102 résultats pour "mammals"

• 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...

• Seal (mammal) - biology.

  remote lakes by swimming thousands of kilometers up rivers from the Arctic Ocean. A few other species such as ringed seals and harbor seals have been found livingyear-round in lakes and rivers near the coasts of Russia, Canada, and Alaska. IV DIET OF SEALS Most seals eat fish and sometimes squid. The leopard seal, an Antarctic species, may have the most diverse diet of all, commonly hunting penguins and other seabirds,smaller seals, as well as fish, squid, krill (small shrimplike crustaceans),...

• Dolphin (aquatic mammal) - biology.

  Scientists have observed dolphins displaying three types of caregiving behaviors: standing by, excitement, and supporting. In standing-by behavior, dolphins remain inthe vicinity of an injured or ill companion without offering aid. In excitement behavior, dolphins swim swiftly in circles around an injured dolphin, responding aggressivelytoward threats to the injured animal. For instance, they may bite harpoon lines or charge boats that come too close to the animal. In supporting behavior, one or...

• 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...

• Reproductive System.

  in which the young develop, and a thinner channel, the vagina, which opens exteriorly. V GENITALS In animals that lay their eggs and discharge their sperm into water, the spermatozoa reach the eggs by chemical attraction; the eggs of individuals of a species attractonly the sperm of members of the same species. When eggs and sperm are deposited at great distances from each other, the number of eggs fertilized is small. Manyamphibians and aquatic vertebrates solve this problem by attaching thems...

• Camel - biology.

  of water in the stomach or hump as was once commonly believed. Unlike other mammals, however, the camel can survive as long as three weeks without drinking,depending on the water content of its food. It can survive a water loss of about 40 percent of its normal body weight. In comparison, a loss of 15 percent is usually fatalfor humans. Camels can go without water due to several unique adaptations to their environment. The camel conserves more water in its body than any other mammal. It excretes...

• Rain Forest.

  dropped into the heart of the forest by helicopters. Suspended from the crane’s long, movable arm is a large gondola that functions as a mobile treetop laboratory.Moving from tree to tree, forest researchers collect specimens, conduct experiments, and observe life in the canopy frontier. The highest stratum of the rain forest is made up of the emergent trees, those individuals that stick up above the forest canopy. Emergents, which do not form acontinuous layer, are usually the giants of the for...

• 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...

• Primate - biology.

  The primate order includes a handful of species that live entirely on meat (carnivores) and also a few that are strict vegetarians (herbivores), but it is composed chieflyof animals that have varied diets (omnivores). The carnivorous primates are the four species of tarsiers, which live in Southeast Asia. Using their long back legs, thesepocket-sized nocturnal hunters leap on their prey, pinning it down with their hands and then killing it with their needle-sharp teeth. Tarsiers primarily eat in...

• 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...

• 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...

• Extinction (biology) - biology.

  III ROLE OF MASS EXTINCTION IN EVOLUTION Historically biologists—most famous among them British naturalist Charles Darwin—assumed that extinction is the natural outcome of competition between newlyevolved, adaptively superior species and their older, more primitive ancestors. These scientists believed that newer, more highly evolved species simply drove less well-adapted species to extinction. That is, historically, extinction was thought to result from evolution. It was also thought that this...

• 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...

• 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...

• 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...

• 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...

• Endangered Species - biology.

  Red List database assesses the status of, and threats to, animal species worldwide. To add to this and other biodiversity databases, nongovernmental organizationssuch as Conservation International and World Wildlife Fund conduct periodic rapid assessments (focused, intensive evaluations) of biodiversity in varioushotspots— regions like Madagascar that are both rich in endemic species and environmentally threatened. This information is used in the administration of international agreements such...

• Killer Whale - biology.

  V REPRODUCTION Mating occurs more often among killer whales of different pods to avoid inbreeding within pods. About 16 to 18 months after mating, females give birth to a single calf.Newborn calves weigh about 200 kg (440 lb) and are about 2.5 m (8 ft) long. Mothers nurse their calf for 14 to 18 months, although mothers continue to be protectiveof their young long after the offspring have been weaned. Scientists do not know how long killer whales live in the wild. Scientists estimate that male...

• 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...

• Ear. I INTRODUCTION Ear, organ of hearing and balance. Only vertebrates, or animals

  line or rotates in any direction. Each canal also contains sensory areas with sensory hair cells that project into a cone-shaped cap of gelatin. Two of the semicircularcanals are in a vertical position and are used to detect vertical movement, such as jumping or falling. The third canal is horizontal and detects horizontal movement,such as turning or spinning. The action of the canals depends on the inertia of the fluid inside. When the motion of the body changes, the fluid lags behind, causing...

• 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...

• Giraffe - biology.

  One of the most striking elements of giraffe behavior is the duel between males fighting for mating privileges. Giraffe duels are among the most extraordinary in theanimal kingdom. They start when two males approach each other and begin to rub and intertwine their necks. This behavior—known as necking—allows the opponentsto assess each other’s size and strength. Often, necking alone is enough to establish seniority. If not, the rivals begin to exchange blows with their heads. Each giraffebraces...

• Animals.

  All animals must breathe oxygen to stay alive. They must breathe out a waste gas called carbon dioxide. Some animals breathe through lungs. Lungs take oxygen out of air. Cattle, dogs, cats, whales, people,and other mammals breathe through lungs. Birds and reptiles also breathe air through lungs. Lungs cannot take air from water. Seals, whales, dolphins, and other mammals that live in waterbreathe through lungs. They can stay underwater a long time because they can hold their breath for along tim...

• 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...

• Oregon - geography.

  B Rivers and Lakes The Columbia River forms most of the Oregon-Washington boundary, and with its tributaries this great river drains a large portion of Oregon. From the point where theColumbia first touches the state, at Wallula Gap, the river runs in a shallow gorge, deepening as it approaches the Cascades. This part of the river once had manyrapids and falls, but is now navigable by large vessels because of dams and locks that have been built along much of its length. An important tributary o...

• Oregon - USA History.

  B Rivers and Lakes The Columbia River forms most of the Oregon-Washington boundary, and with its tributaries this great river drains a large portion of Oregon. From the point where theColumbia first touches the state, at Wallula Gap, the river runs in a shallow gorge, deepening as it approaches the Cascades. This part of the river once had manyrapids and falls, but is now navigable by large vessels because of dams and locks that have been built along much of its length. An important tributary o...

• Antelopes Antelopes are mammals with hooves and hollow horns.

• Deer Deer are mammals with branched horns called antlers.

• Aardvark Aardvarks are mammals with long snouts that live in Africa.

• Bison American bison, also known as buffalo, are large, grass-eating mammals.

• Hedgehog Hedgehogs are mammals with long, pointed spines and soft, furry bellies.

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

• Sloth The sloth is a slow-moving mammal found in Central and South America.

• Ferret The ferret is a small mammal with short legs and a long, slim body.

• 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...

• Tennessee (state) - geography.

  The climate of Tennessee is characterized by hot summers, mild winters, and abundant rainfall. C1 Temperature Average July temperatures range from less than 21° C (70° F) in the Blue Ridge region to 27° C (80° F) at Nashville and Memphis. Maximum daytime temperatures insummer often rise above 35° C (95° F) in central and western Tennessee. Daytime temperatures in the mountains rarely rise above 32° C (90° F). Summer nights tendto be warm and muggy in central and western Tennessee, but temperatu...

• Tennessee (state) - USA History.

  The climate of Tennessee is characterized by hot summers, mild winters, and abundant rainfall. C1 Temperature Average July temperatures range from less than 21° C (70° F) in the Blue Ridge region to 27° C (80° F) at Nashville and Memphis. Maximum daytime temperatures insummer often rise above 35° C (95° F) in central and western Tennessee. Daytime temperatures in the mountains rarely rise above 32° C (90° F). Summer nights tendto be warm and muggy in central and western Tennessee, but temperatu...

• Shark - biology.

  Sharks have two-chambered hearts that are relatively small compared to the rest of their bodies. Blood flows from the heart to the gills, where it collects oxygen fromwater and then distributes it to the other organs and tissues. The small heart produces weak blood pressure, and many sharks must swim continuously to create themuscular contractions needed to circulate blood throughout their bodies. Most sharks are cold-blooded—that is, they do not generate heat by digesting food. Instead, the bod...

• Washington (state) - geography.

  The crest of the Cascade Range divides Washington into two distinct climatic regions. The area west of the Cascades, which is exposed throughout the year to rain-bearing winds from the Pacific Ocean, has a temperate marine type of climate that is characterized by mild wet winters and cool summers. The Cascades prevent themoist air blowing in from the Pacific from reaching eastern Washington. The Rocky Mountains on the eastern border also represent a climatic barrier. As a result, thesevere winte...

• Washington (state) - USA History.

  The crest of the Cascade Range divides Washington into two distinct climatic regions. The area west of the Cascades, which is exposed throughout the year to rain-bearing winds from the Pacific Ocean, has a temperate marine type of climate that is characterized by mild wet winters and cool summers. The Cascades prevent themoist air blowing in from the Pacific from reaching eastern Washington. The Rocky Mountains on the eastern border also represent a climatic barrier. As a result, thesevere winte...

• Utah - geography.

  Temperatures decrease from the south to the north in the state. In the mountains the average temperature drops about 0.5°C (about 1°F) for every about 300 m(about 1,000 ft) rise in elevation. Average July temperatures range from less than 16°C (60°F) in the mountains to more than 27°C (80°F) in a few locations insouthern Utah. At Salt Lake City average July temperatures range from a low of 18°C (64°F) to a high of 33°C (92°F). There is a great variation between daytime andnighttime temperatures,...

• Utah - USA History.

  Temperatures decrease from the south to the north in the state. In the mountains the average temperature drops about 0.5°C (about 1°F) for every about 300 m(about 1,000 ft) rise in elevation. Average July temperatures range from less than 16°C (60°F) in the mountains to more than 27°C (80°F) in a few locations insouthern Utah. At Salt Lake City average July temperatures range from a low of 18°C (64°F) to a high of 33°C (92°F). There is a great variation between daytime andnighttime temperatures,...

• British Columbia - Geography.

  hemlock, Douglas fir, Sitka spruce, and various cedars, grows rapidly in the mild, wet climate and produces the largest trees in Canada. In the dry lowlands of thesouthern and central interior, ponderosa and lodgepole pines, aspen, and bunchgrass are characteristic. Spruce dominates the Prince George region. Prairie grasses andstands of aspen are found in the northeastern corner of the province. At elevations higher than about 1,800 m (about 6,000 ft), an alpine vegetation of shrubs, mosses,and...

• British Columbia - Canadian History.

  hemlock, Douglas fir, Sitka spruce, and various cedars, grows rapidly in the mild, wet climate and produces the largest trees in Canada. In the dry lowlands of thesouthern and central interior, ponderosa and lodgepole pines, aspen, and bunchgrass are characteristic. Spruce dominates the Prince George region. Prairie grasses andstands of aspen are found in the northeastern corner of the province. At elevations higher than about 1,800 m (about 6,000 ft), an alpine vegetation of shrubs, mosses,and...

• Mole Moles are small mammals with large claws that spend most of their time underground.

• 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...

• 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...

• Virginia (state) - geography.

  C Coastline Virginia’s coastline, for both the mainland and the Eastern Shore counties, is 180 km (112 mi) long. The state’s tidal shoreline measures 5,335 km (3,315 mi), includingall bays, inlets, tidal estuaries, and other indentations. Major indentations include Chesapeake Bay; Hampton Roads, the excellent natural harbor on which are locatedNewport News, Norfolk, and Portsmouth; and the wide tidal estuaries of the lower Potomac, James, Rappahannock, and York rivers. Cape Henry, in the southe...

• Virginia (state) - USA History.

  C Coastline Virginia’s coastline, for both the mainland and the Eastern Shore counties, is 180 km (112 mi) long. The state’s tidal shoreline measures 5,335 km (3,315 mi), includingall bays, inlets, tidal estuaries, and other indentations. Major indentations include Chesapeake Bay; Hampton Roads, the excellent natural harbor on which are locatedNewport News, Norfolk, and Portsmouth; and the wide tidal estuaries of the lower Potomac, James, Rappahannock, and York rivers. Cape Henry, in the southe...

• 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...