Waking Up: Coming Out of Hibernation
1 There are animals in most temperate regions in the north that spend approximately six months in hibernation—from October to March. Within the Arctic Circle this period can be extended to nine months for some species. █ Elsewhere, such as the desert regions of the southwestern United States, droughts may result in the normal periods of estivation (inactivity during hot or dry periods) and hibernation running continuously so that animals like the spadefoot toads may be inactive for eighteen months. █ But dormant (inactive) hibernators do not sleep solidly for their whole term as once believed, and even those that sleep deeply awaken quite regularly. █ Why an animal should periodically arouse (wake up) for several hours, or perhaps a whole day, during its long hibernation is unclear and has been the subject of much speculation .
2 █ Arousal, which entails heat production, is a drain on an animal’s precious stored reserves of fat as it raises its body temperature, and there must be a very worthwhile reason for doing it. Possibly life in such a reduced state—called metabolic depression—damages the animal’s nerve cells and affects its ability to develop immune responses as defense against infection and disease. Arousal, even for just a few hours, restores the metabolic processes and perhaps allows the animal to recover from the stress of metabolic depression, giving it an opportunity to really sleep and rejuvenate its body, which does not happen when it is dormant. It is also believed that some animals may need to restart their metabolism in order to excrete waste, and it is possible that physiological imbalances occurring during hibernation, such as the depletion of blood glucose, could be corrected during their brief return to normal temperature.
3 There is also a safety mechanism that functions if the temperature of the hibernator’s shelter drops below a mammal’s set point, the minimum temperature at which an animal can exist without freezing. The hibernating animal arouses from its sleep through shivering and violently contracting its muscles, which increases its heart rate and respiration, and thus its oxygen intake and body temperature. In the case of the external food storers, such as the chipmunk, depleted food reserves in its body are the trigger to arouse and feed and thus replenish its energy.
4 In the early stages of arousal, the front of an animal’s body—the part containing the essential vital organs, the heart and brain—is heated faster than the posterior and the extremities. Blood is directed to the vital organs and especially to the brown fat tissue that occurs along the neck and between the shoulder blades of mammals, indicating its importance in providing heat to power the arousal process. Vasodilation, or widening of the blood vessels, occurs as mammals arouse from hibernation, and arousal time depends on body size. Large hibernators warm up slowly, at the rate of about 1.8°F (1°C) per ten minutes, whereas tiny creatures warm up much faster—at the rate of 1.8°F (1°C) per minute. Heat production warms the body at a much faster rate than the cooling-down process at the start of hibernation, and animals therefore arouse more quickly from the state of hibernation than they enter it.
5 Emergence from hibernation is controlled by the same factors as the entry weeks or months earlier— temperature, amount of daily exposure to light, or body rhythms. The increasing temperatures of springtime are the major factor initiating the arousal and emergence for many species. Terrestrial amphibians such as the wood frog and spring peeper, which hibernate under leaves, are the first to appear as the snow begins to melt, whereas aquatic hibernators like the leopard frog and bullfrog must await the melting of a large part of their pond’s ice cover before awakening. Biological rhythms (daily rhythms to many physiological functions and activities, such as sleep and body temperature) appear to play a greater role in those that sleep deep underground, below several feet of frozen soil, for it seems unlikely that they are influenced by the slightly warmer temperatures or longer days above ground, and they often emerge to find that there is still considerable snow cover. There is rarely food immediately available for animals when they emerge, and it is important that they have enough internal reserves left to sustain them over this essential part of their life cycle.
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1 There are animals in most temperate regions in the north that spend approximately six months in hibernation—from October to March. Within the Arctic Circle this period can be extended to nine months for some species. █ Elsewhere, such as the desert regions of the southwestern United States, droughts may result in the normal periods of estivation (inactivity during hot or dry periods) and hibernation running continuously so that animals like the spadefoot toads may be inactive for eighteen months. █ But dormant (inactive) hibernators do not sleep solidly for their whole term as once believed, and even those that sleep deeply awaken quite regularly. █ Why an animal should periodically arouse (wake up) for several hours, or perhaps a whole day, during its long hibernation is unclear and has been the subject of much speculation .
The word “ speculation ” in the passage is closest in meaning to
research
disagreement
interest
theorizing
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1 There are animals in most temperate regions in the north that spend approximately six months in hibernation—from October to March. Within the Arctic Circle this period can be extended to nine months for some species. █ Elsewhere, such as the desert regions of the southwestern United States, droughts may result in the normal periods of estivation (inactivity during hot or dry periods) and hibernation running continuously so that animals like the spadefoot toads may be inactive for eighteen months. █ But dormant (inactive) hibernators do not sleep solidly for their whole term as once believed, and even those that sleep deeply awaken quite regularly. █ Why an animal should periodically arouse (wake up) for several hours, or perhaps a whole day, during its long hibernation is unclear and has been the subject of much speculation .
According to paragraph 1, which of the following ideas about hibernation is now known to be incorrect?
Some animals sleep quite deeply while in hibernation.
Some hibernating animals arouse for a period of several hours.
Hibernating animals do not wake up until the period of hibernation has ended.
Some animals in Arctic regions spend more time hibernating than animals in temperate regions do.
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2 █ Arousal, which entails heat production, is a drain on an animal’s precious stored reserves of fat as it raises its body temperature, and there must be a very worthwhile reason for doing it. Possibly life in such a reduced state—called metabolic depression—damages the animal’s nerve cells and affects its ability to develop immune responses as defense against infection and disease. Arousal, even for just a few hours, restores the metabolic processes and perhaps allows the animal to recover from the stress of metabolic depression, giving it an opportunity to really sleep and rejuvenate its body, which does not happen when it is dormant. It is also believed that some animals may need to restart their metabolism in order to excrete waste, and it is possible that physiological imbalances occurring during hibernation, such as the depletion of blood glucose, could be corrected during their brief return to normal temperature.
In paragraph 2, all of the following are mentioned as possible reasons why animals might arouse from hibernation EXCEPT:
It reduces the drain on their stored reserves of fat.
It improves their ability to fight off infections and diseases.
It allows them to rid themselves of waste products.
It helps them correct physiological imbalances.
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3 There is also a safety mechanism that functions if the temperature of the hibernator’s shelter drops below a mammal’s set point, the minimum temperature at which an animal can exist without freezing. The hibernating animal arouses from its sleep through shivering and violently contracting its muscles, which increases its heart rate and respiration, and thus its oxygen intake and body temperature. In the case of the external food storers, such as the chipmunk, depleted food reserves in its body are the trigger to arouse and feed and thus replenish its energy.
Why does the author provide information about the ” depleted food reserves ” in the body of the chipmunk?
To illustrate what happens when external temperatures drop below an animal’s set point
To identify an additional reason why some animals arouse from hibernation
To explain why the hibernating animal violently contracts its muscles
To explain how some animals are able to prevent their bodies from freezing while hibernating
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4 In the early stages of arousal, the front of an animal’s body—the part containing the essential vital organs, the heart and brain—is heated faster than the posterior and the extremities. Blood is directed to the vital organs and especially to the brown fat tissue that occurs along the neck and between the shoulder blades of mammals, indicating its importance in providing heat to power the arousal process. Vasodilation, or widening of the blood vessels, occurs as mammals arouse from hibernation, and arousal time depends on body size. Large hibernators warm up slowly, at the rate of about 1.8°F (1°C) per ten minutes, whereas tiny creatures warm up much faster—at the rate of 1.8°F (1°C) per minute. Heat production warms the body at a much faster rate than the cooling-down process at the start of hibernation, and animals therefore arouse more quickly from the state of hibernation than they enter it.
According to paragraph 4, why is blood directed especially to the brown fat tissue near the neck during the early stages of arousal?
The fat is located close to a large number of blood vessels.
The fat is important for protecting the vital organs.
The fat provides energy for waking up the animal.
The fat requires very little energy to heat.
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4 In the early stages of arousal, the front of an animal’s body—the part containing the essential vital organs, the heart and brain—is heated faster than the posterior and the extremities. Blood is directed to the vital organs and especially to the brown fat tissue that occurs along the neck and between the shoulder blades of mammals, indicating its importance in providing heat to power the arousal process. Vasodilation, or widening of the blood vessels, occurs as mammals arouse from hibernation, and arousal time depends on body size. Large hibernators warm up slowly, at the rate of about 1.8°F (1°C) per ten minutes, whereas tiny creatures warm up much faster—at the rate of 1.8°F (1°C) per minute. Heat production warms the body at a much faster rate than the cooling-down process at the start of hibernation, and animals therefore arouse more quickly from the state of hibernation than they enter it.
According to paragraph 4, which of the following is true of the arousal process?
The arousal process takes less time to complete than does the cooling-down process that leads to hibernation.
The arousal process takes less time to complete for large hibernators than for smaller ones.
At the beginning of the process, hibernators warm up at a much slower rate than they do toward the end of the process.
The size of the animal determines what parts of the body get heated first.
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5 Emergence from hibernation is controlled by the same factors as the entry weeks or months earlier— temperature, amount of daily exposure to light, or body rhythms. The increasing temperatures of springtime are the major factor initiating the arousal and emergence for many species. Terrestrial amphibians such as the wood frog and spring peeper, which hibernate under leaves, are the first to appear as the snow begins to melt, whereas aquatic hibernators like the leopard frog and bullfrog must await the melting of a large part of their pond’s ice cover before awakening. Biological rhythms (daily rhythms to many physiological functions and activities, such as sleep and body temperature) appear to play a greater role in those that sleep deep underground, below several feet of frozen soil, for it seems unlikely that they are influenced by the slightly warmer temperatures or longer days above ground, and they often emerge to find that there is still considerable snow cover. There is rarely food immediately available for animals when they emerge, and it is important that they have enough internal reserves left to sustain them over this essential part of their life cycle.
The word “ initiating ” in the passage is closest in meaning to
beginning
assisting
predicting
accompanying
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5 Emergence from hibernation is controlled by the same factors as the entry weeks or months earlier— temperature, amount of daily exposure to light, or body rhythms. The increasing temperatures of springtime are the major factor initiating the arousal and emergence for many species. Terrestrial amphibians such as the wood frog and spring peeper, which hibernate under leaves, are the first to appear as the snow begins to melt, whereas aquatic hibernators like the leopard frog and bullfrog must await the melting of a large part of their pond’s ice cover before awakening. Biological rhythms (daily rhythms to many physiological functions and activities, such as sleep and body temperature) appear to play a greater role in those that sleep deep underground, below several feet of frozen soil, for it seems unlikely that they are influenced by the slightly warmer temperatures or longer days above ground, and they often emerge to find that there is still considerable snow cover. There is rarely food immediately available for animals when they emerge, and it is important that they have enough internal reserves left to sustain them over this essential part of their life cycle.
Paragraph 5 suggests that wood frogs and leopard frogs are alike in which of the following ways?
Both begin to emerge from hibernation at about the same time in the spring.
Both spend very little time in hibernation compared with animals that hibernate deep underground.
Unlike deep underground hibernators, neither emerges from hibernation until plenty of food is immediately available for them.
When they begin to emerge from hibernation is determined more by environmental factors than by their own biological rhythms.
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1 There are animals in most temperate regions in the north that spend approximately six months in hibernation—from October to March. Within the Arctic Circle this period can be extended to nine months for some species. █ Elsewhere, such as the desert regions of the southwestern United States, droughts may result in the normal periods of estivation (inactivity during hot or dry periods) and hibernation running continuously so that animals like the spadefoot toads may be inactive for eighteen months. █ But dormant (inactive) hibernators do not sleep solidly for their whole term as once believed, and even those that sleep deeply awaken quite regularly. █ Why an animal should periodically arouse (wake up) for several hours, or perhaps a whole day, during its long hibernation is unclear and has been the subject of much speculation .
2 █ Arousal, which entails heat production, is a drain on an animal’s precious stored reserves of fat as it raises its body temperature, and there must be a very worthwhile reason for doing it. Possibly life in such a reduced state—called metabolic depression—damages the animal’s nerve cells and affects its ability to develop immune responses as defense against infection and disease. Arousal, even for just a few hours, restores the metabolic processes and perhaps allows the animal to recover from the stress of metabolic depression, giving it an opportunity to really sleep and rejuvenate its body, which does not happen when it is dormant. It is also believed that some animals may need to restart their metabolism in order to excrete waste, and it is possible that physiological imbalances occurring during hibernation, such as the depletion of blood glucose, could be corrected during their brief return to normal temperature.
These discoveries were surprising.
Where would the sentence best fit? Click on a square [█] to add the sentence to the passage.
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In most northern temperate regions, some animals spend months in hibernation.
Animals that combine estivation and hibernation to remain inactive for many months frequently return to normal body temperatures in order to replace used fat reserves.
The main explanation why even deeply sleeping hibernators awaken regularly is that by doing so they raise their internal temperatures enough to keep their bodies from freezing.
Environmental factors or biological rhythms primarily control both when an animal enters and arouses from hibernation, depending on whether the animal hibernates aboveground or belowground.
We now know that animals arouse for brief periods during hibernation, and since such arousal is very costly, it must provide important benefits that are not yet all fully understood.
Vasodilation occurs as mammals arouse from hibernation, with heat going to vital organs first, but how long it takes to warm their bodies and emerge from inactivity depends on body size.
Most animals emerge from hibernation only when their internal reserves become so low that any further depletion would leave them unable to sustain themselves while searching for food.
