Biological Sciences

Biology, study of living things and their vital processes. The field deals with all the physicochemical aspects of life. The modern tendency toward cross-disciplinary research and the unification of scientific knowledge and investigation from different fields has resulted in significant overlap of...

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  Leonardo da Vinci
  Leonardo da Vinci, (Italian: “Leonardo from Vinci”) Italian painter, draftsman, sculptor, architect, and engineer whose genius, perhaps more than that of any other figure, epitomized the Renaissance humanist ideal. His Last Supper (1495–98) and Mona Lisa (c. 1503–19) are among the most widely…
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  Tuberculosis
  Tuberculosis (TB), infectious disease that is caused by the tubercle bacillus, Mycobacterium tuberculosis. In most forms of the disease, the bacillus spreads slowly and widely in the lungs, causing the formation of hard nodules (tubercles) or large cheeselike masses that break down the respiratory…
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  Lyme disease
  Lyme disease, tick-borne bacterial disease that was first conclusively identified in 1975 and is named for the town in Connecticut, U.S., in which it was first observed. The disease has been identified in every region of the United States and in Europe, Asia, Africa, and Australia. Lyme disease is…
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  DNA
  DNA, organic chemical of complex molecular structure that is found in all prokaryotic and eukaryotic cells and in many viruses. DNA codes genetic information for the transmission of inherited traits. A brief treatment of DNA follows. For full treatment, see genetics: DNA and the genetic code. The…
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  Charles Darwin
  Charles Darwin, English naturalist whose scientific theory of evolution by natural selection became the foundation of modern evolutionary studies. An affable country gentleman, Darwin at first shocked religious Victorian society by suggesting that animals and humans shared a common ancestry.…
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  Aristotle
  Aristotle, ancient Greek philosopher and scientist, one of the greatest intellectual figures of Western history. He was the author of a philosophical and scientific system that became the framework and vehicle for both Christian Scholasticism and medieval Islamic philosophy. Even after the…
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  Sigmund Freud
  Sigmund Freud, Austrian neurologist, founder of psychoanalysis. Freud’s article on psychoanalysis appeared in the 13th edition of the Encyclopædia Britannica. Freud may justly be called the most influential intellectual legislator of his age. His creation of psychoanalysis was at once a theory of…
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  Cancer
  Cancer, group of more than 100 distinct diseases characterized by the uncontrolled growth of abnormal cells in the body. Though cancer has been known since antiquity, some of the most significant advances in scientists’ understanding of it have been made since the middle of the 20th century. Those…
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  Chronic traumatic encephalopathy
  Chronic traumatic encephalopathy (CTE), degenerative brain disease typically associated with repetitive trauma to the head. Chronic traumatic encephalopathy (CTE) originally was known as dementia pugilistica, a term introduced in the 1920s and ’30s to describe mental and motor deficits associated…
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  Nikolai Vavilov
  Nikolai Vavilov, Soviet plant geneticist whose research into the origins of cultivated plants incurred the animosity of T.D. Lysenko, official spokesperson for Soviet biology in his time. Vavilov studied under William Bateson, founder of the science of genetics, at the University of Cambridge and…
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  Psychology
  Psychology, scientific discipline that studies mental states and processes and behaviour in humans and other animals. The discipline of psychology is broadly divisible into two parts: a large profession of practitioners and a smaller but growing science of mind, brain, and social behaviour. The two…
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  Cocaine
  Cocaine, white crystalline alkaloid that is obtained from the leaves of the coca plant (Erythroxylum coca), a bush commonly found growing wild in Peru, Bolivia, and Ecuador and cultivated in many other countries. The chemical formula of cocaine is C17H21NO4. Cocaine acts as an anesthetic because it…
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  AIDS
  AIDS, transmissible disease of the immune system caused by the human immunodeficiency virus (HIV). HIV is a lentivirus (literally meaning “slow virus”; a member of the retrovirus family) that slowly attacks and destroys the immune system, the body’s defense against infection, leaving an individual…
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  Alzheimer disease
  Alzheimer disease, degenerative brain disorder that develops in mid-to-late adulthood. It results in a progressive and irreversible decline in memory and a deterioration of various other cognitive abilities. The disease is characterized by the destruction of nerve cells and neural connections in…
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  Diabetes mellitus
  Diabetes mellitus, disorder of carbohydrate metabolism characterized by impaired ability of the body to produce or respond to insulin and thereby maintain proper levels of sugar (glucose) in the blood. Diabetes is a major cause of morbidity and mortality, though these outcomes are not due to the…
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  Autism
  Autism, developmental disorder affecting physical, social, and language skills, with an onset of signs and symptoms typically before age three. The term autism (from the Greek autos, meaning “self”) was coined in 1911 by Swiss psychiatrist Eugen Bleuler, who used it to describe withdrawal into…
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  Syphilis
  Syphilis, systemic disease that is caused by the spirochete bacterium Treponema pallidum. Syphilis is usually a sexually transmitted disease, but it is occasionally acquired by direct nonsexual contact with an infected person, and it can also be acquired by an unborn fetus through infection in the…
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  Crohn disease
  Crohn disease, chronic inflammation of the digestive tract, usually occurring in the terminal portion of the ileum, the region of the small intestine farthest from the stomach. Crohn disease was first described in 1904 by Polish surgeon Antoni Leśniowski. It was later named for American…
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  IQ
  IQ, (from “intelligence quotient”), a number used to express the relative intelligence of a person. It is one of many intelligence tests. IQ was originally computed by taking the ratio of mental age to chronological (physical) age and multiplying by 100. Thus, if a 10-year-old child had a mental…
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  Dengue
  Dengue, acute, infectious, mosquito-borne fever that is temporarily incapacitating but rarely fatal. Besides fever, the disease is characterized by an extreme pain in and stiffness of the joints (hence the name “breakbone fever”). Complication of dengue fever can give rise to a more severe form,…
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  Obesity
  Obesity, excessive accumulation of body fat, usually caused by the consumption of more calories than the body can use. The excess calories are then stored as fat, or adipose tissue. Overweight, if moderate, is not necessarily obesity, particularly in muscular or large-boned individuals. Obesity was…
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  Narcissism
  Narcissism, pathological self-absorption, first identified as a mental disorder by the British essayist and physician Havelock Ellis in 1898. Narcissism is characterized by an inflated self-image and addiction to fantasy, by an unusual coolness and composure shaken only when the narcissistic…
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  Tinnitus
  Tinnitus, ringing or buzzing in the ears. An estimated one-third of adults experience tinnitus at some point in their lives, and some 10 to 15 percent of individuals are afflicted by chronic tinnitus. There are two types of tinnitus: subjective, which is the most common form, and objective, which…
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  Renewable energy
  Renewable energy, usable energy derived from replenishable sources such as the Sun (solar energy), wind (wind power), rivers (hydroelectric power), hot springs (geothermal energy), tides (tidal power), and biomass (biofuels). At the beginning of the 21st century, about 80 percent of the world’s…
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  Al Gore
  Al Gore, 45th vice president of the United States (1993–2001) in the Democratic administration of President Bill Clinton. In the 2000 presidential election, one of the most controversial elections in American history, Gore won the nationwide popular vote over George W. Bush by more than 500,000…
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  Anthropology
  Anthropology, “the science of humanity,” which studies human beings in aspects ranging from the biology and evolutionary history of Homo sapiens to the features of society and culture that decisively distinguish humans from other animal species. Because of the diverse subject matter it encompasses,…
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  Malaria
  Malaria, serious relapsing infection in humans, characterized by periodic attacks of chills and fever, anemia, splenomegaly (enlargement of the spleen), and often fatal complications. It is caused by one-celled parasites of the genus Plasmodium that are transmitted to humans by the bite of…
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  Economics
  Economics, social science that seeks to analyze and describe the production, distribution, and consumption of wealth. In the 19th century economics was the hobby of gentlemen of leisure and the vocation of a few academics; economists wrote about economic policy but were rarely consulted by…
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  Smallpox
  Smallpox, acute infectious disease that begins with a high fever, headache, and back pain and then proceeds to an eruption on the skin that leaves the face and limbs covered with cratered pockmarks, or pox. For centuries smallpox was one of the world’s most-dreaded plagues, killing as many as 30…
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  Photosynthesis
  Photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds. It would…