The process of heightened biological productivity in a body of water is call eutrophication. The major factors controlling eutrophication in a body of water, whether large, small, warm, cold, fast-moving, or quiescent, are nutrient input and rates of primary production. Not all lakes experience eutrophication. Warmth and light increase eutrophication, (which in Greek means "well nourished&#…
Gender is an old term in linguistic discourse used to designate whether nouns are masculine, feminine, or neuter. It was not normally used in the language of social or natural sciences or in sexology until 1955, when John Money adopted the term to serve as an umbrella concept to distinguish femininity, or womanliness, and masculinity, or manliness, from biological sex (male or female). Though the …
Evaporation is a process that is commonly used to concentrate an aqueous solution of nonvolatile solutes and a volatile solvent. In evaporation, a portion of the solvent is vaporized or boiled away, leaving a thick liquid or solid precipitate as the final product. The vapor is condensed to recover the solvent or it can simply be discarded. A typical example is the evaporation of brine to produce s…
The term gender has no exact correlate in Middle Eastern sources, but instead is identified by scholars as a major analytical tool in the definition of differences between men and women. Many researchers in every discipline argue that gender has always been embedded in all societies, past and present. Scholars who study gender seek to question dominant, normative definitions of every society…
Evapotranspiration refers to the vaporization of water from both non-living and living surfaces on a landscape. Evapotranspiration is a composite of two words: evaporation and transpiration. Evaporation refers to the vaporization of water from surface waters such as lakes, rivers, and streams, from moist soil and rocks, and any other substrates that are non-living. Transpiration refers to the vapo…
Gender, other than a biological or physical determination of the sexes, is a cultural and social classification of masculinity and femininity. Gender presentations in art are the outcome of the cultural process of defining sexual and social identity. Pictorial art and literature, as means of expression through transformation and stylization, are the predominant media reflecting this cultural proce…
An even number is an integer that is divisible by 2 and an odd number is an integer that is not divisible by 2. Thus 2, 4, 6, 8... are even numbers and 1, 3, 5, 7... are odd numbers. Any even number can be written as 2n where n is an integer and any odd number can be written as 2n + 1 or as 2n - 1, where n is an integer. The sum, difference, or product of even numbers is an even number. On the oth…
Freeways, also called superhighways, are roads specifically designed to allow for the free flow of traffic. Freeways typically feature two or more traffic lanes in each direction, medians to divide the opposing directions, full access control, a system of ramps to prevent merging and diverging traffic from interrupting the traffic flow, and grading to separate intersecting traffic on other roads. …
Gender studies in anthropology has a relatively short history, dating to the latter half of the twentieth century, but its prehistory can be discerned in the discipline's early concern with kinship and social reproduction. At the turn of the twentieth century, anthropologists focused their attentions mainly on small-scale societies in which kinship appeared to provide the organizing structu…
In early 2001, data gathered by NASA's Hubble Space Telescope and the Chandra X-ray Observatory independently provided strong evidence of an event horizon, the observable boundary region surrounding an unobservable black hole. The size of the event horizon surrounding a black hole is termed the Schwarzschild radius, named after the German astronomer Karl Schwarzschild (1873–1916), wh…
Any process that is repetitive or periodic has an associated frequency. The frequency is the number of repetitions, or cycles, during a given time interval. The inverse of the frequency is called the period of the process. Pendulums, as in a grandfather clock, also have a frequency of a certain number of swings per minute. A complete oscillation for a pendulum requires the pendulum bob to start an…
General will (volonté générale) is inextricably associated with the philosophy of Jean-Jacques Rousseau (1712–1778). While Rousseau appropriated the general will from the theological debates of the late seventeenth and early eighteenth centuries, he made the concept his own with the political formulation he gave it in his Du contrat social (1762; On the social contract). Inte…
Freshwater is chemically defined as containing a concentration of less than two parts per thousand (<0.2%) of dissolved salts. Although water is abundant on the surface of Earth, freshwater is a very limited resource. Freshwater, in all forms, makes up less than 2.8% of the world water supply. Freshwater on Earth exists in several forms. These include lakes, which represent 0.009% of the gl…
In its most widely accepted modern sense, a generation is comprised of a group of people born around the same time and sharing certain formative experiences. The concept of generations has been used by social scientists, historians, and anthropologists to explain social change over time and to identify differences within social groups. The term has also been applied loosely to describe literary gr…
Friction is the force that resists motion when the surface of one object slides over the surface of another. Frictional forces are always parallel to the surfaces in contact, and they oppose any motion or attempted motion. No movement will occur unless a force equal to or greater than the frictional force is applied to the body or bodies that can move. While friction is often regarded as a nuisanc…
A frigate bird on its nest on Barbuda Island in the West Indies. Photograph by Ormond Gigli. Stock Market. Reproduced by permission. Frigate birds are five species of oceanic birds that make up the family Fregatidae. Frigate birds occur along the coasts of the tropical oceans, but also hundreds of miles out to sea. Frigate birds typically weigh about 3 lb (1.5 kg), but the spread of their l…
Genetics as a discipline is young, but the concept that forms its subject—inheritance—stretches back in time. The word has been formed from the adjective genetic, found in the sciences of the nineteenth and twentieth centuries—for example, biogenetic law, genetic affinity, genetic psychology—and meaning, according to the Oxford English Dictionary, "pertaining to,…
The frog's-bit or tape-grass family (Hydrocharitaceae) is a relatively small group of herbaceous, aquatic, monocotyledonous plants, occurring in fresh and marine waters. There are about 100 species in the frog's-bit family, distributed among 15 genera. The flowers of members of this family are water pollinated, shedding their pollen into the water, which disperses it to the stigmatic…
One of the most startling and disturbing revelations from the Nuremburg Trials following World War II was the extent of the atrocities committed by the Nazi government in the name of genetics. Massive sterilizations and euthanasia programs for those deemed genetically unfit ("lives not worth living" in Nazi phraseology) had raised ethical issues about the use and abuse of science an…
The notion of genius as it is known in the early twenty-first century emerged most fully during the eighteenth-century Enlightenment period. Although the idea of genius was around before the time of Immanuel Kant (1724–1804), Kant most clearly defined it in the late eighteenth century in his third critique, The Critique of Judgment. In fact, Kant's discussion still influences contemp…
Mass slaughter of human beings by other human beings has been a recurrent phenomenon over the centuries, but until recently neither governments nor international legal specialists had sought to devise formal rules and institutions that could help prevent, or if necessary punish, the perpetrators of large-scale atrocities. Massacres that took place during and immediately after World War I, when Tur…
Evolution refers to biological change. Biological evolution involves change in the genetic constitution of populations over time such that complexity is achieved due to the formation of new genes or gene-encoded functions rather than harmful mutations. These changes are passed on from parents to their offspring, but biological evolution does not involve individual organisms. Individuals develop, b…
Genre is the division and grouping of texts on the basis of formal, thematic, or stylistic criteria. Texts may be produced, it can be argued, in compliance with or against the strictures of an established and identifiable genre, though it is equally feasible to impose a genre identity upon a work in retrospect, thus attributing to it further possibilities of meaning or, conversely, limiting its po…
Only relatively recently accepted as a subject of study by universities, geography has been characterized as a Cinderella among the disciplines. It was not one of the traditional liberal arts, and it appeared in its modern form in the curriculum of universities in the nineteenth and twentieth centuries; it still remains a small component, and is sometimes not present at all, in institutions of hig…
Evidence of evolution can be observed in numerous ways, including distribution of species (both geographically and through time), comparative anatomy, taxonomy, embryology, cell biology, molecular biology, and paleontology. The English naturalist Charles Darwin (1809–1882) formulated the theory of evolution through natural selection in his ground breaking publication The Origin of Species b…
Frogs are tail-less amphibians (class Amphibia, order Anura). With some 3,500 living species, frogs are the most numerous and best known of amphibians. They are found on all continents except Antarctica and are common on many oceanic islands. The terms "frog" and "toad" are derived from early usage in England and northern Europe, where two families of the order Anura oc…
Evolution is the process of biological change over time. Such changes, especially at the genetic level are accomplished by a complex set of evolutionary mechanisms that act to increase or decrease genetic variation. Evolutionary theory is the cornerstone of modern biology, and unites all the fields of biology under one theoretical umbrella to explain the changes in any given gene pool of a populat…
Frostbite is the freezing of tissues. It occurs when body parts, most commonly the fingers, toes, and the tips of ears and the nose, are exposed for long periods to the cold. Frostbite is a direct result of limited blood circulation. The blood is the body's internal heating system; it carries heat to the body tissues. But prolonged exposure to the cold can constrict blood vessels, causing b…
Globalization is a complex and controversial concept. There is little agreement in the literature on what it is, whether it is or is not taking place, whether it is new or old, and if it is good or bad. In its narrower conception, globalization signifies a process of intensification of economic, political, and cultural interconnectedness among the various actors in the global system. In the econom…
Archeological excavation involves the removal of soil, sediment, or rock that covers artifacts or other evidence of human activity. Early excavation techniques involved destructive random digging and removal of objects with little or no location data recorded. Modern excavations often involve slow, careful extraction of sediments in very thin layers, detailed sifting of sediment samples, and exact…
A fruit is an often edible part of a plant that is derived from a fertilized, ripened ovary. As a dietary staple, fruits are appreciated for their sweetness and as a rich source of nutrients, especially vitamins. Gardeners enjoy planting fruit-bearing plants for their usefulness as a food and also for the array of color and diversity they bring into the garden. In agricultural industry, fruits are…
Fuel cells are a clean and quiet way to convert chemical-energy of fuels directly into electricity. Specifically, they transform hydrogen and oxygen into electric power, emitting water as their only waste product. A fuel cell consists of two electrodes, an anode and a cathode, sandwiched around an electrolyte. (An electrolyte is a substance, usually liquid, capable of conducting electricity by mea…
The excretory system removes cellular wastes and helps maintain the salt-water balance in an organism. In providing these functions, excretion contributes to the body's homeostasis, the maintenance of constancy of the internal environment. When cells break down proteins, they produce nitrogenous wastes, such as urea. The excretory system serves to remove these nitrogenous waste products, as…
A function represents a mathematical relationship between two sets of real numbers. These sets of numbers are related to each other by a rule which assigns each value from one set to exactly one value in the other set. The standard notation for a function y = f(x), developed in the 18th century, is read "y equals f of x." Other representations of functions include graphs and tables. …
By definition, exercise is physical activity that is planned, structured, and repetitive for the purpose of conditioning any part of the body. Exercise is utilized to improve health, maintain fitness and is important as a means of physical rehabilitation. Exercise is used in preventing or treating coronary heart disease, osteoporosis, weakness, diabetes, obesity, and depression. Range of motion is…
A fundamental theorem is a statement or proposition so named because it has consequences for the subject matter that are difficult to overestimate. Put another way, a fundamental theorem lies at the very heart of the subject. Mathematicians have designated one theorem in each main branch as fundamental to that branch. The fundamental theorem of arithmetic states that every number can be written as…
Glands in the human body are classified as exocrine or endocrine. The secretions of exocrine glands are released through ducts onto an organ's surface, while those of endocrine glands are released directly into the blood. The secretions of both types of glands are carefully regulated by the body. Exocrine gland secretions include saliva, perspiration, oil, earwax, milk, mucus, and digestive…
Explosives are substances that produce violent chemical or nuclear reactions. These reactions generate large amounts of heat and gas in a fraction of a second. Shock waves produced by rapidly expanded gasses are responsible for much of the destruction seen following an explosion. The power of most chemical explosives comes from the reaction of oxygen with other atoms such as nitrogen and carbon. T…
Fungi are one of the five kingdoms of organisms. Like higher plants (of the kingdom Plantae), most fungi are attached to the substrate they grow on. Unlike plants, fungi do not have chlorophyll and are not photosynthetic. Another key difference from plants is that fungi have cell walls composed of chitin, a nitrogen containing carbohydrate. All fungi have nuclei and the nuclei of most species are …
Exponents have a number of useful properties: Property (6) shows how the operation of exponentiation is extended to the rational numbers. Note that unit-fraction exponents, such as 1/3 or 1/2, are simply roots; that is, 125 to the 1/3 power is the same as the cube root of 125, while 49 to 1/2 power is the same as the square root of 49. By keeping properties (1) through (6) as centra…
A fungus is a tiny plant-like organism that obtains its nourishment from dead or living organic matter. Some examples of fungi include mushrooms, toadstools, smuts, molds, rusts and mildew. Fungi have long been recognized as a serious threat to plants and crops. They attack food both while it is growing and after it has been harvested and placed in storage. One of the great agricultural disasters …
Gaia, Earth, was believed by the ancient Greeks to be a living, fertile ancestor of many of their important gods. The Romans, who adopted many Greek gods and ideas as their own, also believed in this organismic entity, who they renamed Terra. The Gaian notion has been personified in more recent interpretations as "Mother Earth." The Gaia hypothesis is a recent and highly controversia…
Extinction is the death of all members of a species and thus, of the species itself. Extinction may occur as a result of environmental changes (natural or human-caused) or competition from other organisms. A species confronted by environmental change or competitors may (1) adapt behaviorally (e.g., shift to a different diet), (2) adapt by evolving new characteristics, or (3) die out. At the presen…
A galaxy is a large collection of stars similar to the Milky Way galaxy in which our solar system is located. Astronomers classify galaxies according to their shape as either spiral, elliptical, or irregular. Spiral galaxies are further subdivided into normal and barred spirals. Elliptical galaxies can be either giant or dwarf ellipticals, depending on their size. Galaxies can contain anywhere fro…
The eye is the organ of sight in humans and animals which transforms light waves into visual images and provides 80% of all information received by the human brain. These remarkable organs are almost spherical in shape and are housed in the orbital sockets in the skull. Sight begins when light waves enter the eye through the cornea (the transparent layer at the front of the eye) pass through the p…
The fundamental theorem of arithmetic states that every positive integer can be expressed as the product of prime factors in essentially a single way. A prime number is a number whose only factors are itself and 1 (the first few prime numbers are 1, 2, 3, 5, 7, 11, 13). Integers that are not prime are called composite. The number 99 is composite because it can be factored into the product 9 …
The number n! is the product 1 × 2 × 3 × 4 ×... × n, that is, the product of all the natural numbers from 1 up to n, including n itself where 1 is a natural number. It is called either "n factorial" or "factorial n." Thus 5! is the number 1 × 2 × 3 × 4 × 5, or 120. Older books sometimes used the symbol In fo…
Game theory is a branch of mathematics concerned with the analysis of conflict situations. It involves determining a strategy for a given situation and the costs or benefits realized by using the strategy. First developed in the early twentieth century, it was originally applied to parlor games such as bridge, chess, and poker. Now, game theory is applied to a wide range of subjects such as econom…
A gamete is a specialized reproductive cell. The cells usually have one half as many chromosomes in their nuclei as the majority of body cells, which are known as somatic cells. All sexually-reproducing plants, animals, and microbes produce gametes sometime during their life span. During the second and third quarters of the nineteenth century the scientists J. L. Prevost, J. B. Dumas, T. Schwann, …
Gametogenesis is the production of haploid sex cells (in humans, ovum and spermatozoa) that each carry one-half the genetic compliment of the parents from the germ cell line of each parent. The production of ovum is termed oogenesis and the production of spermatozoa is called spermatogenesis. Both oogenesis and spermatogenesis provide a mechanism through which genetic information may be passed to …
A family of chemical elements usually consists of elements that are in the same group (the same column) on the periodic table. The term is also applied to certain closely related elements within the same period (row). Just as the individual members in a human family are all different but have common characteristics, like hair color, so to do the elements in a chemical family have certain propertie…
Falcons are birds of prey in the family Falconidae. There are 39 species of true falcons, all in the genus Falco. Like other species in the order Falconiformes (which also includes hawks, eagles, osprey, and vultures), falcons have strong raptorial (or grasping) talons, a hooked beak, extremely acute vision, and a fierce demeanor. Falcons can be distinguished from other raptors by the small toothl…
Gamma rays are a highly energetic form of electromagnetic radiation. The wavelength of a gamma ray is very short—less than the radius of an atom—the energy they carry can be millions of electron volts. Gamma rays originate in the nucleus of an atom, and are created when cosmic rays collide with atoms in molecules of gas. In the collision, the nucleus of the atom is destroyed, and gam…
The Faraday effect is manifest when a changing magnetic field induces an electric field. Hence the effect is also known as "induction." It is most simply exemplified by a loop of wire and a bar magnet. If one moves the magnet through the loop of wire, the changing magnetic field within the loop gives rise to an electrical current in the wire. The current is larger for stronger magnet…
Gamma ray bursts are brief, seconds-long, blasts of radiation of mysterious origin that, in nature, seem to come from the depths of interstellar space. Bursts of gamma radiation also have been measured coming from severe thunderstorms and are a component of nuclear bomb detonation. The accidental discovery of cosmic gamma ray bursts was confirmed in 1973. Ten years earlier, the United States Air F…
There are many different ways of writing the equation of a line in a coordinate plane. They all stem from the form ax + by + c = 0. Thus 2x + 3y - 5 = 0 is an equation of a line, with a = 2, b = 3, and c = -5. When the equation is written in the form y = mx + b we have slope-intercept form: m is the slope of the line and b is the y-intercept. The equation 2x + 3y - 5 = 0 becomes So the line h…
Cryptography is a division of applied mathematics concerned with developing schemes and formula to enhance the privacy of communications through the use of codes. Cryptography allows its users, whether governments, military, businesses, or individuals, to maintain privacy and confidentiality in their communications. Encryption is any form of coding, ciphering, or secret writing. Encryption of data…
A fat is a solid triester of glycerol. It is formed when a molecule of glycerol, an alcohol with three hydroxyl groups, reacts with three molecules of fatty acids. A fatty acid is a long-chain aliphatic carboxylic acid. The more correct name for a fat is a triglyceride. The three fatty acid fragments in a fat may be all the same (a simple triglyceride) or they may be different from each other (a m…
A fatty acid is a combination of a chain of carbon and hydrogen atoms, known as a hydrocarbon, and a particular acid group (-COOH). Three fatty-acid molecules combined with a glycerol form a triglyceride fat or oil. While several varieties of fatty acid occur in nature, all belong in one of two categories—saturated or unsaturated. In a saturated fatty-acid molecule, all the carbon atoms in …
Gangrene involves the death of human tissue, usually due to ischemia, which is an interruption in the blood supply to a particular area. Loss of blood supply means loss of oxygen delivery to that tissue, as well as loss of other nutritive factors usually carried in the blood circulation. Tissue deprived in this manner will die, and often becomes infected with bacteria during this process. …
Garpike (gar) are bony fish classified in the family Lepisosteidae. These fish are differentiated from garfish which belong to the family Belonidae. Garpike were once Longnose gar (Lepisosteus osseus). Photograph by Robert J. Huffman. Field Mark Publications. Reproduced by permission. abundant and widely distributed, but are now rare. Some species of garpike are found in Mexico, Central Ame…
Elements are identified by the nuclei of the atoms of which they are made. For example, an atom having six protons in its nucleus is carbon, and one having 26 protons is iron. There are over 80 naturally occurring elements, with uranium (92 protons) being the heaviest (heavier nuclei have been produced in reactors on Earth). Nuclei also contain certain neutrons, usually in numbers greater than the…
A fault is a geologic term describing a fracture at which two bodies of rock have been displaced relative to each other. Bedrock faults are those in which bodies of rock meet; small, local movements may occur on bedrock faults. Much larger movements or displacements occur along Faults where plates of Earth's crust abut each other. Faults may be inches (centimeters) to hundreds of miles (kil…
Fauna is a generic term for the list of animal species occurring in a particular, large region. Fauna can refer to a prehistoric collection of animals, as might be inferred from the fossil record, or to a modern assemblage of species living in a region. The botanical analogue is known as flora. More locally, a faunation refers to the communities of individuals of the various animal species and occ…
The facsimile, or fax, machine is both a transmitting and receiving device that "reads" text, maps, photographs, fingerprints, and graphics and communicates via telephone line. Since 1980s, fax machines have undergone rapid development and refinement and are now indispensable communication aids for news services, businesses, government agencies, and individuals. The fax was invented …
Feather stars, or comatulids, are echinoderms that belong to the class Crinoidea (phylum Echinodermata) which they share with the sea lilies. Unlike the latter group, however, feather stars are not obliged to remain in one place; instead they can swim or even crawl over short distances before attaching themselves to some support. Swimming movements are achieved by waving the arms up and down in a …
Gazelles are medium-sized fawn-colored antelopes found in arid parts of the world, mainly in Ethiopia, Somalia, northern Africa and around the Sahara Desert, parts of the Middle East, India, and Central Asia. Gazelles are horned animals with a four-chambered stomach and cloven hooves. Gazelles are cud chewers (ruminants), and they lack upper canine and incisor teeth. Gazelles tear grass, foliage, …
In its broadest sense, fermentation refers to any process by which large organic molecules are broken down to simpler molecules as the result of the action of microorganisms. The most familiar type of fermentation is the conversion of sugars and starches to alcohol by enzymes in yeast. To distinguish this reaction from other kinds of fermentation, the process is sometimes known as alcoholic or eth…
A gear is a toothed disk attached to a rotating rod or shaft that transmits and modifies rotary motion by working in conjunction with another gear. Usually circular in shape, the protrusions of one gear mesh into the profile of its mate to obtain a predetermined mechanical advantage. For example, if one gear wheel has ten times as many teeth as the wheel that drives it, it will make one tenth of a…
Geckos are small night-lizards found in the tropics and subtropics, and number more than 650 species in the A parachute gecko (Ptychozoon kuhli). Photograph by Tom McHugh. The National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission. family Gekkonidae, divided into four subfamilies (the Diplodactylinae, the Gekkoninae, the Sphaerodactylinae, and the Eublepharinae)…
Geese are large birds in the subfamily Anserinae of the waterfowl family Anatidae, consisting of ducks, geese, and swans. Geese occur in many types of aquatic habitats, on all continents but Antarctica. Most geese breed in freshwater marshes, salt marshes, or marsh-fringed, open-water wetlands. Geese typically winter in those sorts of natural habitats and in estuaries, although in some regions the…
Gelatin is an edible protein made from the skin, bones and ligaments of animals. It is clear, usually colorless or pale yellow, odorless and tasteless, and dissolves in water. The hot solution is liquid, but as it cools, it "gels," forming a semi-solid, which is soft and flexible, yet firm enough to hold any shape into which it may be molded or cut. A familiar example of gelatin is t…
Ferns are plants in the Filicinophyta phylum, also called the Pteridophyta phylum. They are intermediate in complexity between the more primitive (i.e., evolutionarily ancient) bryophytes (mosses, liverworts, and hornworts) and the more advanced (or recent) seed plants. Like bryophytes, ferns reproduce sexually by making spores rather than seeds. Most ferns produce spores on the underside or margi…
A gene is the basic structural unit of inheritance in biological organisms. It is made up of a short segment of DNA and contains the necessary information to produce a specific protein. Each gene is separated from each other by non-coding sequences that serve other functions. Genes are strung together and tightly packed into structures called chromosomes. All the genes in an organism are located o…
Ferrets are small carnivores belonging to the weasel family (Mustelidae). The name is most commonly given to the fitch, or European polecat (Mustela putorius), which has been domesticated and used for hunting rodents and as a pet for hundreds of years. Like most weasels, ferrets are long and slender, and are determined hunters. Their color varies from yellowish to all black, and they are about 2 f…
The Human Genome Project began in 1990, with the goal of sequencing the complete human genome. Although estimates to complete the daunting project initially ranged up to forty years, with advances in technolo gy—including gene chip and microarray technology— Gloved hand holding a device for rapidly analyzing samples of DNA at the scene of a crime. Photograph by Sam Ogden. Photo …
In animals, fertilization is the fusion of a sperm cell with an egg cell. The penetration of the egg cell by the chromosome-containing part of the sperm cell causes a reaction, which prevents additional sperm cells from entering the egg. The egg and sperm each contribute half of the new organism's genetic material. A fertilized egg cell is known as a zygote. The zygote undergoes continuous …
The term mutation was originally coined by Dutch botanist Hugo De Vries (1848–1935) to describe a new approach to explain evolution, although it is quite different than the current definition. De Vries discovered new forms of the Evening Primrose (Oenothera lamarcklana) that were growing in a meadow. He attributed these new varieties and the method for which new species arise to what he cal…
A fertilizer is any substance applied to land to increase plant growth and produce higher crop yield. Fertilizers may be made from organic material, such as animal manure or compost, or it may be chemically manufactured. Manufactured fertilizers contain varying amounts of inorganic nitrogen, phosphorus, and potassium, all of which are nutrients that plants need to grow. Since the 1950s crop produc…
Fetal alcohol syndrome (FAS) represents a preventable pattern of clinical abnormalities that develop during embryogenesis (the developmental stages shortly after conception) due to exposure to alcohol during pregnancy. FAS is currently the leading cause of birth defects and developmental delay, with as many as 12,000 babies born affected in the United States each year. Although the prevalence of F…
American physicist Richard Feynman's (1918–1988), work and writings were fundamental to the development of quantum electrodynamic theory (QED theory). With regard to QED theory, Feynman is perhaps best remembered for his invention of what are now known as Feynman diagrams, to portray the complex interactions of atomic particles. Moreover, Feynman diagrams allow visual representation …
Genes are DNA sequences that code for protein. Gene splicing is a form of genetic engineering where specific genes or gene sequences are inserted into the genome of a different organism. Gene splicing can also specifically refer to a step during the processing of deoxyribonucleic acid (DNA) to prepare it to be translated into protein. Gene splicing can also be applied to molecular biology techniqu…
Optical fiber is a very thin strand of glass or plastic capable of transmitting light from one point to another. Optical fiber can also be called an optical waveguide, since it is a device that guides light. Optical fibers consist of a light-carrying core and a cladding surrounding the core. There are generally three types of construction: glass core/cladding, glass core with plastic cladding, or …
The Fibonacci sequence is a series of numbers in which each succeeding number (after the second) is the sum of the previous two. The most famous Fibonacci sequence is 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89.... This sequence expresses many naturally occurring relationships in the plant world. …
Gene therapy is a rapidly growing field of medicine in which genes are introduced into the body to treat diseases. Gene therapy is the name applied to the treatment of inherited diseases by corrective genetic engineering of the dysfunctional genes. It is part of a broader field called genetic medicine, which involves the screening, diagnosis, prevention and treatment of hereditary conditions in hu…
A field is the name given to a pair of numbers and a set of operations which together satisfy several specific laws. A familiar example of a field is the set of rational numbers and the operations addition and multiplication. An example of a set of numbers that is not a field is the set of integers. It is an "integral domain." It is not a field because it lacks multiplicative inverse…
Figurative numbers are numbers which can be represented by dots arranged in various geometric patterns. For example, triangular numbers are represented by the patterns shown in Figure 1. The numbers they represent are 1, 3, 6, 10, and so on. Figurative numbers also include the square numbers which can be represented by square arrays of dots, as shown in Figure 2. The first few square numbers are 1…
Emphysema is an incurable lung disease that results in the destruction of air sacs in the lungs. It is brought about almost exclusively by smoking. In the past, the majority of its victims were male, but the disease has become more common in women as more women smoke. Emphysema is also called chronic obstructive pulmonary (or lung) disease (COPD or COLD). Chronic bronchitis, that is, inflammation …
A generator is a machine by which mechanical energy is transformed into electrical energy. Generators can be sub-divided into two major categories depending on whether the electric current produced is alternating current (AC) or direct current (DC). The basic principle on which both types of generator works is the same, although the details of construction of the two may differ somewhat. Generator…
Filtration is the process by which solid materials are removed from a fluid mixture, either a gas or liquid mixture. One of the most familiar kinds of filtration is that which students of chemistry encounter in their early laboratory experiences. In these experiences, suspensions of a solid precipitate in water are passed through filter paper supported in a glass funnel. The filter paper traps sol…
An emulsion is a two phase system of immiscible liquids in which one liquid is dispersed in the other in the form of microscopic droplets. This dispersion is achieved through the use of emulsifying agents, known as surfactants, which act as chemical bridges between the two liquids. Emulsions provide a variety of benefits such as the ability to deliver water insoluble active materials from water ba…
The theory of relativity was developed by the German physicist Albert Einstein (1879–1955) in the early twentieth century and quickly became one of the basic organizing ideas of physics. Relativity actually consists of two theories, the special theory (announced in 1905) and the general (1915). Special relativity describes the effects of straight-line, constant-velocity motion on the mass a…
Encephalitis is an inflammatory disease of the brain. It is caused by a virus that either has invaded the brain, or a virus encountered elsewhere in the body that has caused a sensitivity reaction in the brain. Most cases of encephalitis are considered secondary to a virus infection that stimulates an immune reaction. An infection that involves the membranes associated with the spinal cord is call…
Finches are species of arboreal, perching birds that make up the large, widespread family, the Fringillidae. There are three subfamilies in this group, the largest being the Carduelinae or cardueline finches, a geographically widespread group that contains about 122 species. The subfamily Fringillinae or fringillid finches consists of three species breeding in woodlands of Eurasia, while the Drepa…
An endangered species of plant, animal, or microorganism is at risk of imminent extinction or extirpation in all or most of its range. Extinct species no longer occur anywhere on Earth, and once gone they are gone forever. Extirpated species have disappeared locally or regionally, but still survive in other regions or in captivity. Threatened species are at risk of becoming endangered in the fores…
The true firs are about 40 species of conifer trees in the genus Abies, occurring in cool-temperate, boreal, and montane forests of the northern hemisphere. Firs are members of the pine family (Pinaceae). Firs are characterized by flattened needles, usually having two white lines running the length of the leaf. Firs do not have a petiole joining the needles to the twigs, and after the foliage is s…
Endemic is a biogeographic term referring to a distinct race or species that originated in a local place or region, and that has a geographically restricted distribution. Endemic species tend to occur in certain ecological contexts, being especially frequent in places that are ecologically isolated, and that have not been affected by a regional-scale, catastrophic disturbance for a very long time.…
More than three quarters of Earth's surface is covered by salt water; in addition, large areas are inundated with freshwater in the form of lakes, rivers, canals, swamps, and marshes. It is therefore not surprising that animals and plants have undergone a wide radiation in such habitats. One of the most successful groups of animals that have evolved to fill all of these habitats is the fish…
Genetic disorders refer to medical conditions that develop as the result of abnormalities in an individuals genetic material, usually that is inherited. Inheriting or developing a genetic disorder leads to a collection of clinical manifestations known as a syndrome. These clinical manifestations can vary from person to person with the same genetic defect or have similar presentations. …
Flagella are long, thread-like appendages which provide some live single cells with the ability to move, motility. Bacteria which have flagella are either rod or spiral-shaped and are known as bacilli and spirochetes, respectively. Cocci, or round bacteria, are almost all nonmotile. Animal sperm cells also have flagella. However, prokaryotic cells (such as bacteria) have flagella made up of the pr…
Genetic engineering is the alteration of genetic material with a view to producing new substances or creating new functions. The technique became possible in the 1950s, when scientists discovered the structure of DNA molecules and learned how these molecules store and transmit genetic information. Largely as a result of the pioneering work of James Watson and Francis Crick, scientists were able to…
The advent of molecular technologies and the application of genetic identification in clinical and forensic microbiology have greatly improved the capability of laboratories to detect and specifically identify an organism quickly and accurately. In the wake of the 2001 anthrax attacks utilizing the United States mail, a great deal of investigative attention turned to identification of the source o…
The use of genetic information to predict future onset of disease in an asymptomatic (presymptomatic) person is called predictive genetic testing. Every aspect of our being is influenced by both genes and environment. In the future, a strategy for influencing development may be to alter genes. At present, the environment in which genes act can sometimes be changed, and thereby moderate their impac…
Allowing analysis of the light (photons) from excited atoms, flame analysis is a form of atomic emission spectroscopy (AES). German chemist Robert Bunsen's (1811–1999) invention of the Bunsen burner—a tool now commonly used in modern chemistry laboratories—also spurred the development of flame analysis. Working with Gustav Kirchhoff (1824–1887), Bunsen helped to …
While the term genetically modified organisms has arisen within the past decade, humans have for centuries been using microorganisms to make products like beer and cheese, and plants and animals have been carefully bred to improve the quality and quantity of the food supply. The elucidation of the structure of DNA and the development of the discipline of molecular biology has made possible the acc…
Flamingos are five species of large, colorful, very unusual-looking wading birds that encompass the family Phoenicopteridae. The flamingo lineage is ancient, with fossils of these birds being known from the early Tertiary. These birds occur in tropical and temperate regions of Africa, Madagascar, India, southern Europe, Caribbean coasts, highlands of the Andes in South America, and on the Galapago…
Flatfish are a group of mostly saltwater, carnivorous, bottom-dwelling fish in which both eyes are located the same side of the head. The under side of a flatfish is white while the upper side with the two eyes may be brightly colored. Many of these fish can change color to match their surroundings, making them hard to detect. When flatfish hatch, the eyes are located normally on each side of the …
Flatworms are small, multicelled animals with elongated bodies that have clearly defined anterior (front) and posterior (rear) ends. These worms are bilaterally symmetrical, meaning that their two sides reflect each other. They usually have a recognizable head, which houses gravity and light-receptive organs, and eye spots. They lack circulatory and respiratory systems and have only one opening th…
The endocrine system is the body's network of nine glands and over 100 hormones which maintain and regulate numerous events throughout the body. The glands of the endocrine system include the pituitary, thyroid, parathyroids, thymus, pancreas, pineal, adrenals, and ovaries or testes: in addition, the hypothalamus, in the brain, regulates the release of pituitary hormones. Each of these glan…
The phylum Endoprocta is a group of about 60 species that closely resemble moss animals or members of the phylum Bryozoa. With the exception of the genus Urnatella all endoprocts are marine-dwelling species. Like moss animals they are sessile, being attached to a wide range of submerged objects such as rocks, shells, sponges, corals, and other objects. These tiny animals—the largest measure…
Genetics is the branch of biology concerned with the science of heredity, or the transfer of specific characteristics from one generation to the next. Genetics focuses primarily on genes, coded units found along the DNA molecules of the chromosomes, housed by the cell nucleus. Together, genes make up the blueprints that determine the entire development of the species of organisms down to specific …
Endoscopy is the use of a thin, lengthy, flexible scope that can be inserted into the body for the diagnosis and treatment of various conditions. Until the last third of the twentieth century, one of the limiting factors in the treatment of internal injuries or diseases was the need to perform open surgery on the patient. That meant putting him under anesthesia, carrying out the operation, sewing …
The flax plant, genus Linum, family Linaceae, is the source of two important commodities. Linen is a historic, economically important cloth made from the fiber of flax. Linseed oil is obtained from the pressed seeds of the plant. There are about 200 species of Linum. The species that is cultivated most extensively is L. usitatissimum, an annual plant grown for its fiber and seed. Varieties of L. u…
Genets are mongoose-like mammals in the family Viverridae in the order Carnivora. Other members of this family include civets, linsangs, mongooses and the fossa. The genet genus Genetta has three subgenera and nine species. Genets are found in Africa south of the Sahara desert, in the southwestern Arabian Peninsula, and in southern Europe. Genets have a long body, short legs, a pointed snout, prom…
The term endothermic has two distinct meanings, depending on the context in which it is used. In chemistry, endothermic means that a chemical reaction or phase transition absorbs heat. (A phase transition is the transformation of matter from a gas, liquid, or solid into a different one of these states.) In physiology, the term endothermic refers to organisms which metabolically generate heat to ma…
The genome (sometimes spelled geneome) is, in the broadest use of the term, the full set of genes or genetic material carried by a particular organism representing a particular species or population. The size of a genome is usually measured in numbers of genes or base pairs. With the success of the Human Genome Project and other international genome projects and programs, by 2003, scientists have,…
The study of an organism's total complement of genetic material, called its genome, has become indispensable for shedding light on its biochemistry, physiology, and patterns of inheritance. Even more can be gained by comparing the genomes of multiple organisms to discern how their DNA sequences have changed over evolutionary time. This technique has become increasingly valuable with the exp…
A genotype describes the actual set (complement) of genes carried by an organism. In contrast, phenotype refers to the observable expression of characters and traits coded for by those genes. Although phenotypes are based upon the content of the underlying genes comprising the genotype, the expression of those genes in observable traits (phenotypic expression) is also, to varying degrees, influenc…
Fleas are about one thousand species of small insects in the order Siphonaptera, including several hundred species in North America. Adult fleas are external parasites (that is, ectoparasites) of mammals or birds, living on skin or in fur or feathers, and feeding on the blood of their hosts. Some fleas are serious parasites of birds or mammals, and may cause important damage to domestic animals, a…
Rejected by modern science, the geocentric theory (in Greek, ge means earth), which maintained that Earth was the center of the universe, dominated ancient and medieval science. It seemed evident to early astronomers that the rest of the universe moved about a stable, motionless Earth. The Sun, Moon, planets, and stars could be seen moving about Earth along circular paths day after day. It appeare…
Flies belong to the order Diptera, a group that also includes mosquitoes, gnats, and midges. Flies make up the fourth largest order of insects, with about 100,000 species recognized. Dipterans are amongst the most advanced insects in terms of morphology and biological adaptations. Their versatility and extreme range of anatomical and behavioral adaptations have enabled them to thrive in almost eve…
Geochemical analysis is the process through which scientists discover and unravel the chemical compounds that make up the earth, its atmosphere, and its seas. The process requires a thorough grounding in chemistry and the earth sciences, and an understanding of the different ways elements can interact in a given geologic situation. Geochemical analysis can predict where petroleum, metals, water, a…
Energy is a state function commonly defined as the capacity to do work. Since work is defined as the movement of an object through a distance, energy can also be described as the ability to move an object through a distance. As an example, imagine that a bar magnet is placed next to a pile of iron filings (thin slivers of iron metal). The iron filings begin to move toward the iron bar because magn…
Ratites are flightless birds that lack the keel (high ridge) on the breastbone to which the flight muscles of flying birds are attached. Instead, the entire breastbone looks rather like a turtle's shell. It has also been described as a raft, which gives this group of flightless birds its name, Ratitae (Ratis means raft in Latin). Ratites have heavy, solid bones, while flying birds have ligh…
Geochemistry is the science or study of the chemistry of the earth. Geochemists who practice this science are interested in the origin of chemical elements, their evolution, the classes and many divisions of minerals and rocks and how they are created and changed by earth processes, and the circulation of chemical elements through all parts of the earth including the atmosphere and biological form…
Geodes are hollow rock masses that are lined with crystals that have grown toward the center of the cavity. Geodes are usually roughly spherical in shape, up to 12 A blue geode. © Royalty-Free/Corbis. Reproduced by permission. in (30 cm) or more in diameter. Most frequently, the crystals growing within a geode are quartz, calcite, or fluorite, though occurrences of other minerals are …
An energy budget describes the ways in which energy is transformed from one state to another within some defined system, including an analysis of inputs, outputs, and changes in the quantities stored. Ecological energy budgets focus on the use and transformations of energy in the biosphere or its components. Solar electromagnetic radiation is the major input of energy to Earth. This external sourc…
A geodesic is the shortest path between two points along a surface. On a plane, it is the straight line segment joining the two points. On a sphere, it is the shorter arc of a great circle joining the two points. …
A geodesic dome is a spherical building in which the supporting structure is a lattice of interconnecting tetrahedrons (a pyramid with three sides and a base) and octahedrons (an eight sided figure—two pyramids with four sides and a base, placed base to base). The first contemporary geodesic dome on record is Walter Bauersfeld's, who realized the utility of projecting the constellati…
Earth's geographic poles are fixed by the axis of Earth's rotation. On maps, the north and south geographic poles are located at the congruence of lines of longitude. Earth's geographic poles and magnetic poles are not located in the same place – in fact they are hundreds of miles apart. As are all points on Earth, the northern magnetic pole is south of the northern geo…
Geologic maps are graphical representations of rocks, sediments, and other geologic features observed or inferred to exist at or beneath Earth's surface. They can be based on observations of outcrops in the field, interpretation of aerial photographs or satellite images, and information obtained during the drilling of exploratory boreholes. Outcrops can be obscured, particularly in areas co…
Flooding, although it usually carries a negative connotation, is quite a natural process and is simply the response of a natural system (a river system) to the presence of too much water during an interval of time. Rivers and streams are governed by a simple equation, Q = A × V, where Q is discharge (amount of water), A is area of the river channel, and V is velocity. When excess discharge …
Flora is a word used to describe the assemblage of plant species that occurs in some particular area or large region. Flora can refer to a modern assemblage of plant species, or to a prehistoric group of species that is inferred from the fossil record. The zoological analogue is known as a fauna, although this word is usually used in reference to a large region. More locally, "vegetation&#x…
Although historical time covers centuries, and archeological times covers millennia, geologic time describes the immense span of time—billions of years—revealed in the fossil and rock record of Earth. Geochronology is the science of finding out how old rocks and minerals are. Absolute time and relative time are terms used to describe the age of rocks and events used by geologists. Ra…
Geology is the study of Earth. Modern geology includes studies in seismology (earthquake studies), volcanology, energy resources exploration and development, tectonics (structural and mountain building studies), hydrology and hydrogeology (water-resources studies), geologic mapping, economic geology (e.g., mining), paleontology (ancient life studies), soil science, historical geology and stratigra…
Energy efficiency refers to any process by which the amount of useful energy obtained from some process is increased compared to the amount of energy put into that process. As a simple example, some automobiles can travel 40 mi (17 km) by burning a single gallon (liter) of gasoline, while others can travel only 20 mpg (8.5 km/l). The energy efficiency achieved by the first car is twice that achiev…
A flower is the reproductive structure of an Angiosperm plant. Flowers have ovaries with ovules that develop into fruits with seeds. There are over 300,000 species of Angiosperms, and their flowers and fruits vary significantly. Flowers and fruits are among the most useful features for the identification of plant species and determination of their evolutionary relationships. …
Energy transfer describes the changes in energy (a state function) that occur between organisms within an ecosystem. Living organisms are constantly changing as they grow, move, reproduce, and repair tissues. These changes are fueled by energy. Plants, through photosynthesis, capture some of the Sun's radiant energy and transform it into chemical energy, which is stored as plant biomass. Th…
Engineering is the art of applying science, mathematics, and creativity to solve technological problems. The accomplishments of engineering can be seen in nearly every aspect of our daily lives, from transportation to communications, and entertainment to health care. And, although each of these applications is unique, the process of engineering is largely independent. This process begins by carefu…
Fluid dynamics is the study of the flow of liquids and gases, usually in and around solid surfaces. The flow patterns depend on the characteristics of the fluid, the speed of flow, and the shape of the solid surface. Scientists try to understand the principles and mechanisms of fluid dynamics by studying flow patterns experimentally in laboratories and also mathematically, with the aid of powerful…
Fluid mechanics is the study of gases and liquids at rest and in motion. Fluid statics studies the behavior of stationary fluids and tells us, for instance, how much air to put in our tires and whether a boat in a lake will float or sink. Fluid dynamics studies the flow behavior of moving fluids. Both global weather patterns and the flow of water from a faucet are governed by the laws of fluid dyn…
Engraving and etching are processes used to make intaglio prints. An intaglio print is made from a plate, usually a metal one, which has been had lines drawn into its surface. These lines trap ink when the ink is rolled across the surface of the plate. When the surface of the plate is wiped with a cloth, the lines retain their ink. A piece of damp paper is placed on the plate, and the two are run …
Fluorescence is the process by which a substance absorbs electromagnetic radiation (visible or invisible light) from another source, then re-emits the radiation with a wavelength that is longer than the wavelength of the illuminating radiation. It can be observed in gases at low pressure and in certain liquids and solids, such as the ruby gemstone. Fluorescence is the principle that is the basis o…
Fluorescent in situ hybridization (FISH) is a powerful technique for detecting RNA or DNA sequences in cells, tissues, and tumors. FISH provides a unique link among the studies of cell biology, cytogenetics, and molecular genetics. Fluorescent in situ hybridization is a technique in which single-stranded nucleic acids (usually DNA, but RNA may also be used) are permitted to interact so that comple…
Enterobacteria are bacteria from the family Enterobacteriaceae, which are primarily known for their ability to cause intestinal upset. Enterobacteria are responsible for a variety of human illnesses, including urinary tract infections, wound infections, gastroenteritis, meningitis, septicemia, and pneumonia. Some are true intestinal pathogens; whereas others are merely opportunistic pests which at…
Entropy is a physical quantity that is primarily a measure of the thermodynamic disorder of a physical system. Entropy has the unique property in that its global value must always increase or stay the same; this property is reflected in the second law of thermodynamics. The fact that entropy must always increase in natural processes introduces the concept of irreversibility, and defines a unique d…
Fluorescent light is the most common type of electrical light found in the United States; it is used for practically all commercial lighting, i.e. offices, factories, stores and schools, and it is estimated that there are 1.5 billion fluorescent lamps in use nationwide. Fluorescent lighting is popular due to its high efficacy, i.e. it produces between three to five times more light than an incande…
Ethics is a branch of philosophy that primarily discusses issues dealing with human behavior and character. Ethics attempts to establish a basis for judging right from wrong and good from bad. Environmental ethics employs concepts from the entire field of philosophy, especially aesthetics, metaphysics, epistemology, philosophy of science, and social and political philosophy in an effort to relate …
Fluoridation consists of adding fluoride to a substance (often drinking water) to reduce tooth decay. Fluoridation was first introduced into the United States in the 1940s in an attempt to study its effect on the reduction of tooth decay. Since then many cities have added fluoride to their water supply systems. Proponents of fluoridation have claimed that it dramatically reduced tooth decay, which…
The ancient Roman conception of empire differed from the Greek. The term came from the Roman concept of imperium, meaning jurisdiction or lawful authority. A Roman official who ruled a subject population or who commanded troops possessed imperium, an authority symbolized by the fasces, which was borne as a sign of authority before the consuls who ruled Rome. The fasces, a band of rods bound around…
An empire presupposes an unequal relationship between an elite of an ethnicity, or polity and the peoples of a dependent and subservient ethnicity or polity, the periphery, on issues such as service or tribute and dominant language and culture, as shown by unequal material or service exchanges and the spread of art styles, architectural forms, and politico-religious practices. The Americas have a …
In the United States, the National Environmental Policy Act (NEPA) requires federal agencies to file an Environmental Impact Statement (EIS) for any major project or legislative proposal that may have significant environmental effects. According to the U.S. Environmental Protection Agency (EPA), "NEPA requires federal agencies to integrate environmental values into their decision making pro…
Flying fish belong to the family Exocoetidae in the bony fish order Atheriniformes. They are close relatives of the needlefish, halfbeaks, and sauries. Flying fish are characterized by a low lateral line, soft fins without spines, and a caudal fin with the lower lobe larger than the upper lobe. The lower jaw of the young flying fish has an extended filament longer than the body, which becomes deta…
While this was going on, the rest of the Asian landmass to the Urals and the Caucasus was dominated by four other powerful and expanding empires: Mughal India in the south, Safavid Iran in the southwest, Ottoman Turkey and the Middle East in the west, and Romanov Russia in the central region and the north. The last was led by Russian-speaking Slavs from northeastern Europe, but the other three sha…
The introduction of the techniques of modern molecular biology, beginning in the 1970s, have made possible the genetic engineering of proteins. New proteins can be created and existing proteins altered. Enzymes are proteins that function in chemical reactions by making the reaction occur more easily than if the enzyme was absent. Enzymatic engineering includes a wide variety of techniques related …
Focused ion beams have been used since the 1960s to investigate the chemical and isotopic composition of In addition to precise imaging, FIB technology can be used in a variety of manufacturing environments requiring high levels of precision and accuracy. The image above, using time-lapse, shows a computer-controlled ion beam helping shape a mirror for the Keck telescope. © Roger Ressmey…
Few subjects have generated as much controversy as that of European imperialism in the nineteenth and twentieth centuries. Because of the term's pejorative connotations, even attempting to define it causes difficulties. What, precisely, constitutes an empire? Is any relationship between two societies involving an imbalance of power in some way "imperial"? For many years, imper…
In the modern era, the Middle East, broadly defined to include North Africa, was the seat of a major empire, that of the Ottoman Turks. Ottoman rule at its height dominated Eastern Europe through Hungary and extended across the Middle East and North Africa to include Algeria, with Iran and Morocco excluded from Turkish authority. …
The question of whether the United States is an imperial power that, like other previous imperial powers, has been acquiring an empire of its own has been hotly contested in U.S. political history. On the one hand, the United States likes to think of itself as different from other powers in the past who have acquired empires, because its motives are supposedly superior (democracy, human rights, a…
Empiricism is a family of theories of knowledge (epistemology) claiming that all knowledge about the extant universe is based on experience, primarily on perception via the five senses. Some empiricists add introspection, a moral sense, or a special sensitivity to religious or aesthetic experience. Strong empiricists claim that all knowledge whatever derives from experience. They must show how emp…
Encyclopedism is not restricted to the history of encyclopedias as we now know them. Certainly, since the eighteenth century, this identification has been the dominant one; however, the term encyclopedism is best seen as a heuristic device that can legitimately be applied to other intellectual projects. Three main forms of encyclopedism can be discerned: first, the classical Greek and Roman notion…
Fog is caused by the condensation of water at or near Earth's surface. The atmosphere is obscured—essentially by cloud formation—near the surface and fog conditions are generally characterized as existing when atmospheric visibility is reduced to about one-half mile (approximately 0.8 km). Precipitation fog is a type of evaporation fog that happens when relatively warm rain or…
In the years since the publication of the first Dictionary of the History of Ideas, the Enlightenment has become an increasingly fragmented and decreasingly coherent historical rubric. In fact that fragmentation began in the Dictionary of the History of Ideas itself, in an article titled "Counter-Enlightenment," written by Isaiah Berlin and categorized out of alphabetical order, appe…
A fold is a bend in a body of rock or sediment that forms due to a change in pressure. Wave-like folds are composed of layers of the earth's crust that bend and buckle under enormous pressure as the crust hardens, compresses, and shortens. Folds form much the same way as a hump arises in a sheet of paper pushed together from both ends. Folds may be softly rolling or severe and steep, depend…
The term environment became specialized beginning in about the 1960s to designate the context of human and animal groups, with a special emphasis on the natural world and its physical and vegetal components. Within this framework, the word took on an even more limited meaning and in the early twenty-first century refers primarily to the interaction between human and animal activity on the one hand…
Enzymes are biological catalysts, agents which increase the rate of chemical reactions without being used up in the reaction. They are proteins which possess special binding sites for a certain biochemicals. Weak binding interactions with the biochemical allow enzymes to accelerate specific reaction rates millions of times. Enzyme kinetics is the study of enzyme reactions and mechanisms. Enzyme in…
Environmental ethics emerged as a subdiscipline of philosophical ethics in the early 1970s, following the first Earth Day in 1970 and a sharply increased awareness of environmental problems at that time. Courses began appearing in university curricula, and books, articles, and journals proliferated to meet the growing interest. To judge by student demand and university courses and programs, enviro…
An epidemic is an outbreak of a disease among members of a specific population that exceeds the extent of occurrence of the disease normally found in that population. Epidemics affect those members of the population who do not have an acquired or inherent immunity to the disease. Although most epidemics are caused by infectious organisms, the term can be applied to an outbreak of any chronic disea…
Environmental history is the study of the changing affairs of humans within the natural world. This definition, in contrast to other useful phrasings, such as the study of "interactions between humans and nature" (Merchant, 2002, p. xv), embodies a fundamental, not merely semantic, point of emphasis. First, and obviously, humans are part of nature, biological organisms subject to the…
Epidemiology is the study of the occurrence, frequency, and distribution of diseases in a given population. As part of this study, epidemiologists—scientists who investigate epidemics (widespread occurrence of a disease that occurs during a certain time)—attempt to determine how the disease is transmitted, and what are the host(s) and environmental factor(s) that start, maintain, and…
While Epicureanism is not strictly an ethical theory, it has been most influential in the field of ethics. Epicurus emphasized empiricism, and his theories were foundationalist in the sense that he believed all sense perceptions were true (Inwood and Gerson, A53.63). In keeping with this, he denied that a theory of meaning was possible. Rather, we come to a "basic grasp" (prolepsis)…
Many ancient cultures had sophisticated methods for organizing knowledge. However, systematic, self-conscious reflection on the nature of knowledge itself appears to have originated in Greek philosophy. …
Modern philosophy is generally thought to be distinguished by an "epistemological turn." Prior philosophical tradition accorded special status to metaphysics, or "first philosophy" (the general philosophical investigation into the nature of reality). The modern tradition, by contrast, holds that it is necessary to determine the nature and bounds of human knowledge befor…
The understanding of knowledge at work, implicitly or explicitly, in much of ancient and modern epistemology is that of knowledge as justified true belief. According to this traditional account (TAK), a subject, S, knows that p if and only if the following three conditions are met: (i) p is true; (ii) S believes that p; (iii) S is justified in, or has adequate evidence for, believing that p. While…
Though the cause of epilepsy remains unknown, the manner in which the condition is demonstrated indicates the area of the brain that is affected. Jacksonian seizures, for example, which are localized twitching of muscles, originate in the frontal lobe of the brain in the motor cortex. A localized numbness or tingling indicates an origin in the parietal lobe on the side of the brain in the sensory …
A food chain is a series of organisms dependent on each other for food; a food web is an interconnected set of food chains in the same ecosystem. Organisms that eat similar foods are assigned to a particular trophic level, or feeding level, within a food web. Food web is a more accurate term because food chains only exist on paper. In nature feeding habits are complex because many organisms feed o…
Though simple as a mathematical concept, equality is complex and contested as a political goal and philosophical concept. Many political struggles, both historical and ongoing, have engaged in the contests over the nature of equality. This contestation revolves around the basic question, What kinds of equality matter? The answer to this in part depends on whether the topic is approached from a pre…
An episome is a portion of genetic material that can exist independent of the main body of genetic material (called the chromosome) at some times, while at other times is able to integrate into the chromosome. Examples of episomes include insertion sequences and transposons. Viruses are another example of an episome. Viruses that integrate their genetic material into the host chromosome enable the…
The coupling of equality and gender may indicate a paradox, if not an oxymoron. If equality were to exist, would gender? Does the persistent salience of the idea of gender with regard to equality provide evidence of fundamental flaws or contradictions in theories and practices of equality? Can the pursuit of equality reproduce rather than undermine gender dominance? While these questions are centr…
Racial equality is the belief that individuals, regardless of their racial characteristics, are morally, politically, and legally equal and should be treated as such. Furthermore, it is the belief that different racial groups, as groups, are equal, with none being inherently superior or inferior in intelligence, virtue, or beauty. In the United States the term is commonly linked to the belief in e…
Food irradiation refers to a process where food is exposed to a type of radiation called ionizing radiation. The high-energy of the radiation, which can come from a radioactive or a non-radioactive source, breaks apart the genetic material of microorganisms that are on the surface of the food. Microorganisms and other surface contaminants, including insects, are killed as a result. This scrutiny o…
The concept of eschatology was created by the Lutheran theologian Abraham Calov (1612–1686) and became popular through the works of the Prussian Reformed theologian F. D. E. Schleiermacher (1768–1834). It is derived from a sentence in Jesus Sirach: "In whatever you do, remember your last days [Greek: ta eschata ], and you will never sin" (Sir. 7:36). Calov's conc…
Food poisoning refers to an illness that is caused by the presence of bacteria, poisonous chemicals, or another kind of harmful compound in a food. Bacterial growth in the food is usually required. Food poisoning is different from food intoxication, which is the presence of preformed bacterial toxin in food. There are over 250 different foodborne diseases. The majority of these are infections, and…
Essentialism is a response to problems of recognition and meaning. Amid all the variety of empirical experience and the multiple forms that objects assume, how do we recognize many differently appearing things as instances of the same phenomenon? Where do the categories in and through which we organize empirical experience come from? As the Scottish philosopher David Hume (1711–1776) and ot…
Epstein-Barr virus (EBV) is part of the family of human herpes viruses. Infectious mononucleosis (IM) is the most common disease manifestation of this virus which, once established in the host, can never be completely eradicated. Very little can be done to treat EBV; most methods can only alleviate resultant symptoms. Sleep and rest—complete bedrest in severe cases—is still the best …
There is an abiding paradox in the concept of race. It is a biological fiction but a social reality. Biologically it is now established beyond doubt that there are no distinct races among human beings and that the genetic variation within particular groups of people is much higher than between groups. The view that people possess inherent personality characteristics attached to particular irreduc…
Ethnicity, as defined in the public domain, is "the cultural characteristics that connect a particular group or groups of people to each other" (http://en.wikipedia.org/wiki/Ethnicity). Twenty-first-century anthropologists, however, are likely to complicate simple notions of ethnicity, or they might refuse to accept a general definition of the concept without first demanding accounts…
The Koran makes only passing reference to racial or ethnic categories. One verse refers to "the variety of your tongues and hues" as one of the many signs of God's divine power (30:22). Another proclaims the primacy of piety over racial or tribal distinction: "O mankind, we have created you male and female, and appointed you races and tribes, so that you may know one an…
Ethnocentrism is a notion not widely used in the early twenty-first century. Coined by William Graham Sumner in the early twentieth century, the term owes what conceptual life it has to the likes of anthropology and intercultural communication. Dominant strains of these disciplines, especially anthropology, have examined the lives and cultural expressions of ethnically defined or identified groups…
Ethnography, often paraphrased as "participant observation," is a mode of deriving knowledge about particular, local worlds through direct engagement with their peoples and ways of life. As a mode of inquiry, it is primarily associated with the discipline of anthropology, the comparative study of human societies and cultures that took definitive shape as a scholarly field in the earl…
Ethnohistory, first used in Vienna in the 1930s by ethnologist Fritz Roack and the Viennese Study Group for African Cultural History, and a subfield of anthropology, is the use of ethnological and historical methods and materials to gain knowledge of the nature and causes of change in a culture defined by ethnological concepts and categories. This definition, as the ethnohistorian Robert C. Euler …
The term food preservation refers to any one of a number of techniques used to prevent food from spoiling. It includes methods such as canning, pickling, drying and freeze-drying, irradiation, pasteurization, smoking, and the addition of chemical additives. Food preservation has become an increasingly important component of the food industry as fewer people eat foods produced on their own lands, a…
Though the Middle Ages in Europe witnessed the harnessing of knights to a code of chivalry and the flourishing of a romance troubadour culture demanding particular rules of conduct, it was the Renaissance that brought social codes and conventions to new heights of importance. Courts now served elites and sycophants as thriving centers of power, requiring the ability to fashion one's identit…
The Latin meaning of equinox is "equal night," the times of the year when day and night are equal in length. In astronomy, the equinox is the point at which the Sun appears to cross the equator as a result of Earth's rotation around the Sun. The vernal equinox, which occurs as the Sun moves from south to north across the equator, takes place around March 21 and marks the begin…
The term eugenics, derived from the Greek eugenes, was first coined by the English mathematician and geographer Francis Galton (1822–1911) in his Inquiries into Human Faculty and Its Development (1883) to refer to one born "good in stock, hereditarily endowed with noble qualities." As an intellectual and social movement in the early twentieth century, eugenics came to mean, in…
The food pyramid was developed by the U.S. Department of Agriculture (USDA) as a nutrition guide for healthy persons over the age of two years. The guide stresses eating a wide variety of foods from the five major food groups while minimizing the intake of fats and sugars. The daily quantity of foods from each group is represented by the triangular shape. The pyramid is composed of four levels. Th…
Eurocentrism refers to a discursive tendency to interpret the histories and cultures of non-European societies from a European (or Western) perspective. Common features of Eurocentric thought include: Although Eurocentrism has been common through the ages, it has not been constant, nor has it affected the way Europeans have viewed all non-European societies equally. Moreover, Europeans have not al…
In classical times Europe was above all a geographical and mythological notion, the word referring to one of the three known continents—Asia and Africa (or Libya) being the other two. In the famous story of "the rape of Europa," the daughter of Phoenix, king of Phoenicians, was kidnapped and abducted by the Greek god Zeus, who in the guise of a white bull brought her to the is…
When everyday life was first considered a proper subject for reflection it is obviously impossible to say, but an increasing interest in the subject can be traced over the last few centuries, at least in the West. Mystics have long regarded everyday things and everyday routines as a way to become closer to God. From the fifteenth century onward, painters in the Netherlands in particular paid more …
Foot and mouth disease is caused by a particular type of virus. The disease affects cloven hooved animals; that is, animals with hooves that are split into two main segments. Examples of domestic cloven hooved animals include cattle, sheep, pigs, and goats. Wild cloven hooved animals that are susceptible to foot and mouth disease include elephants, hedgehogs, and rats. Foot and mouth disease occur…
The descriptive-normative term evil is a significant anomaly in our relativistic and noncognitivist age. Otherwise careful thinkers deploy it as if its extension were obvious and indisputable. And yet it is used in widely differing ways even in our own time. A narrow meaning confines it to the deliberate infliction of harm. This corresponds to only part of the so-called problem of evil, and it is …
Force is the term used for an outside influence exerted by one body on another which produces a change in state of motion or state of configuration. This limited meaning in science compared to our everyday usage is most important because of the specific results of this out-side influence. Force producing a change in state of motion gives a body acceleration. If forces acting on a body produces no …
Although it can encompass cosmic and cultural change, evolution is a term usually associated with the modern scientific theory of species change and is most closely associated with the work of Charles Darwin (1809–1882) and, to a lesser extent, Alfred Russel Wallace (1823–1913). Darwin himself did not refer to his specific theory as "evolution" but instead used the phra…
Civil examinations in late imperial China (1400–1900) intersected with politics, society, economy, and Chinese intellectual life. Both local elites and the imperial court influenced the dynastic government to reexamine and adjust the classical curriculum and to entertain new ways to improve the system for selecting officials. As a result, civil examinations represented a test of educational…
Existentialism is a philosophical movement that became associated with the philosophy of Jean-Paul Sartre (who rejected the name as too confining) and whose roots extend to the works of Søren Kierkegaard and Martin Heidegger. Sartre, like most of his existentialist colleagues, was too much the individualist to accept the idea of being part of a movement, no matter how exclusive. Both Heidegge…
This entry traces the life of experiment from its emergence in the early seventeenth century to its transformation to a collective activity after World War II. The topics discussed include the rise of experimental philosophy and its institutional expression in the new scientific societies of the seventeenth century; the spread and character of experimentation in the eighteenth century; the quest f…
Erosion is a group of processes that, acting together, slowly decompose, disintegrate, remove, and transport materials on the surface of Earth. Among geologists, there is no general agreement on what processes to include as a part of erosion. Some limit usage to only those processes that remove and transport materials. Other geologists also include weathering (decomposition and disintegration). Th…
Of all the "isms" in the early twentieth century, Expressionism is one of the most elusive and difficult to define. Whereas, on the one hand, Expressionism has been said to reveal its "universal character," abandoning all theories that imply a narrow, exclusive nationalistic attitude, on the other, it has been considered a "specific and familiar constant in Germa…
Forensic science reflects multidisciplinary scientific approach to examining crime scenes and in examining evidence to be used in legal proceedings. Forensic science techniques are also used to verify compliance with international treaties and resolutions regarding weapons production and use. Forensic science techniques incorporate techniques and principles of biology, chemistry, medicine, physics…
The term extirpation is most commonly associated with the Catholic Church's project to eradicate traditional religious practices in the Americas after the Spanish conquest. The Andean highlands, Mesoamerica, and other areas of high indigenous cultural development have rich religious traditions that predate the Spanish conquest by millennia. Ending these practices became an early and determi…
Error is the amount of deviation in a physical quantity that arises as a result of the process of measurement or approximation. Another term for error is uncertainty. Physical quantities such as weight, volume, temperature, speed, or time must all be measured by an instrument of one sort or another. No matter how accurate the measuring tool—be it an atomic clock that determines time based o…
Early mountaineers from India named the Himalayas "snow abode" based on two Sanskrit words hima and laya. These early climbers were attracted to the mountains by the same features that, today, challenge climbers from all over the world. The range includes the highest peaks in the world, notably Mount Everest; glaciated valleys and snow that never melts create unsurpassable vistas; an…
It is standard practice to distinguish formal and informal fallacies. Formal fallacies break one or more of the rules of a system of logic and can be seen when an argument is presented in either schematic form or in a natural language. Informal fallacies, by contrast, can often only be seen when the argument is presented in natural language, since they depend often on ambiguity or some other misus…
Escherichia coli is one of the most well-known and intensively studied bacteria. Often shortened to E. coli, the bacterium was discovered in 1885 by the German bacteriologist Dr. Theodor Escherich. Initially, the bacterium was termed Bacterium coli, but later the name was changed to honor Dr. Escherich. Escherichia coli inhabits the intestinal tract of humans and other warm-blooded mammals. It con…
Karl Popper (1902–1994) made falsifiability the key to his philosophy of science. It became the most commonly invoked "criterion of demarcation" of science from nonscience. According to the simple, hypothetico-deductive (H-D) model of scientific inquiry, a law claim, theory, or hypothesis H is falsifiable when a potentially checkable prediction O can be logically deduced from …
Ester is an organic functional group that forms many sweet-smelling compounds. The chemical structure of an ester is represented by the general formula, R-CO-OR', where a central carbon atom that has two bonds to an oxygen atom (the carbonyl group), C=O, a single bond to another carbon atom represented by R, and a single bond to an oxygen atom connected to a carbon atom represented by R�…
In their efforts to bring some analytical rigor to the study of this confusing but important concept, anthropologists have come to speak not of "the family" but of "kinship," a larger, more inclusive category that can refer to any and all of the ways in which we find or forge relationships between ourselves and others, although it is usually confined to those relationsh…
Esterification is the chemical process for making esters, which are compounds of the chemical structure R-COOR', where R and R' are either alkyl or aryl groups. The most common method for preparing esters is to heat a carboxylic acid, R-CO-OH, with an alcohol, R'-OH, while removing the water that is formed. A mineral acid catalyst is usually needed to make the reaction occur a…
Until the last decades of the twentieth century, anthropological definitions of the family were heavily influenced by largely unexamined Western cultural assumptions about biology and its relationship to kinship. Indeed, disentangling the history of family studies from kinship studies in anthropology is very difficult because, among researchers, kinship early on became the basis for understanding …
Forestry is the science of harvesting, planting, and tending trees, within the broader context of the management of forested landscapes. Traditionally, forestry has focused on providing society with sustainable yields of economically important products, especially wood for the manufacturing of lumber or paper, or for the generation of energy. Increasingly, however, forestry must consider other, no…
Family planning refers to the use of modern contraception and other methods of birth control to regulate the number, timing, and spacing of human births. It allows parents, particularly mothers, to plan their lives without being overly subject to sexual and social imperatives. However, family planning is not seen by all as a humane or necessary intervention. It is an arena of contestation within b…
For the purposes of this article, fascism will be treated as a politicized and revolutionary form of ultranationalism bent on mobilizing all remaining "healthy" social and political energies to resist the perceived onslaught of decadence so as to achieve the goal of a regenerated national community. It is a project that involves the rebirth (palingenesis) of both the political system…
Fatalism is the thesis that whatever happens must happen. This is not to be confused with the completely innocuous idea that whatever happens, happens. Nor is fatalism to be conflated with the proposition that, necessarily, whatever happens happens, where this assertion simply expresses the tautologous nature of the prior innocuous idea. Fatalism is a substantive thesis that claims that the occurr…
Feminism may broadly be defined as a movement seeking the reorganization of the world upon the basis of sex equality, rejecting all forms of differentiation among or discrimination against individuals upon grounds of sex. It urges a worldview that rejects male-created ideologies. At another level, it is also a mode of analysis and politics, committed to freeing all women of gender-based oppression…
Ethanol is an alcohol fuel that is manufactured by fermenting and distilling crops with a high starch or sugar content, such as grains, sugarcane, or corn. In the energy sector, ethanol can be used for space and water heating, to generate electricity, and as an alternative vehicle fuel, which has been its major use to date. Worldwide, ethanol is the mostly widely used alternative liquid fuel. Etha…
Feminism is broadly defined as the struggle for the liberation of women, and encompasses epistemologies, methodologies, theories, and modes of activism that seek to bring an end to the oppression and subordination of women by men. An individual person espousing feminism is referred to as a feminist, while collective mobilizations of women against the oppression of women are referred to as feminist…
Ether was first used as an anesthetic to kill pain by W. T. G. Morton (1819-1868), a Boston dentist. Morton had learned about ether from a chemist named Charles T. Jackson (1805-1880). Eventually Morton convinced Dr. J. C. Warren (1778-1856) to let him use ether as an anesthetic on one of his patients. In Massachusetts General Hospital on October 16, 1846, Morton put a Mr. Abbott to sleep with eth…
A forest is any ecological community that is structurally dominated by tree-sized woody plants. Forests occur anywhere that the climate is suitable in terms of length of the growing season, air and soil temperature, and sufficiency of soil moisture. Forests can be classified into broad types on the basis of their geographic range and dominant types of trees. The most extensive of these types are b…
There are many definitions of feminism, and many scholars now assert that the word should be used in its plural form to encompass women's various social locations. As such, Chicana feminisms address the specific historical, economic, and social experiences of women of Mexican descent in the United States. The field of Chicana feminisms developed within the context of feminist movements in t…
Ethnoarchaeology, a subfield of archaeology, is the study of contemporary cultures in order to interpret social organization within an archeological site. Traditionally, archaeology has been concerned with the identification, classification, and chronological ordering of remains. Archaeologists were able to describe a civilization according to its artifacts, but not to fully understand its culture…
The term Islamic feminism was first used in the 1990s. It is not certain who coined the term. Nor is it evident that those who first used it were aware of the explosive impact that the juxtaposition of these two words was to have. Rather than imagining and promoting a revolution in the heart of Islam, these women in Saudi Arabia, South Africa, and some Asian Muslim communities were merely describi…
Historically, women's participation in revolutionary struggles or mass sociopolitical movements has been linked with the development of a feminist consciousness. Studies of women involved in revolutionary movements, such as the Chinese, Cuban, Mexican, and Nicaraguan revolutions, document the origins of feminist movements within the context of male-dominated nationalist struggles. Women may…
Since the seventeenth century, thought about fetishism has been concerned with four overriding questions, all of them emerging in conflicts over representation that arose at the borders between cultural and historical worlds. These four questions concern the relationship between images and their referents in religious discourse; the attribution of causality and the nature of reason; the means for …
Fetishism is a term widely disseminated in literary and cultural studies. It carries a variety of generic meanings. Most of these derive to some degree from Marxist and psychoanalytic discourses, where the term fetishism has technical significance. …
In everyday speech, f eudal can mean "aristocratic" (in contrast to democratic), "sumptuous," "reactionary," "hierarchic" (as opposed to egalitarian), "primitive," "medieval," or simply "despotic" or "oppressive" when speaking about political, social, or economic regimes. Since the ninet…
Ethnobotany is the study of the relationships between plants and people. Most often, however, the term is used in relation to the study of the use of plants by aboriginal people living relatively simple, pre industrial lifestyles. Plants have always played a central role within indigenous cultures. Plant products are used as food, as sources of medicine, and as raw materials for the weaving of fab…
Fossas are cat-like Madagascan carnivores in the family Viverridae, which also includes civets, linsangs, genets, and mongooses. Fossas are quite different from other viverrids and are the sole members of the subfamily Cryptoproctinae. They are the largest Madagascan carnivores, measuring 24-30 in (60-75 cm) long. With a number of cat-like features-including a rounded head, long whiskers, large fr…
In physics, the field concept describes the distribution and propagation of effects such as magnetism and gravity through space. Field theories have helped implement the program of unifying the "forces" of nature. …
Ethane is a gas at room temperature and burns very easily. The word ethane is derived from aithein, the Greek word for to blaze or to kindle. Ethane makes up about 15% of natural gas and can also be isolated from crude oil. It is used by industries for the production of ethylene and ethyl chloride. The incorporation of an ethyl group or chain of two carbon atoms into a molecule's structure …
The metaphysical notion of form (eidos, morphe, Gr.; idea, forma, species, Lat.), as it emerged in the works of Plato, must be carefully distinguished from the everyday notion from which it derived, namely, the shape or outer appearance of a thing as it presents itself to the eyes. The outer appearance of a mannequin, for instance, may be deceptively similar to that of a human being, yet, the form…
Ethylene glycol is an organic (carbon based) molecule most widely used as antifreeze in automobile engines and as an industrial solvent, a chemical in which other substances are dissolved. The addition of ethylene glycol to water raises the boiling point of the engine coolant and reduces the chances of a car's radiator "boiling over." The name ethylene glycol communicates much…
Formalism in literary studies was not merely about formal elements of literature, though it stressed the importance of studying form. In fact, it proclaimed the unity of form and content by emphasizing that in a literary work the former cannot properly be understood when separated from the latter and vice versa. At the same time, formalism stressed the need to view literature as an autonomous verb…
Ethylenediaminetetra-acetic acid, typically shortened to EDTA, is a chemical compound with the ability to form multiple bonds with metal ions, making it an important chemical to analytical scientists and industry alike. The compounds used to create EDTA include ethylenediamine, formaldehyde, and sodium cyanide. When these compounds are mixed in an appropriate fashion, a series of chemical reaction…
When reasons are beliefs, we have inferential justification: one belief is justified on the basis of another belief. How is the latter, supporting belief itself justified? Is another supporting belief always needed? According to foundationalism, another supporting belief is not always needed. …
Etiology is study of the cause of disease. More specifically, etiology is the sum of knowledge regarding a disease, or knowledge of all pathological processes leading to a disease. There may be just one causative agent, but no one cause of disease. For example, as stated in Boyd's Introduction To The Study Of Disease, we know tuberculosis is caused by the tubercle bacillus. Many people are …
The concept of "free will" developed slowly. Discussions of the "will" arose only when ancient philosophical descriptions of intentional action came into contact with religious concerns about human and divine freedom. The predominant contemporary understanding of freedom as a completely undetermined choice between any two alternatives was introduced at the end of the Mi…
The eubacteria are the largest and most diverse taxonomic group of bacteria. Some regard this as an artificial assemblage, merely a group of convenience rather than a natural grouping. The eubacteria are all easily stained, rod-shaped or spherical bacteria. They are generally unicellular, but a small number of multicellular forms do occur. They can be motile or non-motile and the motile forms are …
Fossils are a significant window into Earth's history and organic evolution. The term fossil literally means something that has been 'dug up,' but its modern meaning has been restricted to evidence of past life. Such evidence may take the form of body fossils (both plant and animal), trace fossils or ichnofossils (physical features formed in rock due to animal-sediment interac…
The visibility of "friendship" in historical writings has fluctuated over time. For the ancient Greeks and Romans, friendship was the dominant paradigm. In medieval Europe, Christian teachings subordinated human friendship to spiritual friendship. In the modern period, with its focus on impartiality, friendship was relegated to the private sphere. Toward the end of the twentieth cent…
Eugenics is the study of improving the human race by selective breeding. Its rationale is to remove bad or deleterious genes from the population, increasing the overall fitness of humanity as a result. Campaigns to stop the criminal, the poor, the handicapped, and the mentally ill from passing on their genes were supported in the past by such people as British feminist Marie Stopes and Irish playw…
Fossil fuels are buried deposits of petroleum, coal, peat, natural gas, and other carbon-rich organic compounds derived from the dead bodies of plants and animals that lived many millions of years ago. Over long periods of time, pressure and heat generated by overlying sediments concentrate and modified these materials into valuable energy sources for human purposes. Fossil fuels currently provide…
A term used loosely to describe a reaction of (neo)traditional religion against the pressures of modernity, fundamentalism became a widespread topic of interest in the media and the academy during the last quarter of the twentieth century. According to many observers, fundamentalism is a worldwide phenomenon, arising in various societies with differing cultural backgrounds and experiences of moder…
Eukaryotae, or eukaryotic cells, are large and complex cells bounded by an outer plasma membrane. They contain many organelles within their cytoplasm and a nucleus separated from the cytoplasm by the nuclear membrane. Fossils of eukaryotic cells are present in rocks dated as 1.5 billion years old. All living things on Earth, except bacteria and blue-green algae (cyanobacteria), which are Prokaryot…
A fractal is a geometric figure, often characterized as being self-similar; that is, irregular, fractured, fragmented, or loosely connected in appearance. Benoit Mandelbrot coined the term fractal to describe such figures, deriving the word from the Latin "fractus" meaning broken, fragmented, or irregular. He also pointed out amazing similarities in appearance between some fractal se…
Futurology is the study of the future to obtain knowledge of it on the basis of present trends. Beginning in the 1960s, it is a relatively new field of study. The word futurology was first used in 1943 by Ossip Flechteim, a political scientist, to describe a new scientific field of human knowledge based on a critical, systematic, and normative analysis of questions related to future. However, fut…
Game theory, the formal analysis of conflict and cooperation, has pervaded every area of economics and the study of business strategy in the past quarter-century and exerts increasing influence in evolutionary biology, international relations, and political science, where the rational-choice approach to politics has been highly controversial. In a strategic game, each player chooses a strategy (a …
The term garden, which is of Germanic origin, means "yard" or "enclosure" and denotes ways of organizing earth, water, plants and, sometimes, people, animals, and art (sculpture, architecture, theater, music, and poetry), the formal qualitities of which are determined as much by pleasure, artistry, or aesthetics as by convenience or necessity. This definition excludes a…
The continent of Europe is a landmass bounded on the east by the Ural mountains, on the south by the Mediterranean Sea, and on the north and west by the Arctic and Atlantic Oceans. Numerous islands around this landmass are considered a part of Europe. Europe is also the westernmost part of the Eurasian supercontinent (several continental masses joined together). Europe holds a unique place among t…
Fraunhofer lines are dark absorption lines in the solar spectrum that can be seen when sunlight is passed through a prism to separate it into the colors of the rainbow. They occur because cooler gas, which is higher in the Sun's atmosphere, absorbs some colors of the light emitted by hotter gas lower in the Sun's atmosphere. Sir Isaac Newton (1642-1727) discovered that if white light…
Gay studies in the early twenty-first century is a lively interdisciplinary field encompassing studies of literature, anthropology, sociology, psychology, the visual arts, indeed all fields in which nonheteronormative sexuality—and its institutionalized suppression—has become a point of politico-philosophical argument. It has two origins: a more recent starting point in twentieth-cen…
