AcharyaChanakya/simple-wikipedia huggingface dataset:
While trying to save Nemo, Marlin meets Dory, a good-hearted and optimistic Regal blue tang with short-term memory loss. While meeting three sharks on a fish-free diet, Bruce, a great white shark; Anchor, a hammerhead shark; and Chum, a mako shark, Marlin discovers the diver's mask that was dropped from the boat and notices an address written on it. However, when he argues with Dory and accidentally gives her a nosebleed, the scent of blood causes Bruce to lose control of himself and attempt to eat Marlin and Dory. The two escape from Bruce but the mask falls into a trench in the deep sea. During a hazardous struggle with an anglerfish in the trench, Dory realizes she is able to read the address written on the mask, which leads to Sydney, Australia, and manages to remember it. She repeats " P. Sherman 42 Wallaby Way Sydney" to keep it in her memory. After receiving directions to Sydney from a large school of Silver moony, Marlin and Dory accidentally run into a bloom of jellyfish that nearly sting them to death; Marlin falls exhausted after the risky escape and wakes up to see a surf-cultured Green sea turtle named Crush, who takes Dory and him on the East Australian Current, referred to as the EAC by the animals. In the current, Marlin shares the story of his journey with a group of young sea turtles who spread the story around the ocean.
Meanwhile, Nemo's captor - P. Sherman, a dentist - places him into a fish tank in his office on Sydney Harbour. There, Nemo meets a group of aquarium fish called the "Tank Gang", led by a crafty and ambitious moorish idol named Gill. The "Tank Gang" includes Bloat, a puffer fish; Bubbles, a Yellow tang; Peach, a starfish; Gurgle, a Royal gramma; Jacques, a pacific cleaner shrimp; and Deb, a Blacktailed humbug. The fish are frightened to learn that the dentist plans to give Nemo to his niece, Darla. She is infamous for killing a goldfish given to her previously by constantly shaking the bag. In order to avoid this fate, Gill gives Nemo a role in an escape plan, which involves jamming the tank's filter and forcing the dentist to remove the fish from the tank to clean it manually. The fish would be placed in plastic bags, at which point they would roll out the window and into the harbor. After a friendly pelican named Nigel visits with news of Marlin's adventure, Nemo succeeds in jamming the filter, but the plan backfires when the dentist installs a new high-tech filter.
While leaving the East Australian Current, Marlin and Dory get lost in the blooms of plankton and krill and are caught by a blue whale. Inside the whale's immense mouth, Marlin tries to escape while Dory talks with it in whale-speak. So, the whale carries them to Sydney Harbour and expels them through his blowhole. They are met by Nigel, who recognizes Marlin from the stories he has heard and rescues him and Dory from a flock of hungry seagulls by scooping them into his beak and taking them to the dentist's man's office. By this time, Darla has arrived and the dentist is prepared to give Nemo to her. Nemo tries to play dead in hopes of saving himself, and, at the same time, Nigel arrives. Marlin sees Nemo and mistakes this act for the actual death of his son. After a struggle, Gill helps Nemo escape into a drain through a sink.
Sad, Marlin leaves Dory and begins to swim back home. Dory then loses her memory and becomes confused, but meets Nemo, who has reached the ocean through an underwater drainpipe. Dory's memory is restored after she reads the word "Sydney" on a nearby drainpipe and, remembering her journey, she guides Nemo to Marlin. After the two joyfully reunite, Dory is caught in a fishing net with a school of grouper. Nemo bravely enters the net and directs the group to swim downward to break the net, reminiscent of a similar scenario that occurred in the fish tank earlier. The fish, including Dory, succeed in breaking the net and escape. After some days, Nemo leaves for school once more and Marlin who is no longer overprotective or doubtful of his son's safety, proudly watches Nemo swim away into the distance.
Back at the dentist's office, the high-tech filter breaks down and The Tank Gang escape into the harbor. But, they realize that they are trapped in the bags of water that the dentist put them into when cleaning the tank.
"Finding Nemo" currently holds a 99% fresh rating at Rotten Tomatoes with 100% by top critics, and an average of 89% on Metacritic. Roger Ebert gave the film four stars, calling it "one of those rare movies where I wanted to sit in the front row and let the images wash out to the edges of my field of vision." Broadway star Nathan Lane who was the voice of Timon the meerkat in "The Lion King", said "Finding Nemo" was his favorite animated film.
The film's use of clownfish prompted mass purchase of the animal as pets in the United States, even though the movie portrayed the use of fish as pets negatively and suggested that saltwater aquariums are notably tricky and expensive to maintain. The demand for clownfish was supplied by large-scale harvesting of tropical fish in regions like Vanuatu.
At the same time, the film had a quote that "all drains lead back to the ocean" (Nemo escapes from the aquarium by going down a sink drain, ending up in the sea). Since water typically undergoes treatment before leading to the ocean, the JWC Environmental company quipped that a more realistic title for the movie might be "Grinding Nemo". However, in Sydney, much of the sewer system does pass directly to outfall pipes deep offshore, without a high level of treatment (although pumping and some filtering occur). Additionally, according to the DVD, there was a cut sequence with Nemo going through a treatment plant's mechanisms before ending up in the ocean pipes. However, in the final product, logos for "Sydney Water Treatment" are featured prominently along the path to the ocean, implying that Nemo did pass through some water treatment.
The Australian Tourism Commission (ATC) launched several marketing campaigns in China and the USA in order to improve tourism in Australia, many of them using "Finding Nemo" clips. Queensland also used "Finding Nemo" to draw tourists to promote its state for vacationers.
On the 3-D re-release, Lisa Schwarzbaum of Entertainment Weekly wrote that its emotional power was deepened by "the dimensionality of the oceanic deep" where "the spatial mysteries of watery currents and floating worlds are exactly where 3-D explorers were born to boldly go."
The 3-D re-release also prompted a retrospective on the film then nine years after its initial release. Stephen Whitty of the Newark Star-Ledger described it as "A genuinely funny and touching film that, in less than a decade, has established itself as a timeless classic," with Roger Moore of the McClatchy-Tribune News Service calling the movie "the gold standard against which all other modern animated films are measured."
"Finding Nemo" was released on DVD and VHS on November 4, 2003. The film was also released on DVD in a "Gold Edition", which came with a "Finding Nemo" stuffed toy character. The film had a home video release on both Blu-ray and Blu-ray 3D on December 4, 2012, with both a 3-disc and a 5-disc set.
The inspiration for Nemo was made up of multiple experiences. The idea goes back to when director Andrew Stanton was a child, when he loved going to the dentist to see the fish tank, assuming that the fish were from the ocean and wanted to go home. In 1992 shortly after his son was born, he and his family took a trip to Six Flags Discovery Kingdom (which was called Marine World at the time). There he saw the shark tube and various exhibits he felt that the underwater world could be done beautifully in computer animation. Later, in 1997 he took his son for a walk in the park, but found that he was over protecting him constantly and lost an opportunity to have any "father-son experiences" on that day. In an interview with "National Geographic" magazine, he stated that the idea for the characters of Marlin and Nemo came from a photograph of two clownfish peeking out of an anemone:"It was so arresting. I had no idea what kind of fish they were, but I couldn't take my eyes off them. And as an entertainer, the fact that they were called clownfish—it was perfect. There's almost nothing more appealing than these little fish that want to play peekaboo with you." Also, clownfish are very colourful, but don't tend to come out of an anemone very often, and for a character who has to go on a dangerous journey, Stanton felt a clownfish was the perfect kind of fish for the character.
Pre-production of the film took place in early 1997. Stanton began writing the screenplay during the post-production of "A Bug's Life". As such, it began production with a complete screenplay, something that co-director Lee Unkrich called "very unusual for an animated film." The artists took scuba diving lessons so they could go and study the coral reef. The idea for the initiation sequence came from a story conference between Andrew Stanton and Bob Peterson while driving to record the actors. Ellen DeGeneres was cast after Stanton was watching "Ellen" with his wife and seeing Ellen "change the subject five times before finishing one sentence" as Stanton recalled. There was a pelican character known as Gerald (who in the final film ends up swallowing and choking on Marlin and Dory) who was originally a friend of Nigel. They were going to play against each other as Nigel being neat fastidious while Gerald being scruffy and sloppy. However the filmmakers could not find an appropriate scene for them that didn't slow the pace of the picture down, so Gerald's character was minimized.
Stanton himself provided the voice of Crush the sea turtle. Stanton originally did the voice for the film's story reel, and assumed they would find an actor later. When Stanton's performance was popular in test screenings, Stanton decided to keep his performance in the film. Stanton recorded all his dialogue while lying on a sofa in co-director Lee Unkrich's office.
Crush's son Squirt was voiced by Nicholas Bird, the young son of fellow Pixar director Brad Bird. According to Stanton, the elder Bird was playing a tape recording of his young son around the Pixar studios one day. Stanton felt the voice was "this generation's Thumper" and immediately cast Nicholas.
Megan Mullally revealed that she was originally doing a voice in the film. According to Mullally, the producers were dissatisfied to learn that the voice of her character Karen Walker on the television show "Will & Grace" was not her natural speaking voice. The producers hired her anyway, and then strongly encouraged her to use her Karen Walker voice for the role. When Mullally refused, she was dismissed.
The film was dedicated to Glenn McQueen, a Pixar animator who died of melanoma in October 2002.
Finding Nemo shares many plot elements with "Pierrot the Clownfish", a children's book published in 2002, but allegedly conceived in 1995. The author, Franck Le Calvez, sued Disney for infringement of his intellectual rights. The judge ruled against him, citing the color differences between Pierrot and Nemo.
To ensure that the movements of the fish in the film were believable the animators essentially took a crash course in fish biology and oceanography. They visited aquariums, went diving in Hawaii and received in-house lectures from an ichthyologist.
"Finding Nemo" earned $380,673,009 in North America, and $540,900,000 in other countries, for a worldwide total of $921,573,009. It is the second highest-grossing film of 2003, behind "". In North America, outside North America, and worldwide, it was the highest-grossing Pixar film, up until 2010 when "Toy Story 3" surpassed it.
"Finding Nemo" set an opening-weekend record for an animated feature, making $70,251,710 (first surpassed by "Shrek 2"). It became the highest-grossing animated film in North America ($339.7 million), outside North America ($528.2 million) and worldwide ($867.9 million), in all three occasions outgrossing "The Lion King". In North America, it was surpassed by both "Shrek 2" in 2004, and "Toy Story 3" in 2010. After the re-release of "The Lion King" in 2011, it stands as the fourth highest-grossing animated film in these regions. Outside North America, it was surpassed by "", "Toy Story 3", and "". Worldwide, it now ranks third among animated films.
The film had impressive box office runs in many international markets. In Japan, its highest-grossing market after North America, it grossed $102.4 million becoming the highest-grossing Western animated film until it was out-grossed by "Toy Story 3" ($126.7 million). Following in biggest grosses are the UK, Ireland and Malta, where it grossed £37.2 million ($67.1 million), France and the Maghreb region ($64.8 million), Germany ($53.9 million), and Spain ($29.5 million).
After the success of the 3D re-release of "The Lion King", Disney and Pixar re-released "Finding Nemo" in 3D on September 14, 2012, with a conversion cost estimated below $5 million. For the opening weekend of its 3D re-release in North America, "Finding Nemo" grossed $16.7 million, debuting at the No. 2 spot behind "". From seven foreign markets, it earned a total of $5.1 million.
Finding Nemo won the Academy Award and Saturn Award for Best Animated Film. It also won the award for best Animated Film at the Kansas City Film Critics Circle Awards, the Las Vegas Film Critics Society Awards, the National Board of Review Awards, the Online Film Critics Society Awards, and the Toronto Film Critics Association Awards.
The film received many awards, including:
"Finding Nemo" was also nominated for:
In June 2008, the American Film Institute revealed its "Ten top Ten", the best ten films in ten "classic" American film genres, after polling over 1,500 people from the creative community. "Finding Nemo" was acknowledged as the 10th best film in the animation genre. It was the most recently released film among all ten lists, and one of only three movies made after the year 2000, the others being "" and "Shrek".
A video game based on the film was released in 2003, for PC, Xbox, PS2, GameCube and GBA.
In 2005, after disagreements between Disney's Michael Eisner and Pixar's Steve Jobs over the distribution of Pixar's films, Disney announced that they would be creating a new animation studio, Circle 7 Animation, to make sequels to the seven Disney-owned Pixar films (which consisted of the films released between 1995 and 2006). The studio had put "Toy Story 3" and "Monsters, Inc. 2" in development, and had also hired screenwriter Laurie Craig to write a draft for "Finding Nemo 2". Circle 7 was subsequently shut down after Robert Iger replaced Eisner as CEO of Disney and arranged the acquisition of Pixar.
In July 2012, it was reported that Andrew Stanton is developing a sequel to "Finding Nemo", with Victoria Strouse writing the script and a schedule to be released in 2016. However, the same day the news of a potential sequel broke, director Andrew Stanton posted a message on his personal Twitter calling into question the accuracy of these reports. The message said, "Didn't you all learn from "Chicken Little"? Everyone calm down. Don't believe everything you read. Nothing to see here now. #skyisnotfalling" According to the report by Hollywood Reporter published in August 2012, Ellen DeGeneres is in negotiations to reprise her role of Dory. In September 2012, it was confirmed by Stanton saying: "What was immediately on the list was writing a second "Carter" movie. When that went away, everything slid up. I know I'll be accused by more sarcastic people that it's a reaction to "Carter" not doing well, but only in its timing, but not in its conceit."
Fibonacci, also known as Leonardo Bonacci, Leonardo Fibonacci and Leonardo of Pisa, lived c. 11701250. He was an Italian mathematician. He was thought "the most talented Western mathematician of the Middle Ages".
Fibonacci popularized the Hindu–Arabic numeral system to the Western World. He did this in his composition in 1202 of "Liber Abaci" ("Book of Calculation"). He also introduced to Europe the sequence of Fibonacci numbers which he used as an example in "Liber Abaci".
Fibonacci is best known for the list of numbers called the Fibonacci Sequence. The list never stops, but it starts this way:
In this list, a person can find the next number by adding the last two numbers together.
This series is also interesting because the ratio of two adjacent numbers in the series approaches the golden ratio.
Richard Stallman (born March 16, 1953) is the founder of the free software movement, the GNU project, and the Free Software Foundation. He is also a famous hacker. He created GNU Emacs, the GNU C Compiler, and the GNU Debugger. He is one of the main authors of the GNU General Public License ("GNU GPL" or "GPL"), the most used free software license, which pioneered the concept of the copyleft.
Since the mid-1990s, he has spent most of his time as a political campaigner, talking about free software and campaigning against proprietary software, software idea patents and expansions of copyright law. The time that he still spends on programming is spent on GNU Emacs. He is currently supported by various fellowships and maintains a modest standard of living.
National Hockey League
The National Hockey League or NHL, is the highest-level ice hockey league in the world. It has 31 teams - seven are from Canada and the other 24 are from the United States. The winner of the league each year wins the Stanley Cup.
The NHL began in 1917. Some of the owners in the National Hockey Association had problems with owner Edward Livingstone, so they got rid of him by creating a new league. There were five teams in 1917:
They played 22 games a year. The Wanderers had to stop playing in the first year because their arena burned down. Over the years some teams died out, and others were created: the Boston Bruins, New York Americans, Montreal Maroons, Pittsburgh Pirates (later Philadelphia Quakers), New York Rangers, Chicago Black Hawks and Detroit Cougars (later Falcons, then Red Wings).
Some teams folded during the Great Depression, so by 1942 there were only six teams:
There were only these six teams for 25 years, so they became known as the "Original Six".
By the 1940s, they were playing 50 games a year, but this increased slowly to 80 games by the 1970s. In 1967, the league increased to 12 teams. By 1979 it had 21 teams, and today it has 31. Some of the teams that no longer exist are the Oakland Seals, Minnesota North Stars (now the Dallas Stars), Winnipeg Jets (now the Arizona Coyotes), Kansas City Scouts (which became the Colorado Rockies and are now the New Jersey Devils), Hartford Whalers (now the Carolina Hurricanes), Quebec Nordiques (now the Colorado Avalanche) and Atlanta Thrashers (now the current Winnipeg Jets).
Today they play 82 games a year, plus four rounds of playoffs. The players make a lot of money (many make over a million dollars a year). Because they could make so much money, many Europeans came over to North America to play in the NHL. Today almost all the world's best hockey players are in the NHL.
Isaac Asimov ( – April 6, 1992) was a writer of science fiction. He was also a biochemist with a PhD from Columbia University.
Asimov was born in Petrovichi, Smolensk Oblast, Russian SFSR to a Jewish family, on an unknown date between October 4, 1919 and January 2, 1920. Asimov celebrated his birthday on January 2. He was taken to the United States when he was three, and learned English and Yiddish as his native languages. He wrote many books. People know about Isaac Asimov because of his science fiction books and his science books for non-scientists.
Asimov's most famous books were the Foundation series. He also wrote the "Galactic Empire" and the "Robot" Series. He also wrote mystery, fantasy, and non-fiction books. He wrote or edited over 500 books and about 90,000 letters. Other subjects he wrote about were history, the Bible, literature, and sexuality.
Many of Asimov's early writings were short stories published in cheap science fiction and fantasy magazines. Years later, most of them were collected and republished as collections. Well-known collections include "I, Robot", "The Rest of the Robots", "Earth is Room Enough" and "The Early Asimov".
Asimov made a list of 15 of his science fiction books, which he advised should be read in this order:
Numbers 1–5 are 'Robot' books; 6–8 are 'Galacticos Empire' books; 9–15 are Foundation series books.
Asimov's novels have influenced science fiction on television and movie. Especially his 'Three Laws of Robotics' is a lasting contribution to our thinking.
Although ethnically a Jew, Asimov was an atheist:
When he had heart surgery in 1983, he received blood infected with HIV. He developed AIDS, and died of the effects of the medical condition in 1992. His widow did not speak of this until years later.
1980 (MCMLXXX) was .
1963 (MCMLXIII) is .
1977 (MCMLXXVII) was .
1907 (MCMVII) was a common year starting on Tuesday of the Gregorian calendar.
September 14
September 28
February 6
1911 (MCMXI) was a common year starting on Sunday of the Gregorian calendar.
February 24
1962 (MCMLXII) was .
Evolution is a biological process. It is how living things change over time and how new species develop. The theory of evolution explains how evolution works and how living and extinct things have come to be the way they are. The theory of evolution is a very important idea in biology. Theodosius Dobzhansky, a well-known evolutionary biologist, has said: "Nothing in biology makes sense except in the light of evolution".
Evolution has been happening since life started on Earth and is happening now. Evolution happens mostly by natural selection. Living things are all different from each other. Even living things of the same species look, move, and behave differently. Some differences make it easier for living things to survive and have babies. Differences may make it easier to find food, hide from danger, or have babies. The babies keep some of the differences that made it easier for their parents to have them. Over time, these differences get bigger and living things change enough to be a new species.
It is known that living things have changed over time, because their remains can be seen in the rocks. These remains are called 'fossils'. This proves that the animals and plants of today are different from those of long ago. The older the fossils, the bigger the differences from modern forms. This has happened because evolution has taken place. That evolution has taken place is a fact, because it is overwhelmingly supported by many lines of evidence. At the same time, evolutionary questions are still being actively researched by biologists.
Comparison of DNA sequences allows organisms to be grouped by how similar their sequences are. In 2010 an analysis compared sequences to phylogenetic trees, and supported the idea of common descent. There is now "strong quantitative support, by a formal test", for the unity of life.
The evidence for evolution is given in a number of books. Some of this evidence is discussed here.
The realization that some rocks contain fossils was a very important event in natural history. There are three parts to this story:
This is a topic which fascinated both Charles Darwin and Alfred Russel Wallace. When new species occur, usually by the splitting of older species, this takes place in one place in the world. Once it is established, a new species may spread to some places and not others.
Australasia has been separated from other continents for many millions of years. In the main part of the continent, Australia, 83% of mammals, 89% of reptiles, 90% of fish and insects and 93% of amphibians are endemic. Its native mammals are mostly marsupials like kangaroos, bandicoots, and quolls. By contrast, marsupials are today totally absent from Africa and form a small portion of the mammalian fauna of South America, where opossums, shrew opossums, and the monito del monte occur (see the Great American Interchange).
The only living representatives of primitive egg-laying mammals (monotremes) are the echidnas and the platypus. They are only found in Australasia, which includes Tasmania, New Guinea, and Kangaroo Island. These monotremes are totally absent in the rest of the world. On the other hand, Australia is missing many groups of placental mammals that are common on other continents (carnivora, artiodactyls, shrews, squirrels, lagomorphs), although it does have indigenous bats and rodents, which arrived later.
The evolutionary story is that placental mammals evolved in Eurasia, and wiped out the marsupials and monotremes wherever they spread. They did not reach Australasia until more recently. That is the simple reason why Australia has most of the world's marsupials and all the world's monotremes.
The evolution of the horse family (Equidae) is a good example of the way that evolution works. The oldest fossil of a horse is about 52 million years old. It was a small animal with five toes on the front feet and four on the hind feet. At that time, there were more forests in the world than today. This horse lived in woodland, eating leaves, nuts and fruit with its simple teeth. It was only about as big as a fox.
About 30 million years ago the world started to become cooler and drier. Forests shrank; grassland expanded, and horses changed. They ate grass, they grew larger, and they ran faster because they had to escape faster predators. Because grass wears teeth out, horses with longer-lasting teeth had an advantage.
For most of this long period of time, there were a number of horse types (genera). Now, however, only one genus exists: the modern horse, "Equus". It has teeth which grow all its life, hooves on single toes, great long legs for running, and the animal is big and strong enough to survive in the open plain. Horses lived in western Canada until 12,000 years ago, but all horses in North America became extinct about 11,000 years ago. The causes of this extinction are not yet clear. Climate change and over-hunting by humans are suggested.
So, scientists can see that changes have happened. They have happened slowly over a long time. How these changes have come about is explained by the theory of evolution.
In about , the Hawaiian Islands have the most diverse collection of "Drosophila" flies in the world, living from rainforests to mountain meadows. About 800 Hawaiian fruit fly species are known.
Genetic evidence shows that all the native fruit fly species in Hawaii have descended from "a single ancestral species" that came to the islands, about 20 million years ago. Later adaptive radiation was caused by a lack of competition and a wide variety of vacant niches. Although it would be possible for a single pregnant female to colonise an island, it is more likely to have been a group from the same species.
The combination of continental drift and evolution can explain what is found in the fossil record. "Glossopteris" is an extinct species of seed fern plants from the Permian period on the ancient supercontinent of Gondwana.
"Glossopteris" fossils are found in Permian strata in southeast South America, southeast Africa, all of Madagascar, northern India, all of Australia, all of New Zealand, and scattered on the southern and northern edges of Antarctica.
During the Permian, these continents were connected as Gondwana. This is known from magnetic striping in the rocks, other fossil distributions, and glacial scratches pointing away from the temperate climate of the South Pole during the Permian.
When biologists look at living things, they see that animals and plants belong to groups which have something in common. Charles Darwin explained that this followed naturally if "we admit the common parentage of allied forms, together with their modification through variation and natural selection".
For example, all insects are related. They share a basic body plan, whose development is controlled by master regulatory genes. They have six legs; they have hard parts on the outside of the body (an exoskeleton); they have eyes formed of many separate chambers, and so on. Biologists explain this with evolution. All insects are the descendants of a group of animals who lived a long time ago. They still keep the basic plan (six legs and so on) but the details change. They look different now because they changed in different ways: this is evolution.
It was Darwin who first suggested that all life on Earth had a single origin, and from that beginning "endless forms most beautiful and most wonderful have been, and are being, evolved". Evidence from molecular biology in recent years has supported the idea that all life is related by common descent.
Strong evidence for common descent comes from vestigial structures. The useless wings of flightless beetles are sealed under fused wing covers. This can be simply explained by their descent from ancestral beetles which had wings that worked.
Rudimentary body parts, those that are smaller and simpler in structure than corresponding parts in ancestral species, are called vestigial organs. Those organs are functional in the ancestral species but are now either nonfunctional or re-adapted to a new function. Examples are the pelvic girdles of whales, halteres (hind wings) of flies, wings of flightless birds, and the leaves of some xerophytes ("e.g." cactus) and parasitic plants ("e.g." dodder).
However, vestigial structures may have their original function replaced with another. For example, the halteres in flies help balance the insect while in flight, and the wings of ostriches are used in mating rituals, and in aggressive display. The ear ossicles in mammals are former bones of the lower jaw.
In 1893, Robert Wiedersheim published a book on human anatomy and its relevance to man's evolutionary history. This book contained a list of 86 human organs that he considered vestigial. This list included examples such as the appendix and the 3rd molar teeth (wisdom teeth).
The strong grip of a baby is another example. It is a vestigial reflex, a remnant of the past when pre-human babies clung to their mothers' hair as the mothers swung through the trees. This is borne out by the babies' feet, which curl up when it is sitting down (primate babies grip with the feet as well). All primates except modern man have thick body hair to which an infant can cling, unlike modern humans. The grasp reflex allows the mother to escape danger by climbing a tree using both hands and feet.
Vestigial organs often have some selection against them. The original organs took resources, sometimes huge resources. If they no longer have a function, reducing their size improves fitness. And there is direct evidence of selection. Some cave crustacea reproduce more successfully with smaller eyes than do those with larger eyes. This may be because the nervous tissue dealing with sight now becomes available to handle other sensory input.
From the eighteenth century it was known that embryos of different species were much more similar than the adults. In particular, some parts of embryos reflect their evolutionary past. For example, the embryos of land vertebrates develop gill slits like fish embryos. Of course, this is only a temporary stage, which gives rise to many structures in the neck of reptiles, birds and mammals. The proto-gill slits are part of a complicated system of development: that is why they persisted.
Another example are the embryonic teeth of baleen whales. They are later lost. The baleen filter is developed from different tissue, called keratin. Early fossil baleen whales did actually have teeth as well as the baleen.
A good example is the barnacle. It took many centuries before natural historians discovered that barnacles were crustacea. Their adults look so unlike other crustacea, but their larvae are very similar to those of other crustacea.
Charles Darwin lived in a world where animal husbandry and domesticated crops were vitally important. In both cases farmers selected for breeding individuals with special properties, and prevented the breeding of individuals with less desirable characteristics. The eighteenth and early nineteenth century saw a growth in scientific agriculture, and artificial breeding was part of this.
Darwin discussed artificial selection as a model for natural selection in the 1859 first edition of his work "On the Origin of Species", in Chapter IV: Natural selection:
Nikolai Vavilov showed that rye, originally a weed, came to be a crop plant by unintentional selection. Rye is a tougher plant than wheat: it survives in harsher conditions. Having become a crop like the wheat, rye was able to become a crop plant in harsh areas, such as hills and mountains.
There is no real difference in the genetic processes underlying artificial and natural selection, and the concept of artificial selection was used by Charles Darwin as an illustration of the wider process of natural selection. There are practical differences. Experimental studies of artificial selection show that "the rate of evolution in selection experiments is at least two orders of magnitude (that is 100 times) greater than any rate seen in nature or the fossil record".
Some have thought that artificial selection could not produce new species. It now seems that it can.
New species have been created by domesticated animal husbandry, but the details are not known or not clear. For example, domestic sheep were created by hybridisation, and no longer produce viable offspring with "Ovis orientalis", one species from which they are descended. Domestic cattle, on the other hand, can be considered the same species as several varieties of wild ox, gaur, yak, etc., as they readily produce fertile offspring with them.
The best-documented new species came from laboratory experiments in the late 1980s. William Rice and G.W. Salt bred fruit flies, "Drosophila melanogaster," using a maze with three different choices of habitat such as light/dark and wet/dry. Each generation was put into the maze, and the groups of flies that came out of two of the eight exits were set apart to breed with each other in their respective groups.
After thirty-five generations, the two groups and their offspring were isolated reproductively because of their strong habitat preferences: they mated only within the areas they preferred, and so did not mate with flies that preferred the other areas.
Diane Dodd was also able to show how reproductive isolation can develop from mating preferences in "Drosophila pseudoobscura" fruit flies after only eight generations using different food types, starch and maltose.
Dodd's experiment has been easy for others to repeat. It has also been done with other fruit flies and foods.
Some biologists say that evolution has happened when a trait that is caused by genetics becomes more or less common in a group of organisms. Others call it evolution when new species appear.
Changes can happen quickly in the smaller, simpler organisms. For example, many bacteria that cause disease can no longer be killed with some of the antibiotic medicines. These medicines have only been in use about eighty years, and at first worked extremely well. The bacteria have evolved so that they are no longer affected by antibiotics anymore. The drugs killed off all the bacteria except a few which had some resistance. These few resistant bacteria produced the next generation.
The Colorado beetle is famous for its ability to resist pesticides. Over the last 50 years it has become resistant to 52 chemical compounds used in insecticides, including cyanide. This is natural selection speeded up by the artificial conditions. However, not every population is resistant to every chemical. The populations only become resistant to chemicals used in their area.
Although there were a number of natural historians in the 18th century who had some idea of evolution, the first well-formed ideas came in the 19th century. Three biologists are most important.
Jean-Baptiste de Lamarck (1744–1829), a French biologist, claimed that animals changed according to natural laws. He said that animals could pass on traits they had acquired during their lifetime to their offspring, using inheritance. Today, his theory is known as Lamarckism. Its main purpose is to explain adaptations by natural means. He proposed a tendency for organisms to become more complex, moving up a ladder of progress, plus "use and disuse".
Lamarck's idea was that a giraffe's neck grew longer because it tried to reach higher up. This idea failed because it conflicts with heredity (Mendel's work). Mendel made his discoveries about half a century after Lamarck's work.
Charles Darwin (1809–1882) wrote his "On the Origin of Species" in 1859. In this book, he put forward much evidence that evolution had occurred. He also proposed natural selection as the way evolution had taken place. But Darwin did not understand about genetics and how traits were actually passed on. He could not accurately explain what made children look like their parents.
Nevertheless, Darwin's explanation of evolution was fundamentally correct. In contrast to Lamarck, Darwin's idea was that the giraffe's neck became longer because "those with longer necks survived better". These survivors passed their genes on, and in time the whole species got longer necks.
Alfred Russel Wallace OM FRS (1823–1913) was a British naturalist, explorer, biologist and social activist. He proposed a theory of natural selection at about the same time as Darwin. His idea was published in 1858 together with Charles Darwin's idea.
An Austrian monk called Gregor Mendel (1822–1884) bred plants. In the mid-19th century, he discovered how traits were passed on from one generation to the next.
He used peas for his experiments: some peas have white flowers and others have red ones. Some peas have green seeds and others have yellow seeds. Mendel used artificial pollination to breed the peas. His results are discussed further in Mendelian inheritance. Darwin thought that the inheritance from both parents blended together. Mendel proved that the genes from the two parents stay separate, and may be passed on unchanged to later generations.
Mendel published his results in a journal that was not well-known, and his discoveries were overlooked. Around 1900, his work was rediscovered. Genes are bits of information made of DNA which work like a set of instructions. A set of genes are in every living cell. Together, genes organise the way an egg develops into an adult. With mammals, and many other living things, a copy of each gene comes from the father and another copy from the mother. Some living organisms, including some plants, only have one parent, so get all their genes from them. These genes produce the genetic differences which evolution acts on.
Darwin's "On the Origin of Species" has two themes: the evidence for evolution, and his ideas on how evolution took place. This section deals with the second issue.
The first two chapters of the "Origin" deal with variation in domesticated plants and animals, and variation in nature.
All living things show variation. Every population which has been studied shows that animal and plants vary as much as humans do. This is a great fact of nature, and without it evolution would not occur. Darwin said that, just as man selects what he wants in his farm animals, so in nature the variations allow natural selection to work.
The features of an individual are influenced by two things, heredity and environment. First, development is controlled by genes inherited from the parents. Second, living brings its own influences. Some things are entirely inherited, others partly, and some not inherited at all.
The colour of eyes is entirely inherited; they are a genetic trait. Height or weight is only partly inherited, and the language is not at all inherited. Just to be clear: the fact that humans can speak is inherited, but what language is spoken depends on where a person lives and what they are taught. Another example: a person inherits a brain of somewhat variable capacity. What happens after birth depends on many things such as home environment, education and other experiences. When a person is adult, their brain is what their inheritance and life experience have made it.
"Evolution only concerns the traits which can be inherited", wholly or partly. The hereditary traits are passed on from one generation to the next through the genes. A person's genes contain all the traits which they inherit from their parents. The accidents of life are not passed on. Also, of course, each person lives a somewhat different life: that increases the differences.
Organisms in any population vary in reproductive success. From the point of view of evolution, 'reproductive success' means the total number of offspring which live to breed and leave offspring themselves.
Variation can only affect future generations if it is inherited. Because of the work of Gregor Mendel, we know that much variation is inherited. Mendel's 'factors' are now called genes. Research has shown that "almost every individual in a sexually reproducing species is genetically unique".
Genetic variation is increased by gene mutations. DNA does not always reproduce exactly. Rare changes occur, and these changes can be inherited. Many changes in DNA cause faults; some are neutral or even advantageous. This gives rise to genetic variation, which is the seed-corn of evolution. Sexual reproduction, by the crossing over of chromosomes during meiosis, spreads variation through the population. Other events, like natural selection and drift, reduce variation. So a population in the wild always has variation, but the details are always changing.
Evolution mainly works by natural selection. What does this mean? Animals and plants which are best suited to their environment will, on average, survive better. There is a struggle for existence. Those who survive will produce the next generation. Their genes will be passed on, and the genes of those who did not reproduce will not. This is the basic mechanism which changes a population and causes evolution.
Natural selection explains why living organisms change over time to have the anatomy, the functions and behaviour that they have. It works like this:
There are now many cases where natural selection has been proved to occur in wild populations. Almost every case investigated of camouflage, mimicry and polymorphism has shown strong effects of selection.
The force of selection can be much stronger than was thought by the early population geneticists. The resistance to pesticides has grown quickly. Resistance to "warfarin" in Norway rats ("Rattus norvegicus") grew rapidly because those that survived made up more and more of the population. Research showed that, in the absence of "warfarin", the resistant homozygote was at a 54% disadvantage to the normal wild type homozygote. This great disadvantage was quickly overcome by the selection for "warfarin" resistance.
Mammals normally cannot drink milk as adults, but humans are an exception. Milk is digested by the enzyme lactase, which switches off as mammals stop taking milk from their mothers. The human ability to drink milk during adult life is supported by a lactase mutation which prevents this switch-off. Human populations have a high proportion of this mutation wherever milk is important in the diet. The spread of this 'milk tolerance' is promoted by natural selection, because it helps people survive where milk is available. Genetic studies suggest that the oldest mutations causing lactase persistence only reached high levels in human populations in the last ten thousand years. Therefore, lactase persistence is often cited as an example of recent human evolution. As lactase persistence is genetic, but animal husbandry a cultural trait, this is gene–culture coevolution.
Adaptation is one of the basic phenomena of biology. Through the process of adaptation, an organism becomes better suited to its habitat.
Adaptation is one of the two main processes that explain the diverse species we see in biology. The other is speciation (species-splitting or cladogenesis). A favourite example used today to study the interplay of adaptation and speciation is the evolution of cichlid fish in African rivers and lakes.
When people speak about adaptation they often mean something which helps an animal or plant survive. One of the most widespread adaptations in animals is the evolution of the eye. Another example is the adaptation of horses' teeth to grinding grass. Camouflage is another adaptation; so is mimicry. The better adapted animals are the most likely to survive, and to reproduce successfully (natural selection).
An internal parasite (such as a fluke) is a good example: it has a very simple bodily structure, but still the organism is highly adapted to its particular environment. From this we see that adaptation is not just a matter of visible traits: in such parasites critical adaptations take place in the life cycle, which is often quite complex.
Not all features of an organism are adaptations. Adaptations tend to reflect the past life of a species. If a species has recently changed its life style, a once valuable adaptation may become useless, and eventually become a dwindling vestige.
Adaptations are never perfect. There are always tradeoffs between the various functions and structures in a body. It is the organism as a whole which lives and reproduces, therefore it is the complete set of adaptations which gets passed on to future generations.
In populations, there are forces which add variation to the population (such as mutation), and forces which remove it. Genetic drift is the name given to random changes which remove variation from a population. Genetic drift gets rid of variation at the rate of 1/(2N) where N = population size. It is therefore "a very weak evolutionary force in large populations".
Genetic drift explains how random chance can affect evolution in surprisingly big ways, but only when populations are quite small. Overall, its action is to make the individuals more similar to each other, and hence more vulnerable to disease or to chance events in their environment.
How species form is a major part of evolutionary biology. Darwin interpreted 'evolution' (a word he did not use at first) as being about speciation. That is why he called his famous book "On the Origin of Species".
Darwin thought most species arose directly from pre-existing species. This is called "anagenesis": new species by older species changing. Now we think most species arise by previous species splitting: "cladogenesis".
Two groups that start the same can also become very different if they live in different places. When a species gets split into two geographical regions, a process starts. Each adapts to its own situation. After a while, individuals from one group can no longer reproduce with the other group. Two good species have evolved from one.
A German explorer, Moritz Wagner, during his three years in Algeria in the 1830s, studied flightless beetles. Each species is confined to a stretch of the north coast between rivers which descend from the Atlas mountains to the Mediterranean. As soon as one crosses a river, a different but closely related species appears. He wrote later:
This was an early account of the importance of geographical separation. Another biologist who thought geographical separation was critical was Ernst Mayr.
One example of natural speciation is the three-spined stickleback, a sea fish that, after the last ice age, invaded freshwater, and set up colonies in isolated lakes and streams. Over about 10,000 generations, the sticklebacks show great differences, including variations in fins, changes in the number or size of their bony plates, variable jaw structure, and color differences.
The wombats of Australia fall into two main groups, common wombats and hairy-nosed wombats. The two types look very similar, apart from the hairiness of their noses. However, they are adapted to different environments. Common wombats live in forested areas and eat mostly green food with lots of moisture. They often feed in the daytime. Hairy-nosed wombats live on hot dry plains where they eat dry grass with very little water or nutrition in it. Their metabolic rate is slow and they sleep most of the day underground.
When two groups that started the same become different enough, then they become two different species. Part of the theory of evolution is that all living things started the same, but then split into different groups over billions of years.
This was an important movement in evolutionary biology, which started in the 1930s and finished in the 1950s. It has been updated regularly ever since.