302 résultats pour "spec"

• New Brunswick - Canadian History.

  Grand Lake, the largest lake in New Brunswick, is in the lowlands, east of Fredericton. Most other lakes are located in the northern and southwestern parts of NewBrunswick. D Climate New Brunswick has a continental climate that is moderated by maritime influences in the coastal areas. As a result, coastal regions are slightly warmer in the winter andslightly cooler in the summer than are interior regions. Annual temperature variations are large, with the January mean usually at least 25 to 28°C...

• Michigan - geography.

  The interior location of Michigan in the northern part of North America results in a continental climate, characterized by four definite seasons with moist, mild to hotsummers and snowy, cold winters. Winds off of Lakes Michigan and Superior in winter create heavy snow accumulations in nearby areas. The tempering effects of LakeMichigan account for the presence of the state’s famous fruit-growing belt along the lake’s shore. Since the water is colder than the land in spring, the westerly windspa...

• Michigan - USA History.

  The interior location of Michigan in the northern part of North America results in a continental climate, characterized by four definite seasons with moist, mild to hotsummers and snowy, cold winters. Winds off of Lakes Michigan and Superior in winter create heavy snow accumulations in nearby areas. The tempering effects of LakeMichigan account for the presence of the state’s famous fruit-growing belt along the lake’s shore. Since the water is colder than the land in spring, the westerly windspa...

• Python (snake) - biology.

  pythons are prey for monitor lizards, crocodiles, storks, eagles, and predatory mammals ranging from hyenas to leopards and other cats depending on the region. V PYTHONS AND HUMANS Modern humans have lived alongside pythons for thousands of years. The giant species have been treated with both reverence and fear. Pythons have been widelyassociated with fertility, water, and the Earth. Some African tribes have worshiped pythons as protective spirits. Among Aboriginal Australians the Rainbow Serpe...

• Québec - Geography.

  facilities. Tributaries south of the St. Lawrence include the Richelieu, the Saint-François, and the Chaudière rivers, which are only a few hundred kilometers long. TheRimouski and Matane rivers, also south of the St. Lawrence, are popular areas for recreation and salmon fishing. In the Canadian Shield, the longest rivers are theRupert, Eastmain, Grande Baleine, and La Grand-Rivière, which is the site of a huge hydroelectric complex. C Coastlines Québec has two systems of saltwater coastline. O...

• Québec - Canadian History.

  facilities. Tributaries south of the St. Lawrence include the Richelieu, the Saint-François, and the Chaudière rivers, which are only a few hundred kilometers long. TheRimouski and Matane rivers, also south of the St. Lawrence, are popular areas for recreation and salmon fishing. In the Canadian Shield, the longest rivers are theRupert, Eastmain, Grande Baleine, and La Grand-Rivière, which is the site of a huge hydroelectric complex. C Coastlines Québec has two systems of saltwater coastline. O...

• Fungus - biology.

  Many fungi can reproduce by the fragmentation of their hyphae. Each fragment develops into a new individual. Yeast, a small, single-celled fungus, reproduces bybudding, in which a bump forms on the yeast cell, eventually partitioning from the cell and growing into a new yeast cell. V CLASSIFICATION OF FUNGI Scientists have long disagreed about how to classify fungi, and the classification systems are still developing. The first description of fungi was published in 1729 byItalian botanist Pier...

• 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...

• 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...

• Bear - biology.

  programs sponsored by zoos or other breeding centers have attempted to breed giant pandas in captivity, although most of these programs have proved unsuccessful.Among the difficulties faced by captive breeders has been the problem of encouraging a female giant panda to mate with a selected male during the two to three daysof the year when she is most fertile, a period known as estrus. B Spectacled Bear Creamy-white rings surrounding the eyes give the spectacled bear its name. Its shaggy coat of...

• 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...

• Environment.

  escape into space of the infrared energy radiated back out by Earth. This process is referred to as the greenhouse effect. These gases, primarily carbon dioxide,methane, nitrous oxide, and water vapor, insulate Earth’s surface, helping to maintain warm temperatures. Without these gases, Earth would be a frozen planet with anaverage temperature of about -18°C (about 0°F) instead of a comfortable 15°C (59°F). If the concentration of these gases rises, they trap more heat within theatmosphere, caus...

• Alabama (state) - geography.

  indentations along the coast are measured, the state’s shoreline is 977 km (607 mi) long. It includes the shores of Mobile Bay, an inlet 56 km (35 mi) long at the mouthof the Mobile River. Barrier beaches partly block the entrance to the bay, leaving narrow openings on either side of Dauphin Island. Dauphin and other islands alongAlabama’s coast west of Mobile Bay are separated from the mainland by Mississippi Sound. D Climate Alabama has a humid subtropical climate, with short, relatively mild...

• Alabama (state) - USA History.

  indentations along the coast are measured, the state’s shoreline is 977 km (607 mi) long. It includes the shores of Mobile Bay, an inlet 56 km (35 mi) long at the mouthof the Mobile River. Barrier beaches partly block the entrance to the bay, leaving narrow openings on either side of Dauphin Island. Dauphin and other islands alongAlabama’s coast west of Mobile Bay are separated from the mainland by Mississippi Sound. D Climate Alabama has a humid subtropical climate, with short, relatively mild...

• New Mexico - geography.

  New Mexico’s major river is the Río Grande, originating in southern Colorado, and flowing southward for 760 km (470 mi) through the state. Between the San LuisValley and Española Valley the river flows in a deep canyon known as the Río Grande Gorge; then, below White Rock Canyon, it flows through several valleys containingagricultural land. Most of the water of the Río Grande is used to irrigate these valleys. The Río Grande’s waterflow in New Mexico is extremely low. One of the major tributarie...

• New Mexico - USA History.

  New Mexico’s major river is the Río Grande, originating in southern Colorado, and flowing southward for 760 km (470 mi) through the state. Between the San LuisValley and Española Valley the river flows in a deep canyon known as the Río Grande Gorge; then, below White Rock Canyon, it flows through several valleys containingagricultural land. Most of the water of the Río Grande is used to irrigate these valleys. The Río Grande’s waterflow in New Mexico is extremely low. One of the major tributarie...

• Conservation.

  cancers, Hodgkin’s disease and leukemia. Unfortunately, human activities have greatly reduced biodiversity around the world. The 20th century encompasses one of the greatest waves of extinction, orelimination of species, to occur on the planet. The greatest threat to biodiversity is loss of habitat as humans develop land for agriculture, grazing livestock, industry,and habitation. The most drastic damage has occurred in the tropical rain forests, which cover less than seven percent of the Earth’...

• Lewis and Clark Expedition.

  took a small detachment into present-day north central Montana, thinking that the course of the Marias River might provide an American claim to fur-rich country inwhat is now the Canadian province of Alberta. In August the groups reunited on the Missouri River, near the mouth of the Yellowstone. They arrived in St. Louis onSeptember 23, 1806. C Relations with the Native Americans and Spanish The Lewis and Clark Expedition made a journey through the homelands of native people. What American expl...

• Lewis and Clark Expedition - explorer.

  took a small detachment into present-day north central Montana, thinking that the course of the Marias River might provide an American claim to fur-rich country inwhat is now the Canadian province of Alberta. In August the groups reunited on the Missouri River, near the mouth of the Yellowstone. They arrived in St. Louis onSeptember 23, 1806. C Relations with the Native Americans and Spanish The Lewis and Clark Expedition made a journey through the homelands of native people. What American expl...

• Pollination - biology.

  rapidly as in cross-pollination, because one plant with a beneficial gene can transmit it only to its own offspring and not to other plants. Self-pollination evolved laterthan cross-pollination, and may have developed as a survival mechanism in harsh environments where pollinators were scarce. IV POLLEN TRANSFER Unlike animals, plants are literally rooted to the spot, and so cannot move to combine sex cells from different plants; for this reason, species have evolved effectivestrategies for ac...

• Cobra (snake) - biology.

  Most cobras prey on small rodents or other small mammals. They also eat birds, snakes, lizards, frogs, toads, insects, and even eggs. Water cobras catch fish and kingcobras specialize in eating other snakes. Similar to other venomous snakes, cobras use venom to subdue their prey before swallowing it whole, generally head first. Thevenom may contain substances that also break down the prey for digestion. Despite their potent venom and dramatic threat displays, cobras are hunted and eaten by a num...

• Iowa - geography.

  Okoboji, Lost Island, Silver, and West Swan lakes. In addition, reservoirs have been created by damming several smaller Iowa rivers. There are a number of largereservoirs behind dams on the Mississippi River along the Iowa state line. C Climate Iowa’s climate is characterized by warm, generally moist summers and cold winters. Temperatures vary considerably from season to season and, at times, from day today. However, monthly averages are relatively uniform throughout the state and usually vary...

• Iowa - USA History.

  Okoboji, Lost Island, Silver, and West Swan lakes. In addition, reservoirs have been created by damming several smaller Iowa rivers. There are a number of largereservoirs behind dams on the Mississippi River along the Iowa state line. C Climate Iowa’s climate is characterized by warm, generally moist summers and cold winters. Temperatures vary considerably from season to season and, at times, from day today. However, monthly averages are relatively uniform throughout the state and usually vary...

• South Carolina - geography.

  (20° F) or lower, occur each winter. July temperatures average 27° C (80° F) in most of the state, with temperatures in the lower 20°s C (lower 70°s F) in themountains. Except in the mountains, summer daytime highs throughout South Carolina often enter the lower 30°s C (lower 90°s F). The temperature in July in Columbiaranges from 21° to 33° C (70° to 92° F). D2 Precipitation Central South Carolina has an average annual precipitation (both rainfall and snowfall) of 1,140 mm (45 in). Greater amo...

• South Carolina - USA History.

  (20° F) or lower, occur each winter. July temperatures average 27° C (80° F) in most of the state, with temperatures in the lower 20°s C (lower 70°s F) in themountains. Except in the mountains, summer daytime highs throughout South Carolina often enter the lower 30°s C (lower 90°s F). The temperature in July in Columbiaranges from 21° to 33° C (70° to 92° F). D2 Precipitation Central South Carolina has an average annual precipitation (both rainfall and snowfall) of 1,140 mm (45 in). Greater amo...

• Wolf - biology.

  VIII RED WOLF The red wolf is smaller than the gray wolf. An adult red wolf stands about 65 cm (about 2 ft) high at the shoulder, measures 100 to 130 cm (3 to 4 ft) in lengthexcluding the tail, and weighs 20 to 36 kg (45 to 80 lb). It has long legs and ears and its head is not as wide as that of the gray wolf. The coat of red wolves varies incolor from light tan to black with reddish head, ears, and legs. Scientists have debated whether the red wolf is a subspecies of the gray wolf, a separate...

• Turtle.

  Turtles use their jaws to cut and handle food. Instead of teeth, a turtle’s upper and lower jaws are covered by horny ridges, similar to a bird’s beak. Meat-eating turtlescommonly have knife-sharp ridges for slicing through their prey. Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants.Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food. C Limb Structu...

• Turtle - biology.

  Turtles use their jaws to cut and handle food. Instead of teeth, a turtle’s upper and lower jaws are covered by horny ridges, similar to a bird’s beak. Meat-eating turtlescommonly have knife-sharp ridges for slicing through their prey. Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants.Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food. C Limb Structu...

• Animal - biology.

  Vertebrates are customarily divided into cold-blooded and warm-blooded animals, but these labels are not very precise. Biologists normally use the terms ectoderm and endoderm to describe temperature regulation more accurately. An ectoderm is an animal whose temperature is dictated by its surroundings, while an endoderm is one that keeps its body at a constant warm temperature by generating internal heat. Reptiles, amphibians, and fish are ectoderms. Although they do not maintain a constant wa...

• Mammal - biology.

  On land, mammals live in many different habitats, and at a wide range of altitudes. Many mammals dig burrows as refuges or as places to raise their young, but somehave developed a largely subterranean lifestyle, feeding on small animals or plant roots beneath the soil's surface. These animals, including moles and mole-rats, digthrough the ground either with spadelike front paws or with their teeth, and they detect danger by being highly sensitive to vibrations transmitted through the soil.Most m...

• National Parks and Preserves.

  Some ibex raised in Italy’s 700 sq km (220 sq mi) Gran Paradiso National Park (1922) were transferred to aid herd restoration elsewhere in the country. Switzerlandreturned lynx to Swiss National Park to keep red deer populations in check. The growth of national parks also enabled many European countries to restore forests thathad given way to industrialization by the early 20th century. Africa’s wildlife was hunted heavily from the late 19th century well into the 20th century. By 1920 big-game h...

• Honey Bee - biology.

  B Reproduction and Development The queen controls the sex of her offspring. When an egg passes from her ovary to her oviduct, the queen determines whether the egg is fertilized with sperm from thespermatheca. A fertilized egg develops into a female honey bee, either worker or queen, and an unfertilized egg becomes a male honey bee, or drone. The queen lays the eggs that will develop into more queens in specially constructed downward-pointing, peanut-shaped cells, in which the egg adheres to the...

• Australia - country.

  itself forms most of the border between New South Wales and Victoria. Considerable lengths of the Murray, Darling, and Murrumbidgee rivers are navigable during thewet seasons. The central plains region, also known as the Channel Country, is interlaced by a network of rivers. During the rainy season these rivers flood the low-lying countryside,but in dry months they become merely a series of water holes. The Victoria, Daly, and Roper rivers drain a section of the Northern Territory. In Queensland...

• Australia - Geography.

  itself forms most of the border between New South Wales and Victoria. Considerable lengths of the Murray, Darling, and Murrumbidgee rivers are navigable during thewet seasons. The central plains region, also known as the Channel Country, is interlaced by a network of rivers. During the rainy season these rivers flood the low-lying countryside,but in dry months they become merely a series of water holes. The Victoria, Daly, and Roper rivers drain a section of the Northern Territory. In Queensland...

• 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...

• Great White Shark - biology.

  The great white shark is a rare species that takes long to reach sexual maturity and that reproduces slowly. Populations cannot easily increase if depleted. The biggestthreat to great whites comes from being unintentionally caught in fishing nets. Some targeted fisheries and sport fishing for great white sharks also occur. Trade ingreat white shark products includes the jaws (which can sell for thousands of dollars as curios), individual teeth, and leather from its skin. Fins from all sharks, in...

• 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...

• Indiana - geography.

  Michigan in Michigan. There are about 1,000 small natural lakes in Indiana, chiefly in the northern part of the state. The largest is Lake Wawasee, which covers almost 13 sq km (5 sq mi). Inthe central part of the state there are several lakes that were created behind dams on a number of smaller streams. They include Monroe Lake, near Bloomington; Geistand Eagle Creek reservoirs, northeast and northwest of Indianapolis; and Mississinewa and Huntington reservoirs, north of Marion. C Climate Most...

• Indiana - USA History.

  Michigan in Michigan. There are about 1,000 small natural lakes in Indiana, chiefly in the northern part of the state. The largest is Lake Wawasee, which covers almost 13 sq km (5 sq mi). Inthe central part of the state there are several lakes that were created behind dams on a number of smaller streams. They include Monroe Lake, near Bloomington; Geistand Eagle Creek reservoirs, northeast and northwest of Indianapolis; and Mississinewa and Huntington reservoirs, north of Marion. C Climate Most...

• Duck - biology.

  from water. When ducks feed they push their tongue against the top of their mouth to squeeze water through the lamellae, leaving the food behind. Mergansers arefish-eating ducks with slender bills that are notched on the edges like the blade of a saw. These saw-toothed beaks help the ducks catch and hold their slippery prey. VI COURTSHIP AND REPRODUCTION Ducks form pairs long enough to mate, but most species find new mates each year. In a few species, including buffleheads and whistling ducks,...

• Stone Age.

  limestone, quartzite, and indurated shale. Ground stone tools could be made on a wider range of raw material types, including coarser grained rock such as granite. Flaking produces several different types of stone artifacts, which archaeologists look for at prehistoric sites. The parent pieces of rock from which chips have beendetached are called cores, and the chips that have been removed from cores are called flakes. A flake that has had yet smaller flakes removed from one or more edgesin orde...

• Arctic - Geography.

  The Arctic is not a frozen desert devoid of life on land or sea, even during the cold, dark winter months. Spring brings a phenomenal resurgence of plant and animal life.Low temperatures are not always the critical element—moisture, the type of soil, and available solar energy are also extremely important. Some animals adapt well toArctic conditions; for instance, a number of species of mammals and birds carry additional insulation, such as fat, in cold months. Arctic summers with extended dayli...

• Arkansas - geography.

  temperature rises to the upper 30°s C (lower 100°s F). C2 Precipitation Arkansas receives about 1,000 to 1,300 mm (about 40 to 50 in) of precipitation a year, and some areas receive even more. Most of the rain comes during winter andspring and at times is so heavy as to cause flooding. Snow is rare in the south but amounts to more than 250 mm (10 in) a year in the mountains. C3 Growing Season Arkansas has a long growing season. It averages 211 days for the state as a whole and ranges from 241...

• Arkansas - USA History.

  temperature rises to the upper 30°s C (lower 100°s F). C2 Precipitation Arkansas receives about 1,000 to 1,300 mm (about 40 to 50 in) of precipitation a year, and some areas receive even more. Most of the rain comes during winter andspring and at times is so heavy as to cause flooding. Snow is rare in the south but amounts to more than 250 mm (10 in) a year in the mountains. C3 Growing Season Arkansas has a long growing season. It averages 211 days for the state as a whole and ranges from 241...

• South Korea - country.

  forest habitat, and overhunting. The Siberian tiger has not been sighted in the wild in South Korea since the 1920s; the Asiatic black bear can still be found in someremote mountain areas. Several species of deer are indigenous to the peninsula, including the roe deer, water deer, and Siberian musk deer. The musk deer, which hasbeen overhunted for its musk glands, is legally protected as a threatened species. Smaller mammals indigenous to the peninsula include the wild boar, red fox, badger,rabb...

• Colombia - country.

  In Bogotá the average high temperature in January is 20°C (68°F), and in July the average high is 19°C (65°F). The highs for the same months in Barranquilla are 32°C(89°F) and 33°C (91°F). Throughout the year, three-month periods of rain and dry weather alternate. Along the Pacific coast precipitation is heavy. At Bogotá the annual rainfall averages about1,060 mm (about 42 in), and in Barranquilla it averages about 800 mm (about 32 in). Dry weather prevails on the slopes of the Cordillera Orient...

• South Africa - country.

  The major soil zones are conditioned largely by climatic factors. In the semiarid north and west, soils are alkaline and poorly developed. In the southern part of WesternCape Province, rain falls mostly in the winter months, and soils there form slowly and are generally thin and immature. The moderate temperatures and summer rainfallof the High Veld and eastern coastal areas create conditions for more productive organic decomposition, leading to dark, fertile soils, or chernozems, similar to tho...

• West Virginia - geography.

  Forests, mostly of hardwood varieties, cover 79 percent of West Virginia. The principal commercial species are the oak, yellow poplar, maple, birch, beech, black walnut,hickory, and gum. Softwoods include pines and hemlock firs. Flowering trees include the wild crab apple, dogwood, hawthorn, and redbud. Among the many floweringbushes and plants are the rhododendron, which is the state flower, the laurel, blueberry, hepatica, wild geranium, and black-eyed Susan. Insects and disease, mostly introd...

• West Virginia - USA History.

  Forests, mostly of hardwood varieties, cover 79 percent of West Virginia. The principal commercial species are the oak, yellow poplar, maple, birch, beech, black walnut,hickory, and gum. Softwoods include pines and hemlock firs. Flowering trees include the wild crab apple, dogwood, hawthorn, and redbud. Among the many floweringbushes and plants are the rhododendron, which is the state flower, the laurel, blueberry, hepatica, wild geranium, and black-eyed Susan. Insects and disease, mostly introd...