A supportive cell in the central nervous system -- the brain and spinal cord. Glial cells do not conduct electrical impulses (as opposed to neurons, which do). The glial cells surround neurons and provide support for them and insulation between them. Glial cells are capable of extensive signaling in response to a diversity of stimuli. Bidirectional communication exists between glial cells and neurons, and between glial cells and vascular cells.
Glial cells are the most abundant cell types in the central nervous system. There are three types of glial cells: astrocytes, oligodendrocytes, and microglia. Astrocytes are concerned with neurotransmission and neuronal metabolism. Oligodendrocytes are involved in the production of myelin, the insulating material around neurons.. And microglia are part of the immune system.
Lake Malawi is a large, beautiful African Rift Valley lake, bordered by Malawi, Tanzania and
Mozambique. Its biodiversity(생물 다양성) is simply extraordinary by any standard – it has the greatest wealth of fish species of all the lakes in the world. The vast majority of this ichthyofauna (물고기
군락)belongs to just one family, the Cichlidae, and most of the cichlid species are endemic(지방 특유의) to the lake. These fishes are of major economic importance as an important source of protein for the riparian people(강기슭에 사는 사람들). They are also of great value as research subjects in a wide array of biological disciplines and are currently at the forefront (가장 중요한 위치)of evolutionary research.
Many of these cichlids, especially the mbuna, enjoy considerable popularity in the specialized aquarium hobby.
Less than half of the 800 or more estimated cichlid species from Lake Malawi are described, and many of those only in superficial terms. All kinds of taxonomic problems(분류학상의 문제) abound at both species and genus level. This makes studying these fishes quite a challenge.
Mount St. Helens is an active stratovolcano(층이 있는 화산) in Skamania County, Washington, in the Pacific Northwest region of the United States. It is 96 miles (154 km) south of Seattle and 53 miles
(85 km) northeast of Portland, Oregon. Mount St. Helens takes its English name from the British diplomat Lord St Helens, a friend of explorer George Vancouver who made a survey of the area in the late 18th century. The mountain is in the Cascade Range and is part the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire that includes over 160 active volcanoes. This volcano is well known for its ash explosions and pyroclastic flows.(화산암 조각으로 이루어진 용암)
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Mount St. Helens is most famous for its catastrophic eruption (최악의 화산분출) on May 18, 1980, which was the deadliest and most economically destructive volcanic event in the history of the United
States. Fifty-seven people were killed; 250 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (300 km) of highway were destroyed. The eruption caused a massive debris avalanche, reducing the elevation of the mountain's summit(산 정상) from 9,677 ft (2,950 m) to 8,365 ft (2,550 m), and replacing it with a mile-wide (1.5 km-wide) horseshoe-shaped crater. The debris avalanche was up to 0.7 cubic miles (2.3 km³) in volume.
As with most other volcanoes in the Cascade Range, Mount St. Helens is a large eruptive cone consisting of lava rock interlayered with ash, pumice, and other deposits. The mountain includes layers of basalt and andesite(안산암) through which several domes of dacite lava have erupted. The largest of the dacite domes formed the previous summit and off its northern flank(측면) sat the smaller Goat
Rocks dome. Both were destroyed in the 1980 eruption.
Before 1920s, we did not know that galaxies are objects far away. We thought they were in our galaxy and were called spiral nebulae(나선형 성운). Today, we mainly use two methods to measure the distances to other galaxies. The first one is the Cepheid variables that we have talked about in Chapter
13. The second one is the Type I supernova. Recall that Type I supernova is the strong explosion of a nova that even the white dwarf is destroyed. We found that the luminosities(빛을 발하는 물체) of Type I supernovae are about the same. Therefore, we can compute the distance to a galaxy by measuring the apparent brightness of a Type I supernova in that galaxy, if we can find one.
Cepheid variables are dimmer(분명하지 않다) than the Type I supernova. As a result, the supernova allows us to measure the distances of galaxies further away, but it happens much less often. Each one has its advantages and disadvantages. Both of them are called the distance indicators.
Interacting and Active Galaxies
The typical distance between galaxies is only about 20-40 times the sizes of a galaxy. (The ratio of typical distance between stars to the size of a star is in the order of tens of millions.) Galaxy collisions are very common.
When galaxies collide, the stars never collide with each other. Just the distribution of the stars are distorted(변형되다) by the mutual gravity. Streams of stars may be ejected out to form something like antennae and the two galaxies will merge(병합하다) together. Some galaxies with multiple nuclei may
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be the end result of the merging of two galaxies long time ago. Galaxy collision will also trigger star births.
Galaxy collision may also lead to the formation of an active galaxy. An active galaxy is a galaxy that radiates unusual large amount of energy in the form of infrared, ultraviolet and X-rays; always from the nucleus of the galaxy. So, it is also termed the active galactic nuclei (AGN). We are not completely sure how an active galaxy is formed and how it generates such a large amount of energy. One of the most popular hypotheses(가설) is the supermassive black hole theory. When materials surrounding the black hole fall into it, large amount of energy is released. Galaxy collision may create the supermassive black hole at the center.
*Diversity (다양성)
Termites are soil or wood inhabiting eusocial insects(진사회성 곤충) which generally have soft, white bodies and secretive habits. Most termites each dead plant material, which is digested with the help of bacterial or protozoan symbiosis(공생) in their gut. Globally, termites play an important role in reducing dead plant material, but they can be quite destructive to human-built structures.
In many species of termite the nest is simply the cavities created in the wood as the termites eat, but in African and Australian grasslands some termites construct large nests of soil which is cemented with feces and saliva. In tropical rainforests
species attach their nests of chewed plant material and feces to trees, fence posts, and other aboveground locations.
workers construct covered walkways from their nest to foraging areas.
* Reproduction
At the appropriate season for establishing new colonies, winged females and males (alates) leave their nest and join in a mass mating flight which is composed of many (thousands or even millions) of alates from that species' colonies. Males and females form pair bonds, and you may see pairs of males and females running, with the male closely following the female (this is called tandem running) in search of nesting location. Once the male and female have paired, they break off their wings, and spend the remainder of their life flightless.
These mass mating flights are easy pickings for predators--frogs, lizards, birds, and spiders all may benefit greatly from the easy availability of termite alates as food. This may be an example of predator saturation ; the termite colonies produce far more alates than could possibly find nesting sites in order to insure that at least a few survive. Unlike ants, bees and wasps, termite workers may be male or
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female. The king continues to live after his initial mating with the queen and lives in the nest; the king and queen may remote occasionally.
*Caste(계급제도)and division of labor
Termites have incomplete metamorphosis. This means that, like cockroaches and grasshoppers, immatures look very much like adults, lacking only wings. Termite workers are essentially immatures, and in the "lower" termites, workers may ultimately develop into reproductives.
At hatching termite immatures lack the intestinal symbionts(공생자) which enable them to digest cellulose. They gain their initial infection of symbionts by feeding on feces from other termites in the colony. Usually such feeding is directly from the anus of the other individual--this is called proctodael feeding.
In order to grow, insects must shed their exoskeleton by molting. When a termite molts it also loses the linings of its foregut and hindgut, as well as the symbionts living in the gut. Termites rely on proctodael feeding in order to reinfect themselves with their symbionts after they molt; the symbionts are regained from the feces of another termite.
Studies of caste in termites are based on measurements of workers. The measurements allow the scientist to determine to which molt the worker belongs. Both males and females serve as workers, and in some species there are sex differences among the workers in their role in the colony. In general, termite workers can be divided into nest workers, who construct the nest and care for the eggs, foragers, who are equipped for chewing wood or other plant material, and soldiers, whose large heads, strong jaw muscles, and sharp jaws enable them to defend the colony from attackers such as ants. Nest worker and foragers have smaller heads. Head size, gender, and behavioral role can be combined in a diagram of termite caste
*Communication
Termites often work in the dark, and their best-known modes of communication are pheromones.
Trail pheromones guide foragers to food. Other pheromones may regulate how many members of each caste are produced, or may inhibit workers from becoming reproductives.
Some species also produce vibrational signals by striking a surface with their heads. Thousands of termites simultaneously bashing their heads produces a noise that is audible to humans at a distance of several meters. Head bashing communicates alarm, alerting the entire nest to a threat. Termites
Desertification is the process which turns productive into non- productive desert as a result of poor land-management. Desertification occurs mainly in semi-arid areas (average annual rainfall less than 600 mm) bordering on deserts. In the Sahel, (the semi-arid area south of the Sahara Desert), for example, the desert moved 100 km southwards between 1950 and 1975.
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WHAT CAUSES DESERTIFICATION?
* Overgrazing is the major cause of desertification worldwide. Plants of semi-arid areas are adapted to being eaten by sparsely scattered, large, grazing mammals which move in response to the patchy rainfall common to these regions. Early human pastoralists living in semi-arid areas copied this natural system.
They moved their small groups of domestic animals in response to food and water availability. Such regular stock movement prevented overgrazing of the fragile plant cover.
In modern times, the use of fences has prevented domestic and wild animals from moving in response to food availability, and overgrazing has often resulted. However, when used correctly, fencing is a valuable tool of good veld management.
The use of boreholes and windmills also allows livestock to stay all-year round in areas formerly grazed only during the rains when seasonal pans held water. Where not correctly planned and managed, provision of drinking water has contributed to the massive advance of deserts in recent years as animals gather around waterholes and overgraze the area.
* Cultivation of marginal lands, i.e lands on which there is a high risk of crop failure and a very low economic return, for example, some parts of South Africa where maize is grown.
* Destruction of vegetation in arid regions, often for fuelwood.
* Poor grazing management after accidental burning of semi-arid vegetation.
* Incorrect irrigation practices in arid areas can cause salinization, (the build up of salts in the soil) which can prevent plant growth.
When the practices described above coincide with drought, the rate of desertification increases dramatically. Increasing human population and poverty contribute to desertification as poor people may be forced to overuse their environment in the short term, without the ability to plan for the long term effects of their actions. Where livestock has a social importance beyond food, people might be reluctant to reduce their stock numbers.
WHAT ARE THE EFFECTS OF DESERTIFICATION?
Desertification reduces the ability of land to support life, affecting wild species, domestic animals, agricultural crops and people. The reduction in plant cover that accompanies desertification leads to accelerated soil erosion by wind and water. South Africa losing approximately 300-400 million tonnes of topsoil every year. As vegetation cover and soil layer are reduced, rain drop impact and run-off increases.
Water is lost off the land instead of soaking into the soil to provide moisture for plants. Even longlived plants that would normally survive droughts die. A reduction in plant cover also results in a
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reduction in the quantity of humus and plant nutrients in the soil, and plant production drops further.
As protective plant cover disappears, floods become more frequent and more severe. Desertification is self-reinforcing, i.e. once the process has started, conditions are set for continual deterioration.
HOW WIDESPREAD IS DESERTIFICATION?
About one third of the world's land surface is arid or semi-arid. It is predicted that global warming will increase the area of desert climates by 17% in the next century. The area at risk to desertification is thus large and likely to increase.
Worldwide, desertification is making approximately 12 million hectares useless for cultivation every year. This is equal to 10% of the total area of South Africa or 87% of the area of cultivated lands in our country. In the early 1980s it was estimated that, worldwide, 61% of the 3257 million hectares of all productive drylands (lands where stock are grazed and crops grown, without irrigation) were moderately to very severely desertified. The problem is clearly enormous.
DESERTIFICATION IN SOUTHERN AFRICA
About half of southern Africa is semi-arid and thus at risk of desertification. The area already transformed into desert-like conditions is not accurately known because uncertainty surrounds the precise definition of a desert, and what the original state of the vegetation was in the semi-arid areas of southern Africa.
The areas which are known to have deteriorated this century are mainly on the edges of the southern Kalahari. The deterioration of the Karoo is less well established. It is possible that desertification of the Karoo began in the last century, when sheep were first introduced, and before good records were available for the area.
In recent years the introduction of artificial water points into the Kalahari within Botswana, together with the widespread erection of veterinary fences, has led to the rapid desertification of huge areas.
Similar schemes have had the same effect in the southern Kalahari within South Africa and
Bophuthatswana.
HOW CAN DESERTIFICATION BE HALTED?
To halt desertification the number of animals on the land must be reduced, allowing plants to regrow. Soil conditions must be made favourable for plant growth by, for example, mulching. Mulch (a layer of straw, leaves or sawdust covering the soil) reduces evaporation, suppresses weed growth, enriches soil as it rots, and prevents runoff and hence erosion. Reseeding may be necessary in badly degraded areas. Mulching and reseeding are expensive practices. However, the only realistic large-scale approach is to prevent desertification through good land management in semi-arid areas.
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Feudalism was the system of loyalties and protections during the Middle Ages. As the Roman
Empire crumbled, emperors granted land to nobles in exchange for their loyalty. These lands eventually developed into manors. A manor is the land owned by a noble and everything on it. A typical manor consisted of a castle, small village, and farmland.
During the Middle Ages, peasants could no longer count on the Roman army to protect them.
German, Viking and Magyar tribes overran homes and farms throughout Europe. The peasants turned to the landowners, often called lords, to protect them. Many peasants remained free, but most became serfs. A serf was bound to the land. He could not leave without buying his freedom, an unlikely occurrence in the Middle Ages. Life for a serf was not much better than the life of a slave. The only difference was that a serf could not be sold to another manor.
Serfs would often have to work three or four days a week for the lord as rent. They would spend the rest of their week growing crops to feed their families. Other serfs worked as sharecroppers. A sharecropper would be required to turn over most of what he grew in order to be able to live on the land.
The earliest empires had been in the east. Egypt, Mesopotamia, China, India, and Greece were all home to at least one powerful civilization. About 387BC, a city on the Italian peninsula began acquiring land and building an empire. That city was Rome. For more than one thousand years,
Rome controlled the western world.
Rome grew into an empire in part because of how it treated the people it conquered. If a city was defeated by another empire, its citizens were forced from the land if they were lucky, and enslaved if they were not. Initially, the Romans extended the rights of citizenship to the people they conquered. Rome conquered many of its allies by force, but once the new people became citizens, they often joined the Roman army. Rome managed to unify most of the modern nation of Italy by
265BC.
Rome is an ideal place for a city. It is located along the banks of the Tiber River. The river made it easy to travel to and from the sea. The Tiber is very shallow near Rome. A shallow portion of a river is called a ford. The ford made it easier for people to cross the river. Seven hills surround
Rome. The hills make it harder for invaders to approach the city and served as lookout areas for the
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Romans. Rome is also close to excellent farmland and an abundance of wood and stone.
Civilizations have grown and prospered in Rome for thousands of years, which is why Rome is nicknamed “the Eternal City.”
Like other plants, Venus' Flytraps gather nutrients from gases in the air and nutrients in the soil.
However, they live in poor soil and are healthier if they get nutrients from insects. Carnivorous plants live all over the world but Venus' Flytraps live only in select boggy areas in North and South Carolina.
Because of people's fascination with these plants, they collected many of them and they became endangered. Venus' Flytraps today are grown in greenhouses.
The leaves of Venus' Flytrap open wide and on them are short, stiff hairs called trigger or sensitive hairs. When anything touches these hairs enough to bend them, the two lobes of the leaves snap shut trapping whatever is inside. The trap will shut in less than a second. The trap doesn't close all of the way at first. It is thought that it stays open for a few seconds in order to allow very small insects to escape because they wouldn't provide enough food. If the object isn't food, e.g., a stone., or a nut, the trap will reopen in about twelve hours and 'spit' it out.
When the trap closes over food, the cilia. finger-like projections, keep larger insects inside. Fold your hands together lacing your fingers to see what the trap looks like. In a few minutes the trap will shut tightly and form an air-tight seal in order to keep the digestive fluids inside and bacteria out. If an insect is too large it will stick out of the trap. This allows bacteria and molds on the insect to thrive. Eventually the trap turns black, rots and falls off.
The trap constricts tightly around the insect and secretes digestive juices, much like those in your stomach. It dissolves the soft, inner parts of the insect, but not the tough, outer part called the exoskeleton. At the end of the digestive process, which takes from five to twelve days, the trap reabsorbs the digestive fluid and then reopens. The leftover parts of the insect, the exoskeleton, blow away in the wind or are washed away by rain. The time it takes for the trap to reopen depends on the size of the insect, temperature, the age of the trap, and the number of times it has gone through this process.
If you feed a Venus Flytrap something that doesn't move, e.g., a dead insect, it will not close tightly over it. You need to squeeze the trap and move the food around so it imitates the action of a live insect.
The lobe manufactures digestive juices and an antiseptic juice. This keeps the insect from decaying over the few days it is in the trap and purifies prey that it captures.
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People still do not understand fully how the trap closes. The Venus' Flytrap does not have a nervous system or any muscles or tendons. Scientists theorize that it moves from some type of fluid pressure activated by an actual electrical current that runs through each lobe.
The butterfly effect is a phrase that encapsulates the more technical notion of
in chaos theory. Small variations of the initial condition of a nonlinear dynamical system may produce large variations in the long term behavior of the system. So this is sometimes presented as esoteric behavior, but can be exhibited by very simple systems: for example, a ball placed at the crest of a hill might roll into any of several valleys depending on slight differences in initial position.
The phrase refers to the idea that a butterfly's wings might create tiny changes in the atmosphere that ultimately cause a tornado to appear (or prevent a tornado from appearing). The flapping wing represents a small change in the initial condition of the system, which causes a chain of events leading to large-scale phenomena. Had the butterfly not flapped its wings, the trajectory of the system might have been vastly different.
Recurrence, the approximate return of a system towards its initial conditions, together with sensitive dependence on initial conditions are the two main ingredients for chaotic motion. They have the practical consequence of making complex systems, such as the weather, difficult to predict past a certain time range (approximately a week in the case of weather).
Amedeo Modigliani, a painter and a sculptor, was born July 2, 1884, in Livorno , Italy. Modigliani came from a wealthy background. His family were Sephardic Jews, and when his father's career was ruined as a banker, he was forced to work as a wood and coal merchant. Sadly, Amedeo lost his father while still a young boy.
Modigliani's health was very delicate, as he had very weak lungs, which he had inherited from his family. He had many close calls with pneumonia while he was growing up and spent many years being cared for by his worried mother and sisters. He developed tuberculosis and battled with it for the rest of his life. His mother had been the first one to notice and encourage his incredible talent and she sent him to study at art academies in Florence and Venice . Finally, in 1902, when he was 17yrs, he left for
Venice, excited about beginning his art studies.
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Five years later in 1907, he arrived in Paris, ready for fame and fortune, but within weeks he found himself penniless, and had to move from one seedy hotel to another. He was getting out 'n' about however, and meeting all the famous writers and artists of the day from Picasso to Utrillo. According to a good friend of his, he looked very dashing in his brown corduroy coat that he wore everywhere, the bright scarf around his neck, and his broad felt hat. He was very handsome, brooding and thought of as eccentric by his close friends. Modigliani did crazy things in Paris, like dancing in the moonlight with a famous prostitute and getting jailed for drunkenness constantly. He was very successful at attracting women, who found him quite irresistable, and he could always find willing models to paint. Modigliani was involved in one love affair after another, and was completely swallowed up by the dark side of the
Parisian nightlife. Women quite fascinated him, and he once said, "Women of beauty worth painting or sculpting, often seem encumbered by their clothes".
In 1909, he found himself in a sticky patch. He really needed money, and he had to keep moving from one tiny studio to another, to escape angry landlords. He was even reduced at one time, to pushing his belongings in a wheelbarrow through the streets. He wasn't taking care of himself and was always coming down with infections. Finally, he had to return to his home in Italy that summer, to recover and regain his strength. He returned to Paris and then in 1913, his health worsened. His lungs were giving him a lot of trouble, and each time he got sick, he would go home to recover. He was constantly drinking and using drugs and was thoroughly miserable. He was wasting his talents as much as he wasted his money. He could never make enough money to live and was used to selling his drawings for only a few sous. He drifted from cafe to cafe and attic to attic.
He made friends with the sculptor Brancusi, who introduced him to African sculpture. Modigliani was utterly fascinated with the simplicity of African masks and art and kept it all in mind when he painted his portraits. He never really mastered the medium of sculpture and left many pieces unfinished, but from this time on, his paintings were far more influenced by what he had learnt through sculpture.
At Zborowski's home, a Polish friend and poet, Modigliani met his beloved, Jeanne Hebuterne, who was also a very talented young artist. Amedeo was over the moon with Jeanne and they fell deeply in love, married and soon had a son.
With Zborowski's encouragement, Modigliani agreed to opening an art show on Oct 3rd, 1917. This was to be his first show and he didn't know what to expect. He had gathered together a total of 32 paintings and drawings. Almost nothing sold, except for some drawings. His show was actually closed for 'indecency' the same day it opened. In desperate financial trouble and very ill, his good friend,
Zborowski, paid for the couple to go to Nice for the winter.
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In 1918, Jeanne gave birth to a daughter. Amedeo was overjoyed, but he soon had to begin moving his little family around from hotel to hotel. Amedeo was terribly ashamed at not having enough money to support his family. Jeanne even left their little daughter with her wet nurse, and began to paint once more, using her husband as her model.
Modigliani became weaker and weaker, yet still he continued to paint the people around them. He was a remarkable painter, and it shows through his compelling portraits. He often deliberately chose sickly children to paint, feeling a connection with them and their sickness. He had a love of the humble people, which he expressed in his drawings, his paintings and his choice of models. He would often be seen on the terraces, drawing portraits and then offering them to his subjects, in the hope of getting a drink in return.
In the middle of January, his friends found him as he lay dying in his studio, next to his distraught wife. They took him to a hospital, where he later died of tubercular meningitis, combined with the affects of too much alcohol and drugs. Amedeo Modigliani died while just 36yrs, January 25th, 1920.
The next day, his hysterical wife threw herself from a window of her parent's home. Jeanne was 9 months pregnant and carrying their third child at the time. Sadly, both Jeanne and her unborn child died instantly.
Modigliani was an artist whose paintings are dominated by his sense of linear design. He used line exclusively to suggest body and form, with skill and sensitivity. He used distortion as a way of highlighting characteristics of his subjects, and perhaps, maybe even their personalities? Modigliani developed his own unique style, surrounded by artists experimenting with impressionism, surrealism, and cubism. Many of his subject's heads are elegantly bowed with swan-like necks, and sloping shoulders.
The effect is delicate and gentle, yet you feel the people in these paintings are almost aloof, in a dreamy kind of way. His faces are very distinctive with the long thin noses, the empty almond-shaped eyes, and the tiny pursed lips. The eyes are so haunting and when I look at them, it seems odd that they look quite normal in his paintings, as if everyone has empty eyes. Some people feel he played on the sickness in humanity, while others (myself included), recognize it as a new definition in breathtaking beauty.
A small freshwater mollusk called the zebra mussel (
), has been steadily invading America's rivers and lakes. Zebra mussels originated in the Balkans, Poland, and the former
Soviet Union. They first appeared in North America in 1988 in Lake St. Clair, a small water body connecting Lake Huron and Lake Erie. Biologists believe the zebra mussels were picked up in a freshwater European port in the ballast water of a ship and were later discharged into the Canadian side
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of Lake St. Clair.
Zebra mussels get their name from the striped pattern of their shells, though not all shells bear this pattern. They're usually about fingernail size but can grow to a maximum length of nearly 2 inches.
Zebra mussels live 4 to 5 years and inhabit fresh water at depths of 6 to 24 feet. A female zebra mussel begins to reproduce at 2 years of age, and produces between 30,000 and 1 million eggs per year. About two percent of zebra mussels reach adulthood.
Young zebra mussels are small and free swimming, and can be easily spread by water currents.
Older zebra mussels attach themselves to hard surfaces by an external organ called a byssus, which consists of many threads. The mussels may attach to boats, pilings, water-intake pipes, and other hard surfaces, as well as to crayfish, turtles, other zebra mussels, and native mollusks. While zebra mussels can attach themselves securely, they may also move, and can reattach themselves easily if dislodged by storms.
Zebra mussels upset ecosystems, threaten native wildlife, damage structures, and cause other serious problems. Millions of dollars are spent each year in attempting to control these small but numerous mollusks.
Zebra mussels are filter feeders. An adult zebra mussel filters up to a quart of water per day, which multiplied by millions of mussels means that the mussels may be filtering all the water in a lake or stream in a day. The animals and algae that are the food of zebra mussels are also the food for larval fish and other native species, so a large zebra mussel population may cause a decline in other animals, including native fish, mollusks, and birds. The filter-feeding activity of zebra mussels causes a related and frequently dramatic increase in water clarity in infested lakes and rivers.
Zebra mussels can severely effect native mussels and clams by interfering with their feeding, growth, movement, respiration, and reproduction. For example, zebra mussels can colonize a clam shell to such an extent that the clam cannot open its shell to eat. Some native mussels have been found with more than 10,000 zebra mussels attached to them. In addition to colonizing native mussels and clams, zebra mussels may attach to slow-moving species such as crayf ish and turtles.
Water and environmental management agencies are working to protect endangered native species from the threat of zebra mussels. The primary emphasis of this effort is to education so that boaters and fishermen do not inadvertently transfer mussel larvae from one water body to another. In some rivers, boaters are prohibited from traveling upstream from infected areas in an attempt to keep the mussels from spreading.
Zebra mussels do have a positive impact on some native species. Many native fish, birds, and other animals eat young and adult zebra mussels. Migratory ducks have changed their flight patterns in
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response to zebra mussel colonies. Lake sturgeon feed heavily on zebra mussels, as do yellow perch, freshwater drum, catfish, and sunfish. The increase in aquatic plants due to increased water clarity provides excellent nursery areas for young fish and other animals, leading to increases in smallmouth bass populations in Lake St. Clair and the Huron River. However, these native species do not feed heavily enough on zebra mussels to keep the populations under control.
protective coloration, coloration or color pattern of an animal that affords it protection from observation either by its predators or by its prey. The most widespread form of protective coloration is called
, in which various effects that supplement the similarity of color between the animal and its surroundings enable the creature to blend into the background of its habitat.
or irregular patches of contrasting colors, serve to distract the observer's eye from the outline of the animal. Thus the stripes of the tiger and the zebra make detection among the jungle grasses more difficult, whereas the leopard's spots are more suited to the mottled light and shade of the low branches from which it drops onto its prey. Many other creatures (e.g., frogs, lizards, and snakes) are dappled, barred, speckled, mottled, or otherwise distinctively marked or colored so that they blend with sand, water, snow, or specific vegetation, depending on their natural habitat. The pigmentation of some animals (e.g., the chameleon and the flounder) changes to resemble different backgrounds. In countershading, the upper surface of the animal is darker than the undersurface and produces the illusion of flatness. Countershading also aids many fish and birds by blending them with the sky or with the upper water surface when viewed from below and with the land or the sea bottom when viewed from above. Some animals undergo a seasonal variation in color: The stoat and the caribou turn from brown in summer to white in winter (when the stoat is known as ermine). A second type of protective coloration, in animals whose coloration or markings distinctly contrast with their habitat, serves as a warning device either to its predators (e.g., the skunk's stripe and the brilliant colors of many venomous snakes and distasteful insects) or to other members of their species in the vicinity (as the white tail patches of the pronghorn and the jack rabbit that are flashed on approaching danger). The adaptation of an organism's appearance to resemble that of another organism that is repugnant or dangerous to a potential predator is called mimicry. Coloration may thus be categorized as concealing, revealing, or deceiving. Although these devices are not invariably successful, they do increase the statistical chance for survival of the species. The most widely accepted explanation of the phenomenon of protective coloration is Darwin's theory of natural selection.
Disruptive coloration is a way of confusing the eye. It breaks up the solid outline of an animal’s body so that it is harder to see and recognize. For example, a Sumatran tiger has stripes that help it hide among the tall grasses and slender trees of Sumatra—so that
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it’s hard to tell what is grass and what is tiger! A jaguar, on the other hand, hunts in the broken light and shade of low tree branches, among the leaves and branches. Instead of vertical stripes, it is covered in splotchy spots and patches.
Many other creatures, such as frogs, lizards, and snakes are dappled, striped, speckled or patchy so that they blend in with sand, water, or different kinds of plants, depending on their natural habitat.
Effective camouflage renders a target indistinguishable from irrelevant background objects. Two interrelated but logically distinct mechanisms for this are background pattern matching (crypsis) and disruptive coloration: in the former, the animal's colours are a random sample of the background; in the latter, bold contrasting colours on the animal's periphery break up its outline. The latter has long been proposed as an explanation for some apparently conspicuous coloration in animals, and is standard textbook material. Surprisingly, only one quantitative testof the theory exists, and one experimental test of its effectiveness against non-human predators. Here we test two key predictions: that patterns on the body's outline should be particularly effective in promoting concealment and that highly contrasting colours should enhance this disruptive effect. Artificial moth-like targets were exposed to bird predation in the field, with the experimental colour patterns on the 'wings' and a dead mealworm as the edible
'body'. Survival analysis supported the predictions, indicating that disruptive coloration is an effective means of camouflage, above and beyond background pattern matching .
Two, logically distinct but sometimes compatible, mechanisms of camouflage are background-matching and disruptive coloration.
In the former, an animal's coloration comprises a random sample of the background, and so target–background discrimination is impeded. In the latter, object or feature recognition is compromised by placing bold, high-contrast colors so that they break up the prey's body into apparently unconnected objects.
Recent experimental evidence for the utility of disruptive colors, above and beyond that conferred by background matching, has been based on artificial prey with patterns lacking a plane of symmetry. However, it is plausible that the bilateral symmetry present in natural prey may compromise the efficiency of disruptive coloration, on account of the potency of symmetry as a cue in visual search. In this study, we tested this prediction in the field, by tracking the
"survival" under bird predation of artificial mothlike targets placed on oak trees. These had backgroundmatching color patches placed either disruptively or nondisruptively and with or without bilateral symmetry. We found that symmetry reduced the effectiveness of both nondisruptive and disruptive background-matching coloration to a similar degree so that the negative effects of symmetry on concealment are no greater for disruptive than nondisruptive patterns.
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Opened in 1825, the Erie Canal was the engineering marvel of the 19th Century. When the planning for what many derided as “Clinton's Folly” began, there was not a single school of engineering in the United States. With the exception of a few places where black powder was used to blast through rock formations, all 363 miles were built by the muscle power of men and horses.
The Erie Canal proved to be the key that unlocked an enormous series of social and economic changes in the young nation. The Canal spurred the first great westward movement of American settlers, gave access to the rich land and resources west of the Appalachians and made New York the preeminent commercial city in the United States. At the beginning of the nineteenth century, the
Allegheny Mountains were the Western Frontier. The Northwest Territories that would later become
Illinois, Indiana, Michigan and Ohio were rich in timber, minerals, and fertile land for farming. It took weeks to reach these precious resources. Travelers were faced with rutted turnpike roads that baked to hardness in the summer sun. In the winter, the roads dissolved in a sea of mud.
Then - New York Governor DeWitt Clinton envisioned a better way: a Canal from Buffalo on the eastern shore of Lake Erie to Albany on the upper Hudson River, a distance of almost 400 miles.
“The city will, in the course of time, become the granary of the world, the emporium of commerce, the seat of manufactures, the focus of great moneyed operations,” said Clinton. “And before the revolution of a century, the whole island of Manhattan, covered with inhabitants and replenished with a dense population, will constitute one vast city.”
In 1817, Clinton convinced the State legislature to authorize $7 million for construction of a Canal
363 miles long, 40 feet wide and four feet deep.
In 1825, Governor Dewitt Clinton officially opened the Erie Canal as he sailed the packet boat
Seneca Chief along the Canal from Buffalo to Albany. After traveling from the mouth of the Erie to New
York City, he emptied two casks of water from Lake Erie into the Atlantic Ocean, celebrating the first connection of waters from East to West in the ceremonial "Marriage of the Waters".
The effect of the Canal was immediate and dramatic and settlers poured west. The explosion of trade prophesied by Governor Clinton began, spurred by freight rates from Buffalo to New York of $10 per ton by Canal, compared with $100 per ton by road. In 1829, there were 3,640 bushels of wheat transported down the Canal from Buffalo. By 1837 this figure had increased to 500,000 bushels; four years later it reached one million. In nine years, Canal tolls more than recouped the entire cost of construction.
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Within 15 years of the Canal's opening, New York was the busiest port in America, moving tonnages greater than Boston, Baltimore and New Orleans combined.
The impact on the rest of the State can be seen by looking at a modern map. With the exception of Binghamton and Elmira, every major city in New York falls along the trade route established by the Erie Canal, from New York City to Albany, through Schenectady, Utica and Syracuse, to Rochester and Buffalo. Nearly 80% of upstate New York's population lives within a 25 miles of the
Erie Canal.
The Erie Canal's success was part of a Canal-building boom in New York in the 1820s. Between
1823 and 1828, several lateral Canals opened including the Champlain, the Oswego and the Cayuga-
Seneca.
Between 1835 and the turn of the century, this network of Canals was enlarged twice to accommodate heavier traffic. Between 1905 and 1918, the Canals were enlarged again. This time, in order to accommodate much larger barges, the engineers decided to abandon much of the original man-made channel and use new techniques to “Canalize” the rivers that the canal had been constructed to avoid the Mohawk, Oswego, Seneca, Clyde and Oneida Lake. A uniform channel was dredged; dams were built to create long, navigable pools, and locks were built adjacent to the dams to allow the barges to pass from one pool to the next. When it opened in 1918, the whole system was renamed the New
York State Barge Canal.
With growing competition from railroads and highways, and the opening of the St. Lawrence
Seaway in 1959, commercial traffic on the Canal System declined dramatically in the latter part of the
20th century.
Today, the waterway network has been renamed again. As the New York State Canal System, it is enjoying a rebirth as a recreational and historic resource. The Erie Canal played an integral role in the transformation of New York City into the nation's leading port, a national identity that continues to be reflected in many songs, legends and artwork today.
In 2001, designated as the nation's 23 rd National Heritage Corridor, the New York State Canal
System joined the ranks of America's most treasured historical resources. Comprised of four Canals, the
Canal System is historically significant for the many contributions it has made to establish New York
State as an international center of commerce and finance.
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The term coevolution is used to describe cases where two (or more) species reciprocally affect each other’s evolution. So for example, an evolutionary change in the morphology of a plant, might affect the morphology of an herbivore that eats the plant, which in turn might affect the evolution of the plant, which might affect the evolution of the herbivore...and so on.
Coevolution is likely to happen when different species have close ecological interactions with one another. These ecological relationships include:
1. Predator/prey and parasite/host
2. Competitive species
3. Mutualistic species
Plants and insects represent a classic case of coevolution—one that is often, but not always, mutualistic. Many plants and their pollinators are so reliant on one another and their relationships are so exclusive that biologists have good reason to think that the “match” between the two is the result of a coevolutionary process.
But we can see exclusive “matches” between plants and insects even when pollination is not involved. Some Central American
species have hollow thorns and pores at the bases of their leaves that secrete nectar (see image at right). These hollow thorns are the exclusive nest-site of some species of ant that drink the nectar. But the ants are not just taking advantage of the plant—they also defend their acacia plant against herbivores.
This system is probably the product of coevolution: the plants would not have evolved hollow thorns or nectar pores unless their evolution had been affected by the ants, and the ants would not have evolved herbivore defense behaviors unless their evolution had been affected by the plants.
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The earth consists of several layers. The three main layers are the core, the mantle and the crust. The core is the inner part of the earth, the crust is the outer part and between them is the mantle. The earth is surrounded by the atmosphere. Till this moment it hasn't been possible to take a look inside the earth because the current technology doesn't allow it. Therefore all kinds of research had to be done to find out, out of which material the earth consists, what different layers there are and which influence those have (had) on the earth's surface. This research is called seismology.
The core
Full size
Earth cutaway
Here, sections of the Earth have been removed to show its internal structure.
Image by: Colin
Dorling Kindersley
Rose,
The inner part of the earth is the core. This part of the earth is about 1,800 miles (2,900 km) below the earth's surface. The core is a dense ball of the elements iron and nickel. It is divided into two layers, the inner core and the outer core. The inner core - the center of earth - is solid and about 780 miles (1,250 km) thick. The outer core is so hot that the metal is always molten, but the inner core pressures are so great that it cannot melt, even though temperatures there reach
6700ºF (3700ºC). The outer core is about 1370 miles (2,200 km) thick. Because the earth rotates, the outer core spins around the inner core and that causes the earth's magnetism.
The Mantle
The layer above the core is the mantle. It begins about 6 miles(10 km) below the oceanic crust and about 19 miles(30 km) below the continental crust (see The Crust). The mantle is to divide into the inner mantle and the outer mantle. It is about 1,800 miles(2,900 km) thick and makes up nearly 80 percent of the Earth's total volume.
The Crust
The crust lays above the mantle and is the earth's hard outer shell, the surface on which we are living. In relation with the other layers the crust is much thinner. It floats upon the softer, denser mantle. The crust is made up of solid material but these material is not everywhere the same. There is an Oceanic crust and a Continental crust. The first one is about 4-7 miles (6-11 km) thick and consists of heavy
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rocks, like basalt. The Continental crust is thicker than the Oceanic crust, about 19 miles(30 km) thick. It is mainly made up of light material, like granite.
The Atmosphere
The earth is surrounded by all kind of gases. This layer is called the earth's atmosphere. Without these atmosphere life on earth isn't possible. The atmosphere gives us air, water, warmth and is protecting us against harmful rays of the sun and against meteorites. This layer around the earth is a colorless, odorless, tasteless 'sea' of gases, water and fine dust. The atmosphere is made up of different layers with different qualities. It consists of 78% nitrogen, 21% oxygen, 0,93% argon, 0,03% carbon dioxide and
0,04% of other gases. The Troposphere is the layer where the weather happens, above this layer is the
Stratosphere. Within the Stratosphere is the Ozone layer, that absorbs the Sun's harmful ultraviolet rays.
Above the Stratosphere is the Mesosphere, the Thermosphere - in which the Ionosphere - and the
Exosphere. The atmosphere is about 500 miles (800 km) thick.
Influence of the Sun and the Moon
The sun and the moon both have their influence on the earth. Sometimes they cooperate and sometimes they counteract each other. Such influences are: the gravity, the warmth of the sun, the sunlight and the chronology. Through the gravitational force of the earth the moon orbits the earth. The moon also gravitates the earth, but less powerful. By the way gravity pulls the Earth and Moon toward each other, tides are caused (high tide and low tide). The sun also has some influence here. The sun brings light and is also responsible for the warming up of the earth.
What are volcanoes?
A Volcano is a gap in the earth where molten rock and other materials come to the earth's surface.
Some volcanoes are just cracks in the earth's crusts. Others are weak places in the earth's crust, which occur on places where magma bubbles up through the crust and comes to the earth's surface. Magma is molten rock that occurs by partial melting of the crust and the mantle by high temperatures deep down in the ground. Once magma comes to the earth's surface it is called lava.
Active and non-active volcanoes
There are volcanoes in different phases of activity:
Active volcanoes, which are likely to erupt at any moment, dormant volcanoes, which lie dormant for centuries, but then erupt suddenly and violently, and extinct volcanoes - ones no longer likely to erupt.
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Types of volcanoes
In the surroundings of boundaries of tectonic plates the following types of volcanoes occur:
The fissure volcano: Is a long crack in the earth's surface through which magma erupts. These cracks may form as two tectonic plates pull
You'll find them mainly near mid-ocean ridges. apart.
The ordinary volcanoes can be divided in different types, relating to their forms:
The shield volcano: This is a broad, shallow volcanic cone, which arises because the running lava, which is fluid and hot, cools slowly.
The dome volcano: This one has a steep, convex slope from thick, fastcooling lava
The ash-cinder volcano:
Throws out - besides lava - much ash into the air.
Through this the volcanic cone is built up from alternate layers of ash and cinder.
The composite volcano:
These are also built up from alternate layers of lava and ash but, besides its main crater, it has many little craters on its slope.
The caldera volcano: An older volcano with a large crater which can be 62 miles(100km) wide. In this crater many little new craters are formed.
At other places, not at the margins of the tectonic plates, hot-spots can occur. Hot-spots are formed because a very hot area (focus) in the earth's mantle burns its way through the earth's crust. Examples can be found on the Hawaiian Island Chain.
Other forms of volcanism are the Geysers and the Hot Springs. You often find them in the neighborhood of volcanoes, where the earth's crust is thinner and the heat of the magma further penetrates into the earth's crust. A Geyser is a hole in the earth's crust, spouting fountains of boiling water. Hot rock heats up water in an underground chamber and when the water boils, it sends out a
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fountain of boiling water, up to 1,640 ft. (500 m) into the air. A Hot Spring works in the same way, but the water is not so hot that it spouts with pressure.
An Earthquake is in fact the shaking of the ground caused by sudden movements in the earth's crust . The biggest earthquakes are set off by the movement of tectonic plates . Some plates slide past each other gently, but others can cause a heavy pressure on the rocks, so they finally crack and slide past each other. By this, vibrations or shock waves are caused, which go through the ground. It is these vibrations or seismic waves which cause an earthquake. The closer to the source of the earthquake (the focus or hypocenter), the more damage occurs. Earthquakes are classified according to the depth of the focus.
0-43 miles (0-70 km) below ground: shallow earthquakes
43-186 miles (70-300 km) below ground: intermediate earthquakes deeper than 186 miles (300 km) below ground: deep earthquakes
The closer the focus to the surface, the heavier the earthquake. The earthquake is always the most intense on the surface directly above the focus (Epicenter). In general big earthquakes begin with light vibrations (foreshocks). These are the initial fractures in the rocks. After the main shock, there may be minor aftershocks, most of the time for months. This occurs as the rocks settle down.
(Plate tectonics)
In general people are not so glad with earthquakes because they cause a lot of damage. On the other hand, earthquakes have been very helpful to get information about the inside of the earth. Vibrations
(seismic waves) not only move to the earth's surface, but go to all sides. Big earthquakes can therefore be measured at places all over the world. All these vibrations from the earth are broken or diffracted by the different layers of the earth. The way which seismic waves are diffracted is helpful for scientists to understand the structure of the earth . By measuring many earthquakes and by data processing in computers, three-dimensional images can be made of the variations in the density and the temperature of the mantle .
The earth's crust consists of a number of moving pieces or plates, that are always colliding or pulling apart. The Lithosphere consists of nine large plates and twelve smaller ones. The continents are imbedded in continental plates; the oceanic plates make up much of the sea floor. The study of Tectonic plates - called plate tectonics - helps to explain continental drift, the spreading of the sea floor, volcanic eruptions and how mountains are formed. The force that causes the movement of the tectonic plates may be the slow churning of the mantle beneath them. Mantle rock is constantly moved upwards to the surface by the high temperatures below and then sinks by cooling. This cycle takes millions of years.
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Continental drift:
The drift of the plates across the surface of the earth has been going on over millions of years, which still changes the outward appearance of the earth. When you look at the map of the world, you see how well the east coast of North and South America fits into the west coast of Europe and Africa. Over millions of years these continents have slowly drifted apart.
Continental drift
The continents have slowly drifted across the surface of the Earth over millions of years.
Full size
(continental drift).
Diverging plates:
Where plates pull apart, hot molten rock (fluid magma) emerges as lava and so new matter is added to the plates. In this way new oceanic plates are formed. The place where this happens is known as a mid-ocean ridge. Mid-ocean ridges are rarely more than about 4,920 ft.(1,500 m) high, but they may snake along the ocean bed for thousands of miles.
Beneath each of the world's great oceans there is a
Image by:
Dave Donkin,
Dorling Kindersley mid-ocean ridge. An example is the Mid-Atlantic
Ridge in the Atlantic Ocean, which stretches from the
North Pole to the South Pole. Mid-ocean ridges are areas of much volcanic and earthquake activity.
Converging plates:
In many places the huge plates of the earth's surface are slowly moving together with unimaginable force. Sometimes the edge of one plate is gradually destroyed by the force of collision, sometimes the impact simply crimps the plates' edges, thereby creating great mountain ranges.
When one tectonic plate bends beneath the other, it is called subduction. Most of the time this happens because a dense oceanic plate collides with a lighter continental plate. You can see this along the Pacific coast of South-America. The oceanic plate dips beneath into the Asthenosphere . Through the heat of the Asthenosphere the subducted plate melts. At the surface an ocean trench is created, followed by an arc of islands. In this area also volcanic activities and earthquakes occur.
When continental plates collide, one of the plates splits up into two layers: a lower layer of dense mantle rock and an upper layer of lighter crustal rock. As the mantle layer subducts, the upper layer is peeled off and crumples up against the other plate, thus forming mountain ranges, like the Alps. These are called crumpled mountains.
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The earth's crust consists of a number of moving pieces or plates, that are always colliding or pulling apart. The Lithosphere consists of nine large plates and twelve smaller ones. The continents are imbedded in continental plates; the oceanic plates make up much of the sea floor. The study of Tectonic plates - called plate tectonics - helps to explain continental drift, the spreading of the sea floor, volcanic eruptions and how mountains are formed. The force that causes the movement of the tectonic plates may be the slow churning of the mantle beneath them. Mantle rock is constantly moved upwards to the surface by the high temperatures below and then sinks by cooling. This cycle takes millions of years.
Continental drift:
The drift of the plates across the surface of the earth has been going on over millions of years, which still changes the outward appearance of the earth. When you look at the map of the world, you see how well the east coast of North and South America fits into the west coast of Europe and Africa.
Over millions of years these continents have slowly drifted apart. (continental drift).
Diverging plates:
Where plates pull apart, hot molten rock (fluid magma) emerges as lava and so new matter is added to the plates. In this way new oceanic plates are formed. The place where this happens is known as a midocean ridge. Mid-ocean ridges are rarely more than about 4,920 ft.(1,500 m) high, but they may snake along the ocean bed for thousands of miles. Beneath each of the world's great oceans there is a midocean ridge. An example is the Mid-Atlantic Ridge in the Atlantic Ocean, which stretches from the North
Pole to the South Pole. Mid-ocean ridges are areas of much volcanic and earthquake activity.
Converging plates:
In many places the huge plates of the earth's surface are slowly moving together with unimaginable force. Sometimes the edge of one plate is gradually destroyed by the force of collision, sometimes the impact simply crimps the plates' edges, thereby creating great mountain ranges.
When one tectonic plate bends beneath the other, it is called subduction. Most of the time this happens because a dense oceanic plate collides with a lighter continental plate. You can see this along the
Pacific coast of South-America. The oceanic plate dips beneath into the Asthenosphere . Through the heat of the Asthenosphere the subducted plate melts. At the surface an ocean trench is created, followed by an arc of islands. In this area also volcanic activities and earthquakes occur.
When continental plates collide, one of the plates splits up into two layers: a lower layer of dense mantle rock and an upper layer of lighter crustal rock. As the mantle layer subducts, the upper layer is peeled off and crumples up against the other plate, thus forming mountain ranges, like the Alps. These are called crumpled mountains.
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The principal causative factor in pearl formation in a pearl oyster is the presence of a nucleus. It can be of organic or inorganic origin, such as parasites adults or larvae, molluscan eggs, decaying parts of plants, sand grains, epithelium or blood cells of the same animal, etc. These tiny particles or organisms enter the oyster when the shell valves are open for feeding and respiration. These foreign bodies may become embedded between the shell and mantle. In response to this stimulus, the foreign body is invaginated by the outer epithelium of the mantle and a pearl-sac is formed around it.
Pearls are not produced without the formation of the pearl-sac. The pearl-sac is derived from the internal or external layer of the apithelium of the mantle or of the gill plates. The epithelial cells of the pearl-sac secrets the nacre which becomes deposited over the foreign body, forming a pearl in due course of time. These pearls are produced either within the mantle, in other soft tissues of the oyster, or between the mantle, and the interior surface of the shell. Such pearl production is accidental and occurs very rarely. They are generally small and irregular. Large and spherical pearls are still rarer to find. When the extraneous matter becomes fixed to the shell, only the exposed portion becomes covered by the pearl-sac resulting in a blister pearl.
A meteor, sometimes called a "shooting star," can be the brightest object in the night sky, yet
are the smallest bodies in the solar system that can be observed by eye. Wandering through space, perhaps as debris left behind by a comet, meteoroids enter the earth's atmosphere, are heated by friction, and for a few seconds streak across the sky as a
with a glowing trail.
A brilliant meteor, called a
, may weigh many kilograms, but even a meteor weighing less than a gram can produce a beautiful trail. Some of these visitors from space are large enough to survive
(at least partially) their trip through the atmosphere and impact the ground as
Fireballs are sometimes followed by trails of light that persist for up to 30 minutes; some, called
, explode with a loud thunderous sound.
How can a particle the size of a grain of sand produce such a spectacular sight? The answer is the speed at which the meteoroid enters the earth's atmosphere. Many meteoroids travel at 60-70 kilometers per second. As a comparison, the shuttle moves around the earth at about 8 kilometers per second.
During its trip through the atmosphere, meteoroids collide with air molecules, knocking away materials and stripping electrons from the meteor. When the stripped atoms recapture electrons, light is emitted. The color of the light depends on the temperature and the material being "excited."
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On almost any night a few meteors an hour will be seen from any one place. However, periodically there are
, with hundreds of meteors emanating from the same apparent spot in the sky. These showers typically last from a few hours to several days. These showers are usually associated with comet paths, and are caused by debris expelled by the comet.
Each day as many as 4 billion meteors, most miniscule in size, fall to earth. Their masses total several tons, seemingly a large amount, but negligible compared to the earth's total mass of
6,600,000,000,000,000,000,000 tons.
All About Comets
A comet is a minor planet made up of rock, dust and ice. It originates from a cloud of debris remaining from the condensation of the solar nebula. Comets are unique because they are created in the outer solar system, and are greatly affected by the planets they pass. While a comet is orbiting, its path is constantly being altered as it nears surrounding planets. These changes in orbit can send it on a path approaching the sun, where it will burn up, or can be cast completely out of the solar system.
The tail of a comet is actually called the coma, which is composed of gas and dust streams. When a comet passes through the inner solar system, the sun lights up these streams so that we are able to see it. This is how we have been able to see Halley’s Comet from Earth.
The orbital periods of comets vary, but have been divided into three categories: Short period comets; long period comets; and Single-apparition comets. While Short period comets orbit for 200 years or less, long period comets are bound by gravity to the sun, and remain much longer. Singleapparition comets have unusual orbits and are thrown out of the solar system forever.
All About Asteroids
During the formation of our solar system, hundreds of thousands of particles were pulled by
Jupiter’s gravity rather than being spread out through space. These minor planets, or asteroids, are the products of the protoplanetary disc – dense rings of gas surrounding a newly formed star.
Most asteroids orbit within an area between Jupiter and Mars known as the asteroid belt. These relatively small objects look like tiny specks of light from earth, if they are visible at all. For decades scientists tried to identify specific asteroids, but it wasn’t until 1801 when Giuseppe Piazzi identified the first asteroid: 1 Ceres. As of April, 2006, 330,795 asteroids have been named, and we are constantly finding more.
The possible impact of asteroids and comets with the Earth’s surface could be catastrophic. We need only refer to the extinction of dinosaurs to illustrate this reality. Scientists have made efforts to more closely observe asteroids and detect possible threats.
Beginning with the first close-up images in 1991 by the probe Galileo, we continue to make new efforts of discovery. The three most potentially dangerous groups of asteroids are Apollos, Amors, and
Atens. We are also able to learn about asteroid impact from the effects they have had on other planets and their satellites.
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Meteor – a meteoroid during its brief luminous flight through atmosphere
Meteoroid – a small celestial body, often debris from a comet or asteroid, traveling through space
Meteorite – a meteoroid that has reached the surface of the earth
How do volcanoes form?
Deep inside Earth, between the molten iron core and the thin crust at the surface, there is the mantle, a large layer of rock that is largely solid, but flows like plastic. When, for various reasons, rock from the mantle melts, it sometimes moves to the Earth’s surface through weak spots in the crust, releasing heat, gasses, and rock--a volcanic eruption. But why does this solid rock melt and come to the surface?
From Magma to Lava
Extremely high temperature and pressure can cause the lower mantle to melt and become liquid rock, or magma. When a body of magma rises through the denser rock layers toward Earth's surface, some of it remains liquid. Magma that has reached the surface is called lava.
Lava Types
Magma comes in different "flavors," or compositions. Each of these will produce a different lava, from fluid, fast-moving basalt to slower, more viscous andesite. Because rocks are made up of collections of minerals that melt at different temperatures, the makeup of the rock being melted affects the magma that results.
Why do volcanoes erupt in different ways?
Most volcanoes occur on plate boundaries. Plate boundaries are areas where Earth's shifting plates meet or split apart, usually with violent results.
Plate margins that are coming together are called convergent margins, while those that are splitting apart are called divergent. A third type, transform-fault margins, are sliding against each other, going in opposite directions (like those of the San Andreas Fault). Volcanoes can occur on convergent or divergent plate margins or over a hotspot, a spot inside the mantle that heats an area of the plate above it.
Colliding Plates
Along convergent margins, when two plates meet, sometimes one descends, usually of oceanic composition, beneath the other, usually of continental composition, in a process called subduction. As the descending plate is forced deeper into the mantle, parts of it begin to melt and form magma that rises to the surface, often in explosive eruptions. Subduction zones tend to create large, classic, coneshaped volcanoes called stratovolcanoes, such as Mt. St. Helens in Washington State, or Mt. Shasta in
California.
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Separating Plates
At divergent margins, plates are coming apart and hot rock forces its way to the surface. Many divergent plate margins are under the oceans, creating long undersea rift zones that fill with lava. In some eruptions at divergent margins, the relatively calm, smooth flow of lava creates volcanoes with gently sloping sides, called shield volcanoes.
Hotspots
Hotspots can also cause shield volcanoes to form. As plates move over hotspots, volcanoes spring up and die down in turn, often creating an island chain. The Hawaiian Islands are the result of a hotspot.
What happens when a volcano erupts?
When you think of a volcanic eruption, you probably imagine red-hot lava flowing down the side of a volcano. Lava is a serious hazard, but there are others--some of them far more dangerous.
Lava Flows
Lava flows are a threat, but they are usually slow enough that people can get out of the way. Economic loss from lava flows--including burned buildings and ruined crops--is more common. Because lava flows normally don't cover very large areas, the damage is usually limited.
Falling Ash
In an explosive eruption, pent-up gases escape violently. Magma breaks into pieces and bursts from the volcano in a column of ash and fiery fragments. The cooled fragments that fall back to Earth are called tephra. In a large eruption, tephra can cover vast areas with a thick layer of ash, presenting a much greater hazard than lava flows.
Glowing Avalanches
Pyroclastic flows are mixtures of very hot gas and tephra that cascade down a volcano's sides at high speeds. A pyroclastic flow covered the city of Herculaneum in A.D. 79, killing many residents. Because pyroclastic flows can spread destruction over large areas and move at very high speeds, they are extremely hazardous. Most people are not aware that this danger exists.
Mud and Debris Flows
Debris flows, fragments of mud and other debris that flow down the sides of a volcano, are another serious and little-known hazard. Debris flows often form when part of the volcano collapses, breaking up and flowing downhill. If the collapse is a major one, the large flow that results can travel great distances, often burying everything in its path. These are particularly dangerous on volcanoes that have glaciers on top, as the eruption instantly melts the ice, causing a massive mud slide, much like what happened during the Mt. St. Helens eruption in 1980.
Other Dangers
Lava, ash, and debris flows are the most common and serious volcanic hazards, but others do exist.
Severe eruptions can disrupt the climate for long periods or cause atmospheric shock waves. Eruptions
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can also cause tsunamis, volcanic earthquakes, or the release of suffocating gases. These hazards pose serious threats to both life and property.
Can we predict when a volcano will erupt?
Scientists can often find clues about past eruptions by studying the deposits left behind. Areas affected by lava flows, debris flows, tephra, or pyroclastic flows can be mapped, making disaster planning more effective. In addition to this type of long-range forecasting, scientists are becoming more and more skilled at spotting the warning signs of an eruption.
Before an eruption, magma moves into the area beneath the volcano and collects in a magma chamber, or reservoir. As it comes closer to the surface, the magma releases gases. These events can offer valuable clues about the likelihood of an eruption. For example, the movement of magma produces small earthquakes and vibrations (seismicity). Magma gathering in a chamber causes slight swelling of the volcano's slopes. Gases released near the volcano can be measured for changes in quantity and makeup.
Monitoring Methods
A number of tools can be used to record these warning signs. Seismographs can detect small earthquakes, while tiltmeters and geodimeters can measure the subtle swelling of a volcano. Correlation spectrometers (COSPECS) can measure amounts of sulfur dioxide--a telltale gas that is released in increasing quantities before an eruption. Using these and other tools, it's possible to closely monitor activity at an awakening volcano.
The Problem of Prediction
Volcanologists are becoming very skilled at predicting the likelihood of an eruption. Still, a number of barriers remain. It's very difficult to pinpoint exactly when an eruption will happen. Often, moving magma doesn't result in an eruption, but instead cools below the surface. Monitoring potential eruptions is expensive. With many volcanoes erupting only every few hundred or thousand years, it's not possible to monitor every site. Volcanic eruptions don't occur without warning, however. If we set up monitoring devices, we should not be caught off guard by disastrous eruptions.
How can we reduce the risk?
There are four general approaches to coping with volcanic hazards. We can try to keep the hazard from occurring--often an impossible task. We can try to alter its path or reduce its impact on existing development. We can take steps to protect future development. We can also do our best to have disaster response plans in place before they are needed.
Removing the Threat
Obviously, there is no way to stop an eruption. We can, however, attempt to reduce the eruption's effects by reinforcing structures (for example, strengthening roofs to support the weight of tephra deposits) or by building protective works (such as walls to deflect lava flows away from developed areas).
Such efforts can be and have been successful, but are of limited use in a large-scale eruption.
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Planning for the Future
Protecting future development from volcanic hazards is a simpler task. Before building, we should evaluate the risk. If it seems too great, a safer location should be found. This type of planning is very effective, but all too often, people are drawn to the lush, rolling terrain of a quiet volcano.
Disaster Preparedness
When a volcano comes to life, a few weeks may not be enough time to avert a tragedy. Planning is the key to saving lives. Well before the warning signs occur, people must be educated about volcanic hazards. Evacuation plans must be in place. Communication between scientists, officials, the media, and the general public should be outlined and practiced. Emergency measures must be thought out and agreed upon.
If you doubt the importance of these efforts, take another look at past volcanic tragedies, such as the 1985 eruption of Nevado del Ruiz. Communication failures left the town of Armero unprepared for evacuation. When a deadly mudflow came down the slope, 21,000 people--90 percent of the town's residents--perished.
Although modern Western ideas about romantic love owe a certain amount to the classical Greek and Roman past, they were filtered through the very different culture of the European Middle Ages. One can trace the concepts which dominated Western thinking until recently to the mid-12th Century. Before that time, European literature rarely mentions love, and women seldom figure prominently. After that time, within a decade or two, all has changed. Passionate love stories replace epic combat tales and women are exalted to almost god-like status. Simultaneously, the Virgin Mary becomes much more prominent in Catholic devotions, and emotionalism is rampant in religion.
Romantic stories of courtly love were spread throughout medieval Europe by troubadours and minstrels. The language used by this new poetry was intended to be sung, played on musical instruments brought back from the crusades. This was a new style of expressive writing.
One of the first poems to take a romantic turn was La Chanson de Roland (the Song of Roland) an epic about the nephew of Charlemagne. Battlefield scenes were transformed into those of ideal love.
Arthurian legends brought the tale of Tristan and Iseult. Though no complete copy of this poem, written in French, survived to today, extant German translations made it possible to piece together this poem of overwhelming guilty passions.
Aucassin and Nicolette, written by an unknown author, was one of the first to tell a love story with a happy ending. Aucaussin, son of a noble Provencal count, falls in love with Nicolette, the captive
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servant and god-daughter of a neighboring nobleman. She later turns out to be the daughter of the
King of Carthage-she was a princess.
Le Roman de la Rose (Story of the Rose) was an allegory of a love affair, unusual in that the main characters never appear as real people, but rather as different voices that stand for their qualities. This style was tremendously popular, and dictated a style that would be copied in France and England for two centuries.
The term "Middle Ages" was invented by the 15th century Renaissance scholars to describe that era of history which separated them from the scholars and artists of the Roman Empire. They believed that the
Roman times and their own were two high points in civilization and dismissed the intervening centuries as "middle" or "dark" ages when nothing of any significance really happened. The opposite in fact was true. The latter part of the Middle Ages, or "High Middle Ages" as it is commonly called, was a civilization in its own right.
The "Dark Ages" was the result of a Roman Empire which had become too vast to administer and defend. The Empire had grown continuously until about the 2nd century of the Christian Era but then massive inflation, running at more than 1 000 percent, took its toll. The imperial forces could no longer be maintained and a gradual withdrawal began. The process was speeded up when Emperor
Constantine moved the capital from Italy to Byzantium (then a fishing village on the Dardanelles) from which it was easier to defend the much more populous eastern sector of the empire. He renamed his capital Constantinople (now Istanbul).
The move meant that the sparsely populated west was virtually abandoned and quickly fell victim to the continual encroachments of the "barbarian" tribes from without. When, in the 5th century, Italy itself fell to the onslaught of a number of barbarian groups (such as the Visigoths), the western sector of the empire disintegrated. It must be remembered, however, that this was not the end of the Roman Empire as such because the more important eastern sector would remain for another millennium.
The disintegration of the western or European sector had major consequences. The fact that the
Frankish kings in the north-west fought continual fratricidal wars meant that life became insecure in the extreme. The wealthier Roman landlords in their country villas (known as villeins) took the law into their own hands and started a system of self-preservation which evolved into what is commonly known as feudalism. Families offered themselves as vassals to the lords in return for protection. It was basically a
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two-way system whereby the vassals came to work for the lord while the lord supported and protected his vassals. By the 8th century feudalism, with its economic counterpart called manorialism, was firmly entrenched into European society.
Feudalism was to have a major impact on the concept of kingship as well. Basically, a man had no power unless he had a huge feudal power-base. The Merovingian monarchy, which based its dynasty on traditional tribal authority, found that its power was waning to feudal lords with their vassals. In that way the Carolingians, who were the most powerful feudal lords of their time, managed to usurp the throne and so started the Carolingian dynasty.
Charlemagne was the greatest of the Carolingian kings and built his rule on feudalism and conquest. He was crowned emperor by the pope on Christmas day in the year 800 but his empire was doomed because it could not survive unless it maintained its feudal base, which it could not. After the death of
Louis the Pious (Charlemagne's son), civil war ensued and Europe again fragmented into feudal duchies.
The onslaught of new barbarians (the Vikings, Magyars and Saracens) during the 9th and 10th centuries then cemented the entire feudal system. At the same time, the little trade that still existed ground to a halt and Europe entered into a period where commerce ceased almost entirely, the "economy of no outlets" as Henri Pirenne calls it. Only in the 10th century, with Otto the Great's systematic conquest of the Magyars and his formation of the German Empire, together with the conversion of the Vikings to
Christianity, did trade at last begin to grow and Europe entered into a new civilization, commonly known as the "High Middle Ages".
In the meantime, society of Europe became feudal, with its military power being based on the feudal lords and its economy resting on the manor (manorialism). The peasant's sole task in life was to work the manor for the lord, while the feudal lord's primary function was as soldier, law-giver and judge. He naturally depended upon a reliable army, which in turn depended upon men able to ride and fight on horse-back. Thereby was born the knight, at first a lesser vassal but who was given land on which to sustain himself. Gradually the knight rose in feudal importance until, by the High Middle Ages, he became the essence of feudal society.
At the same time, the Catholic Church rose in importance. Originally a minor sect within the Roman
Empire, the Christian (Catholic) Church became the official state religion by the 4th century and then evolved into an integral part of feudalism itself, with a parallel feudal hierarchy of its own. The birth of the Benedictine monasteries also allowed the Church of the Dark Ages to become the last candle of education and culture, where the only books were maintained and where new editions (especially of the
Bible) were hand-written.
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The Dark Ages were desperate times but, in retrospect, the era marked the occasion when two cultures, the Roman and the Germanic, were able to forge together to become one. The result was the birth of a new civilization which needed a period of peace to produce its first flower. The peace happened in about the 11th century and the High Middle Ages was the first fruit of that civilization. It then grew and adapted until it has become the Western Civilization that we know today.
The "High Middle Ages", 1000-1400
When Otto the Great, the Saxon Duke, defeated the Magyars at the battle of Lechfield in 962, he almost single-handedly ushered in the High Middle Ages. The Viking invasions had at last come to an end and, with the restoration of relative peace in Europe, trade revived. By the beginning of the 11th century a new civilization was flowering and it would be in full bloom during the 12th and 13th centuries.
A major feature of the High Middle Ages was the renewal of learning and the arts. Architecture, which had remained virtually dormant for centuries, began to prosper. Immense cathedrals began to be built, at first designed along Romanesque lines and then, as courage grew and technique was mastered, the magnificent gothic structures appeared. It is estimated that more stone was quarried during the two hundred years of this era than during the entire pyramid-building phase of the ancient Egyptians.
Parish schools began to appear, universities started up in the major cities, poetry, art and sculpture proliferated. These were the days of Chaucer whose tales encompassed knightly honour and debauchery.
Philosophy rose to heights not seen since ancient Greek times, with Thomas Aquinas producing a work in philosophy and theology which would remain the theoretical backbone of the Catholic Church to the present day.
It was also the heyday of the Catholic Church, with the rise of the imperial papacy. Popes, such as
Gregory VII and Innocent III, commanded such power that they could excommunicate kings and emperors at will. Pope Urban II made use of his powers to initiate the Crusades whereby the awesome fighting ability of the feudal kings and knights was flung against the "infidel" Moslems in the Holy Land.
Originally religious wars, later with strong political overtones, the Crusades succeeded in harnessing the destructive nature of the knights into "holy" paths, with the result that warfare sharply declined in
Europe during the High Middle Ages.
It was also the pinnacle of monasticism and religious orders. The Benedictine monasteries, many of which had fallen into abuse by the beginning of the era, were transformed through reform measures initiated by the Cluniac movement. Other monasteries, such as the Carthusians and Cistercians, were founded and prospered. Mendicant orders, such as the Franciscans (founded by St Francis of Assisi) and
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the Dominicans (founded by St Dominic), were started and prospered during times when religion was clearly close to the hearts of the people.
On the economic front, crafts and guilds began to prosper in the towns. Apprenticeship became the norm for young townsmen wishing to learn a craft but only the most expert was considered a master craftsman. He had then to belong to the guild, a society which looked to the protection of its members and which insisted on the highest degree of professionalism from its members.
Socially, new classes of society appeared. Knighthood was now transformed from its rather lowly position of the earlier centuries to the pinnacle of society. Whereas knights once strove to become lords, now all feudal lords became knights and the system was sanctified by the Church which demanded vows of the knights and that they live according to a code of chivalry. On the other hand, the growing towns became the home of the new order of town-dwellers or bourgeoisie who began the struggle to break the economic and legal stranglehold of the country lords who knew little about the affairs of the towns. Mercantile law was thereby invented.
All good things have to end, however, and the 14th century saw a series of crises which were catastrophic in proportion. By then the majority of the forests had been cut down to make way for fields to feed the population explosion. Much was of inferior fertility. The beginning of the century was marked by a little ice age which lowered temperatures and increased rainfall, thereby destroying harvests. It was followed by the Black Death, a bubonic plague transmitted by rats and their fleas, for which there was no cure. Millions died and the population of Europe dropped by an estimated 20 to 40 percent.
Coupled with the catastrophe came a major decline in the papacy. A clash between Pope Boniface VIII and the French king led to the humiliation of the former, which was followed by the removal of the papacy from Rome to Avignon in France. The popes were not bad men as such but their lives of luxury, paid for by taxing the often destitute people, caused a scandal. They also became puppets in a great political game as the rising national monarchies either supported them (in the case of France) or opposed them (in the case of Britain and Germany). The crisis then culminated in the Great Schism where there were no less than three popes all claiming to head the Catholic Church simultaneously, one in France and two in Rome.
The times were clearly changing and would culminate in the Reformation of the 16th century. Other events were also afoot, however, as the Ottoman Empire of the Turks rose to new heights and midway through the 15th century at last succeeded in conquering Byzantium, the remaining segment of the
Roman Empire in the east. The lucrative trade route to the east, to India and China, was abruptly ended and Europe was forced either to withdraw into its shell or find a new way to the east. Several European
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states chose the latter route and, led by Spain and Portugal, voyages of discovery began which would open up the new worlds of Africa, Asia, America and Australia.
The High Middle Ages was the first flowering of a civilization which would then evolve into our modern
Western Society. It flourished suddenly and became a shining beacon at the end of the so-called Dark
Ages. At the same time, however, it ushered in new forces of national monarchies and independent religious thought which would cause major crises in the centuries to come. The High Middle Ages can therefore be seen both as a fulfilment of the "Dark Age" culture, as well as the birth of a society yet to mature
#Even if the medieval literary genres of romance, epic and lyric, as recognized today, did not hold the same identity and significance during the medieval period, as they do today, an effort must be made to study those which have survived even if their survival and importance says more about us than about medieval society. There are indeed many aspects of medieval society which may be traced in the literary genres but these must be analyzed in a more circumspect manner than the student of literature may apply.
To provide some early substantiation for the radical assumptions proposed in the introduction, it might be wise to first consider the physical context in which medieval literature was to develop. During the so-called Dark Ages the extensive Roman and Greek classical literature would have been almost totally lost to the new cultural awakening of the Middle Ages, if the church has not transcribed these works and had kept literacy alive.
Having been the only institution to maintain literacy, the spread of the church in Western Europe became synonymous with the spread of literacy. However, even by the end of the 14th century, very few laymen could read, and in fact, the capacity to read was often regarded as evidence that a man belonged to the church. All literature of significance prior to the middle ages had been in Latin, and although Latin continued to dominate, the early middle ages was marked by an increased use of vernacular languages in literature.
Since the existence of literature depended upon the capacity to write, the vernacular "literature" had previously only existed in oral form. Since a great deal of the "oral literature" was pagan, and the church provided the only means for recording the oral form, pagan stores were "Christianised" during the recording process. Despite the increasing use of the vernacular, and the incorporation of oral folk stories, the growth of literature was hindered by the necessity to laboriously copy out books by hand. Books were a valuable rarity during the whole of the medieval period.
The domination of literature and literacy by the church, and the dependency on previous literary authorities that had developed whilst the church struggled to maintain literacy and literature during the
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Dark Ages, resulted in the new literature that arose during the Middle Ages being largely of what C S
Lewis calls a "bookish or clerkly character".
Despite the gradual incorporation of oral sources, C S Lewis claims that medieval culture was not a response of the writer to observation and the environment, but depended largely upon the content of existing manuscripts. Every writer based himself on a previous writer. This observation by C S Lewis is well supported. Examples of literature encountered in each of the medieval genres were often only one example of a particular story that underwent continual and gradual revision, often shifting from paganism to Christianity as part of this process. The concept of authorship did not exist. Works of literature were not considered worthy by virtue of their being a spontaneous response to society and the author's observations, but rather by virtue of the authority to which they referred.
If this was the case, what then was the contribution of Germanic culture to the literature that arose during the period. We cannot discount that many of the sources for literature were the folklore of the
Germanic peoples, Franks and Celts, and certainly the vernacular of these groups took the place of Latin in the literature. However, we cannot forget the extent to which their stores coincided with the content of the classics, and the possibility that these were only recorded because of the possibility for reference.
The first genre to ascend to literacy permanency during the medieval period, namely the Epic, had as its classical counterpart the genre which produced such Epics as the Iliad and Odyssey. The medieval Epics sprang from oral or folk literature and were a product of primitive societies in which tales of heroes were sung by bards.
Although the sources of such folk stories were distributed across Western Europe, the similarities between the stories led to the identification of a set of characteristics by which earlier medieval literature could be separated from that which developed generally after 1100 AD. These general characteristics are best exemplified in the Old English tradition by the epic Beowulf, in France (where epics were known as Chansons de geste) by The Song of Roland, and in Germany by the Nibelunglied.
Typically the Epic tells us of a hero, leader and protector of his people. He was not only a strong fighter, but a man of foresight. He enjoyed fighting and feasting, and was loyal and generous to his people and fellows. An important aspect of the epic was that the hero had to be a man very like the people that were hearing the Epic; there had to be a possibility for some form of identification with the hero; and he had to be seen as being representative of his people.
Epics are generally full of action, with the heroes able to give full vent to their warlike spirit. The conflicts are generally mass battles in which the heroes have to fight with almost superhuman strength to overcome the odds, and in which loyalty between comrades can be illustrated to the extreme. Epics seem to exalt in the goriness of battle.
Certainly where men delight in fighting, feasting and knightly loyalty, there is little place for love and, with the exception of the bloodthirsty, warlike women who made their way into the epics, this genre was devoid of any civilising femininity. It appears that sources are unanimous regarding the reason for the acceptance of this form of literature to the point that it became recognised as a genre. The Epics
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expressed the warlike spirit and values of military brotherhood that existed in the early Middle Ages. In a time when the survival of fledgling cultures depended upon the strength of the warlord, and the loyalty of his vassals, the stores of heroes that could overcome all odds became increasingly popular.
Although the Epics had originally been composed in a pagan culture, they were recorded by christian writers. In some cases only the more obviously pagan characteristics, such as references to
Nordic and Germanic gods were omitted from the originals, whereas in others a more definite attempt was made to portray the warlords as Christian knights.
From the end of the 12th century onwards, the purely male domain of the epic lost its position of popularity to the more subtle genre of Romance, which began to take its place. The Romantic genre rested on three ideal motives; Love, Adventure and Chivalry. Each of these motives requires separate investigation if we wish to establish the development of this genre.
In the Chanson de geste, or Epic, the prime virtue had been loyalty for one's lord, in the Romance, the prime virtue was love for one's lady. In the case of the Romance this love often militated against feudal loyalty in that the love affairs were often across the barriers of the feudal hierarchy, eg. between a vassal and the Lord's lady.
The necessity for the maintenance of the feudal hierarchy, despite the demands of passion resulted in a love affair which was never taken to a passionate conclusion. According to what became known as
"courtly love", lovers (usually knights) idealised their ladies from afar and turned their every action into some form of devotion for the loved one. According to the rules of this game, the lady would provide the lover with some small token of her recognition of his devotion, which for the lover, was as passionate a gesture as any consummation might have been.
Christian morality may have been an important driving force behind the growth of "courtly love" in literature. In a society in which marriages were often arranged, an object of love outside the marriage must have been a great temptation. The reason for the idealisation of women in this genre, as opposed to the attitudes exhibited in the Epics, has proved difficult to establish. Women had been virtually ignored in the Epics, except as warriors or worthy wives, and mothers, and generally had a very low status in society at the time. One explanation is that the increasing homage paid to women was due to the growth of the cult of the Virgin Mary. Classical literacy influences such as Virgil and Ovid are also credited with having influenced early French romances, and C S Lewis has claimed that there is also an unacknowledged debt owed to the Arabians.
Possibly the greatest influence on the inclusion of the idealisation of women in the genre came as a result of the influence of women themselves. It has been reported that courtly love came to England when Eleanor of Pitou brought with her court a famous Provencal love poet in 1149 AD. Ultimately the idealisation of women in poetry portrayed the fickleness of the sentiment. There was no real sense of equality, and the woman was only really elevated when she was an object of love. In marriage she was the subject of less adoration.
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As the second motive of Romance, adventure received a new interpretation in comparison to its presentation in the Epic. In the Epic, adventure was part of the reality of the heroes' struggle. In
Romance, adventure came to be related with all that was fantastic and marvellous. The hero of romance belonged less to the world of reality and possibility, than to the world of dreams and imagination.
The story lines of Epics depended on the individual characteristics of the heroes, whereas in romances the heroes had generally similar knightly characteristics that did not determine the course of the story. The hero of Romance sought adventure without any need for motive. If the hero of romance does have a motive it is usually nobly nebulous or virtually unattainable. Such a motive came to be known as the "quest".
Chivalry was the third motive of Romance, in which the other two motives were encapsulated, and which provided the genre with its essential features. The hero of Romance was the knight, a man who fought in the tournament to win the devotion of his lady and who fought in battle out of loyalty to his lord. Although the knight was no more than a servant, he carried out his service on horseback and was separated from ordinary men by his martial prowess, birth, rank and conduct. The ideal by which a knight lived came to be known as chivalry.
Chivalry arose amongst the warlords as the civilising influence of Christianity took hold. An ideal of
Christian faith, courage, courtesy and love steadily developed within the knightly class. The chivalric ideal came to encompass many other aspects including generosity, pity, chastity and selfless bravery. In a sense it came to be for the knights a rule very much like the Benedictine rule for monks.
Unfortunately the chivalric ideal found its best expression only within the romance, and not within the actual conduct of the knight. The courtesy that was so characteristic of the literature was a rarity in practise. Nevertheless, in the realm of imagination, where the chivalric ideal could remain untainted, the love of the romance was chivalrous love; its adventures were chivalrous adventures; and its aim was to uphold a chivalrous ideal.
The development of the Romance as a genre was of a different character to the development of the epic genre. The romance genre was more international. It drew its source material from diverse cultures with France fulfilling the primary role in establishing the genre. Stories drawn from English and Germanic folklore were rewritten or recomposed, as Romances were redistributed to the cultures from which they had been drawn. As these stores were internationalised the heroes lost their national significance. In this fashion the Celtic folklore surrounding a 5th century British chieftain, Arthur, and tales such as those of
Tristan and Iseult found new significance.
Possibly the best known Romances are those concerning Arthur. Possibly the reason for the popularity of Arthur was that Geoffrey of Monmouth's Histora Regum Britanniae provided an almost historical treatise on Arthur's alleged Trojan ancestry. A huge cycle of Arthurian Romances, began to develop, drawing on material from classical works, recouched in the Romantic genre. Christianity contributed to the longevity of the Arthurian cycle by adding to the knightly "quest", a quest for the
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"Holy Grail". The quest for the Holy Grail represented a quest not just for the earthly love of a lady, but for heavenly love.
The Grail provided the knights with a spiritual struggle and reward. If the Arthurian cycle, culminating in the search for the Holy Grail, was meant to have a function in Medieval Society, the institution best served was the Catholic Church. The struggle for religious perfection became a romantic ideal; a knightly fight against evil which could fulfil the romantic notions of every Christian.
The Epic and the Romance represent two of the greatest genres of the medieval period. Whether they are truly representative of the period is dubious. They generally portrayed the ideals of the higher echelons of society. They do not represent the opinions of the period, but rather represent numerous writers' attempts to re-narrate the stories of the classics and folklore in accordance with a medieval method. These genres tell us that the earlier medieval writer was more methodical than creative.
It is possibly only in the literature of the laymen and lower classes that we begin to see a truer picture of life in medieval Europe. The growth of literacy amongst laymen was to culminate in the 14th
Century in the writings of Chaucer. Although he was not able to rid himself entirely of the need for reference, Chaucer was to presage a new literary age in which the observation and inspiration of the individual was triumphant, and which allows for the first time an unobstructed analysis of the age.
If everybody else thought that the literary vehicles of romantic love, adventure and chivalry were taken seriously in the medieval period, Chaucer certainly did not share their views, and used satire to deconstruct the Romantic genre. The fabliaux, or short verse tale, was also used by Chaucer. This genre drew its characters from the townspeople who became increasingly important in medieval Europe. The fabliaux were most often satirical, poking fun at conventional morality and institutions.
The success of the fabliaux as a genre lay in its capacity to entertain. It was not instructional or imaginary, but was firmly based on exploiting the characters and the conventions that could be recognised by the people living in the period. Any attempt at reference to classical authorities would have blunted the vigour of this genre.
Chaucer may have used satire more effectively than any other medieval writer, but there were readers and writers of satire even during the height of the periods dominated by the Epic and the
Romance. The earlier medieval satire was however not of the egalitarian nature practised by Chaucer, but was often aimed exclusively at the idealisation of women in the literature. This should not be surprising since most of the writers of such satire where grudgingly celibate monks. Within the genre of
Satire, the medieval urban culture also produced the fable. In these animal stories, which were in the same tradition as Aesop's Fables, medieval characters were placed in the feudal hierarchy of the animal kingdom. Using allegory, the fables were able to express the diversity of human character, and the worldly wisdom which medieval man had to develop in order to prosper.
An analysis of the gulf that separates the genres of Epic and Romance, on the one hand, and the genres of Fabliaux, Satire and Fable on the other, perhaps allows for a 20th Century approach to the genres. Life in the Middle Ages was a brutish, short and dirty affair. Disease and warfare were constant
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threats to life. The genres of the Epic and Romance did not represent the glories and ideals of the period, but rather harkened back to a period when glories and higher ideals were considered to be more commonplace. This has been quite accurately portrayed in the statement "The Golden Age of
Chivalry was always in the past".
While the knight or aristocrat claimed to live by the code, but was rather more Machiavellian, the ordinary people laboured on, seeking what escape they could in a literature that was based more on the realities of life. It is thus unlikely that the medieval literary genre that currently carry the most emphasis, namely the Romance and Epic, truly represented the response of the medieval man to his environment.
The significant literature of the period was not recorded until its composers became literate, and began to produce writings that were truly characteristic of the age. Much may have been lost in the interim, and the Epic and Romance flourished on the shallow soil of classical reference.
The beaver is North America's largest rodent and is built for life in the water. Adults can be up to four feet long and weigh over 60 pounds. The beaver has webbed hind feet and a large, flat, nearly hairless tail. It uses its tail to help maintain its balance when it is gnawing on trees. It will also slap its tail against the water to signal danger or to warn away predators. The beaver has short front legs with heavy claws. Their rear legs are longer and their webbed feet help propel them through the water when they are swimming. When the beaver is under water, its nose and ears close up and a special membrane covers its eyes.
It has dark brown fur on its back and sides and lighter brown fur on its chest and belly. The beaver waterproofs its thick fur by coating it with castoreum , an oily secretion from its scent glands. The beaver has a thick layer of fat under its skin that helps keep it warm underwater. Beavers have long sharp upper and lower incisor teeth that they use to cut into trees and woody vegetation. These teeth grow throughout the beaver's life.
Beavers live near rivers, streams, ponds, small lakes and marshes. They build lodges of sticks and mud on islands, on pond banks or on lake shores. Beaver dams are domed-shaped and can be as high as ten
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feet tall. Beaver lodges have one large central chamber and one or two entrances. The floor of the chamber is a little bit above the water and is usually covered in woodchips to absorb moisture. A vent in the lodge lets in fresh air. Not all beavers build lodges some beavers will build burrows in the banks of rivers.
Most of the beaver's diet is made up of tree bark and cambium, the soft tissue that grow under the bark of a tree. They especially like the bark of willow, maple, birch, aspen, cottonwood, beech, poplar, and alder trees. Beavers also eat other vegetation like roots and buds and other water plants. The beaver has a specialized digestive system that helps it digest tree bark.
Beavers mate for life, but if one mate dies, the other one will find another mate. Beavers mate when they are about three years old. Mating season runs from January and March in cold regions in late
November or December in the south. Gestation lasts about three months and females have one litter of kits a year between April and June. Before birth, the female will make a soft bed in the lodge. The babies eyes are open when they are born and they can swim within 24 hours of birth and will be exploring outside the lodge with their parents within a few days. The young beavers are weaned in about two weeks. Both the male and the female take care of the young beavers. They will stay with their parents for two years. Beavers can live to be 20 years old.
Beavers live in family groups or colonies. A colony is made up of a breeding male and female beaver and their offspring. Beavers are very territorial and will protect their lodges from other beavers.
They mark their territory by building piles of mud and marking it with scent.
Beavers can have both a positive and a negative impact on the environment. When beavers build dams, they create new wetland environments for other species. These wetlands can help slow erosion, raise the water table and help purify the water. Beavers can play a major role in succession, When beavers abandon their lodges and dams, aquatic plants will take over the pond and eventually, shrubs and other plants will grow and the area will become a meadow. The shrubs in the meadow will provide enough shade to allow tree seedlings to grow, once the trees grow, they will take over and the land will turn into a woodland area.
Beaver dams can also cause problems. Dams can slow the flow of water in streams and cause silt to build up and some species can loose habitat. Dams can also cause flooding in low lying areas.
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If you've ever had the pleasure to go tide pooling then you already know that Starfish are the most popular creatures there -- especially among the younger crowd.
Tide pool excursions are a wonderful experience: the sound of surf accompanied by the refreshing sea breeze are reason enough to go. But the diversity of creatures living between sea and sand are the real treat on these trips.
At the shoreline, certain camaraderie pervades the atmosphere. Strangers approach one another to share information about interesting finds; families with younger children ask:
[like the Pink Star (
) to your right]; students follow teachers who are thoroughly enchanted by the tide pool ecosystem; and perfect strangers who may never meet again form close friendships while wandering in search of another unusual living creature in the small pools formed by the receding tide.
Starfish may well be the most unusual well-known creature. They have no front or back: they can move in any direction without turning. Rather than using muscles to move their hundreds of tiny legs, starfish use a complex hydraulic system to move around or cling to rocks. The intake valve for this system is generally located on the top of the Starfish, just off center, as can be seen clearly on the
Leather Star (
) to the left.
If you've ever tried to pry a Starfish off a rock, you know how effective its hydraulic system really is.
Of course, starfish don't have to make themselves symmetrical. They can rearrange their arms any way they please in order to wedge themselves into a small nook in the rocks -- as you can see in this almost human-looking Knobby Star (
) to the right.
Starfish are usually fairly sluggish, have five or six arms and get pretty stiff when you try to pick them up.
The Sunflower Star (
, below) breaks all of these stereotypes. It typically has around 20 arms, moves -- practically flows -- quite gracefully across the surface, and is soft (mushy?) to the touch.
Just for the record, the Starfish at the top of the page are: Ochre Star (
), Bat
Star (
), and Six-rayed Star (
) respectively, from left to right. The mottled Starfish above right is also a Bat Star.
Aye-ayes can be found only on the island of Madagascar. These rare animals may not look like primates at first glance, but they are related to chimpanzees, apes, and humans.
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Aye-ayes are dark brown or black and are distinguished by a bushy tail that is larger than their body.
They also feature big eyes, slender fingers, and large, sensitive ears. Aye-ayes have pointed claws on all their fingers and toes except for their opposable big toes, which enable them to dangle from branches.
Aye-ayes spend their lives in rain forest trees and avoid coming down to earth. They are nocturnal, and spend the day curled up in a ball-like nest of leaves and branches. The nests appear as closed spheres with single entry holes, situated in the forks of large trees.
While perched aloft, the aye-aye taps on trees with its long middle finger and listens for wood-boring insect larvae moving under the bark. It employs the same middle finger to fish them out. The digit is also useful for scooping the flesh out of coconuts and other fruits that supplement the animal's insect diet.
Many people native to Madagascar consider the aye-aye an omen of ill luck. For this reason they often have been killed on sight. Such hunting, coupled with habitat destruction, have made the aye-aye critically endangered. Today they are protected by law.
Long-distance trade played a major role in the cultural, religious, and artistic exchanges that took place between the major centers of civilization in Europe and Asia during antiquity. Some of these trade routes had been in use for centuries, but by the beginning of the first century A.D., merchants, diplomats, and travelers could (in theory) cross the ancient world from Britain and Spain in the west to China and Japan in the east. The trade routes served principally to transfer raw materials, foodstuffs, and luxury goods from areas with surpluses to others where they were in short supply. Some areas had a monopoly on certain materials or goods. China, for example, supplied West Asia and the Mediterranean world with silk, while spices were obtained principally from South Asia. These goods were transported over vast distances— either by pack animals overland or by seagoing ships—along the Silk and Spice Routes , which were the main arteries of contact between the various ancient empires of the Old World. Another important trade route, known as the Incense Route , was controlled by the Arabs, who brought frankincense and myrrh by camel caravan from South Arabia.
Cities along these trade routes grew rich providing services to merchants and acting as international marketplaces. Some, like Palmyra and Petra on the fringes of the Syrian Desert, flourished mainly as centers of trade supplying merchant caravans and policing the trade routes. They also became cultural
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and artistic centers, where peoples of different ethnic and cultural backgrounds could meet and intermingle.
The trade routes were the communications highways of the ancient world. New inventions, religious beliefs, artistic styles, languages, and social customs, as well as goods and raw materials, were transmitted by people moving from one place to another to conduct business. These connections are reflected, for example, in the sculptural styles of Gandhara (modern-day Pakistan and northern India) and Gaul (modern-day France), both influenced by the Hellenistic styles popularized by the Romans.
We've Covered the different pyramids of Egypt in our Monuments section under the Antiquities page; however, this area is dedicated to the construction and architecture of the pyramids, how they were built, and the evolution in design from the step pyramid to the true pyramid. Beginning with the step pyramids of the 3rd Dynasty , and continuing for centuries, the pyramid is a marvel of construction, and is considered one of the "Seven wonders of the world." The pyramids are the only of these seven that remain standing and intact
The Step Pyramid
The earliest form of pyramid, the step, dates back to the 3rd Dynasty, and consists of several steps. A descending passage from the north leads to the burial chamber. Underground galleries surround the pyramid on all but the south sides. The first, and probably the only step pyramid ever completed, is that of King Netjerykhet Djoser at Saqqara. The Step pyramid is not near as pleasing to the eye as the True pyramid, which could explain the quick abandonment of this type of pyramid
True Pyramid
The true pyramid is a natural development and improvement on the step pyramid. The first true pyramids were introduced in at the beginning of the 4th Dynasty. The structure of a True Pyramid is virtually the same as a step pyramid. Packing blocks are stacked until the dimensions were right, and then finishing blocks (usually limestone) were the last touch. The aesthetics are much more pleasing than the step pyramid, but the construction isn't really that different.
Construction
Techniques
A major problem facing the builders of the Ancient
Egyptian Pyramids, was that of getting the Large stone blocks to the height they required. the method shown at left, is the only one proven to have been used. The ramps were built on inclined planes of mud brick and rubble. They then dragged the blocks on sledges to the needed height. As the pyramid grew taller, the ramp had to be extended in
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length, and its base was widened, else it would collapse. It is likely that for the construction of each pyramid, several ramps were probably used
The arrangement of the ramps used for building is in much dispute. Assuming that the step pyramid was built before the outer structure, and then the packing blocks were laid on top, the ramps could have run from one step to another rather than approaching the pyramid face at right angles.
Some of the pyramids indicate an accurate understanding of Pi, but the mathematical knowledge of the
Egyptians did not include the ability to arrive at this by calculation. It is possible that this could have been arrived at "accidentally" through a means such as counting the revolutions of a drum.
The internal construction of most true pyramids consists of a series of buttress walls surrounding a central core. The walls decrease in height from the center outwards. In other words, the core of the true pyramid is essentially a step pyramid. The internal arrangement added stability to the structure. Packing blocks filled the "steps" formed by the faces of the outermost buttress walls and casting blocks (often
Limestone) completed the structure of the true pyramid.
Architects and builders used a different form of construction in the pyramids of the 12th and 13th Dynasties. Mainly because of economy, for it was suitable for relatively modest structures in inferior materials. Solid walls of stone ran from the center, and shorter cross walls formed a series of chambers filled with stone blocks, ruble or mud bricks. An outer casing was usually added, and although quite effective in the short term, it did not even come close to the earlier construction methods. Pyramids which were built with this structural design are quite dilapidated and worn
The ancient Egyptians loved pyramids. There are sixty-seven, of various sizes, scattered around the city of Cairo alone. The most famous, and largest, are at Gizeh, where what is believed to be the three tombs of Khufu, Khafre, and Menkure, are lined up side by side.
The end tomb, Khufu's, which is often referred to as " The Great Pyramid ," just by itself is an impressive structure. It stood 480 feet tall when completed and contains twice as much volume as the Empire State
Building. Until the 19th century it was the tallest building ever erected. Not bad for a structure 45 centuries old.
So, how did the ancient Egyptians construct such an impressive monument so long ago? Some wild theories exist. Swiss Author Erick von Daniken suggested that aliens assisted the construction using advanced technology. Herodotus of Halicarnassus, a Greek writer who viewed the pyramids around 450
B.C. was told that giant machines were used to lift the blocks into place with the aid of 100,000 slaves working, for the entire year, for twenty years.
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Probably neither of these are correct. Most likely the Pharaoh employed a large work force, indeed as many as 100,000 men, but for only a fraction of the year. During the months of July, August, September and October, the Nile River flooded the land. This was actually a blessing for the Egyptian farmers as it allowed new fertile soil to be laid down over the fields. But it meant the farmers were unable to grow crops during this period. It is likely that the Pharaoh required his subjects to work on public projects, like the pyramids, during this season.
Egyptian records indicate that the laborers, while being drafted against their will, were actually well cared for by ancient standards. Regulations have been found covering the maximum amount of work allowed per day, the wages received and holidays entitled to, each worker. By only requiring work to be done during flood periods, the Pharaoh could get a lot done without impacting the normal Egyptian economy.
He probably also employed a much smaller work force year round on the project. Some would have been employed doing the skilled stonework while others planned and prepared the site for the laborers that would be available during the next flood season.
The shape of the pyramid are the logical one for producing buildings of great height when the building material available is stone. The design mimics the natural geometry of a mountain, an incline of about
52 degrees. The Egyptian architects realized the ever widening base would easily support the increasing number of stone blocks above it making the structure very stable.
An average 2 and 1/2 ton limestone block used in the pyramid construction would have probably taken
8 men nine or ten days to move from the quarry, float across the Nile, and drag to the top of the pyramid.
The most likely method of getting the blocks to the top of the structure was through massive construction ramps. Exactly how the ramps were laid out is unknown, but they may have been straight or in a spiral pattern around the pyramid. The ramps may have been topped with a surface of Tafla, a clay. Tafla, when wet, becomes very slippery and may have allowed the
Egyptian builders to use shorter, steeper ramps than might have otherwise been possible. By wetting the ground in front of the block a slick path would be created allowing the stone to be dragged by rope as it sat on sledges.
It is also possible the stones could have been moved on rollers. By placing rounded logs under the stone, crude wheels would have made the load easy to pull. Pictures inscribed on ancient monument walls, though, suggest the blocks were dragged without the aid of rollers. Once a stone was at the top of the pyramid, it was probably moved into its final position with the use of levers.
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We can see the Egyptains didn't become great pyramid builders right away. They needed some practice.
They started by cutting tombs into the rock of the desert floor and building mastabas (from the Arab word meaning "bench") over them. Mastabas were raised, flat, platforms. Some were twenty-five feet high and two-hundred feet square. Imhotep, architect to the Pharaoh Zoser, changed this by building his king a mastaba and then placing another, smaller mastaba right on top of it. On top of that he placed another even smaller mastaba. When he was finally done the structure had six levels and resembled a stepped pyramid.
A number of stepped pyramids were built after that, but the most interesting is the one at Meidum built for Pharaoh Seneferu. It's an example of an early design that failed. The pyramid, which has four levels, is in near ruins today with many of its blocks laying in a heap around the base. Why did it do so poorly when many other pyramids are in much better shape? The architect of this pyramid apparently had not yet learned the importance of laying the foundation on solid rock rather than sand. Also, the construction trick of tilting the blocks on a slope inward toward the center of the pyramid had not been invented. By tilting the blocks slightly inward, the weight of the blocks helped lock them into the structure.
Without this trick and with a poor foundation, the pyramid at Meidum was easily shaken apart during earthquakes. Later, better built pyramids show that the Egyptians learned as they built and their masterpieces have stood the test of the centuries
Why should one study the Ancient Greeks? There exist almost countless contributions that Greek culture has made to western society in the areas of art, literature, philosophy, drama, architecture and politics. Lasting visions of thought and inspiring intellect helped shaped today's western culture with notions of democracy and personal freedoms. Greek scientists made revolutionary discoveries in medicine, mathematics, physics, and astronomy. It was the Greeks who, through philosophy, instilled thoughtful exploration of the mind and consciousness. The beauty of their artwork and the precision of their statues reflected human development and expression of individuality. The most important reason to study the Greeks is for the opportunity to take small glimpses of history related to them, and try to better understand our humanity.
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The early history of Greece is not very detailed. Because of this it is often called the Dark Age of Ancient
Greece. The first people to inhabit Greece built settlements along the shores of Greece. They relied on the Aegean Sea for trade and supplies. Travel by sea introduced the Greeks to other cultures, and they were exposed to western benefits of agriculture and various techniques of metalwork. (Archibald, p. 13)
Different communities began to develop in Greece: the Aegeans, Achaeans, the and Pelasgians. Crete became the center of the Aegean civilization, also called the Minoans, and their culture dominated the region about 2500 BC. The Achaeans built their capital at Mycenae. A volcanic eruption in 1400 BC caused the destruction of the Minoan Thera, an island east of Crete. The destruction crushed the
Minoan functionality and their culture was absorbed by the Mycenaean Greeks (New World, p G254).
Around 1200 BC, a conflict arose at the city of Troy, where a ten year battle took place. Armed invaders hid themselves inside a large wooden horse. As the horse was brought into the city, the soldiers attacked and seized control. This was the subject of an epic poem by Homer. Homer is also well known for his epic poem of the hero Odysseus. These works of literature are now popular school studies.
Greek settlements transformed themselves into city-states, or poleis. Regions ruled by a council and a king. Their political structure was unstable because the kings often acted like tyrants to the citizens. The
Aristocratic people, mostly landowners, served on the council. Many citizens were not fairly represented in this system. This caused tension, and in many cases political uprisings. (Archibald, p. 19) It is ironic that the Greek culture is given so much credit for ideas of democracy, because times of democracy seldom existed in Ancient Greece; only for short whiles in-between unstable governments.
The Olympic Games, a great athletic contest, began in 776 BC. The Olympics marked a rise of the Greek culture, and the beginning of the Archaic Period of Greece. During this time period, foreign culture held a great influence over Greek ideas. Artwork began to focus on human figures and of mythology. The culture soared even higher into the Classical Period, approximately 500 BC. This was the highest point of Greek creativity especially in the areas of philosophy, art, and literature.
The Persian Wars began in 490 BC, with a Persian invasion in Greece led by Darius the Great of Thrace.
The Greek forces were superior and crushed the invasion at Marathon, under Miltiades. In 480 BC, the
Persians launched a second attack led by Xerxes and sacked and ruined Athens. The Greeks later won a decisive military victory at Salamis, they defeated the Persian naval fleet.
More Wars followed, and in 461 BC, the first of the Peloponnesian Wars began between the Athenians and Spartans. Athens had a completely democratic government, and the Spartan aristocratic government saw that as a potential threat. Athens was victorious and they signed a peace treaty with
Persia and made a truce with Sparta (New Standard, p. G254b-B255). Athens lost the second
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Peloponnesian War, and its empire was crushed. The Thirty Tyrants, a group of aristocratic Spartans, took control of Athens. In 399 BC, Socrates, the philosopher, was tried and executed for his objection to the Thirty Tyrants.
In 386 BC, Pluto, a famous pupil of Socrates, founded his philosophical Academy. In 359, Philip II becomes the king of Macedon. Thebes, Athens, and Sparta were three major competing powers. Philip
II eventually took control of the entire Greek penninsula. In 336 BC, King Philip II was assassinated, and his son Alexander took control of the kingdom. Alexander the Great (see Greek maps) took Egypt and conquered the entire Persian empire. Upon his death at Babylon in 323 BC, his empire was divided into three main regions: Ptolemic Egypt, Antigonid Macedonia, and Seleucid Syria.
The time period after Alexander the Great's death became known as the Hellenistic Age. Throughout this time, the seperate kingdoms constantly feuded with one another, crippling each other and foreshadowing the Greek downfall. In 197 BC,
King Philip V lost to Roman forces at Kynoskephalai. The Roman military campaign overtook the Greek warriors, and Rome tried to incorporate Greek culture within its own
In the 19th century, as the United States spread across the continent, transportation systems helped connect the growing nation. First rivers and roads and then canals and railroads moved travelers and agricultural and manufactured goods between farms, towns, and cities. Transportation links helped create a set of distinct local and regional economies. They also contributed to the sectional jealousies and rivalries that set the stage for the Civil War. Not until the end of the century would transportation networks form a national economy.
Connecting the Growing Nation
In 1800, the United States was made up of 16 states, all east of the Appalachians, and most people lived within 50 miles of the Atlantic. Oceans and rivers were the nations’ highways, providing the only viable way to travel long distances. During the 19th century, as the United States expanded across the continent, the transportation landscape changed. Roads, steamboats, canals, and railroads helped link different regions together and spread settlement away from the coast.
Roads
In the early 19th century, most roads were dreadful. They served local needs, allowing farmers to get produce to market. Americans who did travel long distances overland to settle the West rode on wagon trails, like the Oregon Trail, rather than well-defined roads. Still, a few major roads served as important
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transportation links. The National Road, initially funded by the federal government, stretched from
Cumberland, Maryland, to Columbus, Ohio, by 1833.
Steamboats
The first commercially successful steamboat was tested on the Hudson River in 1807. Steamboats were soon introduced on most navigable rivers. They allowed commerce and travel both upstream and down, and encouraged trade by lowering costs and saving time. By 1830, steamboats dominated American river transportation
Canals
The Erie Canal, built with state funding, was completed in 1825. Running from the Hudson River to the
Great Lakes, it was a major economic artery through New York. Its economic success sparked a wave of canal building. By 1840, the United States had 3,326 miles of canals
Railroads
Steam railroads began to appear in the United States around 1830, and dominated the continental transportation system by the 1850s. By 1860 there were roughly 31,000 miles of track in the country, concentrated in the Northeast but also in the South and Midwest.
1800-1900
Between 1800 and 1900, the way Americans moved around their world changed drastically.In 1800, the only practical way to travel and trade across long distances was along the nation’s natural waterways. As a result, settlement clung to the nation’s coasts and rivers. A few roads connected major cities, but travel on them was difficult and time consuming.
One hundred years later, railroads sped along thousands of miles of track. Large ships moved passengers and freight across the oceans and smaller boats plied the nation’s rivers, lakes and canals.
Bicycles, carriages and wagons rolled over thousands of miles of roads. Seventy-five million people lived coast to coast, many in towns and cities that had sprouted up along the new routes.
One of the fastest growing of these young cities was Chicago. In 1800 the state of Illinois didn’t exist; by
1900, its largest city was an economic powerhouse with over 1.6 million residents. Located at the intersection of river, lake and railroad routes, Chicago’s industrial, manufacturing and commercial life depended on the boats and trains traveling into and out of the city. Lake steamers carried coal and iron ore to Chicago’s steel mills. Railroads brought livestock to the city’s stockyards and shipped sides of beef, pork, and lamb to the rest of the country.
Sears, Roebuck and Company and Montgomery Ward—both Chicago firms— sold everything including the kitchen sink and guaranteed delivery to the nation’s doorstep, or at least to the nearest railroad station.
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By 1900, the average American had come to depend on far-flung places for the basic staples of life.
Fruit from California, furniture from Chicago and clothes from New York now criss-crossed the country with a speed and ease unheard of a century earlier.
1900-1950
The dawning of the 20th century. America was in the midst of great change. Although most of the population lived in rural areas, people were moving to cities in record numbers. Electric trolley lines meant people were less dependent on horse and foot to get around. They could travel farther faster and, because it was relatively cheap, they did. For 5 cents, commuters could hop on a streetcar in downtown New Haven or Memphis and ride to their homes in the new streetcar suburbs.far from the crowds and chaos of the cities.
In the early part of the century, a new vehicle entered the fray. At first cars were fragile luxury items, but thanks to mass production, they quickly became affordable. In 1900, Americans owned 8 thousand cars, in 1920, 8 million. Cities and suburbs both spread out. For those with cars work and shopping were now just a short drive away.
Outside of American cities, however, travel by road was still difficult. It was rails and waterways that made it possible to move people and goods across long distances. Railroads were one of the nation’s largest businesses. They employed nearly 10 percent of all industrial workers. During World War II, business boomed. Trains carried over 90 percent of wartime passengers and nearly all of the nation’s long distance freight. After the war, however, as Americans slid behind the wheel in record numbers, railroads lost riders and concentrated on hauling freight.
The nation’s rivers, lakes, and the oceans remained a critical part of the U.S. transportation story.
Millions of immigrants came to this country by ocean liner from Europe or Asia. Others crossed the oceans for business and pleasure.
And an entirely new mode of transportation was introduced in the early years of the 20th century.
Regional airlines began offering regularly scheduled passenger flights in the late 1920s. But it would be another 40 years before air travel would truly take off as a popular and affordable way to travel.
1950-2000
The 1950s. For many, a set of wheels seemed to guarantee the American dream-the house in the suburbs, the family outings, the freedom to come and go as you please. Nearly 50 million cars were on the roads.
In the year 2000, there were more than 220 million—more than one car for every person over the age of 18. More people shopped and worked miles from home—often in sprawling edge cities or far-flung suburbs. Although cars polluted the atmosphere and commuting times rose, for most Americans a car was no longer a luxury.it was a necessity they would be loathe to live without.
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A great increase in air travel also changed how we lived. Beginning in the 1960s, airports expanded to serve the millions of new passengers and the flourishing air cargo business. By 2000, 2 million passengers plus millions of packages and high priority cargo took off from America’s airports every day.
Goods of all kinds continued to be moved by rail, truck and ship, as well. But beginning in the 1960s a new innovation-containers-radically changed the way freight traveled the country and the globe.
Shippers began to pack goods of all kinds in standardized steel boxes that could be easily and cheaply moved from ship to rail to truck and back again. It meant that shoes, shirts, or stereos made anywhere in the world could be shipped anywhere else at a low cost, changing not just what people bought, but the work they did and the lives they lead.
MARK LEHNER, Archaeologist, Oriental Institute of the University of Chicago, and Harvard Semitic
Museum
NOVA: How do we know how old the pyramids are?
LEHNER: It's not a direct approach. There are people coming from a New Age perspective who want the pyramids to be very old, much older than Egyptologists are willing to agree. There are people who want them to be built by extraterrestrials, or inspired by extraterrestrials, or built by a lost civilization whose records are otherwise unknown to us. And similar ideas are said about the Sphinx. And in response to the evidence that we have for the time in which the pyramids are built, the criticism is often leveled at scholars that they're only dealing with circumstantial information. It's all just circumstantial. And sometimes we smile at that, because virtually all information in archaeology is circumstantial.
Rarely do we have people from thousands of years ago who are writing, who are signing confessions. So there's no one easy way that we know what the date of the pyramids happens to be. It's mostly by context. The pyramids are surrounded by cemeteries of other tombs. In these tombs we find bodies.
Sometimes we find organic materials, like fragments of reed, and wood, wooden coffins. We find the bones of the people who lived and were buried in these tombs. All that can be radiocarbon dated, for example. But primarily we date the pyramids by their position in the development of Egyptian architecture and material culture over the broad sweep of 3,000 years. So we're not dealing with any one foothold of factual knowledge at Giza itself. We're dealing with basically the entirety of Egyptology and
Egyptian archaeology.
NOVA: Can you give us an example of a single aspect of material culture, from ancient Egypt that you might use as a starting point for dating the pyramids?
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LEHNER: The pottery, for example. All the pottery you find at Giza looks like the pottery of the time of
Khufu, Khafre, and Menkaure, the kings who built these pyramids in what we call the Fourth Dynasty, the
Old Kingdom. We study the pottery and how it changes over the broad sweep, some 3,000 years. There are people who are experts in all these different periods of pottery or Egyptian ceramics.
So to bring it down to a level that almost anybody can understand, if, for example, you were digging around the base of the Empire State Building, assuming that it was a ruin and the streets around it in
Manhattan were filled with dirt, and you started finding ceramics that were characteristic of the
Elizabethan era or say the Colonial period here in the United States, that would be one thing. But if you started finding the Styrofoam cups and the plastic utensils of the nearby delicatessen, then you would know by virtue of their position in the overall material culture of the 20th century that that's probably a good date for the Empire State Building. Of course then you'd look at the Empire State Building's style and you'd compare it to the Chrysler Building, and you'd compare it to the Citicorp Building, which is considerably different. And you'd work out the different styles in the evolution of Manhattan itself. But by and large, you would, in the broad scope, be able to put the Empire State Building and Manhattan in an overall context of development here in the United States and in the modern 19th and 20th centuries.
And you would know that it didn't date, for example, to the colonial period of George Washington and
Thomas Jefferson, because nothing you'd find in the Empire State Building ruins, around it, in the dirt surrounding it -- maybe it's a stump sticking up above the sloping ruins of Manhattan -- nothing really looks like the flowing blue china, or the other kinds of utensils and material culture that they used in the time of the American Revolution. So it's hard to give a succinct answer to that question, because we date things in archaeology on the basis of its context and a broad mass of information and material culture -- things that were used by people, styles, and so on.
NOVA: When it comes to carbon dating, do you need organic material?
LEHNER: Right. There has been radiocarbon dating, or carbon-14 dating done in Egypt obviously before we did our studies, and it's been done on some material from Giza. For example, the great boat that was found just south of the Great Pyramid, which we think belongs to Khufu, that was radiocarbon dated -- coming out about 2,600 B.C.
NOVA: But how do you carbon date the pyramids themselves when they're made out of stone, an inorganic material?
LEHNER: We had the idea some years back to radiocarbon date the pyramids directly. And as you say, you need organic material in order to do carbon-14 dating, because all living creatures, every living thing takes in carbon-14 during its lifetime, and stops taking in carbon-14 when it dies. And then the
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carbon-14 starts breaking down at a regular rate. So in effect, you're counting the carbon-14 in an organic specimen. And by virtue of the rate of disintegration of carbon-14 atoms and the amount of carbon-14 in a sample, you can know how old it is. So how do you date the pyramids, because they're made out of stone and mortar? Well, in the 1980s when I was crawling around on the pyramids, as I used to like to do and still do, I noticed that contrary to what many guides tell people, even the stones of the Great Pyramid of Khufu are put together with great quantities of mortar. We're looking, you see, at the core.
A pyramid is basically, most basically, two separate constructions: it's an outer shell of very fine polished limestone with great accuracy in its joints, but most of that's missing; and the other construction is the inner core, which filled in this shell. Since most of the outer casing is missing what you see now is the step-like structure of the core. The core was made with a substantial slop factor, as my friend who is a mechanic likes to say about certain automobiles. That is, they didn't join the stones very accurately. You have great spaces between the stones. And you can actually see where the men were up there and they didn't, you know, they may have like four or five, even six inches between two stones. And so they'd jam down pebbles and cobbles and some broken stones, and slop big quantities of gypsum mortar in there.
I noticed that in the interstices between the stones and in this mortar was embedded organic material, like charcoal, probably from the fire that they used to heat the gypsum in order to make the mortar. You have to heat raw gypsum in order to dehydrate it, and then you rehydrate it in order to make the mortar, like with modern cement.
So it occurred to me that if we could take these small samples, we could radiocarbon date them, not with conventional radiocarbon dating so much, but recently there's been a development in carbon-14 dating where they use atomic accelerators to count the disintegration rate of the carbon-14 atoms, atom by atom. So you can date extraordinarily small samples. So we set up a program to do that. And it involved us climbing all over the Old Kingdom pyramids, including the ones at Giza, taking as much in the way of organic samples as we could. We weren't damaging the pyramids, because these are tiny little flecks and it's a very strange experience to be crawling over a monument as big as Khufu's, looking for a bit of charcoal that might be as big as the fingernail on your small finger. We noted, not only the samples of charcoal, sometimes there was reed. Now and then in some of the pyramids we found little bits of wood. But we saw in many places, even on the giant pyramids of Giza, the first pyramid and the second pyramid and the third one, fragments of tools, bits of pottery that are clearly characteristic of the Old Kingdom. And it occurred to us, you know, these are not just objects, these, the pyramids themselves were archaeological sites during the time they were being built. If it took 20 years to build them -- and now we begin to think that Khufu may have reigned double the length of time that we traditionally assign him -- if people were building the Great Pyramid over three decades, it was an occupied site as long as some camp sites that hunters and gatherers occupied that archaeologists dig
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out in the desert.
So you see the pyramids are very human monuments. And the evidence of the people who built them, their material culture is embedded right into the very fabric of the pyramids. And I think I could take just about any interested person and show them this kind of material embedded in the pyramids as well as tool marks in the stones and say, hey, folks, these weren't lasers. These were chisels and hammers and you know, people who were really out there.
NOVA: What does the radiocarbon dating tell us about the date of the pyramids?
LEHNER: Well, we did a first run in 1984, actually, funded by the Edgar Cayce Foundation because they had definite ideas that the pyramids were much older than Egyptologists believed. That they date as early as 10,500 B.C. Well, obviously for them it was a good test case because radio carbon dating does not give you pinpoint accuracy. If you have a plus or minus factor, but I say it's kind of like shooting at a fly on a barn with a shotgun. Well, you're not going to hit the fly exactly, you're going to know which side of the barn, which end of the barn, you know, the buckshot is scattering. And it wasn't scattering at
10,500 B.C. on that first run of some 70 samples from a whole selection of pyramids of the Old Kingdom.
But it was significantly older than Egyptologists believed. We were getting dates from the 1984 study that were on the average 374 years too old for the
, (the
is a reference) dates for the kings who built these monuments. So just recently we took some
300 samples, and in collaboration with our Egyptian colleagues, we are now in the process of dating these samples. The outcome we are going to announce jointly in tandem with our Egyptian colleagues, and maybe we can pick up the subject of the results when we're over there in Egypt together with Dr.
Zahi Hawass (during the February excavation of the bakeries at Giza).
NOVA: Is there any evidence at all that an ancient civilization predating the civilization of Khufu, Khafre and Menkaure was there?
LEHNER: It's a good question. If they were there, you see -- civilizations don't disappear without a trace.
If archaeologists can go out and dig up a campsite of hunters and gatherers that was occupied 15,000 years ago, there's no way there could have been a complex civilization at a place like Giza or anywhere in the Nile Valley and they didn't leave a trace, because people eat, people poop, people leave their garbage around, and they leave their traces, they leave the traces of humanity.
Now at Giza, I should tell people how this has come down to me personally. Because I actually went over there with my own notions of lost civilizations, older civilizations from Edgar Cayce. When I worked at the Sphinx over a five-year period we were mapping every nook and cranny, every block and stone,
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and actually every fissure and crack as well. And I, on a couple of different occasions was able to excavate natural solution cavities in the limestone from which the Sphinx is made. Natural solution cavities are like holes in Swiss cheese. When the limestone formed from sea sediments 50 million years ago there were bubbles and holes and so on, and fissures later developed from tectonic forces cracking the limestone. So for example, right at the hind paw of the Great Sphinx on the north side, this main fissure that cuts through the whole body of the Sphinx and then through the floor opens up to about
30 centimeters wide and about a meter or more in length. And in tandem with Zahi Hawass in 1979-'80, we were clearing out this fissure, which now is totally filled with debris again. But we actually reached down to our armpits, lying on our sides on the floor, scooping out this clay. And in the clay was embedded, not only charcoal, but bits of pottery that were very characteristic of the pottery that was used during the time of Khufu, Khafre and Menkaure, the 4th Dynasty.
We did that again on the floor of the Sphinx temple which is built on a lower terrace directly below the paws of the Sphinx. Directly in front of the Sphinx, we found a solution cavity in 1978, during what's called the SRI Project, which has been written about. We actually cleared out this cavity. We found dolomite pounders, these round balls of hard dolomite that are characteristic hammerstones of the age of the pyramids that they used for roughing out work in stone. Beyond that, Zahi and I excavated deposits on the floor of the Sphinx, even more substantial, deposits that were sealed by an 18th Dynasty temple, built by Tutankamen's great grandfather when the Sphinx was already 1,200 years old. But it was built by a pharaoh named Amenhotep II and his son, Thelmos IV. They put the foundation of this temple right over deposits of the Old Kingdom, and sealed it, so that they were left there and were not cleared away by earlier excavators in our era in the 1930s.
Zahi and I sort of did a stratographic dissection of these ancient deposits. That is we did very careful trenches, recorded the layers and the different kinds of material. The bottom material sealed by a temple built by Tutankamen's great or great great grandfather, was Old Kingdom construction debris. They stopped work cutting the outlines of the Sphinx ditch -- the Sphinx sits down in this ditch or sanctuary.
We were able to show exactly where they stopped work. They didn't quite finish that. We found tools, we found pottery, characteristic of the Old Kingdom time of Khufu, Khafre, and Menkaure.
Now the point is this. That it's not just this crevice or that nook and cranny or that deposit underneath this temple, but all over Giza, you find this kind of material. And as I say in looking for our carbon-14 samples, climbing in the pyramids you find the same material embedded in the very fabric of the pyramids, in the mortar bonding the stones together. So back to the question, is there an earlier civilization? Well, as I say to New Age critics, show me one pot shard of that earlier civilization. Because the only way they could have existed is if they actually got out with whisk brooms, scoop shovels and little spoons and cleared out every single trace of their daily lives, their utensils, their pottery, their wood,
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their tools and so on, and that's just totally improbable. Well, it's not impossible, but it has a very, very low level of probability, that there was an older civilization there.
Definition
Swiss biologist and psychologist Jean Piaget (1896-1980) is renowned for constructing a highly influential model of child development and learning. Piaget's theory is based on the idea that the developing child builds cognitive structures--in other words, mental "maps," schemes, or networked concepts for understanding and responding to physical experiences within his or her environment.
Piaget further attested that a child's cognitive structure increases in sophistication with development, moving from a few innate reflexes such as crying and sucking to highly complex mental activities.
Discussion
Piaget's theory identifies four developmental stages and the processes by which children progress through them. The four stages are:
1.
2.
3.
4.
--The child, through physical interaction with his or her environment, builds a set of concepts about reality and how it works. This is the stage where a child does not know that physical objects remain in existence even when out of sight (object permanance).
--The child is not yet able to conceptualize abstractly and needs concrete physical situations.
--As physical experience accumulates, the child starts to conceptualize, creating logical structures that explain his or her physical experiences. Abstract problem solving is also possible at this stage. For example, arithmetic equations can be solved with numbers, not just with objects.
--By this point, the child's cognitive structures are like those of an adult and include conceptual reasoning.
Piaget outlined several principles for building cognitive structures. During all development stages, the child experiences his or her environment using whatever mental maps he or she has constructed so far.
If the experience is a repeated one, it fits easily--or is assimilated--into the child's cognitive structure so that he or she maintains mental "equilibrium." If the experience is different or new, the child loses equilibrium, and alters his or her cognitive structure to accommodate the new conditions. This way, the child erects more and more adequate cognitive structures.
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How Piaget's Theory Impacts Learning
--Educators must plan a developmentally appropriate curriculum that enhances their students' logical and conceptual growth.
--Teachers must emphasize the critical role that experiences--or interactions with the surrounding environment--play in student learning. For example, instructors have to take into account the role that fundamental concepts, such as the permanence of objects, play in establishing cognitive structures.
Pollination : The transfer of pollen from the anthers of a flower to the stigma of the same flower or of another flower. Pollination is a prerequisite for fertilization: the fusion of nuclei from the pollen grain with nuclei in the ovule. Fertilization allows the flower to develop seeds.
Some flowers will develop seeds as a result of self-pollination , when pollen and pistil are from the same plant, often (but not always) from the same flower. Other plants require cross-pollination: pollen and pistil must be from different plants.
Most plants need help moving pollen from one flower to the pistil of another. Wind moves the pollen for some plants such as grasses like corn. Animal pollinators move pollen for many other flowering plants.
Pollinator : An animal that moves pollen from the anthers to the stigmas of flowers, thus effecting pollination. Animals that are known to be good pollinators of flowers include bees, butterflies, hummingbirds, moths, some flies, some wasps, and nectar feeding bats.
What are the benefits?
Plants benefit from pollinators because the movement of pollen allows them to reproduce by setting seeds. However, pollinators don't know or care that the plant benefits. They pollinate to get nectar and/or pollen from flowers to meet their energy requirements and to produce offspring. In the economy of nature, the pollinators provide an important service to flowering plants, while the plants pay with food for the pollinators and their offspring What does the word "pollination" mean?
P ollination is very important. It leads to the creation of new seeds that grow into new plants.
But how does pollination work? Well, it all begins in the flower. Flowering plants have several different parts that are important in pollination. Flowers have male parts called stamens that produce a sticky powder called pollen. Flowers also have a female part called the pistil. The top of the pistil is called the stigma, and is often sticky. Seeds are made at the base of the pistil, in the ovule.
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To be pollinated, pollen must be moved from a stamen to the stigma. When pollen from a plant's stamen is transferred to that same plant's stigma, it is called self-pollination. When pollen from a plant's stamen is transferred to a different plant's stigma, it is called cross-pollination. Cross-pollination produces stronger plants. The plants must be of the same species. For example, only pollen from a daisy can pollinate another daisy. Pollen from a rose or an apple tree would not work. But how does pollen from one plant get moved to another?
How Do Plants Get Pollinated?
P ollination occurs in several ways. People can transfer pollen from one flower to another, but most plants are pollinated without any help from people. Usually plants rely on animals or the wind to pollinate them.
When animals such as bees, butterflies, moths, flies, and hummingbirds pollinate plants, it's accidental. They are not trying to pollinate the plant. Usually they are at the plant to get food, the sticky pollen or a sweet nectar made at the base of the petals. When feeding, the animals accidentally rub against the stamens and get pollen stuck all over themselves. When they move to another flower to feed, some of the pollen can rub off onto this new plant's stigma.
Plants that are pollinated by animals often are brightly colored and have a strong smell to attract the animal pollinators.
Another way plants are pollinated is by the wind. The wind picks up pollen from one plant and blows it onto another.
Plants that are pollinated by wind often have long stamens and pistils. Since they do not need to attract animal pollinators, they can be dully colored, unscented, and with small or no petals since no insect needs to land on them.
Parallax , or more accurately motion parallax ( Greek :
ή
= alteration) is the change of angular position of two stationary points relative to each other as seen by an observer, caused by the motion of an observer. Simply put, it is the shift of an object against a background caused by a change in observer position. If there is no parallax between two objects then they are side by side at the exact same height
Stellar parallax the difference in direction of a celestial object as seen by an observer from two widely separated points. The measurement of parallax is used directly to find the distance of the body from the
Earth (geocentric parallax) and from the Sun (heliocentric parallax). The two positions of the observer and the position of the object form a triangle; if the base line between the two observing points is
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known and the direction of the object as seen from each has been measured, the apex angle (the parallax) and the distance of the object from the observer can be found simply.
In the determination of a celestial distance by parallax measurement, the base line is taken as long as possible in order to obtain the greatest precision of measurement. For the Sun and Moon, the base line used is the distance between two widely separated points on the Earth; for all bodies outside the solar system, the base line is the axis of the Earth's orbit. The largest measured stellar parallax is 0.76", for the nearest star, Alpha Centauri; the smallest that can be directly measured is about 25 times smaller, but indirect methods permit calculation of the parallax, inversely proportional to the distance, for more and more distant objects but also with more and more uncertainty.
•The cicada is related to the harvest fly.
•Some cicada's live underground for seventeen years.
•The cicada grows up to three inches.
•Cicadas suck juice from tree roots when they are larva.
•Once the female cicada comes above ground, she mates. Then she lays her eggs and dies.
•The cicada can lay four hundred to six hundred eggs.
•The adult cicada lives in trees.
•Adult cicadas live for thirty to forty days.
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•A cicada can chirp so loud you can hear it from half a mile away.
•A male cicada abdomen has two drum like sound chambers.
More Cicada Facts
There are two main kinds of periodical cicadas in the United States. One kind spends 17 years as a nymph feeding on tree roots while living below ground, and the other lives underground for 13 years!
Then each type, as if on some signal, emerges at the same time from the ground. They change into adults, lay eggs, and after a few weeks, they die. We don't see the next generation until 13 or 17 years later!
The McCorry family wrote and asked me to add some information about cicadas that they had recently learned. Here is what they wrote:
"Lately we've noticed hundreds of little branches lying around the yard. We picked them up and put them in the fire ring to be burned later. After thinking about it, we examined the branches and noticed that they were all slitted with the tiny cuts that are cicada egg "nests". We broke a few branches and found tiny larvae inside, many times smaller than a grain of rice that we actually saw move!"
That sure explains how most of the cicada larva get from the trees to the ground! After that, it's just a short crawl into the ground for the next 13-17 years! Thanks to the hands on science by the McCorry girls, the cicada page has a great new fact!
Voted least likely to need a megaphone... The male cicada makes the loudest sound in the insect world.
By vibrating the ribbed plates in a pair of amplifying cavities at the base of the abdomen, the mating sound of the cicada can be heard as far as 440 yards! These insect noisemakers rarely ever stop calling for a mate. The noise from large groups of cicadas can often drown out even the noisiest lawnmower.
The 13-year and 17-year cicadas, known as periodical cicadas, are both large-bodied insects with orange-veined wings.The periodical varieties look, sound and behave alike. The only characteristic making them different from one another is the length of time they spend in the ground during the nymphal stages--either 13 or 17 years.
Periodical cicada adults are spectacular in appearance. The body is mostly black on top. The head is broad, and the abdomen tapers to the rear. Eyes are very red. Their legs and wing veins are reddish orange, and their wings are nearly transparent with an orange tint. Despite their fearsome appearance,
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with bulging, bright red eyes, cicadas are harmless to animal life and all trees except young saplings.
It is easy to tell the sex of cicada adults. Females have blade-like ovipositors visible on the bottom surface of the abdomen, and the males do not. Males possess a pair of sound-producing, or "singing", organs located on the sides of the first abdominal segment. Each sound organ consists of a large platelike structure, the operculum, which covers a cavity containing a white or yellowish membrane and an oval, ribbed, drum-like structure called a timbal. Timbals are vibrated by strong muscles to produce the cicada song.
After cicada eggs hatch, the tiny, antlike nymphs quickly drop from the trees and burrow five to 46 centimeters (two to 18 inches) underground in search of tree roots to feed upon. For the next 13 to 17 years they feed on the juicy roots of plants. After 13 or 17 years, a natural "clock," which remains a mystery to scientists, tells them that it is time to come out of the ground. In the weeks before the nymphs emerge, periodical cicadas dig their tunnels to the soil surface and prepare to leave the ground.
Amazingly all the cicadas seem to come out of the ground at the same time in enormous numbers. The nymphs leave the ground and begin to climb trees and poles. As they climb, they molt, or grow out of their exoskeleton. They split open the back of their brown and brittle exoskeletons, wiggle out, and abandon them, empty and still clinging to the trees. They continue to climb to the treetops to begin their constant buzzing calls, trying to attract a mate. If they are successful, mating occurs, eggs are laid and the cycle begins again.
After mating, adult female cicadas use their blade like ovipositor to make long openings in new growth sections of tree branches. A female usually lays 20 to 30 eggs in each opening, and there can be several egg "nests" per branch. During her short adult life stage, each female lays approximately 600 eggs. The eggs take six to eight weeks to mature--after which the nymphs drop to the ground and immediately begin their descent into an underground world. Their long nymphal stage is unmatched within the animal kingdom and continues to draw the interest of scientists.
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Ecological Succession is an orderly sequence of different communities over a period of time in a particular area.
Important General Principles Associated with Ecological Succession
1. The physical environment determines which communities can exist in a particular place.
2. Succession is community controlled, i.e., succession is caused by modification of the surrounding physical environment by the existing community, i.e., a successional community will alter the environment so that the environment is then more favorable for a different community than the existing one.
3. Ecological succession is directional - and therefore predictable.
4. Succession ends in a stabilized community and ecosystem called the ecological climax. It is in equilibrium with the physical environment of that particular area and perpetuates itself.*
* Usually an external disturbance to the area, e.g., fire, puts the area back into an earlier successional stage.
This tendency for the ecosystem to reach a stage where it stays in equilibrium is an example of
Homeostasis – developing and maintaining stability.
5. High diversity produces stability.
Types of Ecological Succession
1. Primary Succession begins on an area that has not been previously occupied by a community, e.g., newly exposed rock. There is no soil. Soil is a combination of broken down rock plus organic matter
(humus* and small, living organisms).
*Humus is accumulated, decomposed plant and animal material.
Primary succession takes place very slowly with a low rate of production of biological material.
2. Secondary Succession begins on an area where a community has previously existed. Secondary succession usually begins on an already established soil.
Secondary succession has a higher level of production of biological material at a faster rate than primary succession .
by: Robert Huisman
If you want to examine what conditions are necessary for a planet to support live, an important
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question will be: When do you call an object a planet? Or what is the difference between a star and a planet? In this article I will try to explain the exact difference between the two and I will look at the atmosphere, the mass and the temperature, to examine if live is possible on these objects.
A star forms when a very big cloud of gas contracts under the influence of its own gravitational force.
As this contraction takes place the object emits energy. This energy is called fall energy . As a result of this contraction the core gets denser and hotter. When the core reaches a temperature of about 3 million Kelvin, it starts to emit light, because of nuclear fusion ( Krane, K.S) reactions in the core. At this stage the gas cloud will stop its contraction because now the gravitational force is in equilibrium with the pressure build up by the hot gas. When this starts to happen you can say that a new star is born.
A planet on the other hand is build up out of the dust that surrounds a star. When a star is formed there is still a disk of gas surrounding it. As this gas cools, it condenses and forms solid grains. These grain particles accrete into large bodies called planetesimals, which then collide and accrete to make protoplanets. These protoplanets evolve into planets like the planets in our own solar system.
So the formation of a star is totally different from that of a planet. This is the main difference between a star and a planet. If an object has a mass of 0.084 times the mass of our own sun (85 times the mass of
Jupiter) the core reaches a point where it can start the process of nuclear fusion in its core (see fig.1). If the mass is smaller than this, the lowest temperature to support nuclear fusion will never be reached and the object will never shine like a star. But can we call all of these objects planets? No, objects with a mass between 85*Mj (85 times the mass of Jupiter) and 13*Mj can't sustain nuclear fusion of elements like hydrogen (H) and helium (He) but can support the fusion of two protons into deuterium (D), early in their lifetime. These objects are called brown dwarfs. They form the transition between stars and planets.
Brown dwarfs form like stars so you can't call them planets, but they have a mass that is to small to sustain the nuclear fusion process that takes place inside a star, so they aren't really stars either. As such an object contracts under the influence of it's own gravity, it doesn't reach the temperature that is needed to start the nuclear fusion from H-nuclei into He-nuclei. But it does reach a high enough temperature for the fusion of protons into deuterium. Because of this fusion it emits light during the first period of it's lifetime. It also emits light because of the fall energy that is produced as a result of the contraction of the gas, but this forms only a minor contribution to the total emission of light. Because very little or no fusion takes place, the core of the star can't build up enough pressure to prevent the star from further contraction under the influence of the gravitational forces that are working on the gas.
The gas in the center of the star gets so dense that it degenerates. Now the star won't contract any further because of the pressure that is build up by the degenerated matter. This pressure is called
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electron degeneracy pressure (EDP) (Kulkarni, S.R.). The origin of this pressure is explained by quantum mechanics as arising from oscillations of confined electrons. Because the fusion and contraction have stopped, the only light emission that is left is due to the cooling of the atoms of the star. During the rest of it's lifetime the star will get dimmer and dimmer and eventually and up as a cool object emitting light in the infrared. The chemical composition of the atmosphere of a brown dwarf strongly depends on it's temperature. But for an atmosphere similar to that of the first detected brown dwarf (gl229B), chemical equilibrium calculations indicate that the upper layers of it's atmosphere mainly exist out of methane (CH4), ammonia (NH3), water (H2O) hydrogen sulfide (H2S) and phosphine (PH3). However deep in the atmosphere methane is "replaced" by carbon monoxide (CO) and ammonia is "replaced" by nitrogen (N2) (Marley, M.S.).
Planets can be divided into two different groups. The smaller, solid terrestrial planets (like the earth) and the large, liquid Jovian planets (like Jupiter and Saturn). I will concentrate on the jovian planets because the border between brown dwarfs and planets lies in the mass range of these planets. I already explained how planets are formed, but Jupiter and Saturn may have formed in another way. They may have formed like stars. That is they may have formed out of a gas cloud that contracted under the influence of the gravitational force working on it. In this case the only difference between brown dwarfs and jovian planets is the fusion of protons into deuterium in the core of the brown dwarfs. The jovian planets are large gas bulbs with a small massive core, or in the case of bigger planets, the core may exist out of degenerated material. The very thick atmosphere is build up out of several different layers.
The principal constituents of the atmospheres of the jovian planets are molecular hydrogen (H2) and helium (He). The outer most layer of the atmosphere (the photosphere), is build up out of a mixture of these gasses. Underneath this layer is a thick layer of liquid hydrogen. Then you get a layer liquid metallic hydrogen and in the center there possibly exists a rocky core. Although most of the atmosphere consists out of hydrogen and helium there are a lot of other molecules in the atmospheres of the jovian planets. As already mentioned, which elements there are, strongly depends on the temperature of the planets. The temperatures of the extra solar planets that have been discovered until now , differ very much from each other, with values ranging from 100-1500 Kelvin. So the chemical composition of the atmospheres are also very different. Figure 3 gives a rough plot of the chemical species that are likely to condense near the photosphere for a given effective temperature. It is most likely that these kinds of planets can't support life because they aren't solid like terrestrial planets.
The border between stars and planets is not very well defined. There is a transition area with objects that show some resemblance to a star and some to a planet. These objects are called brown dwarfs. The mass of a brown dwarf lies between about 13-85 Mj. They resemble jovian planets very well. The only difference between the two lies in there formation. Planets are normally formed out of the dust clouds
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surrounding the star. Where as brown dwarfs are formed by contraction of a gas cloud. It may be the case that Jupiter and Saturn are formed in the same way that stars are formed. In this case we can't distinguish them from brown dwarfs. Another important difference between the two is the small amount of nuclear fusion that can take place in the center of a brown dwarf. So this is maybe a better way to distinguish them from jovian planets. A problem here is that only the biggest brown dwarfs can sustain this fusion. The structure of brown dwarfs and jovian planets is very much the same. The chemical composition of these objects strongly depends on the temperature of the gasses in there atmospheres.
Because jovian planets aren't solid like terrestrial planets it is most likely that they can't support life.
Because of the rapid progress there is made on this field of science, it won't be long before we can say with more certainty what the atmospheres of these objects are made of and what there temperatures are. Maybe then it is possible to give a better definition of the difference between a star and a planet.
On large scales, the solar system presents us with a sense of orderly motion. The planets move nearly in a plane, on almost concentric (and nearly circular) elliptical paths, in the same direction around the Sun, at steadily increasing orbital intervals. However, the individual properties of the planets themselves are much less regular.
It compares the major planets with one another and with the Sun. A clear distinction can be drawn between the inner and the outer members of our planetary system based on densities and other physical properties. The inner planets—Mercury, Venus, Earth, and Mars—are small, dense, and
in composition. The outer worlds—Jupiter, Saturn, Uranus, and Neptune (but not Pluto)—are large, of low density, and
.
Because the physical and chemical properties of Mercury, Venus, and Mars are somewhat similar to
Earth's, the four innermost planets are called the terrestrial planets.
(The word
derives from the Latin word
, meaning "land" or "earth.") The larger outer planets—Jupiter, Saturn, Uranus, and
Neptune—are all similar to one another chemically and physically (and very different from the
worlds). They are labeled the jovian planets, after Jupiter, the largest member of the group. (The word
comes from
another name for the Roman god Jupiter.) The jovian worlds are all much larger than the terrestrial planets, and quite different from them in both composition and structure.
The four terrestrial planets all lie within about 1.5 A.U. of the Sun. All are small and of relatively low mass, and all have generally rocky composition and solid surfaces. Beyond that, however, the similarities end. When we take into account how the weight of overlying layers compresses the interiors of the
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planets to different extents (greatest for Earth, least for Mercury), we find that the average
of the terrestrial worlds—that is, the densities they would have in the absence of any compression—decrease steadily as we move farther from the Sun. This decrease in density indicates that the overall compositions of these planets differ significantly one from the other.
There are many more differences among the terrestrial worlds. All have atmospheres, but the atmospheres are about as dissimilar as we could imagine, ranging from a near-vacuum on Mercury to a hot, dense inferno on Venus. Earth alone has oxygen in its atmosphere (as well as liquid water on its surface). The present-day conditions on the surfaces of the four planets are also quite distinct from one another. Earth and Mars spin at roughly the same rate—one rotation every 24 (Earth) hours—but
Mercury and Venus both take months to rotate just once, and Venus rotates in the opposite sense from the others. Earth and Mars have moons, but Mercury and Venus do not. Earth and Mercury have measurable magnetic fields, of very different strengths, whereas Venus and Mars have none. Finding the common threads in the evolution of four such diverse worlds is no simple task! Comparative planetology will be our indispensable guide as we proceed through the coming chapters.
Yet for all their differences, the terrestrial worlds still seem very similar when compared with the jovian planets. Perhaps the simplest way to express the major differences between the terrestrial and jovian worlds is to say that the jovian planets are everything the terrestrial planets are not. Table 6.2 compares and contrasts some key properties of these two planetary classes.
The terrestrial worlds lie close together, near the Sun; the jovian worlds are widely spaced through the outer solar system. The terrestrial worlds are small, dense, and rocky; the jovian worlds are large and gaseous, being made up predominantly of hydrogen and helium (the lightest elements), which are rare on the inner planets. The terrestrial worlds have solid surfaces; the jovian worlds have none (their dense atmospheres thicken with depth, eventually merging with their liquid interiors). The terrestrial worlds have weak magnetic fields, if any; the jovian worlds all have strong magnetic fields. The terrestrial worlds have only three moons among them; the jovian worlds have many moons each, no two of them alike and none of them like our own. Furthermore, all the jovian planets have
a feature unknown on the terrestrial planets. Despite their greater size, the jovian worlds all rotate much faster than any terrestrial planet.
Finally, beyond the outermost jovian planet, Neptune, lies one more small world, frozen and mysterious.
Pluto doesn't fit well into either planetary category. Indeed, there is debate among planetary scientists as to whether it should be classified as a planet at all. In both mass and composition, it has much more in common with the icy jovian moons than with any terrestrial or jovian planet. Astronomers speculate
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that it may in fact be the largest member of a newly recognized class of solar system objects that reside beyond the jovian worlds.
Oil painting is done on surfaces with pigments that are ground and mixed into a medium of oil — especially in early modern Europe, linseed oil . Other oils occasionally used include poppyseed oil , walnut oil , and safflower oil. These oils give various properties to the oil paint, such as less yellowing or different drying times. Certain differences are also visible in the sheen of the paints depending on the oil. Painters often use different oils in the same painting depending on specific pigments and effects desired. The paints themselves also develop a particular feel depending on the mediums. A basic rule of oil paint application is ' fat over lean .' This means that each additional layer of paint should be a bit oilier than the layer below, to allow proper drying. Traditional oil painting techniques often begin with paint mixed with turpentine . As a painting gets additional layers, the paint must get oilier (leaner to fatter) or the final painting will crack and peel.
Oil paint was probably developed for decorative or functional purposes in the High Middle Ages.
Surfaces like shields — both those used in tournaments and those hung as decorations — were more durable when painted in oil-based media than when painted in the traditional tempera paints.
Many Renaissance sources credit northern European painters of the 15th century with the
"invention" of painting with oil media on wood panel — Jan van Eyck is often mentioned as the
"inventor". The popularity of oil grew in 16th century Venice, where a water-durable medium was essential. Oil painting was ideal for the northern European painters, because the preferred fresco painting media did not work as well in their cooler climate. The linseed oil itself comes from the flax seeds, and this flax was a common fiber crop. Recent advances in chemistry have produced modern water miscible oil paints that can be used with and cleaned up with water. Small alterations in the molecular structure of the oil creates this water miscible property..
Most artists paint in layers, a method first perfected in the Egg tempera painting technique and adapted in Northern Europe for use with linseed oil paints. The first coat or "underpainting" is laid down first, painted normally with turpentine thinned paint. This layer helps to "tone" the canvas, and cover the white of the gesso. Many artists use this layer to sketch out the composition. This layer can be adjusted before moving forward, which is an advantage over the 'cartooning' method used in Fresco technique.
After this layer dries, one way the artist might then proceed is by painting a "mosaic" of color swatches, working from darkest to lightest. The borders of the colors are blended together when the "mosaic" is completed. This layer is then left to dry before applying details. After it is dry, the artist will apply
"glazes" to the painting, using a process of "Fat over Lean" which means more oil/paint ratio than the previous layer. A classical work might take weeks or even months to layer the paint. Artists in later
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periods such as the impressionist era often blended the wet paint on the canvas without following the
Renaissance layering and glazing method.
Tropism is defined by biologists as the growth or turning of an organism in response to a specific stimulus in its environment. Varieties of tropism are usually named for the motivating stimulus; for example, geotropism is the turning or movement of a plant in response to gravity, and heliotropism is the turning of a plant towards a light source.
Geotropism can be either positive or negative. Roots are positively geotropic in that they grow in the same direction as the gravitational pull, while stems which grow in the opposite direction have negative geotropism. This type of tropism can easily be seen in a potted plant. If the pot is put on its side, the growing stems soon turn to grow upwards, displaying negative geotropism. It was Charles
Darwin, who also put forward the theory of evolution, who first documented geotropism.
Heliotropism refers to the turning of plants to track the movement of the sun. This occurs mainly with flowering plants like the sunflower. The term used to include the growth of plant stems towards a light source, but that is now referred to as phototropism. The reason for the differentiation is that heliotropism, as it is now defined, is temporary, only occurring during daylight hours; at night, the flowers face various directions. At dawn, the flowers turn towards the East again to catch the sunrise.
Heliotropism is actually a response to blue light, hemitropic plants no longer turn to face the sun, but when under a transparent blue covering, they turn to face the sun as usual.
Between them, these two tropisms account for the basic directional growth stimuli in all plants.
There are other stimuli which cause directional growth in specific plants but are none as all encompassing as these.
The first Europeans to reach North America were Icelandic Vikings, led by Leif Ericson, about the year
1000. Traces of their visit have been found in the Canadian province of Newfoundland, but the Vikings failed to establish a permanent settlement and soon lost contact with the new continent.
Five centuries later, the demand for Asian spices, textiles, and dyes spurred European navigators to dream of shorter routes between East and West. Acting on behalf of the Spanish crown, in 1492 the
Italian navigator Christopher Columbus sailed west from Europe and landed on one of the Bahama
Islands in the Caribbean Sea. Within 40 years, Spanish adventurers had carved out a huge empire in
Central and South America.
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THE COLONIAL ERA
The first successful English colony was founded at Jamestown, Virginia, in 1607. A few years later,
English Puritans came to America to escape religious persecution for their opposition to the Church of
England. In 1620, the Puritans founded Plymouth Colony in what later became Massachusetts. Plymouth was the second permanent British settlement in North America and the first in New England.
In New England the Puritans hoped to build a "city upon a hill" -- an ideal community. Ever since,
Americans have viewed their country as a great experiment, a worthy model for other nations to follow.
The Puritans believed that government should enforce God's morality, and they strictly punished heretics, adulterers, drunks, and violators of the Sabbath. In spite of their own quest for religious freedom, the
Puritans practiced a form of intolerant moralism. In 1636 an English clergyman named Roger Williams left Massachusetts and founded the colony of Rhode Island, based on the principles of religious freedom and separation of church and state, two ideals that were later adopted by framers of the U.S.
Constitution.
Colonists arrived from other European countries, but the English were far better established in America.
By 1733 English settlers had founded 13 colonies along the Atlantic Coast, from New Hampshire in the
North to Georgia in the South. Elsewhere in North America, the French controlled Canada and Louisiana, which included the vast Mississippi River watershed. France and England fought several wars during the
18th century, with North America being drawn into every one. The end of the Seven Years' War in 1763 left England in control of Canada and all of North America east of the Mississippi.
Soon afterwards England and its colonies were in conflict. The mother country imposed new taxes, in part to defray the cost of fighting the Seven Years' War, and expected Americans to lodge British soldiers in their homes. The colonists resented the taxes and resisted the quartering of soldiers. Insisting that they could be taxed only by their own colonial assemblies, the colonists rallied behind the slogan
"no taxation without representation."
All the taxes, except one on tea, were removed, but in 1773 a group of patriots responded by staging the Boston Tea Party. Disguised as Indians, they boarded British merchant ships and dumped 342 crates of tea into Boston harbor. This provoked a crackdown by the British Parliament, including the closing of
Boston harbor to shipping. Colonial leaders convened the First Continental Congress in 1774 to discuss the colonies' opposition to British rule. War broke out on April 19, 1775, when British soldiers confronted colonial rebels in Lexington, Massachusetts. On July 4, 1776, the Continental Congress adopted a Declaration of Independence.
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At first the Revolutionary War went badly for the Americans. With few provisions and little training,
American troops generally fought well, but were outnumbered and overpowered by the British. The turning point in the war came in 1777 when American soldiers defeated the British Army at Saratoga,
New York. France had secretly been aiding the Americans, but was reluctant to ally itself openly until they had proved themselves in battle. Following the Americans' victory at Saratoga, France and America signed treaties of alliance, and France provided the Americans with troops and warships.
The last major battle of the American Revolution took place at Yorktown, Virginia, in 1781. A combined force of American and French troops surrounded the British and forced their surrender. Fighting continued in some areas for two more years, and the war officially ended with the Treaty of Paris in
1783, by which England recognized American independence.
A NEW NATION
The framing of the U.S. Constitution and the creation of the United States are covered in more detail in chapter 4. In essence, the Constitution alleviated Americans' fear of excessive central power by dividing government into three branches -- legislative (Congress), executive (the president and the federal agencies), and judicial (the federal courts) -- and by including 10 amendments known as the Bill of
Rights to safeguard individual liberties. Continued uneasiness about the accumulation of power manifested itself in the differing political philosophies of two towering figures from the Revolutionary period. George Washington, the war's military hero and the first U.S. president, headed a party favoring a strong president and central government; Thomas Jefferson, the principal author of the Declaration of
Independence, headed a party preferring to allot more power to the states, on the theory that they would be more accountable to the people.
Jefferson became the third president in 1801. Although he had intended to limit the president's power, political realities dictated otherwise. Among other forceful actions, in 1803 he purchased the vast
Louisiana Territory from France, almost doubling the size of the United States. The Louisiana Purchase added more than 2 million square kilometers of territory and extended the country's borders as far west as the Rocky Mountains in Colorado.
SLAVERY AND THE CIVIL WAR
In the first quarter of the 19th century, the frontier of settlement moved west to the Mississippi River and beyond. In 1828 Andrew Jackson became the first "outsider" elected president: a man from the
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frontier state of Tennessee, born into a poor family and outside the cultural traditions of the Atlantic seaboard.
Although on the surface the Jacksonian Era was one of optimism and energy, the young nation was entangled in a contradiction. The ringing words of the Declaration of Independence, "all men are created equal," were meaningless for 1.5 million slaves. (For more on slavery and its aftermath, see chapters 1 and 4.)
In 1820 southern and northern politicians debated the question of whether slavery would be legal in the western territories. Congress reached a compromise: Slavery was permitted in the new state of Missouri and the Arkansas Territory but barred everywhere west and north of Missouri. The outcome of the
Mexican War of 1846-48 brought more territory into American hands -- and with it the issue of whether to extend slavery. Another compromise, in 1850, admitted California as a free state, with the citizens of
Utah and New Mexico being allowed to decide whether they wanted slavery within their borders or not
(they did not).
But the issue continued to rankle. After Abraham Lincoln, a foe of slavery, was elected president in 1860,
11 states left the Union and proclaimed themselves an independent nation, the Confederate States of
America: South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, Texas, Virginia, Arkansas,
Tennessee, and North Carolina. The American Civil War had begun.
The Confederate Army did well in the early part of the war, and some of its commanders, especially
General Robert E. Lee, were brilliant tacticians. But the Union had superior manpower and resources to draw upon. In the summer of 1863 Lee took a gamble by marching his troops north into Pennsylvania.
He met a Union army at Gettysburg, and the largest battle ever fought on American soil ensued. After three days of desperate fighting, the Confederates were defeated. At the same time, on the Mississippi
River, Union General Ulysses S. Grant captured the city of Vicksburg, giving the North control of the entire Mississippi Valley and splitting the Confederacy in two.
Two years later, after a long campaign involving forces commanded by Lee and Grant, the Confederates surrendered. The Civil War was the most traumatic episode in American history. But it resolved two matters that had vexed Americans since 1776. It put an end to slavery, and it decided that the country was not a collection of semi-independent states but an indivisible whole.
THE LATE 19TH CENTURY
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Abraham Lincoln was assassinated in 1865, depriving America of a leader uniquely qualified by background and temperament to heal the wounds left by the Civil War. His successor, Andrew Johnson, was a southerner who had remained loyal to the Union during the war. Northern members of Johnson's own party (Republican) set in motion a process to remove him from office for allegedly acting too leniently toward former Confederates. Johnson's acquittal was an important victory for the principle of separation of powers: A president should not be removed from office because Congress disagrees with his policies, but only if he has committed, in the words of the Constitution, "treason, bribery, or other high crimes and misdemeanors."
Within a few years after the end of the Civil War, the United States became a leading industrial power, and shrewd businessmen made great fortunes. The first transcontinental railroad was completed in 1869; by 1900 the United States had more rail mileage than all of Europe. The petroleum industry prospered, and John D. Rockefeller of the Standard Oil Company became one of the richest men in America.
Andrew Carnegie, who started out as a poor Scottish immigrant, built a vast empire of steel mills. Textile mills multiplied in the South, and meat-packing plants sprang up in Chicago, Illinois. An electrical industry flourished as Americans made use of a series of inventions: the telephone, the light bulb, the phonograph, the alternating-current motor and transformer, motion pictures. In Chicago, architect Louis
Sullivan used steel-frame construction to fashion America's distinctive contribution to the modern city: the skyscraper.
But unrestrained economic growth brought dangers. To limit competition, railroads merged and set standardized shipping rates. Trusts -- huge combinations of corporations -- tried to establish monopoly control over some industries, notably oil. These giant enterprises could produce goods efficiently and sell them cheaply, but they could also fix prices and destroy competitors. To counteract them, the federal government took action. The Interstate Commerce Commission was created in 1887 to control railroad rates. The Sherman Antitrust Act of 1890 banned trusts, mergers, and business agreements "in restraint of trade."
Industrialization brought with it the rise of organized labor. The American Federation of Labor, founded in 1886, was a coalition of trade unions for skilled laborers. The late 19th century was a period of heavy immigration, and many of the workers in the new industries were foreign-born. For American farmers, however, times were hard. Food prices were falling, and farmers had to bear the costs of high shipping rates, expensive mortgages, high taxes, and tariffs on consumer goods.
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With the exception of the purchase of Alaska from Russia in 1867, American territory had remained fixed since 1848. In the 1890s a new spirit of expansion took hold. The United States followed the lead of northern European nations in asserting a duty to "civilize" the peoples of Asia, Africa, and Latin America.
After American newspapers published lurid accounts of atrocities in the Spanish colony of Cuba, the
United States and Spain went to war in 1898. When the war was over, the United States had gained a number of possessions from Spain: Cuba, the Philippines, Puerto Rico, and Guam. In an unrelated action, the United States also acquired the Hawaiian Islands.
Yet Americans, who had themselves thrown off the shackles of empire, were not comfortable with administering one. In 1902 American troops left Cuba, although the new republic was required to grant naval bases to the United States. The Philippines obtained limited self-government in 1907 and complete independence in 1946. Puerto Rico became a self-governing commonwealth within the United
States, and Hawaii became a state in 1959 (as did Alaska).
THE PROGRESSIVE MOVEMENT
While Americans were venturing abroad, they were also taking a fresh look at social problems at home.
Despite the signs of prosperity, up to half of all industrial workers still lived in poverty. New York, Boston,
Chicago, and San Francisco could be proud of their museums, universities, and public libraries -- and ashamed of their slums. The prevailing economic dogma had been laissez faire: let the government interfere with commerce as little as possible. About 1900 the Progressive Movement arose to reform society and individuals through government action. The movement's supporters were primarily economists, sociologists, technicians, and civil servants who sought scientific, cost-effective solutions to political problems.
Social workers went into the slums to establish settlement houses, which provided the poor with health services and recreation. Prohibitionists demanded an end to the sale of liquor, partly to prevent the suffering that alcoholic husbands inflicted on their wives and children. In the cities, reform politicians fought corruption, regulated public transportation, and built municipally owned utilities. States passed laws restricting child labor, limiting workdays, and providing compensation for injured workers.
Some Americans favored more radical ideologies. The Socialist Party, led by Eugene V. Debs, advocated a peaceful, democratic transition to a state-run economy. But socialism never found a solid footing in the United States -- the party's best showing in a presidential race was 6 percent of the vote in 1912.
WAR AND PEACE
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When World War I erupted in Europe in 1914, President Woodrow Wilson urged a policy of strict
American neutrality. Germany's declaration of unrestricted submarine warfare against all ships bound for
Allied ports undermined that position. When Congress declared war on Germany in 1917, the American army was a force of only 200,000 soldiers. Millions of men had to be drafted, trained, and shipped across the submarine-infested Atlantic. A full year passed before the U.S. Army was ready to make a significant contribution to the war effort.
By the fall of 1918, Germany's position had become hopeless. Its armies were retreating in the face of a relentless American buildup. In October Germany asked for peace, and an armistice was declared on
November 11. In 1919 Wilson himself went to Versailles to help draft the peace treaty. Although he was cheered by crowds in the Allied capitals, at home his international outlook was less popular. His idea of a League of Nations was included in the Treaty of Versailles, but the U.S. Senate did not ratify the treaty, and the United States did not participate in the league.
The majority of Americans did not mourn the defeated treaty. They turned inward, and the United States withdrew from European affairs. At the same time, Americans were becoming hostile to foreigners in their midst. In 1919 a series of terrorist bombings produced the "Red Scare." Under the authority of
Attorney General A. Mitchell Palmer, political meetings were raided and several hundred foreign-born political radicals were deported, even though most of them were innocent of any crime. In 1921 two
Italian-born anarchists, Nicola Sacco and Bartolomeo Vanzetti, were convicted of murder on the basis of shaky evidence. Intellectuals protested, but in 1927 the two men were electrocuted. Congress enacted immigration limits in 1921 and tightened them further in 1924 and 1929. These restrictions favored immigrants from Anglo-Saxon and Nordic countries.
The 1920s were an extraordinary and confusing time, when hedonism coexisted with puritanical conservatism. It was the age of Prohibition: In 1920 a constitutional amendment outlawed the sale of alcoholic beverages. Yet drinkers cheerfully evaded the law in thousands of "speakeasies" (illegal bars), and gangsters made illicit fortunes in liquor. It was also the Roaring Twenties, the age of jazz and spectacular silent movies and such fads as flagpole-sitting and goldfish-swallowing. The Ku Klux Klan, a racist organization born in the South after the Civil War, attracted new followers and terrorized blacks,
Catholics, Jews, and immigrants. At the same time, a Catholic, New York Governor Alfred E. Smith, was a
Democratic candidate for president.
For big business, the 1920s were golden years. The United States was now a consumer society, with booming markets for radios, home appliances, synthetic textiles, and plastics. One of the most admired
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men of the decade was Henry Ford, who had introduced the assembly line into automobile factories.
Ford could pay high wages and still earn enormous profits by mass-producing the Model T, a car that millions of buyers could afford. For a moment, it seemed that Americans had the Midas touch.
But the superficial prosperity masked deep problems. With profits soaring and interest rates low, plenty of money was available for investment. Much of it, however, went into reckless speculation in the stock market. Frantic bidding pushed prices far above stock shares' real value. Investors bought stocks "on margin," borrowing up to 90 percent of the purchase price. The bubble burst in 1929. The stock market crashed, triggering a worldwide depression.
THE GREAT DEPRESSION
By 1932 thousands of American banks and over 100,000 businesses had failed. Industrial production was cut in half, wages had decreased 60 percent, and one out of every four workers was unemployed. That year Franklin D. Roosevelt was elected president on the platform of "a New Deal for the American people."
Roosevelt's jaunty self-confidence galvanized the nation. "The only thing we have to fear is fear itself," he said at his inauguration. He followed up these words with decisive action. Within three months -- the historic "Hundred Days" -- Roosevelt had rushed through Congress a great number of laws to help the economy recover. Such new agencies as the Civilian Conservation Corps and the Works Progress
Administration created millions of jobs by undertaking the construction of roads, bridges, airports, parks, and public buildings. Later the Social Security Act set up contributory old-age and survivors' pensions.
Roosevelt's New Deal programs did not end the Depression. Although the economy improved, full recovery had to await the defense buildup preceding America's entry into World War II.
WORLD WAR II
Again neutrality was the initial American response to the outbreak of war in Europe in 1939. But the bombing of Pearl Harbor naval base in Hawaii by the Japanese in December 1941 brought the United
States into the war, first against Japan and then against its allies, Germany and Italy.
American, British, and Soviet war planners agreed to concentrate on defeating Germany first. British and
American forces landed in North Africa in November 1942, proceeded to Sicily and the Italian mainland in 1943, and liberated Rome on June 4, 1944. Two days later -- D-Day -- Allied forces landed in
Normandy. Paris was liberated on August 24, and by September American units had crossed the German border. The Germans finally surrendered on May 5, 1945.
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The war against Japan came to a swift end in August of 1945, when President Harry Truman ordered the use of atomic bombs against the cities of Hiroshima and Nagasaki. Nearly 200,000 civilians were killed.
Although the matter can still provoke heated discussion, the argument in favor of dropping the bombs was that casualties on both sides would have been greater if the Allies had been forced to invade Japan.
THE COLD WAR
A new international congress, the United Nations, came into being after the war, and this time the
United States joined. Soon tensions developed between the United States and its wartime ally the Soviet
Union. Although Soviet leader Joseph Stalin had promised to support free elections in all the liberated nations of Europe, Soviet forces imposed Communist dictatorships in eastern Europe. Germany became a divided country, with a western zone under joint British, French, and American occupation and an eastern zone under Soviet occupation. In the spring of 1948 the Soviets sealed off West Berlin in an attempt to starve the isolated city into submission. The western powers responded with a massive airlift of food and fuel until the Soviets lifted the blockade in May 1949. A month earlier the United States had allied with Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway,
Portugal, and the United Kingdom to form the North Atlantic Treaty Organization (NATO).
On June 25, 1950, armed with Soviet weapons and acting with Stalin's approval, North Korea's army invaded South Korea. Truman immediately secured a commitment from the United Nations to defend
South Korea. The war lasted three years, and the final settlement left Korea divided.
Soviet control of eastern Europe, the Korean War, and the Soviet development of atomic and hydrogen bombs instilled fear in Americans. Some believed that the nation's new vulnerability was the work of traitors from within. Republican Senator Joseph McCarthy asserted in the early 1950s that the State
Department and the U.S. Army were riddled with Communists. McCarthy was eventually discredited. In the meantime, however, careers had been destroyed, and the American people had all but lost sight of a cardinal American virtue: toleration of political dissent.
From 1945 until 1970 the United States enjoyed a long period of economic growth, interrupted only by mild and brief recessions. For the first time a majority of Americans enjoyed a comfortable standard of living. In 1960, 55 percent of all households owned washing machines, 77 percent owned cars, 90 percent had television sets, and nearly all had refrigerators. At the same time, the nation was moving slowly to establish racial justice.
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In 1960 John F. Kennedy was elected president. Young, energetic, and handsome, he promised to "get the country moving again" after the eight-year presidency of Dwight D. Eisenhower, the aging World
War II general. In October 1962 Kennedy was faced with what turned out to be the most drastic crisis of the Cold War. The Soviet Union had been caught installing nuclear missiles in Cuba, close enough to reach American cities in a matter of minutes. Kennedy imposed a naval blockade on the island. Soviet
Premier Nikita Khrushschev ultimately agreed to remove the missiles, in return for an American promise not to invade Cuba.
In April 1961 the Soviets capped a series of triumphs in space by sending the first man into orbit around the Earth. President Kennedy responded with a promise that Americans would walk on the moon before the decade was over. This promise was fulfilled in July of 1969, when astronaut Neil Armstrong stepped out of the Apollo 11 spacecraft and onto the moon's surface.
Kennedy did not live to see this culmination. He had been assassinated in 1963. He was not a universally popular president, but his death was a terrible shock to the American people. His successor, Lyndon B.
Johnson, managed to push through Congress a number of new laws establishing social programs.
Johnson's "War on Poverty" included preschool education for poor children, vocational training for dropouts from school, and community service for slum youths.
During his six years in office, Johnson became preoccupied with the Vietnam War. By 1968, 500,000
American troops were fighting in that small country, previously little known to most of them. Although politicians tended to view the war as part of a necessary effort to check communism on all fronts, a growing number of Americans saw no vital American interest in what happened to Vietnam.
Demonstrations protesting American involvement broke out on college campuses, and there were violent clashes between students and police. Antiwar sentiment spilled over into a wide range of protests against injustice and discrimination.
Stung by his increasing unpopularity, Johnson decided not to run for a second full term. Richard Nixon was elected president in 1968. He pursued a policy of Vietnamization, gradually replacing American soldiers with Vietnamese. In 1973 he signed a peace treaty with North Vietnam and brought American soldiers home. Nixon achieved two other diplomatic breakthroughs: re-establishing U.S. relations with the People's Republic of China and negotiating the first Strategic Arms Limitation Treaty with the Soviet
Union. In 1972 he easily won re-election.
During that presidential campaign, however, five men had been arrested for breaking into Democratic
Party headquarters at the Watergate office building in Washington, D.C. Journalists investigating the
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incident discovered that the burglars had been employed by Nixon's re-election committee. The White
House made matters worse by trying to conceal its connection with the break-in. Eventually, tape recordings made by the president himself revealed that he had been involved in the cover-up. By the summer of 1974, it was clear that Congress was about to impeach and convict him. On August 9,
Richard Nixon became the only U.S. president to resign from office.
DECADES OF CHANGE
After World War II the presidency had alternated between Democrats and Republicans, but, for the most part, Democrats had held majorities in the Congress -- in both the House of Representatives and the
Senate. A string of 26 consecutive years of Democratic control was broken in 1980, when the
Republicans gained a majority in the Senate; at the same time, Republican Ronald Reagan was elected president. This change marked the onset of a volatility that has characterized American voting patterns ever since.
Whatever their attitudes toward Reagan's policies, most Americans credited him with a capacity for instilling pride in their country and a sense of optimism about the future. If there was a central theme to his domestic policies, it was that the federal government had become too big and federal taxes too high.
Despite a growing federal budget deficit, in 1983 the U.S. economy entered into one of the longest periods of sustained growth since World War II. The Reagan administration suffered a defeat in the 1986 elections, however, when Democrats regained control of the Senate. The most serious issue of the day was the revelation that the United States had secretly sold arms to Iran in an attempt to win freedom for American hostages held in Lebanon and to finance antigovernment forces in Nicaragua at a time when Congress had prohibited such aid. Despite these revelations, Reagan continued to enjoy strong popularity throughout his second term in office.
His successor in 1988, Republican George Bush, benefited from Reagan's popularity and continued many of his policies. When Iraq invaded oil-rich Kuwait in 1990, Bush put together a multinational coalition that liberated Kuwait early in 1991.
By 1992, however, the American electorate had become restless again. Voters elected Bill Clinton, a
Democrat, president, only to turn around two years later and give Republicans their first majority in both the House and Senate in 40 years. Meanwhile, several perennial debates had broken out anew -- between advocates of a strong federal government and believers in decentralization of power, between advocates of prayer in public schools and defenders of separation of church and state, between those
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who emphasize swift and sure punishment of criminals and those who seek to address the underlying causes of crime. Complaints about the influence of money on political campaigns inspired a movement to limit the number of terms elected officials could serve. This and other discontents with the system led to the formation of the strongest Third-Party movement in generations, led by Texas businessman H.
Ross Perot.
Although the economy was strong in the mid-1990s, two phenomena were troubling many Americans.
Corporations were resorting more and more to a process known as downsizing: trimming the work force to cut costs despite the hardships this inflicted on workers. And in many industries the gap between the annual compensations of corporate executives and common laborers had become enormous. Even the majority of Americans who enjoy material comfort worry about a perceived decline in the quality of life, in the strength of the family, in neighborliness and civility. Americans probably remain the most optimistic people in the world, but with the century drawing to a close, opinion polls showed that trait in shorter supply than usual.
The environment around an animal or a plant is constantly changing. The temperature of the air or water that a living organism lives in is especially important. During the day it may be warm but at night the temperature falls. The temperature of the environment also changes with the seasons; winter is colder than summer.
The temperature also depends upon the altitude and the latitude. As you climb up a mountain the air becomes colder. The temperature falls by about 6°C for every 1000 metres that you climb. Also, at the
North and South Poles it is so cold that there is snow and ice all year round.
Even though the air temperature can be as low as -70°C in the Antarctic or as high as +50°C in desert regions, we can find living organisms all over the Earth and all through the year. How can living organisms survive in these conditions?
*How animals control their body temperature
Animals can be divided into two types: "warm-blooded" animals and "cold-blooded" animals.
"Cold-blooded" animals include all the invertebrates, such as insects, worms and molluscs. Amongst the vertebrates fish, amphibians and reptiles are also "cold-blooded". The "warm-blooded" animals include all the birds and mammals.
You probably already know that the temperature of your body is nearly always 37°C. Like all warmblooded animals we can keep our body temperature constant .
This does not mean that all warmblooded animals have a body temperature of 37°C.
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*How "warm-blooded" animals stay cool
When a mammal or a bird is too hot it can do several things to cool down:
This covers the skin in a layer of water. As the water evaporates it takes away some heat.
You may have noticed that when someone is hot he becomes very red in the face. This is because the body is sending blood to the skin to carry away heat. Elephants make this method of cooling even more efficient by sending more blood into their large ears. The elephant's ears radiate the heat away from the body.
Not all warm-blooded animals sweat. Some cool themselves by breathing in and out very quickly. Dogs and seagulls pant. The tongue of a dog has a good supply of blood. The panting moves air over the tongue and carries heat away from the blood by conduction.
An alternative to sweating is used by cats and rabbits. They lick their front legs and chest. The saliva evaporates from their fur and acts like sweat does on our body. The large herbivores of Africa try to keep their bodies cool by bathing in mud or water.
Mammals are covered with hair and birds are covered with feathers. As we shall see these cover the body to keep it warm. Fur and feathers insulate the body. This is useful when the air is cold but it is not useful when the air is hot. In summer time mammals and birds lose fur or feathers so that their coat is thinner and they can stay cooler. We do not have much fur on our bodies but we do wear lighter clothes when the weather is hot.
Movement produces a lot of heat; if a bird or a mammal is too hot it rests, usually in the shade.
*How "warm-blooded" animals stay warm
As soon as the air temperature falls below 27°C a naked human begins to feel cold. In order to keep their bodies warm, mammals and birds do the opposite of what they do when they want to cool down:
They stop sweating, panting or licking themselves.
The blood is kept in the centre of the body, to stop heat from being lost. This is why people often look pale or white when they are feeling cold.
Birds and mammals grow a thicker layer of feathers or fur to prepare for winter. We wear thicker layers of clothes. Some animals will grow a layer of fat under the skin. The fat is not only an energy reserve but it is also a good insulator against the cold. Fat is very useful to animals which live in water.
The muscles of the body produce a lot of heat as they contract and relax. This can be used to keep an
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animal warm.
Some organs in our body, especially the liver and the kidneys, can respire more when we are cold.
Respiration makes heat energy which is passed to the blood as it circulates through these organs. The warm blood carries heat to all the vital organs. The pie chart opposite shows where we produce the most heat in our bodies.
As you can see, when the weather is cold "warm-blooded" animals are indeed warmer than their environment. In warm weather, however, "warm-blooded" animals are colder than their environment, so the term "warm-blooded" is not very precise. It is best to remember that "warm-blooded" animals keep their body temperature constant when the weather is cold. They can do this because their bodies make heat energy from their food.
*
"Cold-blooded" Animals
If a reptile such as a lizard is kept in a laboratory, we can change the temperature of the air surrounding the lizard. When we do this we observe that the body temperature of the lizard changes with the temperature of the laboratory. When the air is hot the lizard's body becomes hot and when the air is cooled down the lizard's body becomes cool. This made scientists think that reptiles and other "coldblooded" animals always have the same body temperature as their environment.
When the scientists started to observe these animals where they live in the wild they observed something different. They saw that animals like the lizard change their behaviour when the temperature of the air changes.
Insects are considered to be "cold-blooded" animals. When insects are resting their bodies do have the same temperature as the air that surrounds them. Some insects, such as the bumble bee, are well protected from cold weather.
Bumble bees are covered in a thick layer of furry scales. This insulates their bodies against the cold air.
Bumble bees like most insects can only fly if their flight muscles are above 27°C. When they are flying the body temperature of a bumble bee is between 30°C and 40°C. When the air is cold, such as early in the morning, the bumble bee will hang from a leaf or a flower to warm up in the sunshine. To raise its body temperature even higher the bumble bee can shiver its flight muscles like we shiver when we are cold. This means that the bumble bees will be amongst the first insects to start flying each day.
Dragonflies are large insects that may be found in many different climates. Dragonflies, like bumble bees can warm up their muscles by shivering. If the air temperature is 12°C a dragonfly can warm its flight muscles up to 30°C in about 4 minutes by shivering.
Dragonflies also bask in the sunshine to warm up. Some species have dark patches on their wings to help them warm up quickly in the sun because dark bodies warm up more quickly than pale bodies.
If the sun is too hot the dragonfly tries to avoid exposing its body to the sun by raising its abdomen into the air or it will retreat to the shade of a tree.
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Moths which fly at night are probably the insects which are most resistant to cold temperatures. Some species of moths can fly in the winter when the air temperature is 0°C. However, their flight muscles can only work at 30°C and it takes the moth 22 minutes to warm up by shivering. Once they are flying their body is maintained at 30°C by their active flight muscles and their body is insulated by a thick layer of furry scales.
We have experiences, and as a result, our autonomic nervous system creates physiological events such as muscular tension, heart rate increases, perspiration, dryness of the mouth, etc. This theory proposes that emotions happen
of these, rather than being the cause of them.
The bodily sensation prepares us for action, as in the Fight-or-Flight reaction . Emotions grab our attention and at least attenuate slower cognitive processing.
This is not a new theory and was proposed in 1884 and combined the ideas of William James and
Danish physiologist Carl Lange, who largely independently arrived at the same conclusion. William James described it thus:
"My theory ... is that the bodily changes follow directly the perception of the exciting fact, and that our feeling of the same changes as they occur is the emotion. Common sense says, we lose our fortune, are sorry and weep; we meet a bear, are frightened and run; we are insulted by a rival, and angry and strike. The hypothesis here to be defended says that this order of sequence is incorrect ... and that the more rational statement is that we feel sorry because we cry, angry because we strike, afraid because we tremble ... Without the bodily states following on the perception, the latter would be purely cognitive in form, pale, colorless, destitute of emotional warmth. We might then see the bear, and judge it best to run, receive the insult and deem it right to strike, but we should not actually feel afraid or angry"
Lange particularly added that vasomotor changes
the emotions.
It was largely supplanted by the Cannon-Bard theory, but of late, it has made something of a comeback, although the notion of causality is not as strong and there is ongoing uncertainty as to the chicken-and-egg question of which comes first, physiological and emotional feelings.
Example
I see a bear. My muscles tense, my heart races. I feel afraid.
So What?
Using it
Watch people's physiological signals (facial color, etc.) and deduce what emotions will result.
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Defending
Notice your own physical feelings and muse about how these lead to emotion. If you could relax deliberately, would you feel better?
When we perceive a significant threat to us, then our bodies get ready either for a fight to the death or a desperate flight from certain defeat by a clearly superior adversary.
Physical changes
Fight or flight effects include:
 Our senses sharpening. Pupils dilate (open out) so we can see more clearly, even in darkness.
Our hairs stand on end, making us more sensitive to our environment (and also making us appear larger, hopefully intimidating our opponent).
 The cardio-vascular system leaping into action, with the heart pump rate going from one up to five gallons per minutes and our arteries constricting to maximize pressure around the system whilst the veins open out to ease return of blood to the heart.
 The respiratory system joining in as the lungs, throat and nostrils open up and breathing speeding up to get more air in the system so the increased blood flow can be re-oxygenated. The blood carries oxygen to the muscles, allowing them to work harder. Deeper breathing also helps us to scream more loudly!
 Fat from fatty cells and glucose from the liver being metabolized to create instant energy.
 Blood vessels to the kidney and digestive system being constricted, effectively shutting down systems that are not essential. A part of this effect is reduction of saliva in the mouth. The bowels and bladder may also open out to reduce the need for other internal actions (this might also dissuade our attackers!).
 Blood vessels to the skin being constricted reducing any potential blood loss. Sweat glands also open, providing an external cooling liquid to our over-worked system. (this makes the skin look pale and clammy).
 Endorphins, which are the body's natural pain killers, are released (when you are fighting, you do not want be bothered with pain–-that can be put off until later.)
 The natural judgment system is also turned down and more primitive responses take over–this is a time for action rather than deep thought.
Modern effects
Unfortunately, we are historically too close to the original value of this primitive response for our systems to have evolved to a more appropriate use of it, and many of life’s stresses trigger this response. The surprises and shocks of modern living leave us in a permanent state of arousal that takes
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its toll on our bodies, as described by Hans Selye's General Adaptation Syndrome .
It also happens when a creative new idea makes us feel uncertain about things of which we previously were sure. The biochemical changes in our brain make us aggressive, fighting the new idea, or make us timid, fleeing from it.
So What?
Watch out for angry red faces, cold and clammy skin, signs of a dry mouth, increased breathing rates and jitteriness from activated muscles (in yourself, as well as others).
Also watch out for the various forms of coping that can be dysfunctional and contrary to behavior you are seeking to create.
When others are thus aroused, they are not thinking straight and can be manipulated. You may even want to provoke them into this state. They also may become aggressive and unpredictable, so on the other hand you may want to avoid getting them into this state!
If you get wound up yourself, stop. Get out. Use any excuse to go somewhere and calm down.
The main difference between animal emotions and human emotions is that animals don't have mixed emotions the way normal people do. Animals aren't ambivalent; they don't have love-hate relationships with each other or with people. That's one of the reasons humans love animals so much; animals are loyal. If an animal loves you he loves you no matter what. He doesn't care what you look like or how much money you make.
This is another connection between autism and animals: autistic people have mostly simple emotions, too. That's why normal people describe us as innocent. An autistic person's feelings are direct and open, just like animal feelings. We don't hide our feelings, and we aren't ambivalent. I can't even imagine what it would be like to have feelings of love and hate for the same person.
Some people will probably think this is an insulting thing to say about autistic people, but one thing I appreciate about being autistic is that I don't have to deal with all the emotional craziness my students do. I had one fantastic student who flunked out of school because she broke up with her boyfriend.
There's so much psychodrama in normal people's lives. Animals never have psychodrama.
Children don't, either. Emotionally, children are more like animals and autistic people, because children's frontal lobes are still growing and don't mature until sometime in early adulthood. I mentioned earlier that the frontal lobes are one big association cortex, tying everything together, including emotions like love and hate that would probably be better off staying separate. That's another reason why a dog can be like a person's child: children's emotions are straightforward and loyal like a dog's. A seven-year-old boy or girl will race through the house to greet Dad when he comes from work the same way a dog will. I think animals, children, and autistic people have simpler emotions because
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their brains have less ability to make connections, so their emotions stay more separate and compartmentalized.
Of course, no one knows why an autistic grown-up has trouble making connections, since our frontal lobes are normal-sized. All we know right now is that researchers find "decreased connectivity among cortical regions and between the cortex and subcortex." The way I visualize it is that a normal brain is like a big corporate office building with telephones, faxes, e-mail, messengers, people walking around and talking -- a big corporation has zillions of ways for messages to get from one place to another. The autistic brain is like the same big corporate office building where the only way for anyone to talk to anyone else is by fax. There's no telephone, no e-mail, no messengers, and no people walking around talking to each other. Just faxes. So a lot less stuff is getting through as a consequence, and everything starts to break down. Some messages get through okay; other messages get distorted when the fax misprints or the paper jams; other messages don't get through at all.
The point is that even though autistic people have a normal-sized neocortex including normal-sized frontal lobes, our brains function as if our frontal lobes were either much smaller or not fully developed.
Our brains function more like a child's brain or an animal's brain, but for different reasons.
When the different parts of the brain are relatively separate from each other and don't communicate well, you end up with simple, clear emotions due to compartmentalization. A child can be furious at his mom or dad one second, then completely forget about it the next, because being mad and being happy are separate states. A child hops from one to the other depending on the situation.
You see the exact same thing with animals. Strong emotions in animals are usually like a sudden thunderstorm, They blow in and then blow back out. Two dogs who live together in the same house can be snarling one second, then go back to being best friends the next. Normal people need a lot more time to get over an angry emotion, and even when a normal adult does get over a bad emotion he's made a lasting connection between the angry emotion and the person or situation that made him angry.
When a normal person gets furiously angry with a person he loves, his brain hooks up anger and love and remembers it. Thanks to his highly developed frontal lobes, which connect everything up with everything else, his brain learns to have mixed emotions about that person or situation.
A useful notion in understanding how we feel is that of primary and secondary emotions.
What is felt first
Primary emotions are those that we feel first, as a first response to a situation. Thus, if we are threatened, we may feel fear. When we hear of a death, we may feel sadness. They are unthinking,
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instinctive responses that we have. We will typically see these in animals also, which confirms our suspicion that they have an evolutionary basis.
Typical primary emotions include fear , anger , sadness and happiness (although it is worth noting that these can also be felt as secondary emotions).
Often transient
The problem sometimes with primary emotions is that they disappear as fast as they appear. Their replacement by secondary emotions complicates the situation, making it difficult to understand what is really going on.
What is felt next
Secondary emotions appear after primary emotions. They may be caused directly by them, for example where the fear of a threat turns to anger that fuels the body for a fight reaction. They may also come from more complex chains of thinking.
Simple or mixed feelings
Secondary emotions may be simple feelings or may be a mix as more emotions join the fray. Thus news of a wartime victory may start with feelings of joy, but then get tinged with sadness for the loss of life.
So what?
If you want to diagnose a person's condition, then looking at primary and secondary emotions gives you a fuller picture.
To find the real issue or cause of the person's condition, look for the primary emotion. Do not blindly accept the emotion you see as the primary emotion, but try to find what may have come first.
The secondary emotions give you a picture of the person's mental processing of the primary emotion.
Question them, slowing down their mental process, to determine the internal reasoning as to why they came to feel the secondary emotions. This will often be unconscious and can be as big a surprise to them as it is to you.
A savanna is a rolling grassland scattered with shrubs and isolated trees, which can be found between a tropical rainforest and desert biome. Not enough rain falls on a savanna to support forests. Savannas are also known as tropical grasslands. They are found in a wide band on either side of the equator on the edges of tropical rainforests.
Savannas have warm temperature year round. There are actually two very different seasons in a savanna; a very long dry season (winter), and a very wet season (summer). In the dry season only an average of about 4 inches of rain falls. Between December and February no rain will fall at all. Oddly
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enough, it is actually a little cooler during this dry season. But don't expect sweater weather; it is still around 70° F.
In the summer there is lots of rain. In Africa the monsoon rains begin in May. An average of 15 to 25 inches of rain falls during this time. It gets hot and very humid during the rainy season. Every day the hot, humid air rises off the ground and collides with cooler air above and turns into rain. In the afternoons on the summer savanna the rains pour down for hours. African savannas have large herds of grazing and browsing hoofed animals. Each animal has a specialized eating habit that reduces compitition for food.
There are several different types of savannas around the world. The savannas we are most familiar with are the East African savannas covered with acacia trees. The Serengeti Plains of Tanzania are some of the most well known. Here animals like lions, zebras, elephants, and giraffes and many types of ungulates(animals with hooves) graze and hunt. Many large grass-eating mammals (herbivores) can survive here because they can move around and eat the plentiful grasses. There are also lots of carnivores (meat eaters) who eat them in turn.
South America also has savannas, but there are very few species that exist only on this savanna. In
Brazil, Colombia, and Venezuela, savannas occupy some 2.5 million square kilometers, an area about one-quarter the size of Canada. Animals from the neighboring biomes kind of spill into this savanna.
The Llanos of the Orinoco basin of Venezuela and Columbia is flooded annually by the Orinoco River.
Plants have adapted to growing for long periods in standing water. The capybara and marsh deer have adapted themselves to a semi-aquatic life.
Brazil's cerrado is an open woodland of short twisted trees. The diversity of animals is very great here, with several plants and animals that don't exist anywhere else on earth.
There is also a savanna in northern Australia. Eucalyptus trees take the place of acacias in the
Australian savanna. There are many species of kangaroos in this savanna but not too much diversity of different animals
Plants of the savannas are highly specialized to grow in this environment of long periods of drought.
They have long tap roots that can reach the deep water table, thick bark to resist annual fires, trunks that can store water, and leaves that drop of during the winter to conserve water. The grasses have adaptations that discourage animals from grazing on them; some grasses are too sharp or bitter tasting for some animals, but not others, to eat. The side benefit of this is that every species of animal has something to eat. Different species will also eat different parts of the grass. Many grasses grow from the bottom up, so that the growth tissue doesn't get damaged by grazers. Many plants of the savanna also have storage organs like bulbs and corms for making it though the dry season.
Most of the animals on the savanna have long legs or wings to be able to go on long migrations.
Many burrow under ground to avoid the heat or raise their young. The savanna is a perfect place for birds of prey like hawks and buzzards. The wide, open plain provides them with a clear view of their prey, hot air updrafts keep them soaring, and there is the occasional tree to rest on or nest in. Animals
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don't sweat to lose body heat, so they lose it through panting or through large areas of exposed skin, or ears, like those of the elephant.
The savanna has a large range of highly specialized plants and animals. They all depend on the each other to keep the environment in balance. There are over 40 different species of hoofed mammals that live on the savannas of Africa. Up to 16 different species of browsers (those who eat leaves of trees) and grazers can coexist in one area. They do this by having their own food preferences, browsing/grazing at different heights, time of day or year to use a given area, and different places to go during the dry season.
These different herbivores provide a wide range of food for carnivores, like lions, leopards, cheetahs, jackals and hyenas. Each species has its own preference, making it possible to live side by side and not be in competition for food.
In many parts of the savannas of Africa people have started using it to graze their cattle and goats.
They don't move around and soon the grasses are completely eaten up. With no vegetation, the savanna turns into a desert. Huge areas of savanna are lost to the Sahara desert every year because of overgrazing and farming.
In one of the most remote places in the world, the Canadian Arctic, a people have survived over a thousand of years. They are the Inuit. For the Inuit, the Arctic is a place teeming with life. Depending on how far north they live, the Inuit find everything from caribou herds and polar bears to beluga whales.
The Inuit have adapted themselves to the various regions they inhabit. At one time they were considered to be among the healthiest people in the world. This is no longer the case; the Inuit lifestyle has changed dramatically over the past decades. The arrival of southerners and modern technology resulted in big changes to the Inuit diet and way of life.
Today, the Inuit are rediscovering their rich heritage and they are learning to govern themselves in a modern world.
History
The name Inuit means "the people." When the first Europeans met the Inuit, they called them Eskimo.
This was because the Europeans had heard that name from another Aboriginal group called the Cree. In the Cree language, "Eskimo" means "eaters of raw meat." The Inuit don't like to be called Eskimo. They prefer to be called Inuit or, for one person, Inuk.
The Inuit arrived in their territory around 1 000 years ago from the Alaska region. They had come east hunting the bowhead whale. Originally there had been another people living in the area where some of them settled, in the areas we now call the Northwest Territories, Northern Quebec and Northern Ontario.
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This other group has been called the Dorset culture by archeologists. An archeologist is someone who studies ancient societies by discovering what they left behind. It is believed that the Dorset culture left around the same time as the Inuit arrived. They may have fought one another.
What makes the Inuit unique? For one thing, they are the only Aboriginal people who can be found from one side of the country to the other. It is important to note that Inuit are not related to other
Aboriginal groups. They are their own distinct people who arrived in the North hundreds of years ago.
The Inuit have integrated many of the changes of the last 50 years into their way of life. Today, they live in villages and their houses are made of modern materials. They still go hunting, but they also buy food at the store. Many of them go to church. Some have become famous for their sculptures. The greatest achievement of the Inuit in recent years is the creation of a new territory in Canada--Nunavut, which means "our land" in Inuktitut, the language of the Inuit.
Nunavut is the largest territory in Canada. It was formed out of the eastern Canadian Arctic. The Inuit in Nunavut have special rights to the wealth that comes from the land, including hunting and fishing rights. Most of all, the Inuit govern themselves in Nunavut. This has renewed in them a sense of pride.
Other Aboriginal groups want to follow the Inuit example. The Inuit hope that, given time, they will become a prosperous people in their new territory of Nunavut.
Daily Life
Way of Life
When you live in an environment that has few plants, there is a very good chance you will become a hunter. The Inuit pride themselves on being great hunters. The Inuit had lots of sea and land animals to hunt. The most important of these were the caribou and the seal. These two animals provided the Inuit with food. Their skin was used for clothing, blankets, tents and boats and their oil was used for cooking and lamps. Bones, ivory and wood were used to make tools. Other animals the Inuit hunted were the walrus, whale, polar bear, musk ox, fox and wolf.
You may have seen pictures of strange rock formations shaped like people. These are called inuksuit
(inukshuk if there's only one). The Inuit made inuksuit as markers along caribou trails to make sure they didn't get lost.
Because edible plants are scarce in the Arctic, the Inuit ate mostly meat they got from hunting. They ate animals such as caribou, seals, walruses, polar bears, arctic hares, musk oxen, birds such as ptarmigan, and fish such as arctic char, salmon and whitefish. In the summer they also gathered berries and other edible plants.
Seal or walrus intestine is waterproof, and the Inuit scraped, cleaned, soaked and dried the intestines to make waterproof clothing. This kept the people dry, which was important since water freezes quickly
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in the North. People can get into a lot of trouble if they get wet in the Arctic and then freeze. Besides waterproof clothing, the Inuit also made parkas of caribou fur to wear in the cold winter.
At one point, scientists in Canada did a study to find out what the warmest winter clothes were. This included clothes that were sewn out of cloth, wool and other fabrics. The caribou jacket was the warmest by far. Even in winter, Inuit could not sleep with their jackets on because they got so hot that they would sweat. Sweat is dangerous in a cold climate because, like water, it freezes.
At one time the Inuit had a summer home and a winter home. In the summer, the Inuit often lived in tents that they made from caribou hides with wooden frames. In the winter many Inuit lived in sod homes. They would dig a hole in the ground and pile rocks and sod all around the outside to make walls. Pieces of wood or whalebone were used as a frame for the roof, which the Inuit then covered with sod. In both the tents and the sod houses the Inuit built raised platforms at the back for sleeping.
The Inuit are famous for their igloos. An igloo is built of blocks of snow shaped into a dome. They were mostly used as temporary shelter during winter hunting trips. The igloo is the one of the Inuit's best inventions. It is warm and easy to construct. Most Inuit today have settled in villages and live in houses.
(1775-1851).
One of the finest landscape artists was J.M.W. Turner, whose work was exhibited when he was still a teenager. His entire life was devoted to his art. Unlike many artists of his era, he was successful throughout his career.
Joseph Mallord William Turner was born in London, England, on April 23, 1775. His father was a barber. His mother died when he was very young. The boy received little schooling. His father taught him how to read, but this was the extent of his education except for the study of art. By the age of 13 he was making drawings at home and exhibiting them in his father's shop window for sale.
Turner was 15 years old when he received a rare honor--one of his paintings was exhibited at the
Royal Academy. By the time he was 18 he had his own studio. Before he was 20 print sellers were eagerly buying his drawings for reproduction.
His early training had been as a topographic draftsman. With the years, however, he developed a painting technique all his own. Instead of merely recording factually what he saw, Turner translated scenes into a light-filled expression of his own romantic feelings.
In 1850 he exhibited for the last time. One day Turner disappeared from his house. His housekeeper, after a search of many months, found him hiding in a house in Chelsea. He had been ill for a long time.
He died the following day--Dec. 19, 1851.
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Although known for his oils, Turner is regarded as one of the founders of English watercolor landscape painting. Some of his most famous works are
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Traditionally, maple syrup was harvested by tapping a maple tree through the bark and into the wood xylem , then letting the sap run into a bucket, which required daily collecting; less labour-intensive methods such the use of continuous plastic pipelines have since superseded this, in all but cottage-scale production.
Production is concentrated in February, March and April, depending on local weather conditions.
Freezing nights and warm days are needed in order to induce sap flows. The change in temperature from above to below freezing causes water uptake from the soil, and temperatures above freezing cause a stem pressure to develop, which, along with gravity, causes sap to flow out of tapholes or other wounds in the stem or branches. To collect the sap, holes are bored into the maple trees and tubes
(taps, spouts, spiles ) are inserted. Sap flows through the spouts into buckets or into plastic tubing.
Modern use of plastic tubing with a partial vacuum has enabled increased production. A hole must be drilled in a new location each year, as the old hole will produce sap for only one season due to the natural healing process of the tree, called walling-off. Maple sap is collected from the buckets and taken to the sugar house ; if plastic tubing and pipelines are used, then the pipelines are arranged so that the sap will flow by gravity into the sugar house , or if that is not possible, into holding tanks from which the sap is pumped or transported by tanker truck to the sugar house.
During processing, called sugaring-off , the sap is fed automatically from a storage tank through a valve into a flat pan called an evaporator where the sap boils down until so much water is lost that it forms a sweet syrup. The process is slow, because of amount of water that must be boiled off.
Approximately 40 litres of sap must be boiled down to make one litre of maple syrup (i.e., 39 litres of water must be boiled off). A mature sugar maple produces about 40 litres (10 gallons) of sap during the
4-6 week sugaring season. Trees are not tapped until they have a diameter of 25 centimetres (10 inches) at chest-height and the tree is at least 40 years old. Most contemporary producers use a 5/16" or
19/64" (7.94 mm or 7.54 mm) outside diameter drill bit to drill with. A tap hole depth of 1" to 1 1/2" (25 mm to 38 mm) is a commonly recommended depth.
Starting in the 1970s, some maple syrup producers started using reverse osmosis to remove water from sap before being further boiled down to syrup. The use of reverse osmosis allows approximately
75 to 80% of the water to be removed from the sap prior to boiling, reducing energy consumption and exposure of the syrup to high temperatures. Microbial contamination and degradation of the membranes has to be monitored.
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The Nazca region is a desert that the Nazca turned into a viable agricultural area using their aqueduct technology. Nazca pottery has been divided into eight phases. Around 200 BC, at the end of the Early
Horizon drought, Nazca I began. Pottery from this era contains the mythical content of Paracas art, but added realistic subject matter such as fruits, plants, people, and other animals. Realism increased in importance in the following three phases (II, III, IV) referred to as the Monumental phases. The pottery from these phases includes renditions of their main subject matter against a bold red or white background. In the next phase, Nazca V, the backgrounds are filled in and the subject matter now included bodyless renditions of both demons and humans. Nazca VI, and VII include the earlier motifs but also add militaristic ones, and portraits of elite members of the society. Nazca VI and VII also begin to show the influence of the Moche . Finally, Nazca VIII saw the introduction of completely disjointed figures and a rich iconography which has yet to be deciphered. The phases were created before the advent of carbon dating and today have some problems. While the general order did not change there is a great deal of overlap of the phases, and while the Nazca IX phase ends c. 600 AD, some of the pottery in that category was created at least as late as 755 AD.
Since the Nazca were a coastal people, who depended on the sea for their livelihood, archaeologists are fortunate that they portrayed aspects of their everyday lives in and on their pottery. The motifs generally seen on Nazca pots are those of animals and plants used and seen by the ancient people.
These include sea birds, hummingbirds, whales, sharks, fish, snakes, seeds, flowers, and cacti. Also, more gruesomely, the Nazca portrayed severed heads, presumed to be trophy heads, on their pottery. This is supported in the archaeological record with the the discovery of caches of actual severed and ritually prepared heads. Over one hundred examples are known to exist. (Silverman)
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