93 résultats pour "lacker"
-
Flower - biology.
insects. The sepals unfurl as the flower opens and often resemble small green leaves at the flower’s base. In some flowers, the sepals are colorful and work with thepetals to attract pollinators. E Variations in Structure Like virtually all forms in nature, flowers display many variations in their structure. Most flowers have all four whorls—pistil, stamens, petals, and sepals. Botanists callthese complete flowers. But some flowers are incomplete, meaning they lack one or more whorls. Incomplet...
-
Poverty.
economic and demographic trends, and (7) welfare incentives. A Overpopulation Overpopulation, the situation of having large numbers of people with too few resources and too little space, is closely associated with poverty. It can result from highpopulation density (the ratio of people to land area, usually expressed as numbers of persons per square kilometer or square mile) or from low amounts of resources, or from both. Excessively high population densities put stress on available resources....
- lack of mobile phone
-
Mental Retardation.
For example, measles, chicken pox, and whooping cough may lead to encephalitis and meningitis, which can damage the brain. Physical trauma to the brain can also cause mental retardation. Brain damage may result from accidental blows to the head, near drowning, severe child abuse, andchildhood exposure to such toxins as lead and mercury. Experts believe that poverty and a lack of stimulation during infancy and early childhood can be factors inmental retardation. Children raised in poor environmen...
-
Plant - biology.
B1 Vacuoles Vacuoles are membrane-bound cavities filled with cell sap, which is made up mostly of water containing various dissolved sugars, salts, and other chemicals. B2 Plastids Plastids are types of organelles, structures that carry out specialized functions in the cell. Three kinds of plastids are important here. Chloroplasts contain chlorophyllsand carotenoid pigments; they are the site of photosynthesis, the process in which light energy from the sun is fixed as chemical energy in the b...
-
Human Nutrition.
is one of the most preventable types of cancer. Nutritionists caution that most Americans need to eat more complex carbohydrates. In the typical American diet, only 40 to 50 percent of total calories come fromcarbohydrates—a lower percentage than found in most of the world. To make matters worse, half of the carbohydrate calories consumed by the typical American comefrom processed foods filled with simple sugars. Experts recommend that these foods make up no more that 10 percent of our diet, bec...
-
Afghanistan - country.
D Climate Most of Afghanistan has a subarctic mountain climate with dry and cold winters, except for the lowlands, which have arid and semiarid climates. In the mountains and afew of the valleys bordering Pakistan, a fringe effect of the Indian monsoon, coming usually from the southeast, brings moist maritime tropical air in summer.Afghanistan has clearly defined seasons: Summers are hot and winters can be bitterly cold. Summer temperatures as high as 49°C (120°F) have been recorded in thenorth...
-
Italy - country.
C Natural Resources Italy is poor in natural resources. Much of the land is unsuitable for agriculture because of mountainous terrain or unfavorable climate. Italy, moreover, lacks substantialdeposits of basic natural resources such as coal, iron, and petroleum. Natural gas is the country’s most important mineral resource. Other deposits include feldspar andpumice. Many of Italy’s mineral deposits on the islands of Sicily and Sardinia had been heavily depleted by the early 1990s. Italy is rich...
-
-
Coral - biology.
Soft corals lack a distinct skeleton. Although they live in colonies, the individual polyps are fused into a complex body, usually strengthened by small lumps or spikesknown as sclerites, which are made of protein and calcite. Soft corals come in a variety of shapes, including undulating sheets, upright mushroomlike shapes, andbeautiful shapes that form branches. A number of other octocorals have skeletons made from a hard or horny protein, sometimes strengthened with more brittle calcareous dep...
-
Soccer's Big Show Comes to the United States.
There were many doubters, both overseas and within the United States. Some U.S. sportswriters derided the idea of holding the World Cup in the United States asakin to staging the World Series in India—how could there be any local interest? Foreign critics felt that money was the sole reason for FIFA's decision and that thesport was about to be cheapened to make it acceptable to Americans. The rumors flew: FIFA was going to enlarge the goals, it would allow timeouts (unheard of inthe sport) to ac...
-
Amphibian (animal) - biology.
strong enough to kill potential predators. C Hearing, Vision, and Vocalizations Amphibians rely on their senses to find food and evade predators. Amphibians lack external ears but have well-developed internal ears. Hearing is most acute in frogs,which typically have a middle ear cavity for transferring sound vibrations from the eardrum, or tympanum, to the inner ear. Frogs and toads also use their keen hearingin communicating with one another. Using a true voice box, or larynx, and a large, exp...
-
United States House of Representatives.
Because of the high cost of elections and the short two-year term of office, members of the House campaign almost constantly. They spend much of their time raisingcampaign funds, and they frequently return to their districts to keep in touch with voters. Because the elections are so frequent, House members tend to pay closeattention to how their votes in Congress will be seen in the short term. House members tend to come from wealthier family backgrounds than average Americans. Few working class...
-
Armenia (country) - country.
because of ethnic tension brought on by a secessionist conflict in Nagorno-Karabakh, a region inhabited predominantly by Armenians in western Azerbaijan. In thereverse direction, many Armenian refugees entered Armenia from Azerbaijan during the conflict. Armenia’s official state language is Armenian, an Indo-European language with no surviving close relatives. It has a unique 38-letter alphabet that dates from the early5th century. Of its many spoken dialects, the most important are Eastern or Y...
-
Bacteria - biology.
A2 b Bacterial Killers Some dramatic infectious diseases result from exposure to bacteria that are not part of our normal bacterial community. Cholera, one of the world’s deadliest diseasestoday, is caused by the bacterium Vibrio cholerae . Cholera is spread in water and food contaminated with the bacteria, and by people who have the disease. After entering the body, the cholera bacteria grow in the intestines, often along the surface of the intestinal wall, where they secrete a toxin (poiso...
-
Essay : Stranger in the village
people are courteous, he still can feel that he is not welcomed in this village where people are racist and narrow-minded. The reactions of the villagers can partially be explained by their lack of culture and their narrow-mindedness. Indeed, these people live in a tiny village which is cut of the outside world. They have to go to the village at the foot of the mountain to see a movie or go to the bank as there is no movie house, no bank nor library in the village. It seems that p...
-
Prison.
Furthermore, experts disagree about whether imprisoning criminals actually prevents further crime. Some critics charge that American prisons simply warehouseviolence—meaning that U.S. prison inmates are confined and incapacitated in large numbers, with little or no effort made to rehabilitate them. Critics have labeled theresult of this process turnstile justice, referring to the fact that most inmates are chronic and persistent offenders and return to prison following conviction for new crime...
-
-
Israel (country) - country.
harbor in the northern part of the country, and Ashdod, an artificial deepwater port to the south, serve as the main seaports on the Mediterranean. The port of Elat onthe Gulf of Aqaba provides Israel’s only access to the Red Sea, making it extremely important to the country’s shipping interests. D Natural Resources Although much of Israel’s desert regions contain poor soils, the northern Negev, the coastal plains, and the interior valleys provide patches of productive soils. Anestimated 18 per...
-
Whale - biology.
III BEHAVIOR OF WHALES Studies of whales in captivity have taught scientists much about the complex social behavior of whales. Since the late 1980s, advances in the use of satellite trackingsystems have also broadened opportunities for scientists to observe how whales behave in the wild. A Swimming and Diving Whales swim by making powerful up-and-down movements of the tail flukes, which provide thrust. The power comes from body muscles that flex the lower spine upand down in a wavelike motion...
-
Saudi Arabia - country.
C Natural Resources Some of the world’s largest oil and natural gas fields lie beneath Saudi Arabia and its offshore waters, representing the country’s most economically important naturalresource. In 2007 Saudi Arabia’s oil reserves were estimated at 264 billion barrels. Before the discovery and exploitation of these reserves in the mid-20th century,Saudi Arabia was one of the poorest countries in the world. Its relatively small population subsisted in a harsh environment with little agricultur...
-
Djibouti (country) - country.
l’Unité et de la Démocratie (FRUD; Front for the Renewal of Unity and Democracy) represents the Afar minority. The Parti National Démocratique (PND; Democratic National Party) and the Parti du Renouveau Démocratique (PRD; Democratic Renewal Party) are both small opposition parties favoring democratic reforms. VI HISTORY Djibouti lies at a major global crossroads where, some 100,000 years ago, early humans migrated from Africa to the Middle East. Livestock herding, which remainsimportant...
-
Virus (life science) - biology.
RNA into DNA earned them their name because this process is the reverse of the usual transfer of genetic information, from DNA to RNA.) The DNA form of theretrovirus genome is then integrated into the cellular DNA and is referred to as the provirus. The viral genome is replicated every time the host cell replicates its DNA and is thus passed on to daughter cells. Hepatitis B virus can also transcribe RNA to DNA, but this virus packages the DNA version of its genome into virus particles. Unlike...
-
Angola (country) - country.
Portugal in 1975, it had approximately 400,000 Portuguese settlers. The vast majority of the Portuguese community has since departed for Portugal. A Population Characteristics The 2008 estimated population of Angola, including Cabinda, was 12,531,357. The population distribution, however, was uneven, with about 70 percent of thepopulation concentrated in the north and along the coast. The rate of population increase was 2.1 percent annually in 2008. The population is overwhelmingly rural; only3...
-
Beetle - biology.
cut, or crush prey. Beetles that consume nectar from flowers use tubelike mouthparts to suck up nectar like a primitive straw. C Thorax The thorax, the body region behind the head, consists of three segments that provide attachments for the legs and wings. Each segment of the thorax carries a pair oflegs. The middle segment also bears the stiff wing sheaths called elytra, and the hind segment holds the membranous hind wings. D Legs Beetles have six jointed legs, each leg with five parts. The f...
-
Aboriginal Australians - History.
Until Europeans began to settle in Australia in 1788, the Aboriginal way of life was supported by hunting, gathering, and fishing. Like other hunting and gatheringpeoples, Aboriginal people had an extremely detailed knowledge of their environment, especially plant ecology and animal behavior. The deep connection betweenAboriginal people and the natural world influenced every part of their culture, including their food gathering, tools, trade, religion, art, music, language, and socialorganizatio...
-
-
Railroads.
III GAUGES The gauge of track is the distance between the inner edges of the rails at points 1.59 cm (0.626 in) below the top of the heads. In the United States, Canada, theUnited Kingdom, Mexico, Norway, Sweden, and much of continental Europe, the standard gauge is 143.51 cm (56.5 in). Why this measurement became the standard isa matter of speculation. Probably the tradition is inherited from early tramroads built to accommodate wagons with axles 1.5 m (5 ft) long; some of the early edge rail...
-
Ancient Greece.
The first culture of Aegean civilization on the Greek mainland is named Mycenaean for the palace at Mycenae on the Pelopónnisos. Scholars call the Mycenaeans the“earliest Greeks” because they are the first people known to have spoken Greek. Mycenaean culture developed later than Minoan. The ancestors of the Mycenaean people wandered onto the mainland from the north and the east from about 4000 to2000 BC, mixing with the people already there, and by about 1400 BC the Mycenaeans had become very...
-
Ancient Greece .
The first culture of Aegean civilization on the Greek mainland is named Mycenaean for the palace at Mycenae on the Pelopónnisos. Scholars call the Mycenaeans the“earliest Greeks” because they are the first people known to have spoken Greek. Mycenaean culture developed later than Minoan. The ancestors of the Mycenaean people wandered onto the mainland from the north and the east from about 4000 to2000 BC, mixing with the people already there, and by about 1400 BC the Mycenaeans had become very...
-
Ancient Greece - USA History.
The first culture of Aegean civilization on the Greek mainland is named Mycenaean for the palace at Mycenae on the Pelopónnisos. Scholars call the Mycenaeans the“earliest Greeks” because they are the first people known to have spoken Greek. Mycenaean culture developed later than Minoan. The ancestors of the Mycenaean people wandered onto the mainland from the north and the east from about 4000 to2000 BC, mixing with the people already there, and by about 1400 BC the Mycenaeans had become very...
-
Race - biology.
distributed as a cline, generally varying along a north-south line. Skin color is lightest in northern Europeans, especially in those who live around the Baltic Sea, andbecomes gradually darker as one moves toward southern Europe, the Mediterranean, the Middle East, and into northern Africa and northern subtropical Africa. Skin isdarkest in people who live in the tropical regions of Africa. The lack of clear-cut discontinuities makes any racial boundary based on skin color totally arbitrary. Sim...
-
From "Song of Myself" - anthology.
Till that becomes unseen and receives proof in its turn.Showing the best and dividing it from the worst age vexes age,Knowing the perfect fitness and equanimity of things, while they discuss I am silent, and go bathe and admire myself.Welcome is every organ and attribute of me, and of any man hearty and clean,Not an inch nor a particle of an inch is vile, and none shall be less familiar than the rest.I am satisfied—I see, dance, laugh, sing;As the hugging and loving bed-fellow sleeps at my side...
-
Checks and Balances.
no political interest has enough power to prevail over the others. In 1997 and early 1998, for example, the Senate refused to take action on many of President BillClinton’s appointments of new federal court judges. Although the Senate’s power to approve or reject federal court nominees is one of the key checks on presidentialauthority, the dispute between Clinton and the Senate meant that there were not enough federal judges to handle the court’s workload. But the system of checks andbalance was...
-
Owl - biology.
Among the largest species of typical owls are the eagle owls. They have tufts of feathers on their heads that are called “ears.” The great horned owl is the only eagleowl found in the Americas. It is about 60 cm (25 in) in length with a wingspan of 1.4 m (60 in). Numerous species of eagle owls inhabit Europe, Africa, and Asia. Mostwidely distributed is the northern eagle owl, found from Scandinavia and Spain to Japan. It is about 71 cm (28 in) long with a wingspan of about 2m (72 in). Nearly asl...
-
-
Eagle - biology.
States, is a member of this group found only in North America. It is named for its snow-white head. However, the name bald does not refer to a lack of feathers but comes instead from an outdated word meaning marked with white, as in piebald. The adult bald eagle is blackish brown, with a white head and tail. Its bill, legs, and feet are bright yellow. The bill, which is longer and heavier than the gray bill of golden eagles, is useful for piercing the skin of fish. Bald eagles vary in size....
-
Suicide.
C Sociological Theories Most social scientists believe that a society’s structure and values can influence suicide rates. French sociologist Émile Durkheim argued that suicide rates are related tosocial integration —that is, the degree to which an individual feels part of a larger group. Durkheim found suicide was more likely when a person lacked social bonds or had relationships disrupted through a sudden change in status, such as unemployment. As one example of the significance of social bond...
-
Ancient Greece - history.
Palace of KnossosThe ancient city of Knossos was a center of the Minoan civilization, an advanced society on Crete named after Minos, a legendaryCretan king. Skilled in such fields as engineering and architecture, the Minoans constructed the palace at Knossos in 1700 bc. Aserious fire at least three centuries later caused the collapse of the palace and foreshadowed the subsequent decline of the city.Wolfgang Kaehler Settlers had begun sailing from Asia Minor to Crete about 6000 BC because the i...
-
Child Abuse.
C Social Isolation and Low Community Involvement Parents and caretakers who abuse children tend to be socially isolated. Few violent parents belong to any community organizations, and most have little contact withfriends or relatives. This lack of social involvement deprives abusive parents of support systems that would help them deal better with social or family stress. Moreover,the lack of community contacts makes these parents less likely to change their behavior to conform with community va...
-
Giant Panda - biology.
In 2007 conservationists announced that a parasitic roundworm was responsible for a significant number of the panda deaths reported in the wild since 1990. Theparasite Baylisascaris schroederi causes the disease visceral larval migrans, which results in bleeding in the lungs, the liver, and the intestines, and can also affect the brain. It is not known if other recent pandas deaths were caused by the same parasite or by a different contagious disease. Loss of habitat from deforestation is forc...
-
Prince Edward Island - Geography.
hectares (109 acres) each. In 2006 there were 1,700 farms, of which the average size was 148 hectares (366 acres). In 2005 the total farm cash receipts were C$510million. The most important agricultural products in terms of value include potatoes, milk and cream, cattle and calves, hogs, tobacco, vegetables, eggs, hens andchickens, and furs. For the most part the island’s agriculture is diversified, rather than specialized, because of the lack of a large urban industrial population within easy r...
-
Prince Edward Island - Canadian History.
hectares (109 acres) each. In 2006 there were 1,700 farms, of which the average size was 148 hectares (366 acres). In 2005 the total farm cash receipts were C$510million. The most important agricultural products in terms of value include potatoes, milk and cream, cattle and calves, hogs, tobacco, vegetables, eggs, hens andchickens, and furs. For the most part the island’s agriculture is diversified, rather than specialized, because of the lack of a large urban industrial population within easy r...
-
Heredity - biology.
allele from the mother and a mutated allele from the father. In both of these cases, the child will be a carrier. The child develops the disease only if he or she receives amutated allele from each parent. When both parents are carriers, there is a 25 percent chance that a child will be disease-free, a 25 percent chance that it will have thedisease, and a 50 percent chance that it will be a carrier. Examples of genetic diseases that follow the dominant-recessive pattern include sickle-cell anemi...
-
-
Anatomy.
The body defends itself against foreign proteins and infectious microorganisms by means of a complex dual system that depends on recognizing a portion of the surfacepattern of the invader. The two parts of the system are termed cellular immunity, in which lymphocytes are the effective agent, and humoral immunity, based on theaction of antibody molecules. When particular lymphocytes recognize a foreign molecular pattern (termed an antigen), they release antibodies in great numbers; other lymphocy...
-
Bangladesh - country.
F Environmental Issues Waterborne diseases such as cholera are a serious threat to public health in Bangladesh. Until the 1970s, many of Bangladesh’s people became sick from drinkingpolluted water drawn from surface rivers. Aid agencies such as the United Nations Children’s Fund (UNICEF) built shallow wells throughout the country to help provide asafe source of drinking water to Bangladesh’s poor. In the 1990s, however, it was discovered that many of these wells were contaminated by arsenic, a...
-
Snake (reptile).
in their heads that conduct sound. They are able to hear low-frequency sounds and to sense vibrations that travel through the ground or water. The majority of snakeshave good eyesight, especially for detecting moving objects, although most burrowing snakes can only distinguish between light and dark. Pit vipers, boas, and pythons have an unusual adaptation for detecting warm-blooded prey and predators. On the heads of these snakes are small pits lined with cellsthat are extremely sensitive to he...
-
Ottoman Empire .
fleets at Suez, Egypt; though the Portuguese were not expelled, Selim did manage to prevent the establishment of a total Portuguese monopoly over the spice trade. Selim I died in 1520 after having spent most of his short reign on matters pertaining to the east. His son and successor Süleyman I (reigned 1520-1566) again turnedthe attention of the Ottomans to the west. In August 1521 Süleyman, later known as Süleyman the Magnificent, opened the road to Hungary by capturing Belgrade, aHungarian str...
-
Ottoman Empire - History.
fleets at Suez, Egypt; though the Portuguese were not expelled, Selim did manage to prevent the establishment of a total Portuguese monopoly over the spice trade. Selim I died in 1520 after having spent most of his short reign on matters pertaining to the east. His son and successor Süleyman I (reigned 1520-1566) again turnedthe attention of the Ottomans to the west. In August 1521 Süleyman, later known as Süleyman the Magnificent, opened the road to Hungary by capturing Belgrade, aHungarian str...
-
Earthquake.
III CAUSES Most earthquakes are caused by the sudden slip along geologic faults. The faults slip because of movement of the Earth’s tectonic plates. This concept is called theelastic rebound theory. The rocky tectonic plates move very slowly, floating on top of a weaker rocky layer. As the plates collide with each other or slide past eachother, pressure builds up within the rocky crust. Earthquakes occur when pressure within the crust increases slowly over hundreds of years and finally exceeds...
-
Washington, D.
structures built according to L’Enfant’s plan. During the War of 1812, British troops set fire to the White House, destroying its interior. President James Madison and hisfamily lived in the Octagon while the White House was being rebuilt. South of the Federal Triangle is the Mall, a narrow park stretching roughly 1.6 km (1 mi) from the Capitol to the Washington Monument. Although the Mall officially endsat 14th Street, landscaped greenery extends to the Potomac. The Washington Monument, whose m...
-
Venezuela - country.
Venezuela has six navigable rivers. Of the thousand or more streams in the country, the majority flow into the Orinoco. The Orinoco flows east across central Venezuelaand drains approximately four-fifths of the total area of the country. With the tributaries—the Apure, Meta, and Negro rivers—it forms the outlet into the Atlantic Oceanfor the waters of much of the interior of Colombia, as well as of inland Venezuela. F Climate The climate of Venezuela is tropical on the Llanos and along the coas...
-
-
Acquired Immunodeficiency Syndrome.
child transmission is particularly prevalent in Africa. D Misperceptions About HIV Transmission The routes of HIV transmission are well documented by scientists, but health officials continually grapple with people’s unfounded fears concerning the potential for HIVtransmission by other means. HIV differs from other infectious viruses in that it dies quickly if exposed to the environment. No evidence has linked HIV transmission tocasual contact with an infected person, such as a handshake, huggi...
-
Newfoundland and Labrador - Geography.
Precipitation averages about 1,120 mm (about 44 in) yearly in Newfoundland. In Labrador precipitation varies from about 1,020 mm (about 40 in) in the southeast toabout 510 mm (about 20 in) in the extreme north. Heavy winter snowfalls are common, especially in Newfoundland. D Plant Life About one-third of Newfoundland is forested, and most of the rest of the island is made up of barren areas of reindeer moss and lichens. The forests consist almostentirely of conifers. The most important species...