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  • 9 Fun Facts About Sleep | Britannica.com
    After two minutes or so you relax further entering into stage 2 sleep Your body temperature drops and breathing becomes regular during that 20 minute stage Stages 3 and 4 where sleepwalking and talking can occur are deep restorative forms of sleep characterized by large slow brain waves Together they last approximately 30 minutes Before entering stage 5 an intriguing stage known as REM rapid eye movement sleep you pass back through stages 3 and 2 Most people repeat that cycle several times before morning 6 REM Sleep Ludmila Yilmaz Shutterstock com REM sleep is the stage in which dreams occur It is characterized by an accelerated heart rate rapid and irregular breathing and periods in which the eyes dart back and forth Approximately 25 percent of the night is spent in REM sleep and people will remember a dream more than 80 percent of the time if woken during a REM period The average person spends nearly 600 hours dreaming each year during REM sleep 5 REM Rebound Hung Chung Chih Shutterstock com Though the precise function of REM sleep is fiercely debated the fact that we need REM sleep is not If frequently interrupted during sleep or deprived of it our bodies will compensate by naturally passing more quickly through the non REM stages of sleep stages 1 2 3 and 4 into REM sleep a phenomenon known as REM rebound Humans are not the only ones who need REM sleep as REM rebound has been observed in a number of other animals as well 4 The Function of Dreams Mary Evans Sigmund Freud Copyrights courtesy of W E Freud The phenomenon of REM rebound suggests that dreams serve a purpose beyond mere entertainment A number of theories seek to explain the function of dreams Psychologist Sigmund Freud whose theories revolve around the concept of the unconscious mind believed that dreams are a way for a person to harmlessly discharge repressed thoughts and desires A more recent theory suggests that dreams allow us to consolidate and arrange our memories and yet another proposes that dreams serve the physiological purpose of preserving and maintaining neural pathways Despite those ideas other experts maintain that dreams are nothing but random meaningless bursts of brain activity 3 Dream Content The Bridgeman Art Library Getty Images Has a friend ever approached you excitedly and announced You ll never believe what I dreamt last night If so they likely followed with a vivid dream story that left you laughing or puzzled Perhaps you have experienced a dream like that yourself While fantastic dreams do occur as well as the occasional nightmare the majority of dreams are actually quite ordinary We tend to relive typical day to day events in our dreams and sometimes factors in our environment are incorporated into our dream story such as a particular scent or in an unfortunate case the buzz of an alarm clock 2 Insomnia A Common Sleep Disorder In a private collection The most commonly reported sleep

    Original URL path: http://www.britannica.com/list/9-fun-facts-about-sleep (2016-02-13)
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  • The 10 Greatest Basketball Players of All Time | Britannica.com
    this list though some sort of vague ethereal winningness Russell was one of the fiercest defenders of all time and he redefined the value of blocking shots in addition to averaging an incredible 22 5 rebounds per game over his career 5 Oscar Robertson Oh jeez this guy While I m too young to have ever seen him play his statistics are so mind blowing that I wish I had a time machine for the express purpose of going back and seeing him in action During the 1961 62 season The Big O averaged a triple double with 30 8 points 12 5 rebounds and 11 4 assists per game Oh and the 12 time All Star also helped initiate true free agency into the NBA through a landmark antitrust suit an accomplishment just as impressive as his jaw dropping on court exploits 4 Wilt Chamberlain AP Admittedly Chamberlain played at a time when post players were significantly smaller and basketball wasn t drawing the types of athletic marvels we see today but the man was so incredibly dominant that he deserves a spot in the top five regardless of context The four highest all time NBA single season scoring averages all belong to Chamberlain in his first four professional seasons The most notable of his scoring feats came on March 2 1962 when he put up an astounding 100 points in a game an NBA record that will likely never be broken In addition to his unprecedented prowess at putting up points Chamberlain was also the only person to grab more rebounds per game than Bill Russell 22 9 all while averaging more minutes played per game than any player in league history 45 8 The one time in his 14 year career that he was not an All Star was in 1970 a season in which an injured Chamberlain was limited to just 12 regular season games and yet he still managed to will his team to the NBA finals upon his return 3 Magic Johnson Stephen Dunn Getty Images One of the most ebullient personalities to ever play in the NBA Johnson s charm was a major factor in the massive increase in the league s popularity during the 1980s But he was so much more than a dazzling smile Johnson s otherworldly passing set the stage for the Showtime L A Lakers teams that captured five championships during his 13 years with the franchise The 6 9 Johnson making him the NBA s tallest point guard not only posted the best assists per game mark in league history 11 2 but had a tremendous all around game as well Famously he played center in place of the injured Abdul Jabbar in the title clinching game six of the 1980 NBA finals as a 20 year old rookie Oh and while this has nothing to do with his ranking on this list it s still incredibly awesome and noteworthy that he has successfully fought off HIV for

    Original URL path: http://www.britannica.com/list/the-10-greatest-basketball-players-of-all-time (2016-02-13)
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  • Top 5 Most Awesome Parasitic Plants | Britannica.com
    what exactly pollinates these teeny tiny flowers or how populations coordinate their flowering Mysterious and adorable It gets a spot on my favorites list for sure 3 Dodder E R Degginger Dodder Cuscuta sp is a fairly well known group of parasitic plants that form iconic masses of yellow leafless vines over their hosts Dodder plants are aggressive and use root like organs called haustoria to penetrate the stems of their hosts and siphon off their water and nutrients often to the point of host death Given that dodder species have little to no chlorophyll with which to make their own nutrients it is crucial for young seedlings to find a host before they run out of the energy supplied by their seeds usually about 5 10 days Studies have shown that these seedlings can use airborne volatile organic compounds to locate their host plants almost like a plant y sense of smell Cuscuta seedlings can even detect which of their neighboring plants are more suitable hosts and will actively grow towards them Once a young plant successfully reaches a host its embryonic root rots away and it becomes wholly dependent on its parasitism The fact that this plant can sense its hosts makes it a candidate for a creepy plant horror film and earns it a place amongst its esteemed parasitic brethren 2 Dwarf mistletoe S Kenaley Not to be confused with their Christmas y namesake which incidentally is also a parasite dwarf mistletoe Arceuthobium species are found throughout the world and primarily parasitize conifer trees Like dodder dwarf mistletoes employ haustoria to exploit their hosts vascular tissues and do little to no photosynthesis of their own While many parasitic plants spread to new hosts with the help of animals or the wind dwarf mistletoe spreads from treetop to treetop using high velocity projectile seeds Yes this plant actually explodes bullet shaped seeds onto new hosts Dwarf mistletoe fruits each house a single seed covered in a sticky substance As the fruit matures pressure builds up inside and causes the thick skin to rupture shooting the seed away from the plant at speeds of up to 90 km hr 56 mph The sticky covering helps the seed attach to the surface on which it landed ideally the branch of a nearby conifer Ballistic parasitic embryos Enough said 1 Australian Christmas tree W H Hodge A tall and beautiful flowering tree the Australian Christmas tree Nuytsia floribunda is an elegant parasitic plant Native to dry regions in southwest Australia N floribunda towers over the other plants in the landscape and flowers when many other species are dormant Equipped with green leaves the plant is able to photosynthesize and provide its own nutrition but acts as facultative parasite and steals water from its neighbors as necessary which enables both its size and dry season flowering In fact the tree maintains an extensive network of parasitic root connections with numerous other plants to exploit their various water supplies Incredibly the plant establishes

    Original URL path: http://www.britannica.com/list/top-5-most-awesome-parasitic-plants (2016-02-13)
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  • 7 of the World’s Most Poisonous Mushrooms | Britannica.com
    leading to an initial misdiagnosis of food poisoning or the stomach flu The patient may appear to recover only to suffer from a life threatening reappearance of the gastrointestinal distress coupled with liver and kidney failure 5 Webcaps Cortinarius species Kesu Fotolia The two species of webcap the deadly webcap Cortinarius rubellus and the fool s webcap Cortinarius orellanus are very similar in appearance to both each other and to a number of edible varieties These mushrooms feature a poison known as orellanin which initially causes symptoms similar to the common flu Orellanin has an insidiously long latency period and may take 2 days to 3 weeks to cause symptoms often leading to a misdiagnosis The toxin ultimately causes kidney failure and death if left untreated In 2008 English author Nicholas Evans mistakenly collected and served webcap mushrooms to his relatives resulting in hospitalization for four of them He his wife and his brother in law all required kidney transplants as a result of the poisoning 4 Autumn Skullcap Galerina marginata Thomas Brandt Fotolia Common throughout the Northern Hemisphere and parts of Australia Galerina marginata is a gilled wood rotting mushroom with the same amatoxins as the death cap mushroom Ingestion causes diarrhea vomiting hypothermia and liver damage and can result in death if left untreated While it is not especially similar to edible species several deaths and poisonings have been attributed to collectors mistaking the autumn skullcap for hallucinogenic Psilocybe mushrooms 3 Destroying Angels Amanita species Mary W Ferguson The destroying angels are actually several species of all white mushrooms in the genus Amanita These incredibly toxic fungi are very similar in appearance to edible button mushrooms and the meadow mushrooms and have been collected by mistake on numerous occassions One of these species Amanita bisporigera is considered to be the most toxic North American mushroom Symptoms take 5 to 24 hours to appear and include vomiting delirium convulsions diarrhea liver and kidney failure and often lead to death 2 Podostroma cornu damae Image Republic Inc Alamy This rare fungus is native to Asia and has been responsible for a number of fatalities in Japan and Korea Its red fruiting bodies contain potent toxins known as trichothecene mycotoxins and can cause multiple organ failure in those unlucky enough to consume them Symptoms of poisoning include stomach pain peeling skin hair loss low blood pressure liver necrosis acute kidney failure and result in death if left untreated 1 Deadly Dapperling Lepiota brunneoincarnata Poppy Alamy The deadly dapperling is a gilled mushroom known to contain amatoxins Widely distributed throughout Europe and parts of Asia the mushroom is fairly innocuous and has been mistaken for edible varieties though poisonings are not very common Accidental consumption leads to severe liver toxicity and can have lethal consequences if immediate treatment is not received Your Reaction Wee Worlds Our 5 Official Dwarf Planets 6 Amazing Facts About Gravitational Waves and LIGO MORE Science LISTS Editor Picks 9 Britannica Articles That Explain the Meaning of Life

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  • 9 of the World’s Deadliest Mammals | Britannica.com
    when young bears can be tamed quite easily and are commonly used in circus animal acts This has often caused people to consider bears as tame and harmless rather than as potentially dangerous creatures deserving wariness and respect This mistake has frequently resulted in tragedy for both humans and bears Grizzly and polar bears are the most dangerous but Eurasian brown bears and American black bears have also been known to attack humans Some species depredate livestock on occasion and some bears such as Asiatic and American black bears may destroy fruit or other crops especially corn 6 Hippopotamuses Hippopotamus amphibius Alan Weaving Ardea London Hippopotamus is Greek for river horse and the animal has been known since ancient times Hippopotamuses are often seen basking on the banks or sleeping in the waters of rivers lakes and swamps next to grasslands The hippopotamus has a bulky body on stumpy legs an enormous head a short tail and four toes on each foot Each toe has a nail like hoof Hippos are well adapted to aquatic life The ears eyes and nostrils are located high on the head so that the rest of the body may remain submerged The ears and nostrils can be folded shut to keep out water The body is so dense that they can walk underwater where they can hold their breath for five minutes Although often seen basking in the sun hippos lose water rapidly through the skin and become dehydrated without periodic dips They must also retreat to the water to keep cool for they do not sweat Numerous skin glands release a pinkish lotion which led to the ancient myth that hippos sweat blood this pigment actually acts as a sunblock filtering out ultraviolet radiation Accounts recording the number of human deaths per year by hippo attack range from about 500 to about 3 000 It is thought that hippo attacks on small boats are antipredator behavior with the hippos mistaking them for crocodiles As a result hippos have long had a largely undeserved reputation as aggressive animals Cows live in schools but they are not permanently associated with other cows though sometimes they maintain bonds with offspring for some years Longevity is up to 49 years in captivity but rarely more than 40 in the wild 5 Tigers Panthera tigris Nick Jewell The tiger is the largest member of the cat family Felidae rivaled only by the lion Panthera leo in strength and ferocity Ranging from the Russian Far East through parts of North Korea China India and Southeast Asia to the Indonesian island of Sumatra all six remaining subspecies are endangered The Siberian or Amur tiger P tigris altaica is the largest measuring up to 4 meters 13 feet in total length and weighing up to 300 kg 660 pounds The Indian or Bengal tiger P tigris tigris is the most numerous and accounts for about half of the total tiger population Next to the elephant and the lion no wild animal is so frequently portrayed in Asian art and lore The persistent practices of using tiger parts as talismans tonics or medicine despite all scientific evidence contrary to their efficacy are manifestations of beliefs that emanate from the aura of the tiger and the awe that it has inspired for millennia Certain animist communities still worship the tiger Every 12th year of the Chinese calendar is the year of the tiger and children born in it are considered especially lucky and powerful In Hindu mythology the tiger is the vahana vehicle of the goddess Durga Tigers are represented on seals from the ancient Indus civilization The greatest of the Gupta emperors of ancient India Samudra minted special gold coins depicting him slaying tigers Tippu Sultan even vented his frustration at his inability to defeat the British by ordering a special life size toy replete with sound of a tiger mauling a British soldier In India tigers have a history of attacking human visitors to zoos who either enter or place their hands into tiger enclosures Tigers are also known to attack people in the wild especially in the Sundarbans a region of forests and swampland straddling the border between India and Bangladesh By some accounts 50 to 250 people per year are killed in the Sundarbans by tigers 4 Horses Equus caballus Sally Anne Thompson EB Inc The relationship of the horse to humans has been unique The horse is a partner and friend It has plowed fields and brought in the harvest hauled goods and conveyed passengers followed game and tracked cattle and carried combatants into battle and adventurers to unknown lands It has provided recreation in the form of jousts tournaments carousels and the sport of riding The influence of the horse is expressed in the English language in such terms as chivalry and cavalier coming from the Latin caballarius horseman which connote honor respect good manners and straightforwardness The horse is the proudest conquest of Man according to the French zoologist Georges Louis Leclerc comte de Buffon Its place was at its master s side in the graves of the Scythian kings or in the tombs of the pharaohs Many early human cultures were centered on possession of the horse Superstition read meaning into the colors of the horse and a horse s head suspended near a grave or sanctuary or on the gables of a house conferred supernatural powers on the place Greek mythology created the centaur the most obvious symbol of the oneness of horse and rider White stallions were the supreme sacrifice to the gods and the Greek general Xenophon recorded that gods and heroes are depicted on well trained horses Despite being held in such high esteem horses kill roughly 100 people in the United States each year in riding accidents and other equestrian related activities Matched against horse ridership some 7 million or so the risk of death is very small however 3 Deer Order Artiodactyla Photos com Jupiterimages Corporation Worldwide deer make

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  • 10 of the World’s Most Dangerous Fish | Britannica.com
    of about 1 5 meters 5 feet but one species Thyrsoidea macrurus of the Pacific is known to grow about 3 5 meters 11 5 feet long Morays are eaten in some areas of the world but their flesh is sometimes toxic and can cause illness or death One species of moray Muraena helena found in the Mediterranean was a great delicacy of the ancient Romans and was cultivated by them in seaside ponds 5 Tigerfish Painted especially for Encyclop dia Britannica by Tom Dolan under the supervision of Loren P Woods Chicago Natural History Museum Spanning several species tigerfishes are so named on the basis of their pugnacity when caught their fiercely predaceous habits or their appearance In African freshwaters tigerfishes of the genus Hydrocynus sometimes Hydrocyon are admired game fishes of the characin family Characidae order Cypriniformes They are marked depending on the species with one or several dark lengthwise stripes and are swift voracious salmon shaped carnivores with daggerlike teeth that protrude when the mouth is closed There are about five species the largest H goliath may be more than 1 8 meters 6 feet long and may weigh more than 57 kg 125 pounds The smaller H vittatus is claimed to be one of the finest game fishes in the world In the Indo Pacific marine and freshwater tigerfishes of the family Theraponidae order Perciformes are rather small and usually marked with bold stripes The three striped tigerfish Therapon jarbua is a common vertically striped species about 30 cm 12 inches long It has sharp spines on its gill covers which can wound a careless handler 4 Piranha John Madere Corbis Piranha also called caribe or piraya are any of more than 60 species of razor toothed carnivorous fish of South American rivers and lakes with a somewhat exaggerated reputation for ferocity In movies such as Piranha 1978 the piranha has been depicted as a ravenous indiscriminate killer Most species however are scavengers or feed on plant material Most species of piranha never grow larger than 60 cm 2 feet long Colors vary from silvery with orange undersides to almost completely black These common fishes have deep bodies saw edged bellies and large generally blunt heads with strong jaws bearing sharp triangular teeth that meet in a scissorlike bite Piranhas range from northern Argentina to Colombia but they are most diverse in the Amazon River where 20 different species are found The most infamous is the red bellied piranha Pygocentrus nattereri with the strongest jaws and sharpest teeth of all Especially during low water this species which can grow up to 50 cm about 20 inches in length hunts in groups that can number more than 100 Several groups can converge in a feeding frenzy if a large animal is attacked although this is rare Red bellied piranhas prefer prey that is only slightly larger than themselves or smaller Generally a group of red bellied piranhas spreads out to look for prey When located the attacking

    Original URL path: http://www.britannica.com/list/10-of-the-worlds-most-dangerous-fish (2016-02-13)
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  • 9 Mind-Altering Plants | Britannica.com
    male and female plants but is most concentrated in the flowering tops of the female These buds are usually dried and crushed and put into pipes or formed into cigarettes joints for smoking but can also be added to foods and beverages Psychological effects tend to predominate with the user commonly experiencing a mild euphoria and alterations in vision and judgment that result in distortions of time and space Acute intoxication may occasionally induce visual hallucinations anxiety depression paranoid reactions and psychoses lasting four to six hours Marijuana s physical effects include reddening of the eyes dryness of the mouth and throat moderate increase in rapidity of the heartbeat tightness of the chest if the drug is smoked drowsiness unsteadiness and muscular incoordination Hashish a more powerful form of the drug is made by collecting and drying the plant s resin and is about eight times as strong as the marijuana typically smoked in the United States 5 Ayahuasca Banisteriopsis caapi Dr Morley Read Shutterstock Ayahuasca is a South American vine used as the primary ingredient for a psychoactive drink of the same name Culturally important to a number of Amazonian peoples the brew has grown in popularity among tourists seeking a spiritual awakening particularly in Peru Ayahuasca is said to generate intense spiritual revelations with users often reporting a sensation of rebirth and a deeper understanding of themselves and the universe However some users experience significant psychological distress under the influence of the drug and a number of deaths have been reported Ingestion is commonly followed by vomiting or diarrhea which shamans deem to be the purging of negative energies 4 Betel nut Areca catechu Wayne Lukas Group IV The National Audubon Society Collection Photo Researchers Although not well known in the West betel chewing is a habit of an estimated one tenth of the world s population and betel is considered to be the fourth most common psychoactive drug in the world following nicotine alcohol and caffeine Betel nuts grow on the areca palm and are cultivated in India Sri Lanka Thailand Malaysia and the Philippines For chewing a betel quid is formed by wrapping a small piece of the areca palm seed the betel nut in a leaf of the unrelated betel pepper plant along with a pellet of slaked lime calcium hydroxide Betel chewing releases a number of addictive alkaloids that cause sensations of mild euphoria and regular users often have red stained teeth and lips Although it is important in many cultural traditions of southern Asia betel chewing is linked to a number of serious health problems including oral and esophageal cancer and is of growing concern for health officials 3 Tobacco Nicotiana tabacum LianeM Shutterstock com Native to the Americas the tobacco plant bears distinctive large leaves that are a particularly concentrated source of nicotine Nicotine is the chief active ingredient in the tobacco used in cigarettes cigars and snuff and is an addictive drug The drug has a unique biphasic psychoactive effect when

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  • 7 Animals That Turn White in Winter | Britannica.com
    species is perhaps best known as the ermine also the name of its winter fur which is white except for the black tip of the tail The uniquely patterned fur was once used to trim the robes of royalty and clergy Weasels of the same species that live in more southerly climates usually don t change color though their more northerly relatives do In transition zones some weasels only partially change color resulting in patchy white and brown fur Interestingly color changing weasels have been shown to change color regardless of temperature or location suggesting that they too rely on photoperiod to cue their molts 5 Peary Caribou Paul Loewen iStock Thinkstock A subspecies of caribou native to the High Arctic of Canada and Greenland Peary caribou Rangifer tarandus pearyi exchange their silvery summer coats for white ones with the coming of winter They are the only subspecies of caribou to undergo such a change Other subspecies remain brown or gray year round though the shades may lighten slightly with the growth of their winter coats Peary caribou are the smallest subspecies of caribou and because of their morphological differences were once considered a separate species 4 Collared Lemmings Andrey Zvoznikov SuperStock Lemmings in the genus Dicrostonyx which comprises an indeterminate number of species turn from brown or gray in the warmer months to white when the snows come They belong to a different genus than true lemmings which remain brown Strangely they spend most of their time burrowing beneath the snow which would seem to render camouflage unnecessary They even grow special winter claws really extensions of the toe pads for digging through the drifts to create nests and reach the stems of the Arctic willows upon which they feed Their skins were once used by Eskimo peoples as clothing embellishments 3 Ptarmigans NPS Photos Katie Thoresen All three species of ptarmigans a genus of birds related to grouse chickens and pheasants trade their scalloped brown plumage for white feathers They spend spring and fall in a mottled state matching the patchy snow cover The white tailed ptarmigan Lagopus leucura turns entirely white while the willow ptarmigan L lagopus and rock ptarmigan L muta retain some black feathers in their tails Ptarmigans even develop white boots to match the downy foot covering also helps them to walk atop the snow The air bubbles in their winter feathers which may help with insulation scatter light making them appear more brightly white than other white birds 2 Siberian Hamsters GrrlScientist This is probably the only animal on this list that you can actually keep as a pet The Siberian hamster or Dzhungarian hamster Phodopus sungorus often sold as the winter white will change from a silvery chinchilla shade to mostly white if it is kept in a room that receives natural light Temperature does not seem to affect the molt 1 Arctic Foxes Photos com Thinkstock Arctic foxes Vulpes lagopus are typically brownish gray in the summer and frosty white in

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