Arctic Survivors
The Arctic is an area located at the northernmost part of the Earth and includes the Arctic Ocean, Canada, Russia, Greenland, the United States, Norway, Sweden, Finland and Iceland. It consists of an ice-covered ocean, surrounded by treeless permafrost. The area can be defined as north of the Arctic Circle, the approximate limit of the midnight sun and the polar night. The average temperature in July, which is the warmest month, is below 10°C. Colder summer temperatures cause the size, abundance, productivity and variety of plants to decrease. Trees cannot grow in the Arctic, but in its warmest parts, shrubs are common and can reach 2 metres in height.
A thick blanket of snow lies several feet deep all over the ground. The sun appears for only a few brief hours each day before sinking below the horizon as blackness cloaks the land. As it vanishes, a bitter chill tightens its grip. The Arctic is not a place to be in the throes of winter; it is hostile to almost all animal life. Amphibians would freeze solid here. Nor can reptiles withstand the extreme cold. And yet there are animals here, animals that exhibit a remarkable tolerance of the most inhospitable conditions on the planet.
Less than half a metre beneath the surface of the snow, a furry white creature, no bigger than a hamster, scurries along a tunnel. It is a collared lemming. It and other members of its family have excavated a complex home within the snow field, but it costs the lemmings a great deal to survive here. They pay by using some of their precious and scarce food supply to generate heat within their bodies so that their biochemical processes can continue to function efficiently. But in order to keep fuel costs to a minimum, they must conserve as much energy as they can. A thick insulating coat of fine fur covering all but the lemmings’ eyes achieves this. Fur is the life preserver of the Arctic.
Only one class of animals has fur – the mammals. Fur is comprised of dense layers of hair follicles. Hair is composed of a substance called keratin. It grows constantly, its roots embedded in the skin and surrounded by nerve fibres so that its owner can sense any movement of the hair. It is this precious fur that gives land mammals the edge necessary to survive the harsh Arctic winter. Without it, wolves, lemmings and arctic foxes alike would surely perish.
The insulation provided by fur comes not from the fur itself, but largely from the layer of air trapped within the fur. Air is an extremely effective insulator, which is the same as saying it is a poor conductor, i.e. it has a very limited ability to conduct heat away from a warm surface. Studies reveal that if a layer of air of about five centimetres could be held in place close to the skin, it would provide the same insulation as does the impressively dense winter coat of the arctic fox. If an arctic fox or wolf is exposed to an air temperature of about minus ten degrees, the temperature near the tips of the fur will match the air temperature, but at the surface of the skin it will be closer to thirty degrees. This represents a temperature difference of around forty degrees. Such effective insulation is only made possible by the layer of trapped air contained within the long, fine and densely packed fur.
But Arctic mammals have more in their arsenal than just fur to protect them from the elements. Unlike amphibians, reptiles and other classes of animals, they are endotherms, meaning they can generate their own body heat. This is another of the defining characteristics of mammals. It is the mammalian ability to generate heat internally that enables the arctic fox or the lemming to remain warm and active in very cold conditions. Generating heat internally, Arctic mammals can regulate their body temperature independent of external conditions; this is known as thermoregulation. When Arctic mammals are cold, they raise their metabolic rate and produce more heat. When they are warm, the reverse happens. Together, thermoregulation and fur make Arctic mammals perfectly equipped to face the toughest conditions the Arctic can throw at them.
SECTION 2: QUESTIONS 14-26
Questions 14-20
Choose the correct answer A, B, C or D.
14Animals that live in the Arctic
Acan withstand extremely difficult living conditions.
Boften freeze solid during winter.
Care mainly reptilian.
Dare mostly frogs or toads.
15Where do lemmings live?
Aon the surface of the snow
Bin tunnels built under the frozen ocean
Cin wide tunnels deep underground
Dabout 50cm below the surface of the snow
16Fur is
Athick layers of hair.
Bcommon to all animal classes.
Cunhelpful to Arctic animals.
Dthe life preserver only for small Arctic mammals.
17Why is trapped air a good insulator?
AIt is a good conductor of heat.
BAir helps us to breathe.
CIt is a bad conductor of heat.
DIt absorbs heat and cold very well.
18If the temperature at the tip of the fur of an arctic fox is minus ten degrees, the temperature at the surface of the skin will be closer to
Aforty degrees.
Bten degrees.
Cthirty degrees.
Dthirty-five degrees.
19What is an endotherm?
Aan animal that can generate heat inside its body.
Ban animal that cannot generate heat inside its body.
Can animal that never gets cold
Dan animal that has special insulation
20Thermoregulation and fur help Arctic mammals
Acope with hot temperatures.
Bprotect themselves from the elements.
Cregulate the temperature of their surroundings.
Dcreate a layer of trapped air within their fur.
Questions 21-26
Complete the summary below.
Choose ONE WORD ONLY from the passage for each answer.
|
The Arctic: winter is something few animals can survive, but there are a select few that show an amazing 21 _________________ of the severe winter conditions. Those animals have to use their food resources to keep their body temperature high so that the biochemical 22 _________________inside them continue to run. One thing that helps them keep their bodies warm is their 23 _________________ which consists of thick layers of hair that provide insulation for their bodies; it is their life 24 _________________ . The layer of trapped air that they also have provides very effective insulation from cold because it is not a good 25 _________________ of heat. In the case of an Arctic mammal getting cold, it deals with it by increasing its 26 _________________ rate to generate more heat. |
答案及定位请付费后查阅：
code>
14A
15D
16A
17C
18C
19A
20B
21tolerance
22processes
23fur
24preserver
25conductor
26metabolic
Arctic Survivors
The Arctic is an area located at the northernmost part of the Earth and includes the Arctic Ocean, Canada, Russia, Greenland, the United States, Norway, Sweden, Finland and Iceland. It consists of an ice-covered ocean, surrounded by treeless permafrost. The area can be defined as north of the Arctic Circle, the approximate limit of the midnight sun and the polar night. The average temperature in July, which is the warmest month, is below 10°C. Colder summer temperatures cause the size, abundance, productivity and variety of plants to decrease. Trees cannot grow in the Arctic, but in its warmest parts, shrubs are common and can reach 2 metres in height.
A thick blanket of snow lies several feet deep all over the ground. The sun appears for only a few brief hours each day before sinking below the horizon as blackness cloaks the land. As it vanishes, a bitter chill tightens its grip. The Arctic is not a place to be in the throes of winter; it is hostile to almost all animal life. Q14Amphibians would freeze solid here. Nor can reptiles withstand the extreme cold. And yet there are animals here, animals that exhibit a remarkable Q21tolerance of the most inhospitable conditions on the planet.
Q15Less than half a metre beneath the surface of the snow, a furry white creature, no bigger than a hamster, scurries along a tunnel. It is a collared lemming. It and other members of its family have excavated a complex home within the snow field, but it costs the lemmings a great deal to survive here. They pay by using some of their precious and scarce food supply to generate heat within their bodies so that their biochemicalQ22 processes can continue to function efficiently. But in order to keep fuel costs to a minimum, they must conserve as much energy as they can. A thick insulating coat of fineQ23 fur covering all but the lemmings’ eyes achieves this. Fur is the lifeQ24 preserver of the Arctic.
Q16Only one class of animals has fur – the mammals. Fur is comprised of dense layers of hair follicles. Hair is composed of a substance called keratin. It grows constantly, its roots embedded in the skin and surrounded by nerve fibres so that its owner can sense any movement of the hair. It is this precious fur that gives land mammals the edge necessary to survive the harsh Arctic winter. Without it, wolves, lemmings and arctic foxes alike would surely perish.
Q17The insulation provided by fur comes not from the fur itself, but largely from the layer of air trapped within the fur. Air is an extremely effective insulator, which is the same as saying it is a poor Q25conductor, i.e. it has a very limited ability to conduct heat away from a warm surface. Studies reveal that if a layer of air of about five centimetres could be held in place close to the skin, it would provide the same insulation as does the impressively dense winter coat of the arctic fox.Q18 If an arctic fox or wolf is exposed to an air temperature of about minus ten degrees, the temperature near the tips of the fur will match the air temperature, but at the surface of the skin it will be closer to thirty degrees. This represents a temperature difference of around forty degrees. Such effective insulation is only made possible by the layer of trapped air contained within the long, fine and densely packed fur.
But Arctic mammals have more in their arsenal than just fur to protect them from the elements.Q19 Unlike amphibians, reptiles and other classes of animals, they are endotherms, meaning they can generate their own body heat. This is another of the defining characteristics of mammals. It is the mammalian ability to generate heat internally that enables the arctic fox or the lemming to remain warm and active in very cold conditions. Generating heat internally, Arctic mammals can regulate their body temperature independent of external conditions; this is known as thermoregulation. When Arctic mammals are cold, they raise theirQ26 metabolic rate and produce more heat. When they are warm, the reverse happens.Q20 Together, thermoregulation and fur make Arctic mammals perfectly equipped to face the toughest conditions the Arctic can throw at them
