21 résultats pour "covering"

• Skin. I INTRODUCTION Skin, outer body covering of an animal. The term skin

  III SKIN APPENDAGES In humans, the skin appendages, or structures embedded in the skin, include hair, nails, and several types of glands. Glands are groups of cells that produce andsecrete substances needed by other parts of the body. In other vertebrates, the skin appendages include scales (in fish and reptiles) and feathers (in birds). Together,the skin and the skin appendages are known as the integumentary system of the body. A Hair Hair is a distinguishing characteristic of mammals, a gro...

• Comparative Anatomy.

  In comparing two species, anatomists have to be careful to differentiate between homologous structures, which are ones that have evolved from a shared ancestor, andanalogous structures, which have developed from different origins. Homologous structures are built on the same underlying plan. A human arm, a bat’s wing, and awhale’s flipper look quite different from the outside, but the bones inside reveal that these limbs all have the same basic structure. Analogous structures, by contrast,often l...

• Antarctica - Geography.

  The maximum area of sea ice surrounding Antarctica each winter varies from year to year. A marked decline during the 1970s appears to have reversed in more recentdecades, except in the Antarctic Peninsula area. This area has lost almost 40 percent of its sea ice since the start of the 1980s. Sea ice is important to marine life. Krillfeed on algae that live under the sea ice and are released when the ice melts in spring and summer. In turn, many marine animals feed on krill. Emperor penguinsbreed...

• Vertebrate - biology.

  E Reptiles Compared to amphibians, reptiles are much more fully adapted to life on land. They have scaly, waterproof skin, and they either give birth to live young or lay eggs withwaterproof shells. There are about 7,000 species alive today, including snakes, alligators, and turtles. During the age of the dinosaurs, about 230 million to 65 millionyears ago, reptiles outnumbered all other land vertebrates put together. F Birds Birds evolved from flightless reptiles but underwent some major chan...

• Japan - country.

  island’s fertile soils support agriculture and provide the vast majority of Japan’s pasturelands. In addition, Hokkaidō contains coal deposits, and the cold currents off itsshores supply cold-water fish. Winters are long and harsh, so most of Hokkaid ō is lightly settled, housing about 5 percent of Japan’s population on approximately 20 percent of its land area. However,its snowy winters and unspoiled natural beauty attract many skiers and tourists. Hokkaid ō is thought of as Japan’s northern fr...

• test AIO

  Test AIO : Case Kellogg’s The company Consumers around the world enjoy Kellogg Company products, one of which – Kellogg’s Corn Flakes ® – has been part of a wholesome, delicious morning for more than a century. The company began with only 44 employees in Battle Creek, Michigan, in 1906. Today they manufacture in 18 countries and sell our products in more than 180 countries around the world, first expanding to similar markets to keep expansion controllable. For more than 100 years, in...

• Central Processing Unit.

  Development of the computer chip started in 1958 when Jack Kilby of Texas Instruments demonstrated that it was possible to integrate the various components of aCPU onto a single piece of silicon. These computer chips were called integrated circuits (ICs) because they combined multiple electronic circuits on the same chip.Subsequent design and manufacturing advances allowed transistor densities on integrated circuits to increase tremendously. The first ICs had only tens of transistorsper chip com...

• Antarctica - geography.

  The geographic South Pole lies near the center of the continent in East Antarctica. This point is where all map lines of longitude converge at the southern end ofEarth’s axis of rotation. Distinct from the geographic south pole is the south magnetic pole, where the lines of force of Earth’s magnetic field emerge vertically,arching upward over the planet to enter Earth again at the north magnetic pole. The south-seeking end of a compass needle points to the south magnetic pole. Thesouth magnetic...

• Eye. I INTRODUCTION Eye, light-sensitive organ of vision in animals. The eyes of

  Several structures, not parts of the eyeball, contribute to the protection of the eye. The most important of these are the eyelids, two folds of skin and tissue, upper andlower, that can be closed by means of muscles to form a protective covering over the eyeball against excessive light and mechanical injury. The eyelashes, a fringe ofshort hairs growing on the edge of either eyelid, act as a screen to keep dust particles and insects out of the eyes when the eyelids are partly closed. Inside the...

• Massachusetts - geography.

  mi). Other large artificial lakes include Wachusett Reservoir, East Brimfield Reservoir, and Cobble Mountain Reservoir. Assawompsett Pond, covering about 10 sq km(about 4 sq mi), is the largest natural lake. North Watuppa Pond and Long Pond are other large natural lakes. Lake Chaubunagungamaug, near Webster, is usuallycalled Webster Lake, because the Algonquian name is difficult to pronounce and spell. The full version of the Native American name is said to be the longest place-namein North Amer...

• Baseball.

  pitcher or argue a call with an umpire. Two or more coaches, positioned closer to the field, assist the manager by communicating with the players. For example,managers may decide what pitches should be thrown, when batters should swing at a pitch, and how runners should move around the bases. The manager relays thesedecisions through special hand signals that the coaches repeat to communicate to the players. Umpires are responsible for interpreting and enforcing the rules of play. They rule on...

• Native American Architecture.

  B Relationship to the Universe and Nature A more profound difference between European American and Native American perceptions lay in how human beings saw themselves in relationship to the universe andin what they believed their responsibilities were to the natural world and to each other. Most European Americans saw themselves as separate from creation andadversaries of nature, ever struggling to conquer and subdue nature and force it to yield to their will. Native Americans saw themselves as...

• Colorado - geography.

  Although the rivers of Colorado are navigable only by small boats, they are important as a source of irrigation water for use in Colorado and adjoining states. However,the water level of the rivers fluctuates seasonally and from year to year. The level is generally low in winter and high in spring and summer, during the runoff of meltedsnow from the mountains. Colorado has no large lakes of natural origin, but there are numerous small lakes in the mountains. The largest bodies of water in Colora...

• Colorado - USA History.

  Although the rivers of Colorado are navigable only by small boats, they are important as a source of irrigation water for use in Colorado and adjoining states. However,the water level of the rivers fluctuates seasonally and from year to year. The level is generally low in winter and high in spring and summer, during the runoff of meltedsnow from the mountains. Colorado has no large lakes of natural origin, but there are numerous small lakes in the mountains. The largest bodies of water in Colora...

• Penguin - biology.

  B Parents and Offspring Once female penguins lay their eggs, both the parents incubate the eggs. The incubation period varies according to species, ranging from 33 days for the little penguinto about 63 days for the emperor penguin. In most medium-sized penguins incubation takes 35 to 38 days. The incubation routine is highly variable among penguinspecies, although in general both sexes participate in incubation and feeding of young. Male and female Adélie penguins take turns incubating their e...

• 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...

• Tree - biology.

  The major parts of a tree are its roots, trunk, leaves, flowers, and seeds. These components play vital roles in a tree’s growth, development, and reproduction. A Roots Trees are held in place by anchoring organs called roots. In addition to anchoring the tree, roots also absorb water and minerals through tiny structures called roothairs. From the roots the water and mineral nutrients are carried upward through the wood cells to the leaves. Although the internal structure of most kinds of roots...

• Prints and Printmaking I INTRODUCTION Prints and Printmaking, pictorial images that can be inked onto paper, and the art of creating and reproducing them.

  Bewick’s The SkylarkBritish engraver Thomas Bewick’s The Skylark is part of his History of British Birds (2 vols., 1797 and 1804). Bewick wasthe first artist to demonstrate the full potential of wood engraving and is renowned for his fine natural history illustrations.Each illustration shows some of the bird’s natural habitat.Folio Society, London/Bridgeman Art Library, London/New York Historically, the wood engraving was chiefly used for illustrations in magazines and books. It is similar to th...

• 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...

• Alaska - geography.

  depression surrounded by highlands and have the coldest winter and hottest summer temperatures in Alaska. Once the Kuskokwim River passes through theKuskokwim Mountains, it forms the southern edge of a vast lake-studded alluvial plain bounded on the north by the Yukon River. This water-logged lowland is a majorsummer nesting area for birds. Fairbanks is the major city in this region, while Fort Yukon is the major community in the Yukon Flats and Bethel the largest settlementon the Lower Kuskokwi...

• Alaska - USA History.

  depression surrounded by highlands and have the coldest winter and hottest summer temperatures in Alaska. Once the Kuskokwim River passes through theKuskokwim Mountains, it forms the southern edge of a vast lake-studded alluvial plain bounded on the north by the Yukon River. This water-logged lowland is a majorsummer nesting area for birds. Fairbanks is the major city in this region, while Fort Yukon is the major community in the Yukon Flats and Bethel the largest settlementon the Lower Kuskokwi...