复时间
2022-09-28
2023-12-13
2024-04-13
2025-04-12
Adaptations of Marine Mammals
Warm-blooded marine mammals and birds require some special adaptations to permit them to live in ocean waters. One important set of adaptations is concerned primarily with maintaining the animal’s temperature. Water has a higher thermal conductivity than air, which means that water is quick to extract heat from a warm body. Humans experience this property when they become chilled after a short time in water of even 80°F(27°C); in air of the same temperature, they would be comfortable indefinitely. Marine mammals, which maintain elevated body temperatures with respect to the surrounding water, must adapt to prevent their body heat from being drained away.
One means of slowing the rate of heat loss is to have a large body. The ratio of the surface area to the volume of any body is lower for a large organism than for a small organism. The larger the body, the smaller the surface area relative to the volume of the body. Since heat production is a function of the volume of a body whereas heat loss is a function of a wetted surface area, this means that large animals, which have a low ratio of surface area to volume, can thermoregulate better than small animals can. Thermoregulation is aided by the smaller surface area that is in contact with the environment through which heat may escape. All swimming marine mammals are large, and it may be that the reason there are no mouse- sized marine mammals is that they would simply die from chilling. There are small marine birds (petrels, auklets), but these animals are completely immersed in the water only for a short time, during intermittent dives. Others, such as gulls, rarely dive, and only a fraction of a bird’s body is in contact with the water at any time.
A second adaptation that prevents or reduces heat loss is a thick insulating layer of blubber or fat just beneath the skin. This layer reaches its greatest thickness in whales, where it may be 2 feet thick. In pinnipeds such as the walrus and elephant seal, subcutaneous fat may constitute as much as 33 percent of the weight. Blubber and fat are poor conductors of heat; hence, they protect the animal from losing internal heat. The thicker the blubber or fat layer, the less the heat loss. Marine mammals inhabiting polar waters, therefore, have thicker layers of fat than temperate and tropical species.
A final adaptation concerns the circulatory system. The areas of a marine mammal that offer the greatest surface area to the water (and, therefore, the greatest opportunity for heat loss) and that also lack much of the protective layer of fat are the fins, flippers, and flukes. What adaptations prevent massive heat loss through these extremities? In cetaceans (aquatic mammals), the answer is that the arteries that bring the warm blood out to these extremities are surrounded by a number of smaller veins that bring blood back to the central core of the mammal. Because of this arrangement, the heat of the blood in the arteries can be absorbed by the cooler blood returning in the veins before it is lost to the external water through the thin flesh of the outer extremities. In effect, these animals have a countercurrent system of circulation designed to save heat.
Because most of their adaptations conserve body heat, marine mammals (especially pinnipeds) may, on occasion, become too warm. Hot, still days may mean considerable stress from overheating. On these uncommon occasions, the animals must act to dissipate heat. They do so by waving their flippers in the air while increasing the blood flow to the extremities and restricting the flow back to the core through the veins. The result is heat loss and subsequent cooling. Seals and sea lions may also open their mouths and pant like a dog. If they are resting on land, they may go into the water to cool off.
1
Warm-blooded marine mammals and birds require some special adaptations to permit them to live in ocean waters. One important set of adaptations is concerned primarily with maintaining the animal’s temperature. Water has a higher thermal conductivity than air, which means that water is quick to extract heat from a warm body. Humans experience this property when they become chilled after a short time in water of even 80°F(27°C); in air of the same temperature, they would be comfortable indefinitely. Marine mammals, which maintain elevated body temperatures with respect to the surrounding water, must adapt to prevent their body heat from being drained away.
Why does the author discuss what happens to humans “after a short time in water of even 80°F(27°C)”?
Rhetorical Purpose Questions修辞目的题
ATo explain the adaptations humans need to make in order to survive in ocean waters
BTo contrast the effects of high and low water temperatures on humans
CTo suggest that humans and marine mammals have similar adaptations to cold water
DTo illustrate that water is a better conductor of heat than air
2
Warm-blooded marine mammals and birds require some special adaptations to permit them to live in ocean waters. One important set of adaptations is concerned primarily with maintaining the animal’s temperature. Water has a higher thermal conductivity than air, which means that water is quick to extract heat from a warm body. Humans experience this property when they become chilled after a short time in water of even 80°F(27°C); in air of the same temperature, they would be comfortable indefinitely. Marine mammals, which maintain elevated body temperatures with respect to the surrounding water, must adapt to prevent their body heat from being drained away.
The word “indefinitely” in the passage is closest in meaning to
Vocabulary Questions词汇题
Aimmediately
Bwithout effort
Cwithout exception
Dfor an unlimited time
3
One means of slowing the rate of heat loss is to have a large body. The ratio of the surface area to the volume of any body is lower for a large organism than for a small organism. The larger the body, the smaller the surface area relative to the volume of the body. Since heat production is a function of the volume of a body whereas heat loss is a function of a wetted surface area, this means that large animals, which have a low ratio of surface area to volume, can thermoregulate better than small animals can. Thermoregulation is aided by the smaller surface area that is in contact with the environment through which heat may escape. All swimming marine mammals are large, and it may be that the reason there are no mouse- sized marine mammals is that they would simply die from chilling. There are small marine birds (petrels, auklets), but these animals are completely immersed in the water only for a short time, during intermittent dives. Others, such as gulls, rarely dive, and only a fraction of a bird’s body is in contact with the water at any time.
Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information
Sentence Simplification Questions句子简化题
AThe advantage in thermoregulation that large animals have over small ones is reduced when the surface area of large animals becomes wet
BLarge animals maintain their body temperatures better than smaller animals because of their lower surface to volume ratios
CLarge animals’ bodies produce increased heat to replace heat that is lost through the wetted parts of their large surface areas.
DLarge animals can regulate heat production and loss better than smaller ones because their bodies have both larger surface areas and volume
4
One means of slowing the rate of heat loss is to have a large body. The ratio of the surface area to the volume of any body is lower for a large organism than for a small organism. The larger the body, the smaller the surface area relative to the volume of the body. Since heat production is a function of the volume of a body whereas heat loss is a function of a wetted surface area, this means that large animals, which have a low ratio of surface area to volume, can thermoregulate better than small animals can. Thermoregulation is aided by the smaller surface area that is in contact with the environment through which heat may escape. All swimming marine mammals are large, and it may be that the reason there are no mouse- sized marine mammals is that they would simply die from chilling. There are small marine birds (petrels, auklets), but these animals are completely immersed in the water only for a short time, during intermittent dives. Others, such as gulls, rarely dive, and only a fraction of a bird’s body is in contact with the water at any time.
According to paragraph 2, which of the following is true of small marine mammals?
Factual Information Questions事实信息题
AThey have a lower ratio of surface area to body volume than do large organisms.
BThey overheat easily due to their small surface area in contact with the environment
CThey have a slow rate of heat loss in comparison with their rate of heat production.
DThey lose body heat too easily to survive well in marine environments.
5
One means of slowing the rate of heat loss is to have a large body. The ratio of the surface area to the volume of any body is lower for a large organism than for a small organism. The larger the body, the smaller the surface area relative to the volume of the body. Since heat production is a function of the volume of a body whereas heat loss is a function of a wetted surface area, this means that large animals, which have a low ratio of surface area to volume, can thermoregulate better than small animals can. Thermoregulation is aided by the smaller surface area that is in contact with the environment through which heat may escape. All swimming marine mammals are large, and it may be that the reason there are no mouse- sized marine mammals is that they would simply die from chilling. There are small marine birds (petrels, auklets), but these animals are completely immersed in the water only for a short time, during intermittent dives. Others, such as gulls, rarely dive, and only a fraction of a bird’s body is in contact with the water at any time.
According to paragraph 2, which of the following explains the ability of petrels, auklets, and gulls to survive in marine environments?
Factual Information Questions事实信息题
AThey do not spend enough time underwater to experience substantial heat loss.
BThey have developed special adaptations to prevent them from losing too much heat in cold water.
CThey have a lower ratio of surface area to body volume than would normally be expected for such small animals.
DThey live in waters that are warm enough to prevent rapid heat loss from occurring.
6
A second adaptation that prevents or reduces heat loss is a thick insulating layer of blubber or fat just beneath the skin. This layer reaches its greatest thickness in whales, where it may be 2 feet thick. In pinnipeds such as the walrus and elephant seal, subcutaneous fat may constitute as much as 33 percent of the weight. Blubber and fat are poor conductors of heat; hence, they protect the animal from losing internal heat. The thicker the blubber or fat layer, the less the heat loss. Marine mammals inhabiting polar waters, therefore, have thicker layers of fat than temperate and tropical species.
Which of the following statements can be inferred from paragraph 3 about a tropical marine mammal?
Inference Questions推理题
AIt loses body heat more easily than a polar marine mammal of the same size.
BIt depends on blubber to maintain its body temperature.
CIt holds more heat in its body than a temperate or polar marine mammal does.
DIt retains heat better than a polar mammal by staying in warm waters.
7
A final adaptation concerns the circulatory system. The areas of a marine mammal that offer the greatest surface area to the water (and, therefore, the greatest opportunity for heat loss) and that also lack much of the protective layer of fat are the fins, flippers, and flukes. What adaptations prevent massive heat loss through these extremities? In cetaceans (aquatic mammals), the answer is that the arteries that bring the warm blood out to these extremities are surrounded by a number of smaller veins that bring blood back to the central core of the mammal. Because of this arrangement, the heat of the blood in the arteries can be absorbed by the cooler blood returning in the veins before it is lost to the external water through the thin flesh of the outer extremities. In effect, these animals have a countercurrent system of circulation designed to save heat.
According to paragraph 4, which of the following explains why marine mammals do not lose large amounts of heat through their fins flippers, and flukes?
Factual Information Questions事实信息题
AThe fat and skin surrounding these areas prevents massive heat loss
BThe ratio of surface area to body volume is lowest at these areas
CThe number of veins and arteries in these areas is too small for massive heat loss to occur.
DThe veins near the arteries in these extremities prevent heat from escaping.
8
Because most of their adaptations conserve body heat, marine mammals (especially pinnipeds) may, on occasion, become too warm. Hot, still days may mean considerable stress from overheating. On these uncommon occasions, the animals must act to dissipate heat. They do so by waving their flippers in the air while increasing the blood flow to the extremities and restricting the flow back to the core through the veins. The result is heat loss and subsequent cooling. Seals and sea lions may also open their mouths and pant like a dog. If they are resting on land, they may go into the water to cool off.
In paragraph 5, which of the following is NOT mentioned as a strategy used by marine mammals to dissipate heat?
Negative Factual Information Questions否定事实信息题
APanting through their mouths
BMoving from the land to the water
CReducing the amount of blood flowing to the extremities
DWaving their flippers to increase heat loss through the extremities
9
A second adaptation that prevents or reduces heat loss is a thick insulating layer of blubber or fat just beneath the skin. ⬛This layer reaches its greatest thickness in whales, where it may be 2 feet thick. ⬛In pinnipeds such as the walrus and elephant seal, subcutaneous fat may constitute as much as 33 percent of the weight. ⬛Blubber and fat are poor conductors of heat; hence, they protect the animal from losing internal heat. ⬛The thicker the blubber or fat layer, the less the heat loss. Marine mammals inhabiting polar waters, therefore, have thicker layers of fat than temperate and tropical species.
Look at the four squaresthat indicate where the following sentence could be added to the passage
Its thickness varies from one marine mammal to another.
Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Marine mammals have evolved special adaptations that allow them to conserve body heat.
Prose Summary Questions概要小结题
Select 3 answers
ABecause the thermal conductivity of water differs from that of air, marine animals’ adaptations for regulating body temperature differ significantly from those of land animals.
BBecause large, fatty bodies lose less heat than small. thin ones, many marine mammals are adapted to reach adulthood in a relatively short period of time.
CBecause fat is a poor conductor of heat, having a thick layer of blubber beneath the skin helps prevent heat loss.
DMammals that spend any significant amount of time in marine waters are large because a body with a large volume relative to its surface area loses relatively little internal heat.
EMarine mammals need to maintain high internal temperatures in part to prevent the blood in their extremities from freezing when the extremities are in contact with water.
FThe amount of heat the extremities lose to the outside is reduced by having a circulatory system in which blood in the veins absorbs heat from blood in the arteries.
