TF阅读真题第855篇Thermoregulation in Marine Mammals

Thermoregulation in Marine Mammals

Any organism, in terms of regulating its internal body temperature, can be either ectothermic(cold-blooded)or endothermic(warm-blooded). In an ectothermic organism, its internal body temperature and thus metabolic rate largely varies with and is controlled at the surface by the external environment. In an endothermic organism, its internal body temperature is maintained at a constant temperature, usually between 37° and 40C by internal metabolic heat production.

The marine environment offers temperatures that are relatively more stable than those on land because water has a high specific heat capacity, which means substantial amounts of energy need to be absorbed or lost before the temperature of water changes. Therefore, ectothermic species tend to be more common in the ocean than on land. However, the metabolic rates of ectotherms change by a factor of 2 for every 10°C temperature change. Thus the rate at which metabolic reactions occur for ectotherms is substantially reduced as temperatures drop. This gives endothermic species a big advantage over ectothermic prey or competitors in cooler water temperatures. That marine mammals are endothermic explains, in part, why they are so abundant and successful in polar and subpolar regions. However, being endothermic does have a cost, because these species require more energy to support a high metabolic rate, which means they must consume relatively more food to survive.

The thermal conductivity of water is 25 times greater than that of air. Although water temperatures in the marine environment, as noted above, are relatively stable compared with those of the terrestrial environment, marine mammals do have difficulties, nonetheless, with heat loss to the surrounding environment. This is especially true for the many marine mammals that occupy cool waters, where the temperature gradient between their internal body temperature and the surrounding seawater is high, and thus heat loss is greater. Thus, heat loss is greatest for animals with a high surface area (relative to their volume), a body surface that conducts heat well, and a large difference between their internal body temperature and the surrounding water temperature. As a result, marine mammals are able to minimize heat loss by increasing body size, reducing conductance, or transference, by increasing insulation, or, in some cases, avoiding low water temperatures. For example, sea otters experience heat loss because they are relatively small and their surface-area-to volume ratio is high. One way to decrease surface area is to have small appendages. Allen’s rule, an ecological observation made by Joel Allen in 1877， states that endotherms from colder climates usually have shorter limbs (or appendages) than the equivalent animals from warmer climates because this reduces their relative surface area. Sea otters have relatively blunt muzzles (noses) and shorter tails than their otter counterparts in warmer climates.

Although sea otters are one of the smallest of the marine mammals, they can weigh up to 45 kg and be over 1.5 meters in length, making them the heaviest and largest species in their group. Therefore, they have a relatively smaller surface area to volume ratio than other otters. This is an example of another ecological rule: Bergmann’s rule (after Christian Bergmann, who published the rule in 1847) states that animals within a specific group tend to get larger as the latitude increases (and decreases in temperature). For example, Arctic-dwelling polar bears and sea otters are the largest species of bear and otters, respectively.

Heat loss is also minimized by reducing the conductance (increasing insulation) of the exterior surface. Sea otters possess a thick fur layer and have one of the densest furs of all mammals, with up to 150,000 hairs per square centimeter. This fur layer traps air (air has a lower conductance than water) and therefore insulates the otter well. However, when a sea otter dives, water pressure forces air out of their fur and they lose much of their insulation. Salt from seawater also clogs their fur, making hairs stick together. Thus, much of a sea otter’s behavior is dedicated to grooming, cleaning fur, and “fluffing it up” so air can get between the fur hairs. Polar bears face a similar problem; although their fur is an effective insulator on land, when they enter the water their fur becomes waterlogged and loses much of its insulating properties. However, polar bears have a substantial layer of adipose, or fatty, tissue.

 

 

 

 

 

 

 

 

1

Any organism, in terms of regulating its internal body temperature, can be either ectothermic(cold-blooded)or endothermic(warm-blooded). In an ectothermic organism, its internal body temperature and thus metabolic rate largely varies with and is controlled at the surface by the external environment. In an endothermic organism, its internal body temperature is maintained at a constant temperature, usually between 37° and 40C by internal metabolic heat production.

The word “constant” in the passage is closest in meaning to

Vocabulary Questions词汇题

Ahigh

Bspecific

Cfavorable

Dunchanging

2

The marine environment offers temperatures that are relatively more stable than those on land because water has a high specific heat capacity, which means substantial amounts of energy need to be absorbed or lost before the temperature of water changes. Therefore, ectothermic species tend to be more common in the ocean than on land. However, the metabolic rates of ectotherms change by a factor of 2 for every 10°C temperature change. Thus the rate at which metabolic reactions occur for ectotherms is substantially reduced as temperatures drop. This gives endothermic species a big advantage over ectothermic prey or competitors in cooler water temperatures. That marine mammals are endothermic explains, in part, why they are so abundant and successful in polar and subpolar regions. However, being endothermic does have a cost, because these species require more energy to support a high metabolic rate, which means they must consume relatively more food to survive.

Why does the author provide the information that “the metabolic rates of ectotherms change by a factor of 2 for every 10°C temperature change”?

Rhetorical Purpose Questions修辞目的题

ATo emphasize the high specific heat capacity of water

BTo help explain why ectothermic species are more common in the ocean than on land

CTo suggest that metabolic reactions are not significantly affected by temperature changes for marine species

DTo emphasize the advantage that endothermic species have over ectothermic species in cooler waters

 

3

The marine environment offers temperatures that are relatively more stable than those on land because water has a high specific heat capacity, which means substantial amounts of energy need to be absorbed or lost before the temperature of water changes. Therefore, ectothermic species tend to be more common in the ocean than on land. However, the metabolic rates of ectotherms change by a factor of 2 for every 10°C temperature change. Thus the rate at which metabolic reactions occur for ectotherms is substantially reduced as temperatures drop. This gives endothermic species a big advantage over ectothermic prey or competitors in cooler water temperatures. That marine mammals are endothermic explains, in part, why they are so abundant and successful in polar and subpolar regions. However, being endothermic does have a cost, because these species require more energy to support a high metabolic rate, which means they must consume relatively more food to survive.

According to paragraph 2, which of the following is a disadvantage of marine mammals in polar and subpolar regions?

Factual Information Questions事实信息题

AThey lack enough prey in their environment.

BTheir body temperature is relatively low.

CThey require a relatively large amount of food

DThey have a lot of competition for resources in their environment.

 

4

The thermal conductivity of water is 25 times greater than that of air. Although water temperatures in the marine environment, as noted above, are relatively stable compared with those of the terrestrial environment, marine mammals do have difficulties, nonetheless, with heat loss to the surrounding environment. This is especially true for the many marine mammals that occupy cool waters, where the temperature gradient between their internal body temperature and the surrounding seawater is high, and thus heat loss is greater. Thus, heat loss is greatest for animals with a high surface area (relative to their volume), a body surface that conducts heat well, and a large difference between their internal body temperature and the surrounding water temperature. As a result, marine mammals are able to minimize heat loss by increasing body size, reducing conductance, or transference, by increasing insulation, or, in some cases, avoiding low water temperatures. For example, sea otters experience heat loss because they are relatively small and their surface-area-to volume ratio is high. One way to decrease surface area is to have small appendages. Allen’s rule, an ecological observation made by Joel Allen in 1877， states that endotherms from colder climates usually have shorter limbs (or appendages) than the equivalent animals from warmer climates because this reduces their relative surface area. Sea otters have relatively blunt muzzles (noses) and shorter tails than their otter counterparts in warmer climates.

According to paragraph 3, which of the following makes it somewhat surprising that marine mammals can have difficulties with heat loss?

Factual Information Questions事实信息题

AThe temperatures of marine environments are not very changeable compared to terrestrial environments.

BMarine mammals tend to have high surface areas relative to their volume.

CMost marine mammals maintain an internal body temperature very close to that of surrounding water.

DMarine waters are warmer at the surface. where marine mammals spend most of their time.

 

5

The thermal conductivity of water is 25 times greater than that of air. Although water temperatures in the marine environment, as noted above, are relatively stable compared with those of the terrestrial environment, marine mammals do have difficulties, nonetheless, with heat loss to the surrounding environment. This is especially true for the many marine mammals that occupy cool waters, where the temperature gradient between their internal body temperature and the surrounding seawater is high, and thus heat loss is greater. Thus, heat loss is greatest for animals with a high surface area (relative to their volume), a body surface that conducts heat well, and a large difference between their internal body temperature and the surrounding water temperature. As a result, marine mammals are able to minimize heat loss by increasing body size, reducing conductance, or transference, by increasing insulation, or, in some cases, avoiding low water temperatures. For example, sea otters experience heat loss because they are relatively small and their surface-area-to volume ratio is high. One way to decrease surface area is to have small appendages. Allen’s rule, an ecological observation made by Joel Allen in 1877， states that endotherms from colder climates usually have shorter limbs (or appendages) than the equivalent animals from warmer climates because this reduces their relative surface area. Sea otters have relatively blunt muzzles (noses) and shorter tails than their otter counterparts in warmer climates.

 

According to paragraph 3. all of the following help animals keep heat in their bodies EXCEPT

Negative Factual Information Questions否定事实信息题

Ahaving small body sizes

Bhaving small limbs relative to body size

Chaving sufficient insulation

Dremaining in warm environments.

 

6

Although sea otters are one of the smallest of the marine mammals, they can weigh up to 45 kg and be over 1.5 meters in length, making them the heaviest and largest species in their group. Therefore, they have a relatively smaller surface area to volume ratio than other otters. This is an example of another ecological rule: Bergmann’s rule (after Christian Bergmann, who published the rule in 1847) states that animals within a specific group tend to get larger as the latitude increases (and decreases in temperature). For example, Arctic-dwelling polar bears and sea otters are the largest species of bear and otters, respectively.

The word “respectively” in the passage is closest in meaning to

Vocabulary Questions词汇题

Aas recently discovered

Bin that order

Cworldwide

Das expected

 

7

Although sea otters are one of the smallest of the marine mammals, they can weigh up to 45 kg and be over 1.5 meters in length, making them the heaviest and largest species in their group. Therefore, they have a relatively smaller surface area to volume ratio than other otters. This is an example of another ecological rule: Bergmann’s rule (after Christian Bergmann, who published the rule in 1847) states that animals within a specific group tend to get larger as the latitude increases (and decreases in temperature). For example, Arctic-dwelling polar bears and sea otters are the largest species of bear and otters, respectively.

According to paragraph 4. which of the following illustrates Bergmann’s rule?

Factual Information Questions事实信息题

AMarine mammals are larger in size than land mammals living at similar latitudes.

BFewer animals live in higher latitudes than in other areas.

CPolar bears are larger and heavier than sea otters are.

DBears living in colder climates are larger than bears living in warm climates

 

8

Heat loss is also minimized by reducing the conductance (increasing insulation) of the exterior surface. Sea otters possess a thick fur layer and have one of the densest furs of all mammals, with up to 150,000 hairs per square centimeter. This fur layer traps air (air has a lower conductance than water) and therefore insulates the otter well. However, when a sea otter dives, water pressure forces air out of their fur and they lose much of their insulation. Salt from seawater also clogs their fur, making hairs stick together. Thus, much of a sea otter’s behavior is dedicated to grooming, cleaning fur, and “fluffing it up” so air can get between the fur hairs. Polar bears face a similar problem; although their fur is an effective insulator on land, when they enter the water their fur becomes waterlogged and loses much of its insulating properties. However, polar bears have a substantial layer of adipose, or fatty, tissue.

Paragraph 5 suggests that which of the following is one way polar bears keep heat?

Inference Questions推理题

AHaving fur that does not quickly absorb water

BHaving a significant layer of fat

CHaving a thicker fur layer than sea otters do

DStaying underwater for extended periods of time

 

9

The marine environment offers temperatures that are relatively more stable than those on land because water has a high specific heat capacity, which means substantial amounts of energy need to be absorbed or lost before the temperature of water changes. Therefore, ectothermic species tend to be more common in the ocean than on land. However, the metabolic rates of ectotherms change by a factor of 2 for every 10°C temperature change. Thus the rate at which metabolic reactions occur for ectotherms is substantially reduced as temperatures drop. This gives endothermic species a big advantage over ectothermic prey or competitors in cooler water temperatures. That marine mammals are endothermic explains, in part, why they are so abundant and successful in polar and subpolar regions. However, being endothermic does have a cost, because these species require more energy to support a high metabolic rate, which means they must consume relatively more food to survive.[■]

The thermal conductivity of water is 25 times greater than that of air. [■]Although water temperatures in the marine environment, as noted above, are relatively stable compared with those of the terrestrial environment, marine mammals do have difficulties, nonetheless, with heat loss to the surrounding environment. [■]This is especially true for the many marine mammals that occupy cool waters, where the temperature gradient between their internal body temperature and the surrounding seawater is high, and thus heat loss is greater. [■]Thus, heat loss is greatest for animals with a high surface area (relative to their volume), a body surface that conducts heat well, and a large difference between their internal body temperature and the surrounding water temperature. As a result, marine mammals are able to minimize heat loss by increasing body size, reducing conductance, or transference, by increasing insulation, or, in some cases, avoiding low water temperatures. For example, sea otters experience heat loss because they are relatively small and their surface-area-to volume ratio is high. One way to decrease surface area is to have small appendages. Allen’s rule, an ecological observation made by Joel Allen in 1877， states that endotherms from colder climates usually have shorter limbs (or appendages) than the equivalent animals from warmer climates because this reduces their relative surface area. Sea otters have relatively blunt muzzles (noses) and shorter tails than their otter counterparts in warmer climates.

Look at the four squaresthat indicate where the following sentence could be added to the passage

 

This means heat can be lost very quickly in water.

Insert Text Questions句子插入题

Where would the sentence best fit？Click on a square  sentence to the passage.

 

10

Some organisms are ectothermic. while others are endothermic

Prose Summary Questions概要小结题

Select 3 answers

AThe body temperature of ectothermic animals is controlled by the environment, which is why ectothermic animals are more common in seawater, where temperature varies less than in the air.

BEndothermic species are advantaged in cool marine environments, but they suffer from heat loss, especially if their body temperature is much higher than that of the surrounding water.

CAllen’s rule and Bergmann’s rule help explain why sea otters, although smaller, are more effective in preventing heat loss in cold marine environments than polar bears are.

DEctothermic animals need to obtain a large amount of energy to survive in cold environments, which means they need an abundance of food to keep their metabolic rates high.

EEndothermic animals that have a small surface-area-to-volume ratio and effective insulation, like sea otters, effectively reduce the amount of heat they lose to the surrounding environment.

FFor marine mammals that suffer from heat loss, fur layers are more effective than other forms of protection in seawater, which has a high specific heat capacity.