题目：
Biological Rhythms
Biologists have identified many types of biological rhythms, including daily, monthly, and annual rhythms. Among many animals, physiological cycles such as body temperature fluctuations and hormone secretion are rhythmic. Human body temperature, for example, follows a typical daily curve. Biological rhythms control many behaviors, including activity, sleep, feeding, drinking, and migration.
The behavior of many animals is organized around circadian(meaning “approximately one day”)rhythms which are daily(24-hour) cycles of activity. Diurnal animals, such as honeybees and pigeons, are most active during the day. Most bats, moths, and cats are nocturnal animals, most active during the hours of darkness. Crepuscular animals, like many mosquitoes and fiddler crabs, are busiest at dawn or dusk, or both. Generally, there are ecological reasons for these patterns. If an animal’s food is most plentiful in the early morning, its cycle of activity must be regulated so that it becomes active shortly before dawn.
Some biological rhythms of animals reflect the lunar (moon) cycle. The most striking rhythms are those in marine organisms that are attuned to changes in tides and phases of the moon. For instance, a combination of tidal, lunar, and annual rhythms governs the reproductive behavior of the grunion, a small fish that lives off the Pacific coast of North America. Grunions swarm from April through June on those three or four nights when the highest tides of the year occur. At precisely the high point of the tide, the fish squirm onto the beach and deposit eggs and sperm in the sand. They return to the sea in the next wave. By the time the next tide reaches that portion of the beach fifteen days later, the young fish have hatched in the damp sand and are ready to enter the sea. This synchronization may contribute to the protection of fish eggs from aquatic predators.
An animal’s metabolic processes and behavior are typically synchronized with the cyclic changes in its external environment. Its behavior anticipates these regular changes. The little fiddler crabs of marine beaches often emerge from their burrows at low tide to engage in social activities such as territorial disputes. To avoid being washed away, they must return to their burrows before the tide returns. One might guess that the crabs”know”that high tide is about to occur by recognizing clues present in the seashore, but when the crabs are isolated in the laboratory away from any known stimulus that could relate to time and tide, their characteristic behavioral rhythms persist.
Many biological rhythms are regulated by internaltiming mechanisms that serve as biological clocks. These timing mechanisms do not simply respond to environmental cues, but are capable of sustaining biological rhythms independently. Such internal clocks have been identified in almost every eukaryote (organism whose cells contain a nucleus and other structures enclosed within membranes) as well as some bacteria. Molecular biologists have demonstrated that genes control biological clocks. In fruit flies, seven genes produce clock proteins that seem to interact in feedback loops in many cell types both inside and outside the nervous system. Researchers have identified similar genes and proteins in many animal groups, including mammals. The principal clock is located in specific areas of the central nervous system.
In mammals, the master clock is located in the suprachiasmatic nucleus(SCN)in part of the mammalian brain called the hypothalamus. This SCN clock generates approximately 24-hour cycles even without input from the environment. However, the SCN-generated cycles are normally adjusted every day based on visual input received from the retina, the light-sensitive part of the eye. Signals from the retina reflecting changes in light intensity adjust internal circadian rhythms to light-dark cycles in the environment. The SCN sends rhythmic signals, in the form of molecules that transmit information in the nervous system, to the pineal gland, an endocrine gland located in the brain. In response, the pineal gland secretes melatonin, a hormone that promotes sleep in humans. Clock genes in the SCN are turned on and off by the very proteins they encode, setting up complex feedback loops that have a 24-hour cycle. In addition to the master clock, most cells have timing mechanisms that use many of the same clock proteins. These peripheral clocks may function independently of the SCN.
1
Biologists have identified many types of biological rhythms, including daily, monthly, and annual rhythms. Among many animals, physiological cycles such as body temperature fluctuations and hormone secretion are rhythmic. Human body temperature, for example, follows a typical daily curve. Biological rhythms control many behaviors, including activity, sleep, feeding, drinking, and migration.
Why does the author state that “Human body temperature, for example, follows a typical daily curve”?
Rhetorical Purpose Questions修辞目的题
ATo identify one of the many discoveries made by biologists about the human body
BTo illustrate the rhythmic nature of physiological cycles
CTo compare physiological cycles in humans to those in other animals
DTo support the claim that biological rhythms control many animal behaviors
2
The behavior of many animals is organized around circadian(meaning “approximately one day”)rhythms which are daily(24-hour) cycles of activity. Diurnal animals, such as honeybees and pigeons, are most active during the day. Most bats, moths, and cats are nocturnal animals, most active during the hours of darkness. Crepuscular animals, like many mosquitoes and fiddler crabs, are busiest at dawn or dusk, or both. Generally, there are ecological reasons for these patterns. If an animal’s food is most plentiful in the early morning, its cycle of activity must be regulated so that it becomes active shortly before dawn.
Paragraph 2 suggests which of the following about honeybees and pigeons?
Inference Questions推理题
ATheir food sources are generally similar.
BThey are as active as mosquitoes and fiddler crabs at dusk
CTheir food sources are most abundant during daylight hours.
DTheir circadian rhythms are less regular than those of bats, moths, and cats.
3
According to paragraph 3. all of the following statements about grunions are true EXCEPT:
Negative Factual Information Questions否定事实信息题
AThey are found off the Pacific coast of North America.
BTheir reproductive behavior is governed by a combination of tidal, lunar, and annual rhythms
CTheir young stay on the beach for fifteen days after hatching before entering the sea
DThey deposit their eggs and sperm on the sand rather than in the water.
4
An animal’s metabolic processes and behavior are typically synchronized with the cyclic changes in its external environment. Its behavior anticipates these regular changes. The little fiddler crabs of marine beaches often emerge from their burrows at low tide to engage in social activities such as territorial disputes. To avoid being washed away, they must return to their burrows before the tide returns. One might guess that the crabs”know”that high tide is about to occur by recognizing clues present in the seashore, but when the crabs are isolated in the laboratory away from any known stimulus that could relate to time and tide, their characteristic behavioral rhythms persist.
The word “typically” in the passage is closest in meaning to
Vocabulary Questions词汇题
Ausually
BPartly
CPrecisely
DOccasionally
5
According to paragraph 4, all of the following statements about fiddler crabs are true EXCEPT
Negative Factual Information Questions否定事实信息题
AThey take advantage of low tide but avoid high tide.
BThey spend more time in their burrows during low tide than they do during high tide.
CThey engage in different kinds of social activity.
DThey often fight over territory.
6
Many biological rhythms are regulated by internaltiming mechanisms that serve as biological clocks. These timing mechanisms do not simply respond to environmental cues, but are capable of sustaining biological rhythms independently. Such internal clocks have been identified in almost every eukaryote (organism whose cells contain a nucleus and other structures enclosed within membranes) as well as some bacteria. Molecular biologists have demonstrated that genes control biological clocks. In fruit flies, seven genes produce clock proteins that seem to interact in feedback loops in many cell types both inside and outside the nervous system. Researchers have identified similar genes and proteins in many animal groups, including mammals. The principal clock is located in specific areas of the central nervous system.
According to paragraph 5, which of the following statements about biological clocks is true?
Factual Information Questions事实信息题
AThey do not always need environmental cues to maintain biological rhythms.
BThey are found more in bacteria than in eukaryotes.
CThey can be located anywhere in the central nervous system.
DThey depend on the same seven genes in different animal groups.
7
In mammals, the master clock is located in the suprachiasmatic nucleus(SCN)in part of the mammalian brain called the hypothalamus. This SCN clock generates approximately 24-hour cycles even without input from the environment. However, the SCN-generated cycles are normally adjusted every day based on visual input received from the retina, the light-sensitive part of the eye. Signals from the retina reflecting changes in light intensity adjust internal circadian rhythms to light-dark cycles in the environment. The SCN sends rhythmic signals, in the form of molecules that transmit information in the nervous system, to the pineal gland, an endocrine gland located in the brain. In response, the pineal gland secretes melatonin, a hormone that promotes sleep in humans. Clock genes in the SCN are turned on and off by the very proteins they encode, setting up complex feedback loops that have a 24-hour cycle. In addition to the master clock, most cells have timing mechanisms that use many of the same clock proteins. These peripheral clocks may function independently of the SCN.
The word “intensity in the passage is closest in meaning to
Vocabulary Questions词汇题
ADistribution
Bresponse
Ceffect
Dstrength
8
In mammals, the master clock is located in the suprachiasmatic nucleus(SCN)in part of the mammalian brain called the hypothalamus. This SCN clock generates approximately 24-hour cycles even without input from the environment. However, the SCN-generated cycles are normally adjusted every day based on visual input received from the retina, the light-sensitive part of the eye. Signals from the retina reflecting changes in light intensity adjust internal circadian rhythms to light-dark cycles in the environment. The SCN sends rhythmic signals, in the form of molecules that transmit information in the nervous system, to the pineal gland, an endocrine gland located in the brain. In response, the pineal gland secretes melatonin, a hormone that promotes sleep in humans. Clock genes in the SCN are turned on and off by the very proteins they encode, setting up complex feedback loops that have a 24-hour cycle. In addition to the master clock, most cells have timing mechanisms that use many of the same clock proteins. These peripheral clocks may function independently of the SCN.
According to paragraph 6, what is the role of the pineal gland in regulating biological rhythms in mammals?
Factual Information Questions事实信息题
AIt sends rhythmic signals in the form of molecules to various parts of the nervous system.
BIt turns the clock genes on and off.
CIt prevents input from the environment from disrupting the 24hour cycles generated by the SCN.
DIt secretes a hormone in response to signals from the SCN.
9
The behavior of many animals is organized around circadian(meaning “approximately one day”)rhythms which are daily(24-hour) cycles of activity. [■]Diurnal animals, such as honeybees and pigeons, are most active during the day. [■]Most bats, moths, and cats are nocturnal animals, most active during the hours of darkness. [■]Crepuscular animals, like many mosquitoes and fiddler crabs, are busiest at dawn or dusk, or both. [■]Generally, there are ecological reasons for these patterns. If an animal’s food is most plentiful in the early morning, its cycle of activity must be regulated so that it becomes active shortly before dawn.
Look at the four squares [■] that indicate where the following sentence could be added to the passage
Animals differ in their behavioral patterns within these daily cycles.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Biologists have identified many types of biological rhythms that govern the behavior of animals
Prose Summary Questions概要小结题
Select 3 answers
AThe physiological cycles as well as the behavior of many animals are organized around circadian rhythms, with some animals most active during the day, others at night, and others at dawn and/or dusk.
BThe biological rhythms that control metabolic processes are attuned to different cyclic changes in the environment than those that control behaviors such as sleep, feeding, migration, and reproduction
CGenes produce clock proteins that can sustain biological rhythms without environmental cues, and in mammals a master SCN clock generates 24-hour cycles that are adjusted by visual input from the retina.
DSome marine organisms display rhythms that correspond to regular tidal, lunar, and annual changes in their environment to reproduce successfully, engage in social activities, and keep safe
EBiologists have determined that, in almost every eukaryote and even in some bacteria, the same seven genes produce clock proteins that interact in feedback loops to control biological rhythms
FIn mammals, clock genes in the SCN differ from other clock genes in that they are turned on and off by certain proteins at intervals that keep internal circadian rhythms adjusted to external light-dark cycles.
