibers. recent improvements in fiber purity have reduced attenuation losses. state - of - the - art systems can have attenuation on the order of 0. 1 db / km. scattering can couple energy from guided to radiation modes, causing loss of energy from the fiber. there are unavoidable rayleigh scattering losses from small - scale index fluctuations frozen into the fiber when it solidifies. this produces attenuation proportional to l / λ4. irregularities in core diameter and geometry or changes in fiber axis direction also cause scattering. any process that imposes dimensional irregularities such as microbending increases scattering and hence attenuation. typical spectral attenuation in silicafigure 3dispersionfigure 4typical spectral attenuation in silica numerical aperture ( na ) the numerical aperture ( na ) of a fiber is defined as the sine of the largest angle an incident ray can have for total internal reflectance in the core. rays launched outside the angle specified by a fibers na will excite radiation modes of the fiber. a higher core index, with respect to the cladding, means larger na. however, increasing na causes higher scattering loss from greater concentrations of dopant. a fibers na can be determined by measuring the divergence angle of the light cone it emits when all its modes are excited. figure 5numerical aperture qualitatively, na is a measure of the light gathering ability of a fiber. it also indicates how easy it is to couple light into a fiber. the normalized frequency parameter of a fiber, also called the v number, is a useful specification. many fiber parameters can be expressed in terms of v, such as : the number of modes at a given wavelength, mode cut off conditions, and propagation constants. for example, the


fiber, also called the v number, is a useful specification. many fiber parameters can be expressed in terms of v, such as : the number of modes at a given wavelength, mode cut off conditions, and propagation constants. for example, the number of guided modes in a step index multimode fiber is given by v2 / 2, and a step index fiber becomes single - mode for a given wavelength when v < 2. 405. mathematically, v = 2π · na · a / λ where a is the fiber core radius. the outer sheath of fiber cables can be removed using electrical cable stripping tools, and scissors or a razor blade can trim the kevlar strength member. however, the fiber coating must be very carefully removed to avoid damaging the fiber surface flaws and scratches are the cause of most fiber failures. the coating can be removed using our f - str fiber strippers. end surface quality is one of the most important factors affecting fiber connector and splice losses. quality endfaces can be obtained by polishing or by cleaving. polishing is employed in connector terminations when the fiber is secured in a ferrule by epoxy. the following describes the popular connectors and their endface preparation styles. fiber optic connector types sma due to its stainless steel structure and low - precision threaded fiber locking mechanism, this connector is used mainly in applications requiring the coupling of high - power laser beams into large - core multimode fibers. typical applications include laser beam delivery systems in medical, bio - medical, and industrial applications. the typical insertion loss of an sma connector is greater than 1 db. st the st connector is used extensively both in the field and in indoor fiber optic lan applications. its high - precision, ceramic ferrule allows its use with both multimode and single - mode fibers. the bayonet style, keyed coupling mechanism featuring push and turn locking of the connector, prevents over tightening and damaging of the fiber end. the insertion loss of the st connector is less than 0. 5 db, with typical values of 0. 3 db being routinely achieved. drilled - out, metallic st connectors, with insertion losses of > 1 db, are used with newports large - core ( > 140 µm ) fibers. fc the fc has become the connector of choice for single - mode fibers and is mainly used in fiber - optic instruments, sm fiber optic components, and in high - speed fiber optic communication links. this high - precision, ceramic ferrule


fibers. fc the fc has become the connector of choice for single - mode fibers and is mainly used in fiber - optic instruments, sm fiber optic components, and in high - speed fiber optic communication links. this high - precision, ceramic ferrule connector is equipped with an anti - rotation key, reducing fiber endface damage and rotational alignment sensitivity of the fiber. the key is also used for repeatable alignment of fibers in the optimal, minimal - loss position. multimode versions of this connector are also available. the typical insertion loss of the fc connector is around 0. 3 db. drilled - out, metallic fc connectors, having insertion losses of > 1 db, are being used with newports large - core ( > 140 µm ) fibers. sc the sc connector is becoming increasingly popular in single - mode fiber optic telecom and analog catv, field deployed links. the high - precision, ceramic ferrule construction is optimal for aligning single - mode optical fibers. the connectors outer square profile combined with its push - pull coupling mechanism, allow for greater connector packaging density in instruments and patch panels. the keyed outer body prevents rotational sensitivity and fiber endface damage. multimode versions of this connector are also available. the typical insertion loss of the sc connector is around 0. 3 db. connector endface preparation once the optical fiber is terminated with a particular connector, the connector endface preparation will determine what the connector return loss, also known as back reflection, will be. the back reflection is the ratio between the light propagating through the connector in the forward direction and the light reflected back into the light source by the connector surface. minimizing back reflection is of great importance in high - speed and analog fiber optic links, utilizing narrow line width sources such as dfb lasers, which are prone to mode hopping and fluctuations in their output. figure 6connector endfacesfigure 7a typical f - bk3 cleave is clean, flat and perpendicular. flat polish a flat polish of the connector surface will result in a back reflection of about - 16 db ( 4 % ). pc polish the physical contact ( pc ) polish results in a slightly curved connector surface, forcing the fiber ends of mating connector pairs into physical contact with each other. this eliminates the fiber - to - air interface, there by resulting in back reflections of - 30 to - 40 db. the pc polish is the most popular connector endface preparation, used in most applications. spc and upc polish in the super pc


the mode profile of the he11 mode of a step index fiber can be approximated by a gaussian distribution with a 1 / e width w given by : where : d is the core diameter, and v is the v - number. for our f - sv fiber, for which v = 2, the gaussian width is approximately 28 % larger than the core diameter, so the light should be focused to a spot size 1. 28 times the core diameter at the fiber surface. for a gaussian laser beam, the required beam diameter d incident upon focusing lens of focal length f to produce a focused spot of diameter w is d = 4λf / ( πw ). given the laser beam waist and divergence, its easy to determine the distance needed between the focusing lens and the laser to expand the beam to the required diameter. the mode field diameter is now given to provide easier matching of lens to optical fiber for a gaussian beam. a high numerical aperture lens must collimate the diverging output beam of a laser diode. newports f - l series diode laser focusing lenses, are ar - coated for high transmittance at popular laser diode wavelengths and with numerical apertures up to 0. 5 are useful for collimating or focusing. mode scrambling and filtering many multimode fiber experiments are sensitive to the distribution of power among the fibers modes. this is determined by the launching optics, fiber perturbations, and the fibers length. mode scrambling is a technique that distributes the optical power in a fiber among all the guided modes. mode filtering simulates the effects of kilometer lengths of fiber by attenuating higher - order fiber modes. figure 8launching conditions in a multimode optical fiber. one scrambling technique is to splice a length of graded - index fiber between two pieces of step - index fiber this ensures that the downstream fibers core is overfilled regardless of launch conditions. mode filtering can be achieved by wrapping a fiber several times around a finger - sized mandrel ; bending sheds the high - order modes. one way to achieve both scrambling and filtering is to introduce microbending to cause rapid coupling between all fiber modes and attenuation of high - order modes. one approach is to place a stripped section of fiber in a box filled with lead shot. a more precise way is to use newports fm - 1 mode scrambler. this specially designed tool uses a calibrated mechanism to introduce microbending for mode scrambling and filtering. ( a )


of fiber in a box filled with lead shot. a more precise way is to use newports fm - 1 mode scrambler. this specially designed tool uses a calibrated mechanism to introduce microbending for mode scrambling and filtering. ( a ) overfilled ( b ) underfilledfigure 9a schematic of coupling of light into an optical fiberfigure 10mode scrambler for optical fibers. the bends tend to couple out higher - order and radiation modes and to distribute the light into a distribution of modes that will remain stable over long distances. cladding mode removal some light is invariably launched into a fibers cladding. though cladding modes dissipate rapidly with fiber length, they can interfere with measurements. for example, the output of a single - mode fiber will not have a gaussian distribution if light is propagating in the cladding. you can remove cladding modes by stripping a length of fiber coating and immersing the bare fiber in an index matching fluid such as glycerin. common optical parameters the following is a list of common optical parameters associated with fiber optic components. please call or visit newports website for application notes on how to measure these parameters. figure 11 port configuration : number of input ports x number of output ports. e. g. 2 x 2 coupling ratio : the ratio of the power at an output port to the launched power expressed in db. e. g. - 10log ( p2 / p1 ). isolation : the ratio of the power at an output port in the transmitted wavelength band to that in the extinguished wavelength band, expressed in db. directivity : the ratio of the power returned to any other input port to the launched power, expressed in db. e. g. - 10log ( p4 / p1 ). bandwidth : the range of operating wavelengths over which performance parameters are specified. excess loss : the ratio of the total power at all output ports to the launched power, expressed in db. e. g. - 10log [ ( p2 + p3 ) / p1 ]. uniformity : the difference between maximum and minimum insertion losses. extinction ratio : the ratio of the residual power in an extinguished polarization state to the transmitted power, expressed in db. return loss : the ratio of the power returned to the input port to the launched power, expressed in db. e. g. - 10log ( p5 / p1 ). polarization - dependent loss ( pdl ) : the maximum (


return loss : the ratio of the power returned to the input port to the launched power, expressed in db. e. g. - 10log ( p5 / p1 ). polarization - dependent loss ( pdl ) : the maximum ( peak - to - peak ) variation in insertion loss as the input polarization varies, expressed in db. fiber optic communications the theoretical bandwidth of optical fiber transmission in the 1550 nm window alone is on the order of terabits. current fiber optic systems have not even begun to utilize the enormous potential bandwidth that is possible. there are two methods that are employed to achieve an increase in bandwidth. the first is known as time division multiplexing or tdm. multiple channels are transmitted on a single carrier by increasing the modulation rate and allotting a time slot to each channel. however, more sophisticated high - speed electronics, at both the transmitting and receiving ends of the communications link, are required when increasing the bit rate of a system. and as the bit rate increases, inherent modulation limiting characteristics of optical fibers become dominant. chromatic and polarization mode dispersion cause pulse spreading, which affects the signal quality over longer transmission distances. an alternate method for increasing the capacity of fiber optic communications systems is known as wavelength division multiplexing, or wdm. by this method, capacity can be increased by using more than one optical carrier ( wavelength ) on a single fiber. therefore, adding a second transmitter and receiver to an optical fiber can double the bandwidth of that communications system. this method of increasing the capacity of an optical system has appeal for a variety of reasons. if a system were to increase in capacity using tdm alone, the existing transmitter and receiver would be replaced with a faster and more expensive transmitter / receiver pair. using wdm, the existing transmitter and receiver do not need to be replaced. a second transmitter / receiver pair of a different wavelength is simply added. this is done by coupling, or multiplexing the output of the two lasers into a single fiber. at the receiving end, the two wavelengths are then separated, or demultiplexed, and each optical carrier is routed to its own receiver. for transmission systems using a 1310 nm laser, a second laser at 1550 nm is usually added. the reason for choosing these wavelengths is that they lie in the windows or ranges of least attenuation. this allows the signal to travel a longer distance. the itu ( international telecommunication union ) has proposed a set of closely spaced wavelengths in the 1550 nm window. this method of w


that they lie in the windows or ranges of least attenuation. this allows the signal to travel a longer distance. the itu ( international telecommunication union ) has proposed a set of closely spaced wavelengths in the 1550 nm window. this method of wdm is known as dense wavelength division multiplexing, or dwdm. these different wavelengths or channels, are spaced 100 ghz apart, which is approximately 0. 8 nm. this set of channels is commonly known as the itu - t grid, and is specified in frequency. the reason the 1550 nm window was chosen by the itu is twofold : it is in one of the windows that has the smallest amount of attenuation ; and it also lies in the band in which erbium doped optical amplifiers operate. itu - t dwdm grid the following diagram is a conceptual example of a fiber optic network. the all - optical network the all - optical network will be the next evolution in optical communications. current dwdm systems are point - to - point links meaning that the signals have a single distinct starting and ending point. research is being performed to help these networks evolve into fully configurable networks, which are not limited to fixed point - to - point links. transparency in the optical layer opens many possibilities for the future. digital and analog transmission can occur on the same fiber. different bit rates using different protocols will all travel together. current research is being performed on reconfiguring an optical network in real time. wavelength selective switching allows wavelengths to be routed through the network individually. some of the applications of this are for network restoration and redundancy, which may reduce or entirely eliminate the need for an entire back up system to help the network recover from failures such as equipment malfunctions or fiber breaks. a reconfigurable network may offer bandwidth on demand to configure itself to optimize for traffic bottlenecks. the future may also include wavelength translation to convert traffic on one wavelength to another wavelength in the optical domain. all optical switching is still in the research phase ; however, researchers are looking for ways to create reliable, low loss switches with fast switching speeds. investigation into the possibility of optical packet switching and other novel technologies are currently underway. the all - optical network may be just around the corner. photonic crystal fibers ( pcfs ) photonic crystal fiber ( pcf ) is a subset of photonic crystals. the field of pcf was first explored in the latter half of 1990 ' s and quickly


network may be just around the corner. photonic crystal fibers ( pcfs ) photonic crystal fiber ( pcf ) is a subset of photonic crystals. the field of pcf was first explored in the latter half of 1990 ' s and quickly evolved into a commercial technology. pcfs are generally divided into two main categories : index guiding fibers that have a solid core, and photonic bandgap fibers that have periodic microstructured elements and a core of low index material ( e. g. hollow core ). they can provide characteristics that ordinary optical fiber cannot, such as : single - mode operation from the uv to ir with large mode - field diameters, exceptionally high nonlinearity, numerical aperture ( na ) ranging from very low to about 0. 9, and optimized dispersion properties. applications of pcfs are found in a wide range of research fields like spectroscopy, metrology, biomedicine, imaging, telecommunication, industrial machining, and military. fabrication and characteristicsfigure 12close - up view of pcf preform the typical starting point for manufacturing of an index guided pcf is an array of hollow capillary silica tubes bundled around a pure silica rod replacing the center capillary. for photonic bandgap ( pbg ) fibers, one or more capillary tubes may simply be left out in the center of the preform in order to create a hollow ' defect ' core. a sleeving tube surrounds the entire assembly that forms the preform. in a fiber draw tower, the preform is heated to around 2000°c and it is carefully pulled into fiber with the aid of gravity and pressure. typical outer fiber diameter is 125 µm, but diameters from 80 to around 700 µm are routinely fabricated. this fiber maintains the structure of the preform, but now on a microscopic scale. standard protective polymer coatings are applied to the fibers in order to improve handling characteristics. figure 13most pcf fiber can be connectorized too. call newport for more information. the dispersion characteristics of pcfs can be manipulated to create fibers having zero, low, or anomalous dispersion at visible wavelengths. the dispersion can also be flattened. combining these features with small mode field areas results in outstanding nonlinear fibers. by altering the pattern of air holes or the materials used, it is possible to manipulate other characteristics of pcfs, such as the single - mode cut - off wavelength, the na, and the nonlinear coefficient.


field areas results in outstanding nonlinear fibers. by altering the pattern of air holes or the materials used, it is possible to manipulate other characteristics of pcfs, such as the single - mode cut - off wavelength, the na, and the nonlinear coefficient. the design flexibility is very large, and designers can use many different, fascinating, and odd air hole patterns to achieve specific pcf parameters. the triangular arrangement of round air holes in the cladding is typically used to create single - mode fibers. increasing the air - filling fraction in the cladding typically leads to multimode behavior. an elliptical core can create a highly birefringent fiber that is polarization maintaining. silica provides superior fiber performance for most applications with wavelengths between 200 and 2500 nm, but use of other materials can enhance specific parameters like nonlinearity or wave - guiding outside this spectral region. furthermore, a long list of dopants can be added to silica. doped silica is now used in a variety of fiber lasers and amplifiers ; these could be combined with the unique capabilities of pcfs to provide even more useful devices. coupling, splicing and connectorization of pcfs are other important issues because the fibers may have extreme parameters of mode field area and na ; coupling methods are in some cases very different from standard fiber methods. however, users may strip and cleave the pcfs with standard fiber tools. for laboratory use, the fibers are typically just cleaved and used with " open " ends. in such cases, it is important to avoid direct exposure of the fiber ends to any liquids since the capillary forces in the holes may draw the liquids several centimeters into the fiber, and thus disturb the wave - guiding properties. pcfs can be spliced to standard fibers ( and take advantage of the various connector schemes of such fibers ), or the pcfs may be connectorized directly. newport provides both pcfs spliced to standard fibers and directly connectorized on a semi - custom basis. note that the mechanical strength of splices, the connectorized fiber core offset and connector - to - connector coupling are not always the same as standard fibers. directly connectorized fibers may furthermore provide beam expansion to lower the fiber end facet intensity and reduce the risk of damage at high power levels. call newport for more details. newport ' s f - sm, and f - nl series are index guided fibers. similar to conventional fibers, index guiding pcfs transport light through a solid core by total internal reflection. the microstructured air -


. call newport for more details. newport ' s f - sm, and f - nl series are index guided fibers. similar to conventional fibers, index guiding pcfs transport light through a solid core by total internal reflection. the microstructured air - filled region in pcfs effectively lowers the index of the cladding effectively creating a step - index optical fiber. the fiber behaves in many ways like standard step - index fibers, but it has a number of advantages. index guiding pcfs are made of undoped silica that provides very low losses, sustains high powers and temperature levels, and may withstand nuclear radiation. depending on pcf design, the air in the cladding may be utilized to yield fibers with extremely low or extremely high index steps. figure 14schematic of an index guided pcffigure 15cross section of triangular cladding pcf a typical cross section of an index guided pcf is shown in fig 14 and 15. the pcf consists of a triangular lattice of air holes where the core is defined by a missing air hole. the pitch is labeled λ, and measures the period of the hole structure ( the distance between the centers of neighboring air holes ). the hole size is labeled d, and measures the diameter of the holes. figure 16cross section of air - clad pcf some pcfs have a cladding refractive index that exhibits a strong wavelength dependence. together with the inherently large design flexibility, pcfs allow for a whole range of novel properties to be explored. such properties include endlessly single - mode fibers ( f - sm series ), extremely nonlinear fibers and fibers with anomalous dispersion in the visible wavelength region ( f - nl series ). a unique feature of pcfs is that a single fiber may support single - mode operation over a wavelength range from around 300 nm to beyond 2000 nm even for large mode field areas ( of several hundred µm2 ). this allows pcfs to be utilized for transmission of very high powers with high beam quality without running into nonlinear or damage barriers ( several hundred watts for cw operation ). on the other hand, the highly nonlinear fibers made as single - mode fibers have extremely small mode field areas ( typically around 3 µm2 ) and confine light to the core region efficiently. compared to standard fiber technology, where the light is guided using solid glasses with different refractive indices, several new properties may be realized using pcf technology. for example : - fibers that are single - mode in a very broad spectral range ( in principle all wavelengths )


fiber technology, where the light is guided using solid glasses with different refractive indices, several new properties may be realized using pcf technology. for example : - fibers that are single - mode in a very broad spectral range ( in principle all wavelengths ) - very small mode sizes may be obtained ( down to approx. 1 µm ) - very large mode sizes may be obtained ( up to 25 µm or larger ) - zero dispersion wavelengths below 1300 nm is possible ( down to approx. 600 nm ) - exceptionally large birefringence close to 10 - 2 can be realized - very high numerical apertures up to 0. 9 may be obtained hence, pcfs are ideally suited for applications requiring large non - linearities, broadband operation with single - mode guidance, large mode areas, light collection from a large solid angle, etc. figure 17large mode area fiber ( f - sm series ) figure 18near field image of f - sm fiber at 1550 nmfigure 19mode structure of f - sm20 fiber formation of broad continuous spectra through propagation of short femto or picosecond - range high power pulses through nonlinear media ( also known as supercontinuum generation, or scg ) was first observed in 1970 and has since then been studied extensively in many different materials. the term supercontinuum does not cover a specific phenomenon but rather a plethora of nonlinear effects leading to considerable spectral broadening of optical pulses and thereby potentially octave - spanning output. the involved nonlinear effects depend on the dispersion in the material and count effects like self - phase modulation ( spm ), raman scattering, phase matching and solitons. results on scg in pcfs have previously been presented with pumping in the anomalous dispersion regime or at the zero - dispersion wavelength in both the visible and the infrared wavelength range. most experiments utilize femtosecond pumping as this results in spectacularly broad spectra. picosecond pumping yields more narrow spectra, but does so with far cheaper laser sources and is therefore commercially interesting. although scg can be observed in a drop of water given enough pumping power, pcfs are ideal media for scg as the dispersion can be designed to facilitate continuum generation in a specific region. in this way, it is possible to convert light to both higher and lower wavelength, just like super wide spectra covering more than an octave is achievable at previously unthinkable low power levels. practical super


generation in a specific region. in this way, it is possible to convert light to both higher and lower wavelength, just like super wide spectra covering more than an octave is achievable at previously unthinkable low power levels. practical supercontinuum tips scg - 800 and scg - 800 - cars ( see supercontinuum generation fiber devices ) are ideal in generating supercontinuum using an ultrafast laser. when coupling light from a femtosecond laser into a crystal fiber, a number of issues regarding pulse distortion must be addressed to achieve the optimum performance. in this section, we discuss the precautions taken to couple light from a ti : sapphire laser into a 1. 7 µm core pcf. the first issue to be addressed is the 4 % reflection from the fiber surface, which can lead to a distortion of the pulse train and in severe cases will stop the laser from mode - locking. cleaving the fiber at an angle can minimize back reflections. however, we recommend that the problem be avoided by the use of a faraday isolator. coupling out a small portion of the beam and directing it to newport ' s pulsescout autocorrelators ( see pulsescout autocorrelator ) allows for real - time monitoring of the pulse width and beam quality. the femtosecond pulses are easily coupled into the fiber through standard microscope objectives. magnifications of 40x and 60x provide good results. aspheric ball lenses can also be used, but as these are not achromatic, they should not be used with short femtosecond pulses due to the broad spectral range of these pulses. the dispersion in the microscope objective should be compensated using a precompensating prism or grating compressor in order to launch the shortest possible ( i. e. highest intensity ) pulse into the fiber. the diameter of the laser beam should match the aperture of the microscope objective. this is easily achieved with a standard telescope. nonlinear effects are inherently very sensitive to variations in the input power, thus a very stable mount is needed. to avoid displacement of the fiber end due to thermal, acoustic and other unwanted effects, the fiber should be mounted as close to the end as possible. gluing the fiber to the mount, or using a connectorized fiber, can create further stability. if polarization - maintaining fibers are used, the polarization axis of the linearly polarized femtosecond pulses should


colleagues came up with a different explanation. they had gone to northern tanzania to study the foraging habits of the hadza, the last known hunter - gatherers in africa. while there, the scholars were struck by how strong the tribe ' s old women were and how, rather than live off the fruits of others ' labor, they worked hard digging up the tribe ' s main starch staple, a deeply - buried tuber. " their acquisition rates were similar to the rates of younger women, " hawkes told me, " but these old ladies were spending even more time " than their daughters gathering food, leaving camp earlier, coming back later, and bringing back more than they needed. the anthropologists also noticed that many children with grandmothers or great - aunts had faster growth rates than their counterparts. from these slim clues, hawkes and her colleagues developed the " grandmother hypothesis, " which holds that women past childbearing age helped not just their children, but their children ' s children, and lengthened the human lifespan in the process. without babies of their own to lug around, grandmothers had both time and a very good reason to be useful. when they eked out food for their daughters ' children, they reduced the chance that those children would die. that gave the grandmothers a better chance of passing on their own predisposition to longevity. ( in general, grandmothers appear to have helped daughters ' offspring more than sons ' ; evolutionary theorists explain this by pointing out that a daughter ' s maternity affords a surer genetic connection than a son ' s paternity, unless you all but imprison your daughter - in - law. 2 ) the grandmother hypothesis also explains another conundrum : why do humans have shorter birth intervals than other primates? chimp mothers, for instance, wait five or six years to give birth to another neonate. women can pop out infants as soon as they ' ve weaned previous ones. it turns out that, once humans learned the art of collaborative child - rearing, old women started spending more time with their daughters ' toddlers. that freed up the young women to have more. as the grandmother effect spread throughout the population over thousands of generations, it changed humans in another way. it made their brains bigger. as life lengthened, so did each stage of it. children stayed children longer, which let their brains develop a more complex neural architecture. not everyone accepts this triumphantly feminist account of our evolutionary history. when anthropologists first heard it,


bigger. as life lengthened, so did each stage of it. children stayed children longer, which let their brains develop a more complex neural architecture. not everyone accepts this triumphantly feminist account of our evolutionary history. when anthropologists first heard it, most of them dismissed it as ridiculous. for one thing, it cuts man - the - hunter out of the picture. what about all the calories needed to grow our oversized brains? didn ' t those have to come from the meat brought back from the hunt? moreover, throughout recorded history, young women left their villages to move in with their men. so how would mothers have had access to their daughters ' children? the comeback to these objections is that hunter - gatherer families probably made all kinds of arrangements. 3 in the tribes that anthropologists have been able to observe, some couples stayed in the wife ' s village, some moved in with her parents while starting their families, and some women left home. patrilocality — men staying put — probably became the norm only when our ancestors settled down to farm, which made men unwilling to leave their land and wealth. and it ' s not as if hunters alone brought in enough food to let the children thrive. hawkes argues that, while meat boosted a tribe ' s overall nutrition, hunters couldn ' t be counted on to come home with a kill. when they did, the demands of status made them just as likely to share the bounty with the tribe as to hold it back for their children. the food grandmothers provided, on the other hand, was steady and reliable. two decades later, the grandmother hypothesis has gone from oddball conjecture to one of the dominant theories of why we live so long, breed so fast, and are so smart. the extra calories and care supplied by women in their long post - fertile period subsidized the long pre - fertile period that is childhood. and that ' s what made us fully human. in a happy coincidence, the grandmother hypothesis comes along just as americans enter what might be called the age of old age. america ' s biggest generation, the baby - boomers, began retiring in 2011. this gerontocracy is expected to drain our wealth. by 2060, more than 20 percent of all americans will be 65 or older, up from 13 percent in 2010. more than 92 million oldsters will roam the land, if roaming is within their power. people who fret about the federal budget point out that, by 2011, social security and medicare were already eating