46 résultats pour "tails"

• Comet - astronomy.

  may exceed the planet Jupiter in size, however. Observations from telescopes on Earth and in space indicate that most of the gases in the coma and tail of a comet are fragmentary molecules, or radicals, of the mostcommon elements in space: hydrogen, carbon, nitrogen, and oxygen. The radicals, for example, of CH, NH, and OH may be broken away from the stable molecules CH 4 (methane), NH 3 (ammonia), and H 2O (water), which may exist as ices or more complex, very cold compounds in the nucleus. Al...

• Bird. I INTRODUCTION Bird, animal with feathers and wings. Birds are the only

  B Physical Adaptations for Flight The internal body parts of all birds, including flightless ones, reflect the evolution of birds as flying creatures. Birds have lightweight skeletons in which many of themajor bones are hollow. A unique feature of birds is the furculum, or wishbone, which is comparable to the collarbones of humans, although in birds the left and rightportions are fused together. The furculum absorbs the shock of wing motion and acts as a spring to help birds breathe while they...

• Bird - biology.

  B Physical Adaptations for Flight The internal body parts of all birds, including flightless ones, reflect the evolution of birds as flying creatures. Birds have lightweight skeletons in which many of themajor bones are hollow. A unique feature of birds is the furculum, or wishbone, which is comparable to the collarbones of humans, although in birds the left and rightportions are fused together. The furculum absorbs the shock of wing motion and acts as a spring to help birds breathe while they...

• Airplane.

  For example, the Anglo-French Concorde, a commercial supersonic aircraft, was generally limited to over-water routes, or to those over sparsely populated regions ofthe world. This limitation impacted the commercial viability of the Concorde, which ended its regular passenger service in October 2003. Designers today believe theycan help lessen the impact of sonic booms created by supersonic airliners but probably cannot eliminate them. One of the most difficult practical barriers to supersonic fl...

• 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...

• 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...

• 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....

• Elephant - biology.

  B Trunk An elephant's nose and upper lip are combined in a long, limber trunk, an exceptionally supple appendage with an estimated 150,000 muscles. The versatile trunk actslike a hand for grasping low-growing shrubs and other food and placing it into the mouth; an arm for breaking off tree branches; or a snorkel for breathing when theelephant's body is submerged. Elephants also use their trunks to suck up water and squirt it into their mouths for drinking or over their bodies for bathing. Nostr...

• 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...

• 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...

• Dinosaur - biology.

  The behavior of dinosaurs was governed by their metabolism and by their central nervous system. The dinosaurs’ metabolism—the internal activities that supply thebody’s energy needs—affected their activity level. It is unclear whether dinosaurs were purely endothermic (warm-blooded), like modern mammals, or ectothermic (cold-blooded), like modern reptiles. Endotherms regulate their body temperature internally by means of their metabolism, rather than by using the temperature oftheir surroundin...

• Raccoon Raccoons are meat-eating mammals with long fur and bushy tails.

• Ulysses (spacecraft) - astronomy.

  Ulysses was also used to study comet Hale-Bopp, which was first seen in 1995. Hale-Bopp travels an unusual path at a large angle to the ecliptic, and the trajectory ofUlysses was well suited to capture images of Hale-Bopp as it made its way around the Sun. Astronomers paid particular attention to Hale-Bopp’s plasma tail—a plume ofionized, or electrically charged, gas within the main tail that streams away from the comet when it approaches within about 1.5 AU from the Sun. They found that theplas...

• Lemurs Lemurs are primates with long noses, large ears, and long tails.

• Animal Courtship and Mating - biology.

  activity. These animals frequently copulate in water, and the penis helps transfer sperm before it is carried away by the currents Ostriches and rheas also contain apenis within the cloaca. Virtually all snakes and lizards display yet another variation of internal fertilization. Located in the tail are two penises, called hemepenes, which are covered by spinesand knobs that help lock it into place during mating. The male uses one hemepene at a time for copulation. Male salamanders secrete large...

• Dog. I INTRODUCTION Dog, mammal generally considered to be the first domesticated animal.

  French word for butterfly because it has ears that resemble butterfly wings, is a happy, friendly dog, suitable for small living spaces. The final dog group, nonsporting ,includes a wide variety of purebreds that differ in size, coat, overall appearance, and personality, from the shorthaired spotted dalmatian to the curly-haired poodle. V DOG BEHAVIOR Instinctive behaviors of the domestic dog are comparable to those of its wild relatives, the wolf, coyote, fox, and jackal. Unlike trained behavi...

• Dog - biology.

  French word for butterfly because it has ears that resemble butterfly wings, is a happy, friendly dog, suitable for small living spaces. The final dog group, nonsporting ,includes a wide variety of purebreds that differ in size, coat, overall appearance, and personality, from the shorthaired spotted dalmatian to the curly-haired poodle. V DOG BEHAVIOR Instinctive behaviors of the domestic dog are comparable to those of its wild relatives, the wolf, coyote, fox, and jackal. Unlike trained behavi...

• Skiing.

  Safety is very important to all skiers, and all Alpine resorts have a ski patrol. The ski patrol’s responsibility is to take care of injured skiers, to mark hazardous spots ontrails, to make sure that trails are in good condition before opening them, and, at times, to act as traffic police in congested areas. Skiers are also responsible for takingtheir own safety into consideration, as well as that of others. Anyone who participates in the sport should be aware of the Skier’s Responsibility Code...

• Chimera (She-Goat) Greek A fire-breathing monster with a lion's head, a goat's body, and a serpent's tail; the offspring of the monsters Echidna and Typhon.

• Helicopter.

  naturally flaps down so as to increase lift. Flapping allows the differences in lift caused by uneven rotor tip speed to cancel out, producing a stable ride. Many helicoptersuse mechanical hinges with lubricated bearings, but some use flexible straps made of a composite material in order to reduce the required maintenance. Helicopters require different amounts of lift and thrust at different times during flight, because the aerodynamic forces acting on them change during hovering andacceleration...

• Connecticut Yankee - anthology.

  This missionary knight's name was La Cote Male Taile, and he said that this castle was the abode of Morgan le Fay, sister of King Arthur, and wife of King Uriens,monarch of a realm about as big as the District of Columbia—you could stand in the middle of it and throw bricks into the next kingdom. “Kings” and “Kingdoms”were as thick in Britain as they had been in little Palestine in Joshua's time, when people had to sleep with their knees pulled up because they couldn't stretch outwithout a passp...

• Zebra - biology.

  C Life Span Captive zebras have lived into their late 30s. Life expectancy in the wild, where predators abound, is probably not much more than 12 years. IV SOCIAL BEHAVIOR Like horses, zebras have large brains and a wide variety of social behaviors. Although they cannot match the overall intelligence of mammals that hunt, zebras interactwith each other in complex ways. Zebras usually live in groups known as herds, but the social structure of these groups depends on the species. The plains zeb...

• Frog (animal).

  which means that their body temperature depends on the temperature of the surrounding environment. Few species can tolerate temperatures below 4°C (40°F) orabove 40°C (104°F), and many species can survive only within a narrower range of temperatures. In addition, frogs’ thin, moist skin offers little protection againstwater loss, and when on land the animals must guard against drying out. Many frogs are active at night because temperatures are cooler and humidity is higher thanduring the day. In...

• Frog (animal) - biology.

  which means that their body temperature depends on the temperature of the surrounding environment. Few species can tolerate temperatures below 4°C (40°F) orabove 40°C (104°F), and many species can survive only within a narrower range of temperatures. In addition, frogs’ thin, moist skin offers little protection againstwater loss, and when on land the animals must guard against drying out. Many frogs are active at night because temperatures are cooler and humidity is higher thanduring the day. In...

• Solar System - astronomy.

  dwarf planets according to the IAU because they have rounded shapes from their own gravity but have not cleared their neighborhoods in space of other objects—bothorbit through the Kuiper Belt, a region beyond Neptune containing thousands of small icy bodies. Pluto and Eris are composed of layers of ice around a rocky core.Ceres qualifies as a dwarf planet because it is spherical but is found in the asteroid belt, a zone between the orbits of Mars and Jupiter that contains thousands of smallrocky...

• 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,...

• Bat - biology.

  tomb bat has rather small ears. The shapes of bat ears are extremely varied. The wide ears of the Australian false vampire bat meet above the head and are fused.Many bats are able to turn their ears in the direction of faint noises. Bat hearing and its use in echolocation are highly developed. Some bats have large, conspicuous eyes, while others may have small beady eyes. This variation suggests that vision plays different roles in the lives of various species.Despite the familiar expression, 'b...

• Horse - biology.

  Horses reach sexual maturity at about one and a half years. The estrous cycle in the mare—a mature female horse—typically lasts 21 days. During the first five days ofthe cycle, the mare is usually receptive to mating. The estrous cycle stops during winter and resumes in the spring, which is the start of the breeding season. Astallion—a mature male horse—approaching a mare in estrus engages in various courtship rituals. These include uttering nickering sounds and sniffing and licking themare’s ge...

• Cat Family - biology.

  cats have coats that are mainly brown, yellow, or gray, often with white underbellies. The cubs of many species of cats have spotted coats, which helps hide them ingrass and underbrush from predators. Adult cats that have mainly spotted patterns in their fur include cheetahs, leopards, clouded leopards, jaguars, ocelots, margays, Geoffroy’s cat, and servals. Singlecolor coats are found in lions, pumas, and jaguarundis. Some individuals among leopards and jaguars, and more rarely in other species...

• 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...

• Skateboarding.

  The earliest skateboards first appeared in the 1940s and 1950s. Many of the early boards were toy scooters whose handlebars had been removed. Other homemadeskateboards were steel-wheeled roller skates nailed onto a piece of wood. The first commercially produced skateboards appeared in the early 1960s, when MakahaSkateboards established a successful business. The Makaha company later developed the tail. By the 1970s, skateboard design had advanced, and the models produced were much safer than tho...

• 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...

• Kangaroo - biology.

  ungulates, they have evolved multi-chambered stomachs containing bacteria that can break down plant cell walls and release the nutritious cell contents. V SOCIAL ORGANIZATION Kangaroo social life is poorly understood, as few species have been studied in detail. Small species, such as potoroos, bettongs, and musky rat-kangaroos, tend to besolitary and widely dispersed, with a male's territory encompassing those of several females. The animals come together briefly for mating, and mother and offs...

• Dog Family - biology.

  muzzles, long and bushy tails, and large ears. Many foxes hunt by stalking prey and then leaping on it with a distinctive, stiff-legged pounce. Once thought to besolitary animals, foxes are now known to live in groups of up to six individuals. The remaining canids are each highly distinctive. Raccoon dogs and bush dogs are the least doglike canids in appearance. Raccoon dogs, found in eastern Asia, havestubby legs, a stout body, short ears, shaggy fur, and a black face mask that resembles a racc...

• Embryology - biology.

  stage a portion of the minute yolk sac is enclosed in the body of the embryo to form a part of the embryonic alimentary canal. At the beginning of its fourth week theembryo, now about 4 to 5 mm (about 0.16 to 0.2 in) long, has the rudiments of eyes and ears, and each side of the neck shows four gill clefts. A tail is also present. Early in the second month the buds of the arms and legs appear. The major internal organs begin to take shape, and in about the sixth week bones and muscles beginto fo...

• Steven Spielberg I INTRODUCTION Steven Spielberg The imaginative films of Steven Spielberg are known for their technical creativity and memorable characters.

  Courtesy of Everett Collection Spielberg teamed up with writer-producer George Lucas in the 1980s to make the action-adventure Indiana Jones film series: Raiders of the Lost Ark (1981), Indiana Jones and the Temple of Doom (1984), and Indiana Jones and the Last Crusade (1989). Other directorial projects during this period included the science-fiction fantasy E.T.—The Extra-Terrestrial , at the time the highest-grossing film ever made; The Color Purple (1985), a drama based on the novel...

• From Bulfinch's Mythology: Bacchus (Dionysus) - anthology.

  me their fishing rods and nets and their fisherman's trade. This I followed for some time, till growing weary of remaining in one place, I learned the pilot's art and howto guide my course by the stars. It happened as I was sailing for Delos we touched at the island of Dia and went ashore. Next morning I sent the men for fresh water,and myself mounted the hill to observe the wind; when my men returned bringing with them a prize, as they thought, a boy of delicate appearance, whom they hadfound a...

• Fish - biology.

  pectoral fins provide fine movements, add forward thrust, or, together with the pelvic fins, serve as brakes. Typically, fins consist of a thin membrane stretched over afanlike series of thin rods called spines or rays. Most fish breathe underwater with the help of special respiratory organs called gills. Gills are made of a series of thin sheets or filaments through which blood circulates.As water moves into a fish’s mouth and passes over the gills, dissolved oxygen passes across the thin gill...

• 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...

• 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...

• Lizards.

• Hippopotamus - biology.

  hippo backs up to its droppings and uses its tail as a paddle, flicking the dung through the air. This creates a pile that can become several meters wide over time. Male river hippos start to establish territories when they are in their early 20s, and they may eventually control more than 250 m (820 ft) of the water's edge.Subordinate males come and go freely, but a rival male will spark a confrontation if it tries to intrude. The territory owner and intruder face each other open-mouthedand, if...

• Excerpt from A Christmas Carol - anthology.

  External heat and cold had little influence on Scrooge. No warmth could warm, no wintry weather chill him. No wind that blew was bitterer than he, no falling snowwas more intent upon its purpose, no pelting rain less open to entreaty. Foul weather didn’t know where to have him. The heaviest rain, and snow, and hail, and sleet,could boast of the advantage over him in only one respect. They often “came down” handsomely and Scrooge never did. Nobody ever stopped him in the street to say, with g...

• Monkey (animal) - biology.

  traveling in troops, often take turns acting as sentinel, making specific alarm calls to alert their companions to approaching danger. In trees, monkeys have other waysof outwitting their enemies. Capuchins, for example, sometimes fend off inquisitive predators by urinating on them from high above or by jumping up and down tomake dead branches fall on the predators. Most monkeys can breed at any time of the year, so their troops often contain young of many different ages. Courtship is typically...

• Tiger - biology.

  have a simple digestive system designed to process meat so that the nutrients can be readily absorbed into the bloodstream. With the exception of white tigers, which have blue eyes, all tigers have yellow eyes. Tigers mainly use vision to find prey. Although tigers see about as well as humansduring the day, their large eye openings gather more light than do human eyes, making tiger night vision far superior to that of humans. In addition, a special structurein the tiger’s eye, called the tapetu...