title: S-block

text: S- elements are famous for being ingredients in fireworks. The ionic forms of potassium, strontium and barium make appearances in firework displays as the brilliant purples, reds and greens.


title: S-block

text: Francium is considered to be the most rare naturally occurring element on earth. It is estimated that there is only ever one natural atom of Francium present on earth at a time. Francium has a very unstable nucleus and undergoes nuclear decay rapidly.


title: S-block

text: b.These hydrides of alkali metals react with water to form corresponding hydroxides and hydrogen gas.


title: S-block

text: d.Alkali metals also form complex hydrides such as LiAlH which is a good reducing agent.Alkali metal hydrides do not exist in water and this reaction with any other agent is carried out in protic solvent.


title: S-block

text: a.These are most reactive metals and have strong affinity towards Othey form oxides on surface.They are kept under kerosene or paraffin oil to protect them from air.


title: S-block

text: 3. They are purely metallic , as they lose the electrons from the outermost shell readily , they are highly reactive metals and they have low ionization energy .


title: S-block

text: The first element in group one, Lithium, and the first in group two, Beryllium, behave differently to other members of their groups. Their behaviour is like the second element of the next group. So lithium is similar to magnesium, and beryllium is similar to aluminum.


title: S-block

text: In the periodic table this is known as a 'diagonal relationship'. The diagonal relationship is because of similarities in ionic sizes and charge/radius ratio of the element. The similarity between lithium and magnesium is because of their similar sizes:


title: Evolution

text: 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, said: "Nothing in biology makes sense except in the light of evolution".


title: Evolution

text: Evolution has been happening since life started on Earth and is happening now. Evolution is caused mostly by natural selection. Living things are not identical to each other. Even living things of the same species look, move, and behave differently to some extent. Some differences make it easier for living things to survive and reproduce. Differences may make it easier to find food, hide from danger, or give birth to offspring which survive. The offspring have some of the things which made it easier for their parents to have them. Over time, these differences continue, and living things change enough to become new species.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: The realization that some rocks contain fossils was a very important event in natural history. There are three parts to this story:


title: Evolution

text: 1. The realization that things in rocks which "looked" organic actually "were" the altered remains of living things. This was settled in the 16th and 17th centuries by Conrad Gessner, Nicolaus Steno, Robert Hooke and others.


title: Evolution

text: 2. The realization that many fossils represented species which do not exist today. It was Georges Cuvier, the comparative anatomist, who proved that extinction occurred, and that different strata contained different fossils.


title: Evolution

text: 3. The realization that early fossils were simpler organisms than later fossils. Also, the later the rocks, the more like the present day are the fossils.


title: Evolution

text: Where species live 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.


title: Evolution

text: 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).


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: "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.


title: Evolution

text: 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.


title: Evolution

text: 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".


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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).


title: Evolution

text: 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.


title: Evolution

text: 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).


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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:


title: Evolution

text: 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.


title: Evolution

text: 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".


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: Dodd's experiment has been easy for others to repeat. It has also been done with other fruit flies and foods.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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".


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: The first two chapters of the "Origin" deal with variation in domesticated plants and animals, and variation in nature.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: "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.


title: Evolution

text: 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.


title: Evolution

text: 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".


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: Natural selection explains why living organisms change over time to have the anatomy, the functions and behaviour that they have. It works like this:


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: Adaptation is one of the basic phenomena of biology. Through the process of adaptation, an organism becomes better suited to its habitat.


title: Evolution

text: 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.


title: Evolution

text: 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).


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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".


title: Evolution

text: 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.


title: Evolution

text: 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".


title: Evolution

text: 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".


title: Evolution

text: Two groups that start the same can 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 separate species have evolved from one.


title: Evolution

text: 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:


title: Evolution

text: This was an early account of the importance of geographical separation. Another biologist who thought geographical separation was critical was Ernst Mayr.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: 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.


title: Evolution

text: The synthesis explains how the ideas of Charles Darwin fit with the discoveries of Gregor Mendel, who found out how we inherit our genes. The modern synthesis brought Darwin's idea up to date. It bridged the gap between different types of biologists: geneticists, naturalists, and palaeontologists.


title: Evolution

text: When the theory of evolution was developed, it was not clear that natural selection and genetics worked together. But Ronald Fisher showed that natural selection would work to change species. Sewall Wright explained genetic drift in 1931.


title: Evolution

text: Co-evolution is where the existence of one species is tightly bound up with the life of one or more other species.


title: Evolution

text: New or 'improved' adaptations which occur in one species are often followed by the appearance and spread of related features in the other species. The life and death of living things is intimately connected, not just with the physical environment, but with the life of other species.


title: Evolution

text: These relationships may continue for millions of years, as it has in the pollination of flowering plants by insects. The gut contents, wing structures, and mouthparts of fossilized beetles and flies suggest that they acted as early pollinators. The association between beetles and angiosperms during the Lower Cretaceous period led to parallel radiations of angiosperms and insects into the late Cretaceous. The evolution of nectaries in Upper Cretaceous flowers signals the beginning of the mutualism between hymenoptera and angiosperms.


title: Evolution

text: Charles Darwin was the first to use this metaphor in biology. The "evolutionary tree" shows the relationships among various biological groups. It includes data from DNA, RNA and protein analysis. Tree of life work is a product of traditional comparative anatomy, and modern molecular evolution and molecular clock research.


title: Evolution

text: The major figure in this work is Carl Woese, who defined the Archaea, the third domain (or kingdom) of life. Below is a simplified version of present-day understanding.


title: Evolution

text: Macroevolution: the study of changes above the species level, and how they take place. The basic data for such a study are fossils (palaeontology) and the reconstruction of ancient environments. Some subjects whose study falls within the realm of macroevolution:


title: Evolution

text: It is a term of convenience: for most biologists it does not suggest any change in the process of evolution. For some palaeontologists, what they see in the fossil record cannot be explained just by the gradualist evolutionary synthesis. They are in the minority.


title: Evolution

text: Altruism – the willingness of some to sacrifice themselves for others – is widespread in social animals. As explained above, the next generation can only come from those who survive and reproduce. Some biologists have thought that this meant altruism could not evolve by the normal process of selection. Instead a process called "group selection" was proposed. Group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the alleles' effect on the fitness of individuals within that group.


title: Evolution

text: For several decades, critiques cast serious doubt on group selection as a major mechanism of evolution.


title: Evolution

text: In simple cases it can be seen at once that traditional selection suffices. For example, if one sibling sacrifices itself for three siblings, the genetic disposition for the act will be increased. This is because siblings share on average 50% of their genetic inheritance, and the sacrificial act has led to greater representation of the genes in the next generation.


title: Evolution

text: Altruism is now generally seen as emerging from standard selection. The warning note from Ernst Mayr, and the work of William Hamilton are both important to this discussion.


title: Evolution

text: Hamilton's equation describes whether or not a gene for altruistic behaviour will spread in a population. The gene will spread if rxb is greater than c:


title: Evolution

text: At first, sexual reproduction might seem to be at a disadvantage compared with asexual reproduction. In order to be advantageous, sexual reproduction (cross-fertilisation) has to overcome a two-fold disadvantage (takes two to reproduce) plus the difficulty of finding a mate. Why, then, is sex so nearly universal among eukaryotes? This is one of the oldest questions in biology.


title: Evolution

text: The answer has been given since Darwin's time: because the sexual populations adapt better to changing circumstances. A recent laboratory experiment suggests this is indeed the correct explanation.


title: Evolution

text: In the main experiment, nematode worms were divided into two groups. One group was entirely outcrossing, the other was entirely selfing. The groups were subjected to a rugged terrain and repeatedly subjected to a mutagen. After 50 generations, the selfing population showed a substantial decline in fitness (= survival), whereas the outcrossing population showed no decline. This is one of a number of studies that show sexuality to have real advantages over non-sexual types of reproduction.


title: Evolution

text: An important activity is artificial selection for domestication. This is when people choose which animals to breed from, based on their traits. Humans have used this for thousands of years to domesticate plants and animals.


title: Evolution

text: More recently, it has become possible to use genetic engineering. New techniques such as 'gene targeting' are now available. The purpose of this is to insert new genes or knock out old genes from the genome of a plant or animal. A number of Nobel Prizes have already been awarded for this work.


title: Evolution

text: However, the real purpose of studying evolution is to explain and help our understanding of biology. After all, it is the first good explanation of how living things came to be the way they are. That is a big achievement. The practical things come mostly from genetics, the science started by Gregor Mendel, and from molecular and cell biology.


title: Evolution

text: The idea that all life evolved had been proposed before Charles Darwin published "On the Origin of species". Even today, some people still discuss the concept of evolution and what it means to them, their philosophy, and their religion. Evolution does explain some things about our human nature. People also talk about the social implications of evolution, for example in sociobiology.


title: Evolution

text: Some people have the religious belief that life on Earth was created by a god. In order to fit in the idea of evolution with that belief, people have used ideas like "guided evolution" or "theistic evolution". They say that evolution is real, but is being guided in some way.


title: Evolution

text: There are many different concepts of "theistic evolution". Many creationists believe that the creation myth found in their religion goes against the idea of evolution. As Darwin realised, the most controversial part of the evolutionary thought is what it means for human origins.


title: Evolution

text: In some countries, especially in the United States, there is tension between people who accept the idea of evolution and those who do not accept it. The debate is mostly about whether evolution should be taught in schools, and in what way this should be done.


title: Evolution

text: Other fields, like cosmology and earth science also do not match with the original writings of many religious texts. These ideas were once also fiercely opposed. Death for heresy was threatened to those who wrote against the idea that Earth was the center of the universe.


title: Evolution

text: Evolutionary biology is a more recent idea. Certain religious groups oppose the idea of evolution more than other religious groups do. For instance, the Roman Catholic Church now has the following position on evolution: Pope Pius XII said in his encyclical "Humani Generis" published in the 1950s:


title: Evolution

text: Pope John Paul II updated this position in 1996. He said that Evolution was "more than a hypothesis":


title: Evolution

text: Many of those who accepted evolution were not much interested in biology. They were interested in using the theory to support their own ideas on society.


title: Evolution

text: Some people have tried to use evolution to support racism. People wanting to justify racism claimed that certain groups, such as black people, were inferior. In nature, some animals do "survive" better than others, and it does lead to animals better adapted to their circumstances. With humans groups from different parts of the world, all evolution can say is that each group is probably well suited to its original situation. Evolution makes no judgements about better or worse. It does "not" say that any human group is superior to any other.


title: Evolution

text: The idea of eugenics was rather different. Two things had been noticed as far back as the 18th century. One was the great success of farmers in breeding cattle and crop plants. They did this by selecting which animals or plants would produce the next generation (artificial selection). The other observation was that lower class people had more children than upper-class people. If (and it's a big if) the higher classes were there on "merit", then their lack of children was the exact reverse of what should be happening. Faster breeding in the lower classes would lead to the society getting worse.


title: Evolution

text: The idea to improve the human species by selective breeding is called eugenics. The name was proposed by Francis Galton, a bright scientist who meant to do good. He said that the human stock (gene pool) should be improved by selective breeding policies. This would mean that those who were considered "good stock" would receive a reward if they reproduced. However, other people suggested that those considered "bad stock" would need to undergo compulsory sterilization, prenatal testing and birth control. The German Nazi government (1933–1945) used eugenics as a cover for their extreme racial policies, with dreadful results.


title: Evolution

text: The problem with Galton's idea is how to decide which features to select. There are so many different skills people could have, you could not agree who was "good stock" and who was "bad stock". There was rather more agreement on who should "not" be breeding. Several countries passed laws for the compulsory sterilisation of unwelcome groups. Most of these laws were passed between 1900 and 1940. After World War II, disgust at what the Nazis had done squashed any more attempts at eugenics.


title: Evolution

text: Some equations can be solved using algorithms that simulate evolution. Evolutionary algorithms work like that.


title: Evolution

text: Another example of using ideas about evolution to support social action is social Darwinism. Social Darwinism is a term given to the ideas of the 19th century social philosopher Herbert Spencer. Spencer believed the "survival of the fittest" could and should be applied to commerce and human societies as a whole.


title: Evolution

text: Again, some people used these ideas to claim that racism, and ruthless economic policies were justified. Today, most biologists and philosophers say that the theory of evolution should not be applied to social policy.


title: Evolution

text: Some people disagree with the idea of evolution. They disagree with it for a number of reasons. Most often these reasons are influenced by or based on their religious beliefs instead of science. People who do not agree with evolution usually believe in creationism or intelligent design.


title: Evolution

text: Despite this, evolution is one of the most successful theories in science. People have discovered it to be useful for different kinds of research. None of the other suggestions explain things, such as fossil records, as well. So, for almost all scientists, evolution is not in doubt.


title: Rocky Mountains

text: The Rocky Mountains (often called The Rockies) are a range of mountains in the western United States and Canada. They stretch from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States. The Rocky Mountains are more than 3,000 miles long (4,800 kilometers).


title: Rocky Mountains

text: The Rocky Mountains are relatively new, formed from 55 million to 80 million years ago (mya) during the Laramide orogeny. North America began to move westwards as Pangaea broke up. A number of tectonic plates began to slide under the North American plate. The angle of subduction was shallow, resulting in a broad belt of mountains running down western North America. Since then, further tectonic activity and erosion by glaciers has sculpted the Rockies into dramatic peaks and valleys.


title: Rocky Mountains

text: The rocks in the Rocky Mountains were formed long before the mountains were raised. The oldest rock is Precambrian metamorphic rock that forms the core of the North American continent. There is also Precambrian sedimentary argillite, dating back to 1.7 billion years ago. During the Paleozoic, western North America lay underneath a shallow sea, which deposited many kilometers of limestone and dolomite.


title: Rocky Mountains

text: In the southern Rocky Mountains, near present-day Colorado, these ancestral rocks were disturbed by mountain building about 300 mya, during the Pennsylvanian. This mountain building produced the ancestral Rocky Mountains. They consisted largely of Precambrian metamorphic rock forced upward through layers of the limestone. The limestone had been laid down in a shallow sea. The mountains eroded throughout the late Paleozoic and early Mesozoic, leaving extensive deposits of sedimentary rock.


title: Russo-Ukrainian War

text: The Russo-Ukrainian War (, ) is an ongoing conflict between Russia and Ukraine that began in February 2014. The war has been about the status of Crimea and parts of the Donbas, which are internationally seen as part of Ukraine.


title: Russo-Ukrainian War

text: Since 2021, there has been a crisis and military building of the Russian military near Ukraine, causing fears of a possible invasion.


title: Russo-Ukrainian War

text: On 17 January 2022, Russian troops and weapons began arriving in Belarus for the 'Allied Resolve' exercise starting in February.


title: Russo-Ukrainian War

text: On 24 February 2022, President Vladimir Putin announced the invasion of Ukraine. It is believed President Vladimir Putin wishes to conquer the whole of Ukraine and rebuild the USSR.


title: Cloud

text: A cloud is water vapour in the atmosphere (sky) that has condensed into very small water droplets or ice crystals that appear in visible shapes or formations above the ground.


title: Cloud

text: Water on the Earth evaporates (turns into an invisible gas) and rises up into the sky. Higher up where the air is colder, the water condenses: it changes from a gas to drops of water or crystals of ice. We see these drops of water as clouds. The drops fall back down to earth as rain, and then the water evaporates again. This is called the "water cycle".


title: Cloud

text: The atmosphere always has some water vapour. Clouds form when the atmosphere can no longer hold all the invisible air vapor. Any more water vapor condenses into very small water drops.


title: Cloud

text: Warm air holds more water vapor than cool air. So if warm air with lots of water inside cools, it can form a cloud. These are ways air can cool enough to form clouds:


title: Cloud

text: Clouds are heavy. The water in a cloud can have a mass of several million tons. Every cubic metre (m3) of the cloud has only about 5 grams of water in it. Cloud droplets are also about 1000 times heavier than evaporated water, so they are much heavier than air. They do not fall, but stay in the air, because there is warm air all round the heavier water droplets. When water changes from gas to droplets, this makes heat. Because the droplets are very small, they "stick" to the warm air.


title: Cloud

text: Sometimes, clouds appear to be brilliant colors at sunrise or sunset. This is due to dust particles in the air.


title: Cloud

text: Clouds are classified according to how they look and how high the base of the cloud is in the sky. This system was suggested in 1803. There are different sorts of clouds because the air where they form can be still or moving forward or up and down at different speeds. Very thick clouds with large enough water droplets can make rain or snow, and the biggest clouds can make thunder and lightning.


title: Cloud

text: High clouds form from in cold places, in mild regions and in the very hot tropics. They are too high and thin to produce rain or snow.


title: Cloud

text: Middle clouds usually form at in colder areas. However, they may form as high as in the tropics where it's very warm all year. Middle clouds are usually made of water droplets but may also have some ice crystals. They occasionally produce rain or snow that usually evaporates before reaching the ground.


title: Cloud

text: Low-level clouds are usually seen from near ground level to as high as . Low clouds are usually made of water droplets and may occasionally produce very light rain, drizzle, or snow.


title: Cloud

text: These are clouds of medium thickness that can form anywhere from near ground level to as high as . Medium-level cumulus does not have "alto" added to its name. The tops of these clouds are usually not much higher than . Vertical clouds often create rain and snow. They are made mostly of water droplets, but when they push up through cold higher levels they may also have ice crystals.


title: Cloud

text: These clouds are very tall with tops usually higher than . They can create heavy rain and snow showers. Cumulonimbus, the biggest clouds of all, can also produce thunderstorms. These clouds are mostly made of water droplets, but the tops of very large cumulonimbus clouds are often made mostly of ice crystals.


title: Supercomputer

text: A supercomputer is a computer with great speed and memory. This kind of computer can do jobs faster than any other computer of its generation. They are usually thousands of times faster than ordinary personal computers made at that time. Supercomputers can do arithmetic jobs very fast, so they are used for weather forecasting, code-breaking, genetic analysis and other jobs that need many calculations. When new computers of all classes become more powerful, new ordinary computers are made with powers that only supercomputers had in the past, while new supercomputers continue to outclass them.


title: Supercomputer

text: Supercomputer types include: shared memory, distributed memory and array. Supercomputers with shared memory are developed by using a parallel computing and pipelining concept. Supercomputers with distributed memory consist of many (about 100~10000) nodes. CRAY series of CRAYRESERCH and VP 2400/40, NEC의 SX-3 of HUCIS are shared memory types. nCube 3, iPSC/860, AP 1000, NCR 3700, Paragon XP/S, CM-5 are distributed memory types.


title: Supercomputer

text: An array type computer named ILIAC started working in 1972. Later, the CF-11, CM-2, and the Mas Par MP-2 (which is also an array type) were developed. Supercomputers that use a physically separated memory as one shared memory include the T3D, KSR1, and Tera Computer.


title: Tea

text: Tea is a drink that is made from the steeping the leaves of the Camellia sinensis plant. Tea can have other herbs, spices, or fruit flavors in it, like lemon. All teas are made from the Camellia sinensis plant.


title: Tea

text: Sometimes the word "tea" is used for other drinks that have been made by soaking fruit or herbs in hot water, like "rosehip tea" or "camomile tea". These are called "herbal teas".


title: Tea

text: To make black tea, workers take the leaves and spread them out on shelves where they can dry. Next they are rolled and broken into pieces and put into a room where they absorb oxygen, or oxidize. Chemical reactions change the taste and style of the tea. Finally the leaves are dried with hot air until they turn brown or black. Most black tea comes from Sri Lanka, Indonesia and eastern Africa. When black tea leaves are brewed in boiling water, the tea made from them looks deep dark red, so another name used for black tea, especially in China, is red tea.


title: Tea

text: The process for oolong is similar to making black tea. It is made by partially oxidizing the tea leaves, rather than fully oxidizing them. Rutter’s has tea.


title: Tea

text: Green tea is made by putting freshly picked leaves into a steamer. This keeps them green. Then they are crushed and dried in ovens. India is the biggest maker and user of green tea.


title: Tea

text: Tea is mainly grown in China, India, Pakistan, Sri Lanka, Taiwan, Japan, Nepal, Australia, Argentina and Kenya.


title: Tea

text: The word "tea" can also be used as another word for an afternoon meal (mostly in the Commonwealth countries), as in "I am having tea in a short while." The word also applies to "afternoon tea", a small snack meal served sometimes, usually featuring sandwiches, cakes and tea. This small snack meal is also called "tea time".


title: Tea

text: Green tea is usually steeped for 2–3 minutes in water at , while black tea is steeped for 3–5 minutes in boiling water.


title: Device driver

text: A device driver is a program that lets the operating system communicate with specific computer hardware.


title: Device driver

text: Computer parts need a driver because they do not use standard commands. For example, video cards from Advanced Micro Devices (or AMD) and Nvidia do the same job, but each requires its own driver as different hardware requires different commands. Different operating systems also need different drivers, a driver written for macOS can not be used by Microsoft Windows.


title: Device driver

text: Some other computer parts do not need drivers (or the driver is built-in to the operating system) because they use a kind of standard; the operating system recognizes those parts and knows how to use those parts.


title: Thermometer

text: A thermometer is an instrument for measuring or showing temperature (how hot or cold something is). One type of thermometer is a narrow, concealed glass tube containing mercury or alcohol which extends along the tube as it expands. Another type is a digital thermometer, which uses electronics to measure temperature.


title: Thermometer

text: Early thermometers from the time of Galileo measured the expansion and contraction of air. After the middle 17th century many used alcohol or mercury. In the 19th century a mechanical thermometer was in invented that used a bimetallic strip to move a pointer. This kind is still popular where people like to read temperature from a distance.


title: Thermometer

text: A laboratory thermometer is a tool used in laboratories, places where scientists and science techs perform experiments and measure things. A laboratory thermometer can measure temperature very closely. A laboratory thermometer can be put into the liquid or other thing that the scientist wants to measure. A laboratory thermometer has a long stem with a silver bulb at the end. The silver color in the bulb usually means there is mercury in it. Mercury becomes bigger as the temperature becomes hotter. But mercury is a poison to humans. Mercury-in-glass thermometers are less used in the 21st century because people want digital, alcohol-filled, and organic-based thermometers instead.


title: Thermometer

text: In the 20th century, the traditional clinical thermometer was a mercury-in-glass thermometer. People put the end of this in their mouth ("oral" temperature), under their arm, or in their rectum ("rectal" temperature).


title: Thermometer

text: It is only possible to find oral temperatures on patients who can hold the thermometer correctly in their mouth. So small children cannot use this method. It is also a problem for people with a cough or people who are vomiting. In the past it was a big problem because mercury thermometers needed a long time to measure the temperature. Today's digital thermometers are faster. If a person drinks something hot or cold, one still needs to wait before testing their oral temperature.


title: Thermometer

text: When measuring a person's rectal temperature, it helps to use a cream on the thermometer. Rectal thermometers are usually more reliable since they aren't as much influenced by other factors. In some countries people think it is embarrassing to use them for people older than two or three. In other countries, it is considered normal for children and adults to use rectal thermometers.


title: Thermometer

text: In the 1990s, people in many countries thought mercury thermometers were too risky, as mercury is dangerous if it leaks out. Today we use electronic thermometers. Sometimes thermometers with liquids are used, but not with mercury.


title: Thermometer

text: There are other kinds of medical thermometers: "tympanic" thermometers test the temperature of the tympanic membrane (the eardrum) with infrared; "band" thermometers test a person's temperature on the front of their head.


title: Erotic photography

text: Erotic photography is a style of photography, between nude photography and pornography. Erotic photography wants to show the more or less naked human body in a sexual context. It can be difficult to make a difference between erotic photography and pornography - in general erotic photography wants to arouse or stimulate the viewer.


title: Erotic photography

text: This stimulation is generally not done by explicitly showing people having sex. Instead, the models in the photographs will try to create a sexual impression. For example, female models may try to appear alluring. Male models will try to convey sexual arousal, though not through a full erection. In general, erotic photography only suggests, and has a higher artistic value than pornography.


title: Acceleration due to gravity

text: The acceleration which is gained by an object because of gravitational force is called its acceleration due to gravity. Its SI unit is m/s. Acceleration due to gravity is a vector, which means it has both a magnitude and a direction. The acceleration due to gravity at the surface of Earth is represented by the letter "g". It has a standard value defined as . However, the actual acceleration of a body in free fall varies with location.


title: Acceleration due to gravity

text: Isaac Newton worked out that resultant force equals mass times acceleration, or in symbols, formula_1. This can be re-arranged to give formula_2.


title: Acceleration due to gravity

text: The bigger the mass of the falling object, the greater the force of gravitational attraction pulling it towards Earth. In the equation above, this is formula_3. However, the amount of times the force gets bigger or smaller is equal to the number of times the mass gets bigger or smaller, having the ratio remain constant. In every situation, the formula_4 cancels down to the uniform acceleration of around 9.8 m/s. This means that, regardless of their mass, all freely falling objects accelerate at the same rate.


title: Acceleration due to gravity

text: Earth is not exactly spherical. It is similar to a "squashed" sphere, with the radius at the equator slightly larger than the radius at the poles. This has the effect of slightly increasing gravitational acceleration at the poles (since we are close to the centre of Earth and the gravitational force depends on distance) and slightly decreasing it at the equator. Also, because of centripetal acceleration, the acceleration due to gravity is slightly less at the equator than at the poles. Changes in the density of rock under the ground or the presence of mountains nearby can affect gravitational acceleration slightly.


title: Acceleration due to gravity

text: The acceleration of an object changes with altitude. The change in gravitational acceleration with distance from the centre of Earth follows an inverse-square law. This means that gravitational acceleration is inversely proportional to the square of the distance from the centre of Earth. As the distance is doubled, the gravitational acceleration decreases by a factor of 4. As the distance is tripled, the gravitational acceleration decreases by a factor of 9, and so on.


title: Acceleration due to gravity

text: At the surface of the Earth, the acceleration due to gravity is roughly . The average distance to the centre of the Earth is .


title: Acceleration due to gravity

text: Gravitational acceleration at the Kármán line, the boundary between Earth's atmosphere and outer space which lies at an altitude of , is only about 3% lower than at sea level.


title: United Arab Emirates

text: The United Arab Emirates (UAE; in Arabic: الإمارات العربية المتحدة) is a country in Western Asia. It borders Oman, Qatar, and Saudi Arabia. The capital is Abu Dhabi, and the largest city is Dubai. The Burj Khalifa, Earth's tallest artificial structure, is in Dubai. Approximately 600.83 square kilometers is the area of the United Arab Emirates, till December 31, 2017, the UAE counted a population of 9,304,277,  according to the reports of the Federal Competitiveness and Statistics Authority. The most common natural sources in The United Arab Emirates are oil and gas. The oil reserves of the UAE are approximately 8.2% of the global oil reserves according to OPEC. The political system of UAE is federal constitutional and it's one of the most growing countries in the Middle East.


title: United Arab Emirates

text: The oldest human traces in the Emirates date back to 7000 years BCE.The Emirates has more than 330 historical buildings, some have a history from the Stone Age. After the start of Islam a new chapter began in the area, during the Umayyad period, the area of the Arabic Gulf was stable and it became important for navigation and shipping. The Portuguese were the first who arrived in this area after the fall of Al-Andalus. The explorer Vasco da Gama was the first to reach India from Europe after turning around the Cape of Good Hope and passing the Arabic Gulf. The Portuguese controlled all the harbors in the area for more than 2 centuries. During the 18th and 19th centuries Great Britain controlled the area after the Portuguese left. They organized the Trucial States.


title: United Arab Emirates

text: In 1968 the British announced that they are leaving their colonies in the Middle East and on 2nd December 1971, the United Arab Emirates was created. Zayed bin Sultan Al Nahyan became the president of the state and Rashid bin Saeed Al Maktoum, the former ruler of Dubai, became the vice president. After the first president Zayed bin Sultan Al Nahyan, his son Khalifa bin Zayed Al Nahyan became the second president of the UAE. But after his death on the on13th of May 2022, his brother Mohamed bin Zayed Al Nahyan became the 3rd president.


title: United Arab Emirates

text: This country has seven emirates: Dubai, Ajman, Sharjah, Abu Dhabi ,Umm al-Quwain, Fujairah and Ras Al-Khaimah.It has also more than 200 islands, that differ in size, origin, composition and importance. The UAE is characterized by a diversity of natural looks from steep mountains to flat coastal plains and from the high red sand dunes in Liwa to the city Al-Ein, which is considered a natural oasis full of palm trees.


title: United Arab Emirates

text: In 2014, the population in the United Arab Emirates became about 9 million citizens. Due to significant growth in various economic sectors, the United Arab Emirates got a significant increase in population over the past few years, the UAE witnessed a significant influx of labor from different religious and cultural backgrounds. The state of UAE adopts a culture of tolerance and moderation, especially when people from 200 nationalities are living in its territory. The country's inhabitants increased from 4.1 million to 8.3 million between 2005 and 2010 while the Emirati citizens form less than 1 million of them.


title: United Arab Emirates

text: The UAE is a modern state which sticks to its heritage because the citizens are the minority. The officials in UAE support establishing the necessary balance between modernization and tradition and give an illustration of the cultural identity. The United Arab Emirates is colorful and rich in Folklore. The camel and the date palm have nomadic and agricultural bases in its society that are traceable to thousands of years before the spread of Arabs and Muslims. The UAE is also Influenced by other ancient civilizations like Mesopotamia and Greece however the colonial powers which controlled almost everything left very little affect on the folklore of this country. The aggressive behavior of the Portuguese left no space for social interaction and culture exchange


title: United Arab Emirates

text: The United Arab Emirates is based on a federal-state system that is subject to the provisions of the UAE constitution with full sovereignty. The Federation has its capital, logo, flag, and national anthem. Several federal institutions shape the political system of the United Arab Emirates. The Federal Supreme Council (in Arabic: أنبوب كبير) represents the highest authority in the country and the rulers of the seven emirates are members of it. Its mission is to take care of the common interests of the Emirates, the ratification of federal laws, the election of the president and his deputy and other tasks.


title: United Arab Emirates

text: In July 2020, the United Arab Emirates launched the EMM (Emirates Mars Mission) to Mars. It arrived in Mars orbit in February 2020. The mission is to use several scientific instruments to gain useful data about Mars. The Emirates Mars Mission is being operated from the United States (U.S.) and the United Arab Emirates (UAE).


title: United Arab Emirates

text: The most important elements behind the growth and development since the founding of the UAE are oil and gas. The first export of oil took place in the year 1962, the former president Zayed bin Sultan Al Nahyan wanted to use these resources in building infrastructure for starting economic and civilization development. The development of the UAE is going so fast, especially in the last 20 years, so Dubai did realize huge projects like Palm Jumeirah, The World (archipelago) , and Burj Khalifa, the world's tallest building.


title: United Arab Emirates

text: The state of UAE is focusing recently on building the basics for future development, by supporting projects and initiatives that promote qualitative innovation investments, research, technological- and industrial development. The government is preparing an integrated strategy that will enable them to completely dispense with oil as one important compartment of the economy because currently more than 30% of the UAE's GDP is based on oil.


title: Gharial

text: The gharial ("Gavialis gangeticus"), sometimes called the Indian gharial, common gharial or gavial, is one of two surviving members of the family Gavialidae. They are a group of crocodile-like reptiles with long, narrow jaws.


title: Gharial

text: The gharial is the second-longest of all living crocodilians: a large male can be nearly six meters in length. Only saltwater crocodiles and the Nile crocodile can grow larger.


title: Gharial

text: The fossil history of the Gavialoidea is quite well known. The earliest examples split from the other crocodilians in the late Cretaceous. The feature of the group that is easiest to recognise is the very long, narrow snout. This is an adaptation to a diet of small fish. Gharials have sacrificed the great mechanical strength of the robust skull and jaw that most crocodiles and alligators have. For this reason, and they cannot prey on large creatures. But they also have reduced weight and water resistance of their lighter skull and very narrow jaw. This gives gharials the ability to catch rapidly moving fish. They catch them with a side-to-side snapping motion.


title: Gharial

text: The earliest Gavialoidea may or may not have been related to the modern types: some died out at the same time as the dinosaurs (at the end of the Cretaceous), others survived until the early Eocene (about 35 million years ago). The modern forms appeared at much the same time. They evolved in the estuaries and coastal waters of Africa. They crossed the Atlantic to reach South America as well. At their peak, the Gavialoidea were numerous and diverse, they occupied much of Asia and America up until the Pliocene. One species, "Rhamphosuchus crassidens" of India, is believed to have grown to an enormous 15 metres or more.


title: Gharial

text: Northern Indian subcontinent: Bhutan (almost extinct), Bangladesh (close to extinction), India (present in small numbers and increasing), Myanmar (possibly extinct), Nepal, Pakistan (close to extinction). Usually found in the river systems of Indus (Pakistan) and the Brahmaputra (Bangladesh, Bhutan & North eastern India), the Ganges (Bangladesh, India & Nepal), and the Mahanadi River (in the rainforest biome) (India). Small numbers are in Kaladan and the Ayeyarwady in Myanmar. It is sympatric, in respective areas, with the mugger crocodile ("Crocodylus palustris") and the saltwater crocodile ("Crocodylus porosus").


title: Gharial

text: Gharials live in rivers. They are best adapted to the calmer areas in deep fast moving rivers. Their physical attributes do not make the animals very suited to walk on land. In fact the only reasons the gharial leaves the water is to either bask in the sun or to nest on the sandbanks of the rivers.


title: Gharial

text: The Gharial has a long, narrow snout. This is the feature that is most different from most other Crocodilia. The only other species who has such a snout is the False gharial ("Tomistoma schlegelii"), which is closely related. The shape of this snout changes when the animal grows older. The snout becomes progressively thinner the older the gharial gets. There is a bulbous growth on the tip of the male's snout. This is called a 'ghara' (after the Indian word meaning 'pot'). It is only present in mature animals. It is used for different activities, such as making a resonant hum during vocalization. It is also used for attracting females. The mating ritual includes a section where the male uses this ghara to make bubbles.


title: Gharial

text: The long jaws are lined with many interlocking, razor-sharp teeth. This is an adaptation to the diet (predominantly fish in adults). This species is one of the largest of all crocodilian species, approaching the saltwater crocodile ("Crocodylus porosus") and the Nile crocodile in maximum size - males reach at least 5 metres in length, and often approach 6 metres. Reports of 7 metre animals exist, but are unconfirmed. The leg musculature of the gharial is not suited to enable the animal to raise the body off the ground (on land) in order to achieve the high-walk gait - being able only to push its body forward across the ground ('belly-sliding'), although it can do this with some speed when required. However, when in water, the gharial is the most nimble and quick of all the crocodiles in the world. The tail seems overdeveloped and is flattened on the side, more so than other crocodiles. This enables it to achieve the excellent swimming abilities.


title: Gharial

text: The gharial has 27 to 29 upper and 25 or 26 lower teeth on each side. These teeth are not received into interdental pits; the first, second, and third mandibular teeth fit into notches in the upper jaw. The front teeth are the largest. The gharial's snout is narrow and long, with a dilation at the end and its nasal bones are comparatively short and are widely separated from the pre-maxillaries. The nasal opening of a gharial is smaller than the supra-temporal fossae. The gharial's lower anterior margin of orbit (jugal) is raised and its mandibular symphysis is extremely long, extending to the 23rd or 24th tooth. A dorsal shield is formed from four longitudinal series of juxtaposed, keeled and bony scutes.


title: Gharial

text: The length of the snout is 3.5 (in adults) to 5.5 times (in young) the breadth of the snout's base. Nuchal and dorsal scutes form a single continuous shield composed of 21 or 22 transverse series. Gharials have an outer row of soft, smooth or feebly-keeled scutes in addition to the bony dorsal scutes. They also have two small post-occipital scutes.


title: Gharial

text: The outer toes of a gharial are two-thirds webbed, while the middle toe is one-third webbed. Gharials have a strong crest on the outer edge of the forearm, leg and foot. Typically, adult gharials are of a dark olive hue while young ones are pale olive, with dark brown spots or cross-bands.


title: Gharial

text: Young gharials eat insects, larvae, and small frogs. Adults feed almost only on fish, although some individuals have been known to eat dead animals. Their snout morphology is ideally suited for piscivory; their long, narrow snouts afford very little resistance to water in swiping motions to snap up fish in the water. Their numerous needle-like teeth are perfect for holding on to struggling, slippery fish.


title: Gharial

text: The Gharial is not a man-eater. Despite its immense size, its thin, fragile jaws make it physically incapable of devouring any large animal, including a human being. The myth that gharials eat humans may come partly from their similar appearance to crocodiles and because jewelry has been found in the digestive system. However, the gharial may have swallowed this jewelry while scavenging corpses or because used to aid digestion or buoyancy management.


title: Gharial

text: The mating season is during November through December and well into January. The nesting and laying of eggs takes place in the dry season of March, April, and May. This is because during the dry season the rivers shrink a bit and the sandy river banks are available for nesting. Between 30 and 50 eggs are deposited into the hole that the female digs up before it is covered over carefully. After about 90 days, the juveniles emerge, although there is no record of the female assisting the juveniles into the water after they hatch (probably because their jaws are not suited for carrying the young due to the needle like teeth). However the mother does protect the young in the water for a few days till they learn to fend for themselves.


title: Gharial

text: In the 1970s the gharial came to the brink of extinction and even now remains on the critically endangered list. The conservation efforts of the environmentalists in cooperation with several governments has led to some reduction in the threat of extinction. Some hope lies with the conservation and management programs in place as of 2004. Full protection was granted in the 1970s in the hope of reducing poaching losses, although these measures were slow to be implemented at first. Now there are 9 protected areas for this species in India which are linked to both captive breeding and 'ranching' operations where eggs collected from the wild are raised in captivity (to reduce mortality due to natural predators) and then released back into the wild (the first being released in 1981). More than 3000 animals have been released through these programs, and the wild population in India is estimated at around 1500 animals - with perhaps between one and two hundred animals in the remainder of its range.


title: Gharial

text: Recently this species has moved from Endangered to Critically Endangered on the 2007 Red List of endangered species of animals and plants issued by the World Conservation Union, and qualifies for protection under the CITES (Convention on International Trade of Endangered Species) Appendix II.


title: Gharial

text: Janke "et al." (2005), using molecular genetic evidence, found the gharial and the false gharial ("Tomistoma") to be close relatives, and placed them together in the same family.


title: Gharial

text: Common names include: Indian gharial, Indian gavial, Fish-eating crocodile, Gavial del Ganges, Gavial du Gange, Long-nosed crocodile, Bahsoolia, Nakar, Chimpta, Lamthora, Mecho Kumhir, Naka, Nakar, Shormon, Thantia, Thondre, Garial.


title: Handicraft

text: Handicraft is a type of craft where people make things using only their hands or basic tools. The items are usually decorative and have a particular use. Usually the term refers to traditional methods of making things.


title: Handicraft

text: The items often have cultural or religious value. Things made by mass production or machines are not handicraft goods.In Bangladesh we can see many handicrafters living there live only by making handicrafts objects. Also, handicraft things are different from "arts and crafts" because they are meant to be used for something. Handicraft items are generally contrasted with mass production . It stimulates a person's creativity through art . Not only that,it enhances a person's thinking power . It has been protecting our culture in many ways and will further help preserve culture in the future through practice.


title: Copyright

text: With copyright, a work can only be copied if the owner gives permission. If someone copies a work without permission, the owner can say they infringed their copyright. When this happens, the owner may sue for the amount that should have been paid. Most cases are handled by civil law. In more serious cases, a person who copies a work that is protected under copyright could be arrested, fined or even go to prison. Commonly, the copyright law will protect the authors and their heirs for 50 to 100 years since the author's death, or the first day of multiple authors' deaths.


title: Copyright

text: Many countries have modified their copyright law to meet international standards. However, there are still differences in national laws. In some countries, someone violating copyright law will be sued only to the civil law courts but other countries they can also be charged by criminal courts.


title: Copyright

text: Copyright was originally made in the 18th century for books. Before printing presses were made, books could only be copied by hand, which would take time. But when printing presses were made, books could be copied faster and easier. Because of this, some books were copied by people who did not own the book themselves. So lawmakers gave only owners the right to copy. National laws were somewhat standardized by international treaties.


title: Copyright

text: Because technology got better over time, copyright began to cover other types of media such as pictures, sound, and film. Commonly, copyright violation warning would be shown at the beginning of the media to warn audiences against violating copyright law.


title: Copyright

text: In most countries, authors automatically own the copyright to any work they make or create, as long as they do not give the copyright to someone else.


title: Copyright

text: In most countries, there is no need to register the copyright, and some countries do not even have procedures to register copyrights. But, where registration is available, many authors register anyway, especially for works that are sold for money. That is because registration helps to prove that the copyright of a work belongs to a certain author.


title: Copyright

text: If an author gets paid to make a work for someone else, the person who pays for making the work (for example, the author's employer) will often get to own the copyright instead of the author themselves. For example, if a person working for a company, Microsoft creates a new computer software program at work, the Microsoft company would own the copyright. It is very common that the company will instead register the copyright to avoid their employees from claiming their works.


title: Copyright

text: Copyright laws usually protect owners of copyright beyond their lifetime. In some countries, such as Canada and New Zealand, works are protected for 50 years after the last living author dies. In other countries, like the United States and the European Union, the protection lasts for 70 years after death. When the period of copyright protection has ended, the written document, musical composition, book, picture, or other creative work is in the public domain. This means that no one owns the copyright and everyone is free to copy, use and change them without having to ask for permission or pay the owner.


title: Copyright

text: There is an exception to the rules of copyright, called fair use. This means that people can copy a very small amount of a work to use in reviews or in research reports.


title: Copyright

text: An example of fair use is when newspaper writers quote several sentences from a copyright-protected document to tell the story. Another example of "fair use" is when a university professor quotes several sentences from a copyright-protected book in a review of the book, or in a research report.


title: Copyright

text: Because of these differences, a certain piece of work may be under copyright in one country, and in the public domain in another.


title: Copyright

text: Some people argue that copyright laws make it easier for people to make new works and think of new ideas. After all, if authors get to make money for the time, effort and money they put in, then they will want to make more works later, and make more money.


title: Copyright

text: But others believe that copyright laws make it harder to be creative. Without copyright, other people could reuse existing work, and copyright law often stops that.


title: Copyright

text: If an author wants to sell a work, it's often easiest to give the copyright to a publisher. The publisher will do all the selling, and in return for that service, will keep part of the money. But the publisher has many different things to sell, and they may not want to sell the work the author made. Authors often find it very hard to find a publisher willing to sell their work.


title: Copyright

text: But without a publisher, it can be even harder for an author to sell his or her work. In many markets, a few big publishers own the copyrights to almost everything available, and stores will not want to sell works published by small authors themselves. Many people say copyright law helps big publishers stay in control, and keeps smaller authors out of the market. (tragedy of the anticommons).


title: Copyright

text: As a solution to these problems, groups of authors have come up with the idea of open content. With open content, authors give everyone permission to copy, change and give away or sell their works, as long as they follow certain rules. These rules are explained in an open content license. Some possible open content rules are:


title: Frida Kahlo

text: Magdalena Carmen Frida Kahlo y Calderón (6 July 1907 – 13 July 1954), usually known as Frida Kahlo, was a Mexican painter. She was known for her surreal and very personal works. She was married to Diego Rivera, also a well-known painter.


title: Frida Kahlo

text: She was born in Coyoacán, Mexico. She had polio that left her disabled when she was 6 years old and some think


title: Frida Kahlo

text: Kahlo's work is sometimes called "surrealist", and although she organized art shows several times with European surrealists, she herself did not like that label. Her attention to female themes, and the honesty in her painting them, made her something of a feminist cult figure in the last decades of the 20th century. Some of her work is seen at the Frida Kahlo Museum, found in her birthplace and home in suburban Mexico City.


title: Color wheel

text: The color wheel most commonly used today is called the "HSV color wheel" which means "hue, saturation, value". The digital form of the HSV color wheel is called the RGB color wheel (shown below). The HSV/RGB color wheel is described below. There are two versions: one in which red, green and blue are regarded as the primary colors (called the "electronic" or "computer" color wheel); and one in which magenta, yellow, and cyan are regarded as the primary colors (called the "printer's color wheel").the primary colours are on the top.


title: Color wheel

text: In the electronic color wheel used for electronic devices such as televisions and computers, red, green, and blue are regarded as the "primary colors" and magenta, yellow, and cyan are regarded as the "secondary colors".


title: Color wheel

text: The primary colors always appear on the color wheel. There are the three primary colors of light. These are called the three "additive colors". They are red (made in pigment by mixing yellow and magenta), green (made in pigment by mixing cyan and yellow), and blue (made in pigment by mixing magenta and cyan). The three primary colors of light are the secondary colors on the "printer's color wheel".


title: Color wheel

text: The primary colors of light can be mixed together to make secondary colors. A long time ago, people used to think that the primary colors were red, yellow and blue. Now we know they were wrong.


title: Color wheel

text: The secondary colors are on all color wheels. Secondary colors are made by mixing the primary colors of light together. The secondary colors of light are the primary colors of pigment on the printer's color wheel--the color wheel used for color printing. These three colors are called the "subtractive colors". They are magenta (a bright pink), yellow and cyan (a light greenish blue). The primary colors of light are the secondary colors on the "printer's color wheel". The three primary colors of pigment can be mixed to make red (magenta and yellow), green (yellow and cyan), and blue (cyan and magenta), but they do not appear as bright when they are made with pigment instead of light. The secondary colors can be mixed with the primary colors to make tertiary colors.


title: Color wheel

text: "(* Tertiary means third)" The tertiary colors are made by mixing a secondary and primary color together. The tertiary colors are orange, made by mixing red and yellow; chartreuse green ("yellow-green"), made by mixing green and yellow; spring green, made by mixing green and cyan; azure, made by mixing blue and cyan; violet, made by mixing blue and magenta; and rose, made by mixing red and magenta.


title: Color wheel

text: The tertiary colors are the same for both the "printer's color wheel" and the "electronic color wheel".


title: Color wheel

text: The 12 major colors of the color wheel, at 30 degree intervals on the "HSV color wheel" (shown above), are the following: red (0 degrees or 360 degrees), orange (30 degrees), yellow (60 degrees), chartreuse green (90 degrees), green (120 degrees), spring green (150 degrees), cyan (180 degrees), azure (210 degrees), blue (240 degrees), violet (270 degrees), magenta (300 degrees), and rose (330 degrees). This constitutes the complete set of primary, secondary, and tertiary color names.


title: Color wheel

text: On the traditional red-yellow-blue pigment color wheel (in which red, yellow, and blue were regarded as the primary colors and orange, green, and violet were regarded as the secondary colors), the tertiary colors on a red-yellow-blue (RYB) color wheel were called red-violet, blue-violet, blue-green, yellow-green, yellow-orange, and red-orange.


title: Wyoming

text: Wyoming is a state in the western United States. Most of the state is in the Rocky Mountains, a large mountain range in the United States. Wyoming is the least populated U.S. state with a population of 576,412 people. Its capital and biggest city is Cheyenne. It borders Montana, South Dakota, Nebraska, Utah, Idaho, and Colorado. Wyoming is 97,914 square miles in area, which makes it the 9th largest state in the United States.


title: Wyoming

text: Wyoming is known for many things including Yellowstone National Park, Cowboys, the Teton Mountains and coal.


title: Wyoming

text: The first people to live in Wyoming were the Paleo-Indians. By the time the Europeans arrived the land was inhabited by a large number of Native American tribes. Some of the major tribes were the Cheyenne, Arapaho, Crow, Ute, and Shoshone.


title: Wyoming

text: Agriculture has always been an important part of the state economy of Wyoming. The main things grown in Wyoming are livestock (beef), hay, sugar beets, grain (wheat and barley), and wool.


title: Freddie Mercury

text: Farrokh Bulsara (5 September 1946 – 24 November 1991), better known as Freddie Mercury, was a British singer, songwriter, record producer, and lead singer of the rock band Queen. Regarded as one of the greatest singers in popular music history, he was known for his flamboyant stage persona and four-octave vocal range. Mercury wrote numerous hits for Queen, including "Bohemian Rhapsody", "Killer Queen", "Somebody to Love", "Don't Stop Me Now", "Crazy Little Thing Called Love", and "We Are the Champions". He led a solo career while performing with Queen, and occasionally served as a producer and guest musician for other artists.


title: Freddie Mercury

text: He formed Queen in 1970 with guitarist Brian May, and drummer Roger Taylor. Bass guitarist John Deacon joined in 1971. Mercury died in 1991 at age 45 due to complications from AIDS, having confirmed the day before his death that he had the disease. In 1992, Mercury was posthumously awarded the Brit Award for Outstanding Contribution to British Music, and a tribute concert was held at Wembley Stadium, London. As a member of Queen, he was inducted into the Rock and Roll Hall of Fame in 2001, the Songwriters Hall of Fame in 2003, and the UK Music Hall of Fame in 2004. In 2002, he was placed number 58 in the BBC's 2002 poll of the 100 Greatest Britons. He is consistently voted one of the greatest singers in the history of popular music.


title: Freddie Mercury

text: Freddie Mercury was born Farrokh Bulsara on 5 September 1946 in Stone Town in the British protectorate of the Zanzibar (now part of Tanzania). His parents were Jer and Bomi Bulsara both of them are Persian origin from Iran. His father worked as a cashier in the British Colonial Office, a branch of the government. Mercury had a younger sister named Kashmira. His friends at school gave him the name "Freddie." His family then began calling him Freddie, too.


title: Freddie Mercury

text: At age eight, Mercury was sent to a boarding school in India. The school, St. Peters English Boarding school in Panchgani, was about 50 miles outside the city of Bombay (now called Mumbai). He began to show talent as an artist and a sportsman. At age ten, he was named the school champion of Table Tennis. When he was twelve, he received a trophy called the Junior All-rounder.


title: Freddie Mercury

text: While in school he joined a choir and began to learn to play the piano. He had a four-octave vocal range.


title: Freddie Mercury

text: In 1964, Mercury moved to London with his family. He studied art at Ealing Art College. While in London, he became fond of Mary Austin, a woman he met through his guitarist, Brian May. They lived together for several years before and after the band became famous. They moved into a house in London nicknamed "The Court of King Freddie". Mary still lived in that house after she and Mercury broke up.


title: Freddie Mercury

text: Mercury was in love with a local barber when he died. He had been with him in a relationship for six years when it was learned by the media that Mercury had AIDS, which he was tested positive for in 1987. One day after the news was broadcast, Mercury died of Bronchopneumonia caused by AIDS on 24 November 1991 at the age of 45.


title: Vice President of the United States

text: The vice president of the United States (often shortened to VP or VPOTUS) is the second highest executive officer of the United States Federal Government and the chief deputy to the president of the United States. In their capacity as the deputy head of government, the vice president is also the president of the Senate who is the presiding officer of the United States Senate - the upper house of the United States legislature. This position is first in line to succeed as president if the current president resigns, dies or is removed from office.


title: Vice President of the United States

text: Originally, the vice president was the person who got the second most electoral votes in the presidential election. This worked well until Thomas Jefferson and Aaron Burr tied in the . After that, the 12th Amendment to the U.S. Constitution said that the president and vice president are elected separately, and if they tie they would be chosen by the Senate.


title: Vice President of the United States

text: Soon after that, political parties began running the president and vice president on one platform. As such, the vice presidential candidates are usually chosen by that party's presidential candidate. The vice president and president are usually from the same political party (for example, Barack Obama and Joe Biden were both Democrats, and George W. Bush and Dick Cheney were both Republicans).


title: Vice President of the United States

text: The vice president only has one official duty. That is to preside over the Senate and to cast a vote in the Senate if there is a tie. However, recently the duties have been seen to include being a member of the president's Cabinet, or a top advisor to the president (Dick Cheney was the first vice president to take this duty the most seriously). The vice president is a member of the National Security Council and serves on the board of the Smithsonian. Also, the 25th Amendment says that the vice president can act as president if the president is incapacitated (can not do the job of president). For example, Vice President George H.W. Bush acted as president when Ronald Reagan was having an operation.


title: Vice President of the United States

text: Before 1967, if the president died, it was unclear whether the vice president was president or merely acting president. However, John Tyler and others who took over the office said they were not merely acting president. Also, if the vice president died, nobody was vice president until a new one was elected.


title: Vice President of the United States

text: This uncertainty was corrected after the assassination of John F. Kennedy. Under the 25th Amendment to the United States Constitution, if the president dies, the vice president automatically becomes the president. If the vice president dies, resigns, or becomes president, the president can appoint a new vice president. The appointment needs to be confirmed by a majority vote of both the United States House of Representatives and the U.S. Senate. This has happened twice. Gerald Ford became vice president after the resignation of Spiro Agnew, and Nelson Rockefeller became vice president when Gerald Ford became president after Richard Nixon resigned.


title: Vice President of the United States

text: The following vice presidents either became president after the death or resignation of the president, or were elected in their own right:


title: Carbon

text: Carbon is a very important chemical element, with a chemical symbol of C. All known life on Earth needs it. Carbon has atomic mass 12 and atomic number 6. It is a nonmetal, meaning that it is not a metal.


title: Carbon

text: When iron is alloyed with carbon, hard steel is formed. Carbon in the form of coal is an important fuel.


title: Carbon

text: A whole type of chemistry, called organic chemistry, is about carbon and its compounds. Carbon makes many types of compounds. "Hydrocarbons" are molecules with carbon and hydrogen. Methane, Propane, and many other fuels are hydrocarbons. Many of the substances that people use daily are organic compounds.


title: Carbon

text: Carbon, hydrogen, nitrogen, oxygen, and some other elements like sulfur and phosphorus together form most life on earth (see List of biologically important elements). Carbon forms a very large number of organic compounds because it can form strong bonds with itself and with other elements. Because of the amounts of carbon living things have, all organic things are considered "carbon-based".


title: Carbon

text: Each carbon atom usually forms four chemical bonds, which are strong connections to other atoms to form molecules. The kind of bond that carbon makes is called a covalent bond. These bonds allow carbon to form many kinds of small and large molecules. A molecule of methane is the smallest; it has four hydrogen atoms bonded to carbon. The bonds can be double bonds, meaning that two bonds form between carbon and another atom to make a stronger connection. For example, carbon dioxide has two oxygen atoms, and each one is double bonded to carbon. Carbon can even form three bonds with another atom, called a triple bond. For example, in the gas acetylene carbon forms a triple bond with another carbon atom.


title: Carbon

text: By bonding to other carbon atoms, carbon can form long chain-shaped molecules, called polymers, such as plastics and proteins. Atoms of other elements can be part of the long polymer chains, often nitrogen or oxygen.


title: Carbon

text: Pure carbon forms diamond by bonding to four other carbon atoms in a three dimensional crystal. It forms graphite by bonding to three other carbon atoms to form thin flat layers.


title: Carbon

text: The name of carbon comes from Latin "carbo", meaning charcoal. In many foreign languages the words for carbon, coal and charcoal are synonyms.


title: Carbon

text: Carbon in nature is found in three forms called allotropes: diamond, graphite, and fullerenes. Graphite, with clay, is in pencils. It is very soft. The carbon atoms in it make rings, which are on top of each other and slide very easily. Diamonds are the hardest natural mineral. Fullerenes are a "soccer ball" shape of carbon. They are mostly of interest to science. A special, man-made, tube-shaped allotrope of carbon is the carbon nanotube. Carbon nanotubes are very hard, so they might be used in armor. Nanotubes might be useful in nanotechnology.


title: Carbon

text: A radioactive isotope of carbon, carbon-14, can be used to figure out how old some objects are or when something died. As long as something is on the surface of the earth and taking in carbon, the amount of carbon-14 stays the same. When an object stops taking in carbon, the carbon-14 amount goes down. Because the "half-life" (how long it takes for half of a radioactive isotope to go away) of carbon-14 is 5730 years, scientists can see how old the object is by how much carbon-14 is left.


title: Carbon

text: Carbon is in many places in the universe. It was first made in old stars. Carbon is the fourth most common element in the sun. The atmospheres of Venus and Mars are mostly carbon dioxide.