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Agriculture | 627 | Cited sources | This article incorporates text from a free content work. (license statement/permission). Text taken from In Brief: The State of Food and Agriculture 2018. Migration, agriculture and rural development, FAO, FAO. |
Agriculture | 627 | Cited sources | This article incorporates text from a free content work. (license statement/permission). Text taken from In Brief to The State of Food and Agriculture 2022. Leveraging automation in agriculture for transforming agrifood systems, FAO, FAO. |
Agriculture | 627 | Cited sources | This article incorporates text from a free content work. (license statement/permission). Text taken from Enabling inclusive agricultural automation, FAO, FAO. |
Agriculture | 627 | Cited sources | This article incorporates text from a free content work. Licensed under CC BY-SA 3.0 (license statement/permission). Text taken from The status of women in agrifood systems – Overview, FAO, FAO. |
Agriculture | 627 | Cited sources | This article incorporates text from a free content work. Licensed under CC BY-SA IGO 3.0 (license statement/permission). Text taken from World Food and Agriculture – Statistical Yearbook 2023, FAO, FAO. |
Aldous Huxley | 628 | Aldous Leonard Huxley (/ˈɔːldəs/ AWL-dəs; 26 July 1894 – 22 November 1963) was an English writer and philosopher. His bibliography spans nearly 50 books, including novels and non-fiction works, as well as essays, narratives, and poems. |
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Aldous Huxley | 628 | Born into the prominent Huxley family, he graduated from Balliol College, Oxford, with an undergraduate degree in English literature. Early in his career, he published short stories and poetry and edited the literary magazine Oxford Poetry, before going on to publish travel writing, satire, and screenplays. He spent the latter part of his life in the United States, living in Los Angeles from 1937 until his death. By the end of his life, Huxley was widely acknowledged as one of the foremost intellectuals of his time. He was nominated for the Nobel Prize in Literature nine times, and was elected Companion of Literature by the Royal Society of Literature in 1962. |
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Aldous Huxley | 628 | Huxley was a pacifist. He grew interested in philosophical mysticism, as well as universalism, addressing these subjects in his works such as The Perennial Philosophy (1945), which illustrates commonalities between Western and Eastern mysticism, and The Doors of Perception (1954), which interprets his own psychedelic experience with mescaline. In his most famous novel Brave New World (1932) and his final novel Island (1962), he presented his visions of dystopia and utopia, respectively. |
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Aldous Huxley | 628 | Early life | Huxley was born in Godalming, Surrey, England, in 1894. He was the third son of the writer and schoolmaster Leonard Huxley, who edited The Cornhill Magazine, and his first wife, Julia Arnold, who founded Prior's Field School. Julia was the niece of poet and critic Matthew Arnold and the sister of Mrs. Humphry Ward. Julia named him Aldous after a character in one of her sister's novels. Aldous was the grandson of Thomas Henry Huxley, the zoologist, agnostic, and controversialist who had often been called "Darwin's Bulldog". His brother Julian Huxley and half-brother Andrew Huxley also became outstanding biologists. Aldous had another brother, Noel Trevenen Huxley (1889–1914), who took his own life after a period of clinical depression. |
Aldous Huxley | 628 | Early life | As a child, Huxley's nickname was "Ogie", short for "Ogre". He was described by his brother, Julian, as someone who frequently contemplated "the strangeness of things". According to his cousin and contemporary Gervas Huxley, he had an early interest in drawing. |
Aldous Huxley | 628 | Early life | Huxley's education began in his father's well-equipped botanical laboratory, after which he enrolled at Hillside School near Godalming. He was taught there by his own mother for several years until she became terminally ill. After Hillside he went on to Eton College. His mother died in 1908, when he was 14 (his father later remarried). He contracted the eye disease Keratitis punctata in 1911; this "left [him] practically blind for two to three years" and "ended his early dreams of becoming a doctor". In October 1913, Huxley entered Balliol College, Oxford, where he studied English literature. He volunteered for the British Army in January 1916, for the Great War; however, he was rejected on health grounds, being half-blind in one eye. His eyesight later partly recovered. He edited Oxford Poetry in 1916, and in June of that year graduated BA with first class honours. His brother Julian wrote: |
Aldous Huxley | 628 | Early life | I believe his blindness was a blessing in disguise. For one thing, it put paid to his idea of taking up medicine as a career ... His uniqueness lay in his universalism. He was able to take all knowledge for his province. |
Aldous Huxley | 628 | Early life | Following his years at Balliol, Huxley, being financially indebted to his father, decided to find employment. He taught French for a year at Eton College, where Eric Blair (who was to take the pen name George Orwell) and Steven Runciman were among his pupils. He was mainly remembered as being an incompetent schoolmaster unable to keep order in class. Nevertheless, Blair and others spoke highly of his excellent command of language. |
Aldous Huxley | 628 | Early life | Huxley also worked for a time during the 1920s at Brunner and Mond, an advanced chemical plant in Billingham in County Durham, northeast England. According to an introduction to his science fiction novel Brave New World (1932), the experience he had there of "an ordered universe in a world of planless incoherence" was an important source for the novel. |
Aldous Huxley | 628 | Career | Huxley completed his first (unpublished) novel at the age of 17 and began writing seriously in his early twenties, establishing himself as a successful writer and social satirist. His first published novels were social satires, Crome Yellow (1921), Antic Hay (1923), Those Barren Leaves (1925), and Point Counter Point (1928). Brave New World (1932) was his fifth novel and first dystopian work. In the 1920s, he was also a contributor to Vanity Fair and British Vogue magazines. |
Aldous Huxley | 628 | Career | During the First World War, Huxley spent much of his time at Garsington Manor near Oxford, home of Lady Ottoline Morrell, working as a farm labourer. While at the Manor, he met several Bloomsbury Group figures, including Bertrand Russell, Alfred North Whitehead, and Clive Bell. Later, in Crome Yellow (1921), he caricatured the Garsington lifestyle. Jobs were very scarce, but in 1919, John Middleton Murry was reorganising the Athenaeum and invited Huxley to join the staff. He accepted immediately, and quickly married the Belgian refugee Maria Nys (1899–1955), also at Garsington. They lived with their young son in Italy part of the time during the 1920s, where Huxley would visit his friend D. H. Lawrence. Following Lawrence's death in 1930 (he and Maria were present at his death in Provence), Huxley edited Lawrence's letters (1932). Very early in 1929, in London, Huxley met Gerald Heard, a writer and broadcaster, philosopher and interpreter of contemporary science. |
Aldous Huxley | 628 | Career | Works of this period included novels about the dehumanising aspects of scientific progress, (his magnum opus Brave New World), and on pacifist themes (Eyeless in Gaza). In Brave New World, set in a dystopian London, Huxley portrays a society operating on the principles of mass production and Pavlovian conditioning. Huxley was strongly influenced by F. Matthias Alexander, on whom he based a character in Eyeless in Gaza. |
Aldous Huxley | 628 | Career | During this period, Huxley began to write and edit non-fiction works on pacifist issues, including Ends and Means (1937), An Encyclopedia of Pacifism, and Pacifism and Philosophy, and was an active member of the Peace Pledge Union. |
Aldous Huxley | 628 | Career | In 1937, Huxley moved to Hollywood with his wife Maria, son Matthew Huxley, and friend Gerald Heard. Cyril Connolly wrote, of the two intellectuals (Huxley and Heard) in the late 1930s, "all European avenues had been exhausted in the search for a way forward – politics, art, science – pitching them both toward the US in 1937." Huxley lived in the U.S., mainly southern California, until his death, and for a time in Taos, New Mexico, where he wrote Ends and Means (1937). The book contains tracts on war, inequality, religion and ethics. |
Aldous Huxley | 628 | Career | Heard introduced Huxley to Vedanta (Upanishad-centered philosophy), meditation, and vegetarianism through the principle of ahimsa. In 1938, Huxley befriended Jiddu Krishnamurti, whose teachings he greatly admired. Huxley and Krishnamurti entered into an enduring exchange (sometimes edging on debate) over many years, with Krishnamurti representing the more rarefied, detached, ivory-tower perspective and Huxley, with his pragmatic concerns, the more socially and historically informed position. Huxley wrote a foreword to Krishnamurti's quintessential statement, The First and Last Freedom (1954). |
Aldous Huxley | 628 | Career | Huxley became a Vedantist in the group formed around Hindu Swami Prabhavananda, and subsequently introduced Christopher Isherwood to the circle. Not long afterwards, Huxley wrote his book on widely held spiritual values and ideas, The Perennial Philosophy, which discussed the teachings of renowned mystics of the world. |
Aldous Huxley | 628 | Career | Huxley became a close friend of Remsen Bird, president of Occidental College. He spent much time at the college in the Eagle Rock neighbourhood of Los Angeles. The college appears as "Tarzana College" in his satirical novel After Many a Summer (1939). The novel won Huxley a British literary award, the 1939 James Tait Black Memorial Prize for fiction. Huxley also incorporated Bird into the novel. |
Aldous Huxley | 628 | Career | During this period, Huxley earned a substantial income as a Hollywood screenwriter; Christopher Isherwood, in his autobiography My Guru and His Disciple, states that Huxley earned more than $3,000 per week (approximately $50,000 in 2020 dollars) as a screenwriter, and that he used much of it to transport Jewish and left-wing writer and artist refugees from Hitler's Germany to the US. In March 1938, Huxley's friend Anita Loos, a novelist and screenwriter, put him in touch with Metro-Goldwyn-Mayer (MGM), which hired him for Madame Curie which was originally to star Greta Garbo and be directed by George Cukor. (Eventually, the film was completed by MGM in 1943 with a different director and cast.) Huxley received screen credit for Pride and Prejudice (1940) and was paid for his work on a number of other films, including Jane Eyre (1944). He was commissioned by Walt Disney in 1945 to write a script based on Alice's Adventures in Wonderland and the biography of the story's author, Lewis Carroll. The script was not used, however. |
Aldous Huxley | 628 | Career | Huxley wrote an introduction to the posthumous publication of J. D. Unwin's 1940 book Hopousia or The Sexual and Economic Foundations of a New Society. |
Aldous Huxley | 628 | Career | On 21 October 1949, Huxley wrote to George Orwell, author of Nineteen Eighty-Four, congratulating him on "how fine and how profoundly important the book is". In his letter, he predicted: |
Aldous Huxley | 628 | Career | "Within the next generation I believe that the world's leaders will discover that infant conditioning and narcohypnosis are more efficient, as instruments of government, than clubs and prisons, and that the lust for power can be just as completely satisfied by suggesting people into loving their servitude as by flogging them and kicking them into obedience." |
Aldous Huxley | 628 | Career | In 1953, Huxley and Maria applied for United States citizenship and presented themselves for examination. When Huxley refused to bear arms for the U.S. and would not state that his objections were based on religious ideals, the only excuse allowed under the McCarran Act, the judge had to adjourn the proceedings. He withdrew his application. Nevertheless, he remained in the U.S. In 1959, Huxley turned down an offer to be made a Knight Bachelor by the Macmillan government without giving a reason; his brother Julian had been knighted in 1958, while his brother Andrew would be knighted in 1974. |
Aldous Huxley | 628 | Career | In the fall semester of 1960 Huxley was invited by Professor Huston Smith to be the Carnegie Visiting professor of humanities at the Massachusetts Institute of Technology (MIT). As part of the MIT centennial program of events organised by the Department of Humanities, Huxley presented a series of lectures titled, "What a Piece of Work is a Man" which concerned history, language, and art. |
Aldous Huxley | 628 | Career | Robert S. de Ropp (scientist, humanitarian, and author), who had spent time with Huxley in England in the 1930s, connected with him again in the U.S. in the early 1960s and wrote that "the enormous intellect, the beautifully modulated voice, the gentle objectivity, all were unchanged. He was one of the most highly civilized human beings I had ever met." |
Aldous Huxley | 628 | Late-in-life perspectives | Biographer Harold H. Watts wrote that Huxley's writings in the "final and extended period of his life" are "the work of a man who is meditating on the central problems of many modern men". Huxley had deeply felt apprehensions about the future the developed world might make for itself. From these, he made some warnings in his writings and talks. In a 1958 televised interview conducted by journalist Mike Wallace, Huxley outlined several major concerns: the difficulties and dangers of world overpopulation; the tendency towards distinctly hierarchical social organisation; the crucial importance of evaluating the use of technology in mass societies susceptible to persuasion; the tendency to promote modern politicians to a naive public as well-marketed commodities. In a December 1962 letter to brother Julian, summarizing a paper he had presented in Santa Barbara, he wrote, "What I said was that if we didn't pretty quickly start thinking of human problems in ecological terms rather than in terms of power politics we should very soon be in a bad way." |
Aldous Huxley | 628 | Late-in-life perspectives | Huxley's engagement with Eastern wisdom traditions was entirely compatible with a strong appreciation of modern science. Biographer Milton Birnbaum wrote that Huxley "ended by embracing both science and Eastern religion". In his last book, Literature and Science, Huxley wrote that "The ethical and philosophical implications of modern science are more Buddhist than Christian...." In "A Philosopher's Visionary Prediction," published one month before he died, Huxley endorsed training in general semantics and "the nonverbal world of culturally uncontaminated consciousness," writing that "We must learn how to be mentally silent, we must cultivate the art of pure receptivity.... [T]he individual must learn to decondition himself, must be able to cut holes in the fence of verbalized symbols that hems him in." |
Aldous Huxley | 628 | Association with Vedanta | Beginning in 1939 and continuing until his death in 1963, Huxley had an extensive association with the Vedanta Society of Southern California, founded and headed by Swami Prabhavananda. Together with Gerald Heard, Christopher Isherwood and other followers, he was initiated by the Swami and was taught meditation and spiritual practices. |
Aldous Huxley | 628 | Association with Vedanta | In 1944, Huxley wrote the introduction to the Bhagavad Gita – The Song of God, translated by Swami Prabhavananda and Christopher Isherwood, which was published by the Vedanta Society of Southern California. |
Aldous Huxley | 628 | Association with Vedanta | From 1941 until 1960, Huxley contributed 48 articles to Vedanta and the West, published by the society. He also served on the editorial board with Isherwood, Heard, and playwright John Van Druten from 1951 through 1962. |
Aldous Huxley | 628 | Association with Vedanta | Huxley also occasionally lectured at the Hollywood and Santa Barbara Vedanta temples. Two of those lectures have been released on CD: Knowledge and Understanding and Who Are We? from 1955. Nonetheless, Huxley's agnosticism, together with his speculative propensity, made it difficult for him to fully embrace any form of institutionalised religion. |
Aldous Huxley | 628 | Psychedelic drug use and mystical experiences | In early 1953, Huxley had his first experience with the psychedelic drug mescaline. Huxley had initiated a correspondence with Doctor Humphry Osmond, a British psychiatrist then employed in a Canadian institution, and eventually asked him to supply a dose of mescaline; Osmond obliged and supervised Huxley's session in southern California. After the publication of The Doors of Perception, in which he recounted this experience, Huxley and Swami Prabhavananda disagreed about the meaning and importance of the psychedelic drug experience, which may have caused the relationship to cool, but Huxley continued to write articles for the society's journal, lecture at the temple, and attend social functions. Huxley later had an experience on mescaline that he considered more profound than those detailed in The Doors of Perception. |
Aldous Huxley | 628 | Psychedelic drug use and mystical experiences | Huxley wrote that "The mystical experience is doubly valuable; it is valuable because it gives the experiencer a better understanding of himself and the world and because it may help him to lead a less self-centered and more creative life." |
Aldous Huxley | 628 | Psychedelic drug use and mystical experiences | Having tried LSD in the 1950s, he became an advisor to Timothy Leary and Richard Alpert in their early-1960s research work with psychedelic drugs at Harvard. Personality differences led Huxley to distance himself from Leary, when Huxley grew concerned that Leary had become too keen on promoting the drugs rather indiscriminately, even playing the rebel with a fondness for publicity. |
Aldous Huxley | 628 | Eyesight | Differing accounts exist about the details of the quality of Huxley's eyesight at specific points in his life. Circa 1939, Huxley encountered the Bates method, in which he was instructed by Margaret Darst Corbett. In 1940, Huxley relocated from Hollywood to a 40-acre (16 ha) ranchito in the high desert hamlet of Llano, California, in northern Los Angeles County. Huxley then said that his sight improved dramatically with the Bates method and the extreme and pure natural lighting of the southwestern American desert. He reported that, for the first time in more than 25 years, he was able to read without glasses and without strain. He even tried driving a car along the dirt road beside the ranch. He wrote a book about his experiences with the Bates method, The Art of Seeing, which was published in 1942 (U.S.), 1943 (UK). The book contained some generally disputed theories, and its publication created a growing degree of popular controversy about Huxley's eyesight. |
Aldous Huxley | 628 | Eyesight | It was, and is, widely believed that Huxley was nearly blind since the illness in his teens, despite the partial recovery that had enabled him to study at Oxford. For example, some ten years after publication of The Art of Seeing, in 1952, Bennett Cerf was present when Huxley spoke at a Hollywood banquet, wearing no glasses and apparently reading his paper from the lectern without difficulty: |
Aldous Huxley | 628 | Eyesight | "Then suddenly he faltered—and the disturbing truth became obvious. He wasn't reading his address at all. He had learned it by heart. To refresh his memory he brought the paper closer and closer to his eyes. When it was only an inch or so away he still couldn't read it, and had to fish for a magnifying glass in his pocket to make the typing visible to him. It was an agonising moment." |
Aldous Huxley | 628 | Eyesight | Brazilian author João Ubaldo Ribeiro, who as a young journalist spent several evenings in the Huxleys' company in the late 1950s, wrote that Huxley had said to him, with a wry smile: "I can hardly see at all. And I don't give a damn, really." |
Aldous Huxley | 628 | Eyesight | On the other hand, Huxley's second wife Laura later emphasised in her biographical account, This Timeless Moment: "One of the great achievements of his life: that of having regained his sight." After revealing a letter she wrote to the Los Angeles Times disclaiming the label of Huxley as a "poor fellow who can hardly see" by Walter C. Alvarez, she tempered her statement: |
Aldous Huxley | 628 | Eyesight | "Although I feel it was an injustice to treat Aldous as though he were blind, it is true there were many indications of his impaired vision. For instance, although Aldous did not wear glasses, he would quite often use a magnifying lens." |
Aldous Huxley | 628 | Eyesight | Laura Huxley proceeded to elaborate a few nuances of inconsistency peculiar to Huxley's vision. Her account, in this respect, agrees with the following sample of Huxley's own words from The Art of Seeing: |
Aldous Huxley | 628 | Eyesight | "The most characteristic fact about the functioning of the total organism, or any part of the organism, is that it is not constant, but highly variable." |
Aldous Huxley | 628 | Eyesight | Nevertheless, the topic of Huxley's eyesight has continued to endure similar, significant controversy. American popular science author Steven Johnson, in his book Mind Wide Open, quotes Huxley about his difficulties with visual encoding: |
Aldous Huxley | 628 | Eyesight | "I am and, for as long as I can remember, I have always been a poor visualizer. Words, even the pregnant words of poets, do not evoke pictures in my mind. No hypnagogic visions greet me on the verge of sleep. When I recall something, the memory does not present itself to me as a vividly seen event or object. By an effort of the will, I can evoke a not very vivid image of what happened yesterday afternoon ..." |
Aldous Huxley | 628 | Personal life | Huxley married on 10 July 1919 Maria Nys (10 September 1899 – 12 February 1955), a Belgian epidemiologist from Bellem, a village near Aalter, he met at Garsington, Oxfordshire, in 1919. They had one child, Matthew Huxley (19 April 1920 – 10 February 2005), who had a career as an author, anthropologist, and prominent epidemiologist. In 1955, Maria Huxley died of cancer. |
Aldous Huxley | 628 | Personal life | In 1956, Huxley married Laura Archera (1911–2007), also an author, as well as a violinist and psychotherapist. She wrote This Timeless Moment, a biography of Huxley. She told the story of their marriage through Mary Ann Braubach's 2010 documentary, Huxley on Huxley. |
Aldous Huxley | 628 | Personal life | Huxley was diagnosed with laryngeal cancer in 1960; in the years that followed, with his health deteriorating, he wrote the utopian novel Island, and gave lectures on "Human Potentialities" both at the UCSF Medical Center and at the Esalen Institute. These lectures were fundamental to the beginning of the Human Potential Movement. |
Aldous Huxley | 628 | Personal life | Huxley was a close friend of Jiddu Krishnamurti and Rosalind Rajagopal, and was involved in the creation of the Happy Valley School, now Besant Hill School, of Happy Valley, in Ojai, California. |
Aldous Huxley | 628 | Personal life | The most substantial collection of Huxley's few remaining papers, following the destruction of most in the 1961 Bel Air Fire, is at the Library of the University of California, Los Angeles. Some are also at the Stanford University Libraries. |
Aldous Huxley | 628 | Personal life | On 9 April 1962 Huxley was informed he was elected Companion of Literature by the Royal Society of Literature, the senior literary organisation in Britain, and he accepted the title via letter on 28 April 1962. The correspondence between Huxley and the society is kept at the Cambridge University Library. The society invited Huxley to appear at a banquet and give a lecture at Somerset House, London, in June 1963. Huxley wrote a draft of the speech he intended to give at the society; however, his deteriorating health meant he was not able to attend. |
Aldous Huxley | 628 | Death | On his deathbed, unable to speak owing to advanced laryngeal cancer, Huxley made a written request to his wife Laura for "LSD, 100 µg, intramuscular." According to her account of his death in This Timeless Moment, she obliged with an injection at 11:20 a.m. and a second dose an hour later; Huxley died aged 69, at 5:20 p.m. PST on 22 November 1963. |
Aldous Huxley | 628 | Death | Media coverage of Huxley's death, along with that of fellow British author C. S. Lewis, was overshadowed by the assassination of John F. Kennedy on the same day, less than seven hours before Huxley's death. In a 2009 article for New York magazine titled "The Eclipsed Celebrity Death Club", Christopher Bonanos wrote: |
Aldous Huxley | 628 | Death | The championship trophy for badly timed death, though, goes to a pair of British writers. Aldous Huxley, the author of Brave New World, died the same day as C. S. Lewis, who wrote the Chronicles of Narnia series. Unfortunately for both of their legacies, that day was November 22, 1963, just as John Kennedy's motorcade passed the Texas School Book Depository. Huxley, at least, made it interesting: At his request, his wife shot him up with LSD a couple of hours before the end, and he tripped his way out of this world. |
Aldous Huxley | 628 | Death | This coincidence served as the basis for Peter Kreeft's book Between Heaven and Hell: A Dialog Somewhere Beyond Death with John F. Kennedy, C. S. Lewis, & Aldous Huxley, which imagines a conversation among the three men taking place in Purgatory following their deaths. |
Aldous Huxley | 628 | Death | Huxley's memorial service took place in London in December 1963; it was led by his elder brother Julian. On 27 October 1971, his ashes were interred in the family grave at the Watts Cemetery, home of the Watts Mortuary Chapel in Compton, Guildford, Surrey, England. |
Aldous Huxley | 628 | Death | Huxley had been a long-time friend of Russian composer Igor Stravinsky, who dedicated his last orchestral composition to Huxley. What became Variations: Aldous Huxley in memoriam was begun in July 1963, completed in October 1964, and premiered by the Chicago Symphony Orchestra on 17 April 1965. |
Aldous Huxley | 628 | Commemoration | In 2021, Huxley was one of six British writers commemorated on a series of UK postage stamps issued by Royal Mail to celebrate British science fiction. One classic science fiction novel from each author was depicted, with Brave New World chosen to represent Huxley. |
Ada | 630 | Ada may refer to: |
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Aberdeen (disambiguation) | 632 | Aberdeen is a city in Scotland. |
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Aberdeen (disambiguation) | 632 | Aberdeen may also refer to: |
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Algae | 633 | Algae (UK: /ˈælɡiː/, US: /ˈældʒiː/; SG: alga /ˈælɡə/) is an informal term for a large and diverse group of photosynthetic, eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular microalgae, such as Chlorella, Prototheca and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 metres (160 ft) in length. Most are aquatic and lack many of the distinct cell and tissue types, such as stomata, xylem and phloem that are found in land plants. The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and stoneworts. Algae that are carried by water are plankton, specifically phytoplankton. |
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Algae | 633 | Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria. Diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga. Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction. |
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Algae | 633 | Algae lack the various structures that characterize land plants, such as the phyllids (leaf-like structures) of bryophytes, rhizoids of non-vascular plants, and the roots, leaves, and other organs found in tracheophytes (vascular plants). Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy. Some unicellular species of green algae, many golden algae, euglenids, dinoflagellates, and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic, relying entirely on external energy sources and have limited or no photosynthetic apparatus. Some other heterotrophic organisms, such as the apicomplexans, are also derived from cells whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago. |
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Algae | 633 | Because of the wide range of types of algae, they have increasing different industrial and traditional applications in human society. Traditional seaweed farming practices have existed for thousands of years and have strong traditions in East Asia food cultures. More modern algaculture applications extend the food traditions for other applications include cattle feed, using algae for bioremediation or pollution control, transforming sunlight into algae fuels or other chemicals used in industrial processes, and in medical and scientific applications. A 2020 review found that these applications of algae could play an important role in carbon sequestration in order to mitigate climate change while providing lucrative value-added products for global economies. |
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Algae | 633 | Etymology and study | The singular alga is the Latin word for 'seaweed' and retains that meaning in English. The etymology is obscure. Although some speculate that it is related to Latin algēre, 'be cold', no reason is known to associate seaweed with temperature. A more likely source is alliga, 'binding, entwining'. |
Algae | 633 | Etymology and study | The Ancient Greek word for 'seaweed' was φῦκος (phŷkos), which could mean either the seaweed (probably red algae) or a red dye derived from it. The Latinization, fūcus, meant primarily the cosmetic rouge. The etymology is uncertain, but a strong candidate has long been some word related to the Biblical פוך (pūk), 'paint' (if not that word itself), a cosmetic eye-shadow used by the ancient Egyptians and other inhabitants of the eastern Mediterranean. It could be any color: black, red, green, or blue. |
Algae | 633 | Etymology and study | The study of algae is most commonly called phycology (from Greek phykos 'seaweed'); the term algology is falling out of use. |
Algae | 633 | Classifications | One definition of algae is that they "have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells". On the other hand, the colorless Prototheca under Chlorophyta are all devoid of any chlorophyll. Although cyanobacteria are often referred to as "blue-green algae", most authorities exclude all prokaryotes, including cyanobacteria, from the definition of algae. |
Algae | 633 | Classifications | The algae contain chloroplasts that are similar in structure to cyanobacteria. Chloroplasts contain circular DNA like that in cyanobacteria and are interpreted as representing reduced endosymbiotic cyanobacteria. However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events. The table below describes the composition of the three major groups of algae. Their lineage relationships are shown in the figure in the upper right. Many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost plastids entirely. |
Algae | 633 | Classifications | Phylogeny based on plastid not nucleocytoplasmic genealogy: |
Algae | 633 | Classifications | Linnaeus, in Species Plantarum (1753), the starting point for modern botanical nomenclature, recognized 14 genera of algae, of which only four are currently considered among algae. In Systema Naturae, Linnaeus described the genera Volvox and Corallina, and a species of Acetabularia (as Madrepora), among the animals. |
Algae | 633 | Classifications | In 1768, Samuel Gottlieb Gmelin (1744–1774) published the Historia Fucorum, the first work dedicated to marine algae and the first book on marine biology to use the then new binomial nomenclature of Linnaeus. It included elaborate illustrations of seaweed and marine algae on folded leaves. |
Algae | 633 | Classifications | W. H. Harvey (1811–1866) and Lamouroux (1813) were the first to divide macroscopic algae into four divisions based on their pigmentation. This is the first use of a biochemical criterion in plant systematics. Harvey's four divisions are: red algae (Rhodospermae), brown algae (Melanospermae), green algae (Chlorospermae), and Diatomaceae. |
Algae | 633 | Classifications | At this time, microscopic algae were discovered and reported by a different group of workers (e.g., O. F. Müller and Ehrenberg) studying the Infusoria (microscopic organisms). Unlike macroalgae, which were clearly viewed as plants, microalgae were frequently considered animals because they are often motile. Even the nonmotile (coccoid) microalgae were sometimes merely seen as stages of the lifecycle of plants, macroalgae, or animals. |
Algae | 633 | Classifications | Although used as a taxonomic category in some pre-Darwinian classifications, e.g., Linnaeus (1753), de Jussieu (1789), Horaninow (1843), Agassiz (1859), Wilson & Cassin (1864), in further classifications, the "algae" are seen as an artificial, polyphyletic group. |
Algae | 633 | Classifications | Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes. Later, many new groups were discovered (e.g., Bolidophyceae), and others were splintered from older groups: charophytes and glaucophytes (from chlorophytes), many heterokontophytes (e.g., synurophytes from chrysophytes, or eustigmatophytes from xanthophytes), haptophytes (from chrysophytes), and chlorarachniophytes (from xanthophytes). |
Algae | 633 | Classifications | With the abandonment of plant-animal dichotomous classification, most groups of algae (sometimes all) were included in Protista, later also abandoned in favour of Eukaryota. However, as a legacy of the older plant life scheme, some groups that were also treated as protozoans in the past still have duplicated classifications (see ambiregnal protists). |
Algae | 633 | Classifications | Some parasitic algae (e.g., the green algae Prototheca and Helicosporidium, parasites of metazoans, or Cephaleuros, parasites of plants) were originally classified as fungi, sporozoans, or protistans of incertae sedis, while others (e.g., the green algae Phyllosiphon and Rhodochytrium, parasites of plants, or the red algae Pterocladiophila and Gelidiocolax mammillatus, parasites of other red algae, or the dinoflagellates Oodinium, parasites of fish) had their relationship with algae conjectured early. In other cases, some groups were originally characterized as parasitic algae (e.g., Chlorochytrium), but later were seen as endophytic algae. Some filamentous bacteria (e.g., Beggiatoa) were originally seen as algae. Furthermore, groups like the apicomplexans are also parasites derived from ancestors that possessed plastids, but are not included in any group traditionally seen as algae. |
Algae | 633 | Evolution | Algae are polyphyletic thus their origin cannot be traced back to single hypothetical common ancestor. It is thought that they came into existence when photosynthetic coccoid cyanobacteria got phagocytized by a unicellular heterotrophic eukaryote (possibly a protist), giving rise to double-membranous primary plastids. Such symbiogenic events (primary symbiogenesis) are believed to have occurred more than 1.5 billion years ago during the Calymmian period, early in Boring Billion, but it is difficult to track the key events because of so much time gap. Primary symbiogenesis gave rise to three divisions of archaeplastids, namely the Viridiplantae (green algae and later plants), Rhodophyta (red algae) and Glaucophyta ("grey algae"), whose plastids further spread into other protist lineages through eukaryote-eukaryote predation, engulfments and subsequent endosymbioses (secondary and tertiary symbiogenesis). This process of serial cell "capture" and "enslavement" explains the diversity of photosynthetic eukaryotes. |
Algae | 633 | Evolution | Recent genomic and phylogenomic approaches have significantly clarified plastid genome evolution, the horizontal movement of endosymbiont genes to the "host" nuclear genome, and plastid spread throughout the eukaryotic tree of life. |
Algae | 633 | Evolution | Fossils of isolated spores suggest land plants may have been around as long as 475 million years ago (mya) during the Late Cambrian/Early Ordovician period, from sessile shallow freshwater charophyte algae much like Chara, which likely got stranded ashore when riverine/lacustrine water levels dropped during dry seasons. These charophyte algae probably already developed filamentous thalli and holdfasts that superficially resembled plant stems and roots, and probably had an isomorphic alternation of generations. They perhaps evolved some 850 mya and might even be as early as 1 Gya during the late phase of the Boring Billion. |
Algae | 633 | Morphology | A range of algal morphologies is exhibited, and convergence of features in unrelated groups is common. The only groups to exhibit three-dimensional multicellular thalli are the reds and browns, and some chlorophytes. Apical growth is constrained to subsets of these groups: the florideophyte reds, various browns, and the charophytes. The form of charophytes is quite different from those of reds and browns, because they have distinct nodes, separated by internode 'stems'; whorls of branches reminiscent of the horsetails occur at the nodes. Conceptacles are another polyphyletic trait; they appear in the coralline algae and the Hildenbrandiales, as well as the browns. |
Algae | 633 | Morphology | Most of the simpler algae are unicellular flagellates or amoeboids, but colonial and nonmotile forms have developed independently among several of the groups. Some of the more common organizational levels, more than one of which may occur in the lifecycle of a species, are |
Algae | 633 | Morphology | In three lines, even higher levels of organization have been reached, with full tissue differentiation. These are the brown algae,—some of which may reach 50 m in length (kelps)—the red algae, and the green algae. The most complex forms are found among the charophyte algae (see Charales and Charophyta), in a lineage that eventually led to the higher land plants. The innovation that defines these nonalgal plants is the presence of female reproductive organs with protective cell layers that protect the zygote and developing embryo. Hence, the land plants are referred to as the Embryophytes. |
Algae | 633 | Morphology | The term algal turf is commonly used but poorly defined. Algal turfs are thick, carpet-like beds of seaweed that retain sediment and compete with foundation species like corals and kelps, and they are usually less than 15 cm tall. Such a turf may consist of one or more species, and will generally cover an area in the order of a square metre or more. Some common characteristics are listed: |
Algae | 633 | Physiology | Many algae, particularly species of the Characeae, have served as model experimental organisms to understand the mechanisms of the water permeability of membranes, osmoregulation, turgor regulation, salt tolerance, cytoplasmic streaming, and the generation of action potentials. |
Algae | 633 | Physiology | Phytohormones are found not only in higher plants, but in algae, too. |
Algae | 633 | Symbiotic algae | Some species of algae form symbiotic relationships with other organisms. In these symbioses, the algae supply photosynthates (organic substances) to the host organism providing protection to the algal cells. The host organism derives some or all of its energy requirements from the algae. Examples are: |
Algae | 633 | Symbiotic algae | Lichens are defined by the International Association for Lichenology to be "an association of a fungus and a photosynthetic symbiont resulting in a stable vegetative body having a specific structure". The fungi, or mycobionts, are mainly from the Ascomycota with a few from the Basidiomycota. In nature, they do not occur separate from lichens. It is unknown when they began to associate. One mycobiont associates with the same phycobiont species, rarely two, from the green algae, except that alternatively, the mycobiont may associate with a species of cyanobacteria (hence "photobiont" is the more accurate term). A photobiont may be associated with many different mycobionts or may live independently; accordingly, lichens are named and classified as fungal species. The association is termed a morphogenesis because the lichen has a form and capabilities not possessed by the symbiont species alone (they can be experimentally isolated). The photobiont possibly triggers otherwise latent genes in the mycobiont. |
Algae | 633 | Symbiotic algae | Trentepohlia is an example of a common green alga genus worldwide that can grow on its own or be lichenised. Lichen thus share some of the habitat and often similar appearance with specialized species of algae (aerophytes) growing on exposed surfaces such as tree trunks and rocks and sometimes discoloring them. |
Algae | 633 | Symbiotic algae | Coral reefs are accumulated from the calcareous exoskeletons of marine invertebrates of the order Scleractinia (stony corals). These animals metabolize sugar and oxygen to obtain energy for their cell-building processes, including secretion of the exoskeleton, with water and carbon dioxide as byproducts. Dinoflagellates (algal protists) are often endosymbionts in the cells of the coral-forming marine invertebrates, where they accelerate host-cell metabolism by generating sugar and oxygen immediately available through photosynthesis using incident light and the carbon dioxide produced by the host. Reef-building stony corals (hermatypic corals) require endosymbiotic algae from the genus Symbiodinium to be in a healthy condition. The loss of Symbiodinium from the host is known as coral bleaching, a condition which leads to the deterioration of a reef. |
Algae | 633 | Symbiotic algae | Endosymbiontic green algae live close to the surface of some sponges, for example, breadcrumb sponges (Halichondria panicea). The alga is thus protected from predators; the sponge is provided with oxygen and sugars which can account for 50 to 80% of sponge growth in some species. |
Algae | 633 | Life cycle | Rhodophyta, Chlorophyta, and Heterokontophyta, the three main algal divisions, have life cycles which show considerable variation and complexity. In general, an asexual phase exists where the seaweed's cells are diploid, a sexual phase where the cells are haploid, followed by fusion of the male and female gametes. Asexual reproduction permits efficient population increases, but less variation is possible. Commonly, in sexual reproduction of unicellular and colonial algae, two specialized, sexually compatible, haploid gametes make physical contact and fuse to form a zygote. To ensure a successful mating, the development and release of gametes is highly synchronized and regulated; pheromones may play a key role in these processes. Sexual reproduction allows for more variation and provides the benefit of efficient recombinational repair of DNA damages during meiosis, a key stage of the sexual cycle. However, sexual reproduction is more costly than asexual reproduction. Meiosis has been shown to occur in many different species of algae. |
Algae | 633 | Numbers | The Algal Collection of the US National Herbarium (located in the National Museum of Natural History) consists of approximately 320,500 dried specimens, which, although not exhaustive (no exhaustive collection exists), gives an idea of the order of magnitude of the number of algal species (that number remains unknown). Estimates vary widely. For example, according to one standard textbook, in the British Isles the UK Biodiversity Steering Group Report estimated there to be 20,000 algal species in the UK. Another checklist reports only about 5,000 species. Regarding the difference of about 15,000 species, the text concludes: "It will require many detailed field surveys before it is possible to provide a reliable estimate of the total number of species ..." |
Algae | 633 | Numbers | Regional and group estimates have been made, as well: |
Algae | 633 | Numbers | and so on, but lacking any scientific basis or reliable sources, these numbers have no more credibility than the British ones mentioned above. Most estimates also omit microscopic algae, such as phytoplankton. |
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