Evolution - Evolution As A Theory Of Species Change, Charles Darwin And Descent With Modification By Means Of Natural Selection

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…

3 minute read

Convergent Evolution

Convergent evolution represents a phenomenon when two distinct species with differing ancestries evolve to display similar physical features. Environmental circumstances that require similar developmental or structural alterations for the purposes of adaptation can lead to convergent evolution even though the species differ in descent. These adaptation similarities that arise as a result of the sa…

2 minute read

Divergent Evolution

Divergent evolution occurs when a group from a specific population develops into a new species. In order to adapt to various environmental conditions, the two groups develop into distinct species due to differences in the demands driven by the environmental circumstances. A good example of how divergent evolution occurs is in comparing how a human foot evolved to be very different from a monkey&#x…

3 minute read

Evidence of Evolution

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…

6 minute read

Parallel Evolution

Parallel evolution occurs when unrelated organisms develop the same characteristics or adaptive mechanisms due to the nature of their environmental conditions. Or stated differently, parallel evolution occurs when similar environments produce similar adaptations. The morphologies (or structural form) of two or more lineages evolve together in a similar manner in parallel evolution, rather than div…

2 minute read

Rate of Evolutionary Change

Rates of evolution change vary widely over time, among characteristics, and among species. Evolutionary change can be estimated by examining fossils and species that are related to each other. The rate of change is governed by the life span of the species under examination, short-lived species are capable of changing more quickly than those that have a longer life span and reproduce less often. Ye…

4 minute read

Evolutionary Mechanisms

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…

5 minute read

China Examination Systems - Power, Politics, And Examinations, Literacy And Social Dimensions, Fields Of Learning, Delegitimation And Decanonization

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…

2 minute read

Excavation Methods - Excavation Strategies, Mapping And Recording, Publication Of Findings

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…

3 minute read

Pauli Exclusion Principle - Historical Background, The Exclusion Principle, Electronic Configurations, Rationalizing The Periodic Law

Excretory System - Nitrogenous Wastes, Excretion By Organisms Living In Water, Excretion By Land Animals, Excretion In Humans

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…

1 minute read

Exercise - Precautions, Risks - Description, Preparation, Aftercare

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…

5 minute read

Existentialism - Søren Kierkegaard (1813–1855), Friedrich Nietzsche (1844–1900), Martin Heidegger (1889–1971), Jean-paul Sartre (1905–1980)

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…

5 minute read

Exocrine Glands - Structural Classification, Functional Classification

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…

less than 1 minute read

Experiment - The Emergence Of Experiment, Two Experimental Traditions: Classical And Baconian, Galileo Galilei, The Baconian Program And Its Institutional Expression

Explosives - History, Controlling Explosives, Newer Explosives, Types Of Explosives And Their Sources Of Power, Four Classifications Of Chemical Explosives

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…

1 minute read

Exponent

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…

1 minute read

Expressionism - Bibliography

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…

11 minute read

Extinction - The Asteroid-impact Theory, The Great Ice Age, The Current Mass Extinction

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…

1 minute read

Extirpation - Bibliography

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…

7 minute read

Extrasolar Planets - The Search For Extrasolar Planets, New Detection Techniques, New Discoveries

Eye - Evolution Of The Eye, Anatomy And Function Of The Human Eye, Retina, Optic Nerve

Factor

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 …

3 minute read

Factorial

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…

2 minute read

Falcons - Interaction Of Falcons With Humans, Current Status Of North American Falcons

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…

4 minute read

Logical Fallacy - Formal Fallacies, Informal Fallacies

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…

less than 1 minute read

Falsifiability - Popper's Emphasis On Falsifiability, Complications Of The Simple Model, Bibliography

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 …

1 minute read

Family in Anthropology since (1980) - New Directions For Family Studies, Putting Theory Into Practice: Family Studies Of The 1980s And Early 1990s

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 …

2 minute read

Family Planning - Origin And Evolution Of Family Planning, Family Planning In The Global South, The "second Contraceptive Revolution"

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…

2 minute read

Faraday Effect

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…

2 minute read

Fascism - The Origins Of Generic Fascism, An Overview Of The "fascist Epoch", Non-european Fascisms

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…

less than 1 minute read

Fat

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…

2 minute read

Fatalism - Fatalism And Determinism, Aristotle's Sea Battle, Theological Fatalism, Bibliography

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…

2 minute read

Fatty Acids

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 …

2 minute read

Fault - Plate Tectonics, History Of Our Understanding Of Faults, Types Of Faults, Mountain-building By Small Movements Along Faults - Famous or infamous faults

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…

4 minute read

Fauna

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…

2 minute read

Fax Machine

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 …

2 minute read

Feather Stars

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 …

2 minute read

Feminism - Overview - Anglo-american Feminism, Trajectories Within Feminism, Feminist Theory And Women's Studies, Feminism And Other Ideologies

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…

1 minute read

Feminism - Third World U.S. Movement - Bibliography

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…

6 minute read

Twentieth-Century Philosophies Feminist - Social And Political Theory, Ethics, History Of Philosophy, Epistemology And Philosophy Of Science, Conclusion

The term feminism is used both in reference to social movements, such as the late-nineteenth century women's rights movement or the mid-twentieth century women's movement in Europe and the United States, and to theories that identify and critique injustices against women, such as A Vindication of the Rights of Woman by Mary Wollstonecraft (1759–1797) or The Book of the City of…

2 minute read

Fermentation - History, Theory, Uses

Ferns - General Characteristics, Natural History, Life Cycle, Gametophyte, Sporophyte, Polyploidy, Evolution, Modern Ferns

Ferrets - An experiment in captive breeding

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…

4 minute read