Honeybee Juvenile Hormone
The activities of honeybee hives are highly coordinated. Honeybees live in colonies made up of a single queen and up to 80,000 workers.The tasks of a worker usually change dramatically with age,a phenomenon known as age polyethism.A typical honeybee worker newly emerged as an adult,winged insect will live for approximately six weeks and during this time moves through an orderly progression of tasks:Young adults (4 to 12 days old)tend the queen and the pupae (pre-adult insects);middle-aged bees (13 to 20 days old)perform various tasks associated with nest maintenance and food storage;and the oldest bees (over 20 days of age) concentrate on foraging (searching for food)outside the nest.In general,young workers mostly stay inside the hive and tend to nursing and housekeeping,and older workers often leave the hive to forage.Keep in mind,however,that the actual changes in the duties performed by a worker usually involve only changes in the frequencies of particular types of behaviors with age,rather than the addition or loss of entire categories of behaviors.Also,the sequence is flexible,allowing duties to be reassigned if the hive’s needs change.
Age polyethism in worker honeybees is regulated by juvenile hormone (JH);levels of JH increase with age and mediate changes in work habits.These levels vary with age because of changes in the rate of its synthesis by the corpora allata,a pair of glands near the brain.Not only are the naturally occurring levels of JH correlated with a worker’s change in duties but also experimental manipulations of JH levels have resulted in the expected changes in behavior.Treating newly emerged worker bees with a chemical similar to JH speeds up behavioral maturation.On the other hand,removing the corpora allata delays but does not prevent the development of a worker into a forager.But that delay can be eliminated by juvenile-hormone treatments.
How does JH cause an adult worker’s behavior to change so dramatically?At least part of the answer is that JH affects brain structure.The most striking change in behavior during the usual progression of duties occurs when a worker becomes a forager. Unlike younger hive bees,foragers take long-distance flights;learn rapidly and form long-term memories;use the sun as a compass for orientation;and communicate to other foragers the distance to and direction of a food source.As a honeybee matures,there is a 20 percent increase in the size of the insect brain structures known as mushroom bodies.The mushroom bodies are important in learning, memory,and the processing of sensory information.The increase in volume is due to increases in the number of branches on the neurons, which increase the number of synapses (points at which nerve impulses pass from one neuron to another),thereby boosting the brain’s ability to process information.Thus,these changes in the mushroom bodies may prepare a worker to learn to navigate during foraging flights and to find its way back to the hive.
Juvenile hormone,not experience,is responsible for the growth of the mushroom bodies.This was demonstrated by treating one-day- old workers with a chemical that mimics the effects of JH to cause them to begin foraging sooner than usual.Normally,young workers take orientation flights to learn the lay of the land before they begin to forage.But some of the treated bees were prevented from leaving the hive for orientation flights by a large tag attached to their backs. Although the bees were different ages,the mushroom bodies of treated bees grew to about the size of those of untreated workers that were beginning to forage.Furthermore,the growth of the mushroom bodies was equivalent in treated bees with and without foraging experience.
Hormonal regulation of the age-based division of labor in honeybees is not a rigid system of control.Instead,it is a flexible process that permits ongoing adjustments in the proportions of workers involved in any one task.The rise in JH may be modulated due to environmental conditions such as food availability or age structure of the colony.For example,workers from starved colonies begin foraging a few days earlier than workers from well-fed colonies.
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The activities of honeybee hives are highly coordinated. Honeybees live in colonies made up of a single queen and up to 80,000 workers.The tasks of a worker usually change dramatically with age,a phenomenon known as age polyethism.A typical honeybee worker newly emerged as an adult,winged insect will live for approximately six weeks and during this time moves through an orderly progression of tasks:Young adults (4 to 12 days old)tend the queen and the pupae (pre-adult insects);middle-aged bees (13 to 20 days old)perform various tasks associated with nest maintenance and food storage;and the oldest bees (over 20 days of age) concentrate on foraging (searching for food)outside the nest.In general,young workers mostly stay inside the hive and tend to nursing and housekeeping,and older workers often leave the hive to forage.Keep in mind,however,that the actual changes in the duties performed by a worker usually involve only changes in the frequencies of particular types of behaviors with age,rather than the addition or loss of entire categories of behaviors.Also,the sequence is flexible,allowing duties to be reassigned if the hive’s needs change.
According to the passage,the term“age polyethism”in honeybees refers to the phenomenon whereby
Rhetorical Purpose Questions修辞目的题
Athe organization of the colony varies depending on the age of its queen
Bthe activities of a colony become more coordinated as the bees within it age
Cworkers of different ages perform the same task
Dthe age of a worker influences the type of duties the worker performs
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The activities of honeybee hives are highly coordinated. Honeybees live in colonies made up of a single queen and up to 80,000 workers.The tasks of a worker usually change dramatically with age,a phenomenon known as age polyethism.A typical honeybee worker newly emerged as an adult,winged insect will live for approximately six weeks and during this time moves through an orderly progression of tasks:Young adults (4 to 12 days old)tend the queen and the pupae (pre-adult insects);middle-aged bees (13 to 20 days old)perform various tasks associated with nest maintenance and food storage;and the oldest bees (over 20 days of age) concentrate on foraging (searching for food)outside the nest.In general,young workers mostly stay inside the hive and tend to nursing and housekeeping,and older workers often leave the hive to forage.Keep in mind,however,that the actual changes in the duties performed by a worker usually involve only changes in the frequencies of particular types of behaviors with age,rather than the addition or loss of entire categories of behaviors.Also,the sequence is flexible,allowing duties to be reassigned if the hive’s needs change.
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.
Rhetorical Purpose Questions修辞目的题
AFor most workers,only the frequency of particular behaviors changes with age,but some workers actually add or eliminate whole categories of behaviors as they get older.
BChanges in the frequency of the types of duties a worker performs as the worker ages can eventually result in the addition or loss of entire categories of behavior.
COrdinarily,age-related changes in duties are a matter of particular behaviors occurring more often or less often,not a matter of adding or dropping entire categories of behaviors.
DThe age of a worker at the time behavioral change occurs usually determines whether the worker continues performing any behaviors in that category or merely changes the frequency of performing such behaviors.
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The activities of honeybee hives are highly coordinated. Honeybees live in colonies made up of a single queen and up to 80,000 workers.The tasks of a worker usually change dramatically with age,a phenomenon known as age polyethism.A typical honeybee worker newly emerged as an adult,winged insect will live for approximately six weeks and during this time moves through an orderly progression of tasks:Young adults (4 to 12 days old)tend the queen and the pupae (pre-adult insects);middle-aged bees (13 to 20 days old)perform various tasks associated with nest maintenance and food storage;and the oldest bees (over 20 days of age) concentrate on foraging (searching for food)outside the nest.In general,young workers mostly stay inside the hive and tend to nursing and housekeeping,and older workers often leave the hive to forage.Keep in mind,however,that the actual changes in the duties performed by a worker usually involve only changes in the frequencies of particular types of behaviors with age,rather than the addition or loss of entire categories of behaviors.Also,the sequence is flexible,allowing duties to be reassigned if the hive’s needs change.
The word“sequence”in the passage is closest in meaning to
Vocabulary Questions词汇题
Apurpose
Border
Ctype
DBehavior
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Age polyethism in worker honeybees is regulated by juvenile hormone (JH);levels of JH increase with age and mediate changes in work habits.These levels vary with age because of changes in the rate of its synthesis by the corpora allata,a pair of glands near the brain.Not only are the naturally occurring levels of JH correlated with a worker’s change in duties but also experimental manipulations of JH levels have resulted in the expected changes in behavior.Treating newly emerged worker bees with a chemical similar to JH speeds up behavioral maturation.On the other hand,removing the corpora allata delays but does not prevent the development of a worker into a forager.But that delay can be eliminated by juvenile-hormone treatments.
Which of the following can be inferred from paragraph 2 about a worker’s corpora allata glands?
Inference Questions推理题
AThey produce a variety of chemicals that are similar to JH.
BThey can be removed from a worker without killing the bee.
CThey delay maturation in workers experimentally treated with JH.
DThey are more active in newly emerged workers than in foragers.
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Age polyethism in worker honeybees is regulated by juvenile hormone (JH);levels of JH increase with age and mediate changes in work habits.These levels vary with age because of changes in the rate of its synthesis by the corpora allata,a pair of glands near the brain.Not only are the naturally occurring levels of JH correlated with a worker’s change in duties but also experimental manipulations of JH levels have resulted in the expected changes in behavior.Treating newly emerged worker bees with a chemical similar to JH speeds up behavioral maturation.On the other hand,removing the corpora allata delays but does not prevent the development of a worker into a forager.But that delay can be eliminated by juvenile-hormone treatments.
Why does the author include the information that“Treating newly emerged worker bees with a chemical similar to JH speeds up behavioral maturation.”?
Rhetorical Purpose Questions修辞目的题
ATo demonstrate that factors other than age can affect naturally occurring JH levels in workers
BTo provide evidence that age polyethism in worker honeybees is regulated by JH
CTo prove that JH is not the only chemical ordinarily involved in the behavioral maturation of workers
DTo show that artificial JH may be more effective than naturally occurring JH in causing workers to mature behaviorally
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How does JH cause an adult worker’s behavior to change so dramatically?At least part of the answer is that JH affects brain structure.The most striking change in behavior during the usual progression of duties occurs when a worker becomes a forager. Unlike younger hive bees,foragers take long-distance flights;learn rapidly and form long-term memories;use the sun as a compass for orientation;and communicate to other foragers the distance to and direction of a food source.As a honeybee matures,there is a 20 percent increase in the size of the insect brain structures known as mushroom bodies.The mushroom bodies are important in learning, memory,and the processing of sensory information.The increase in volume is due to increases in the number of branches on the neurons, which increase the number of synapses (points at which nerve impulses pass from one neuron to another),thereby boosting the brain’s ability to process information.Thus,these changes in the mushroom bodies may prepare a worker to learn to navigate during foraging flights and to find its way back to the hive.
According to paragraph 3,the mushroom bodies are important for each of the following abilities of forager bees EXCEPT the ability to
Negative Factual Information Questions否定事实信息题
Aidentify food sources from a distance
Blearn quickly
Cform long-term memories
Duse the sun for orientation
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How does JH cause an adult worker’s behavior to change so dramatically?At least part of the answer is that JH affects brain structure.The most striking change in behavior during the usual progression of duties occurs when a worker becomes a forager. Unlike younger hive bees,foragers take long-distance flights;learn rapidly and form long-term memories;use the sun as a compass for orientation;and communicate to other foragers the distance to and direction of a food source.As a honeybee matures,there is a 20 percent increase in the size of the insect brain structures known as mushroom bodies.The mushroom bodies are important in learning, memory,and the processing of sensory information.The increase in volume is due to increases in the number of branches on the neurons, which increase the number of synapses (points at which nerve impulses pass from one neuron to another),thereby boosting the brain’s ability to process information.Thus,these changes in the mushroom bodies may prepare a worker to learn to navigate during foraging flights and to find its way back to the hive.
According to paragraph 3,compared to the mushroom-body neurons of younger honeybees,the mushroom-body neurons of foragers have
Factual Information Questions事实信息题
Amore branches
Bmore space between the branches
Clonger branches
Dfewer synapses
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Juvenile hormone,not experience,is responsible for the growth of the mushroom bodies.This was demonstrated by treating one-day- old workers with a chemical that mimics the effects of JH to cause them to begin foraging sooner than usual.Normally,young workers take orientation flights to learn the lay of the land before they begin to forage.But some of the treated bees were prevented from leaving the hive for orientation flights by a large tag attached to their backs. Although the bees were different ages,the mushroom bodies of treated bees grew to about the size of those of untreated workers that were beginning to forage.Furthermore,the growth of the mushroom bodies was equivalent in treated bees with and without foraging experience.
In paragraph 4,what were scientists trying to determine in the experiment using a chemical that has the effects of juvenile hormone on worker bees?
Factual Information Questions事实信息题
AWhether the chemical was as effective as juvenile hormone in stimulating the growth of the mushroom body in a worker bee’s brain
BWhether orientation flights block the effect of juvenile hormone
CWhether the experience of orientation flights is needed for the growth of the part of the brain that prepares worker bees to become foragers
DWhether worker bees as young as one day old could learn to forage
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Hormonal regulation of the age-based division of labor in honeybees is not a rigid system of control.[■]Instead,it is a flexible process that permits ongoing adjustments in the proportions of workers involved in any one task.[■]The rise in JH may be modulated due to environmental conditions such as food availability or age structure of the colony.[■]For example,workers from starved colonies begin foraging a few days earlier than workers from well-fed colonies.[■]
Look at the four squaresthat indicate where the following sentence could be added to the passage
Conversely,if favorable conditions allow the proportion of foragers to become uncommonly high,young workers remain in the hive longer than usual.
Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
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As a worker honeybee in a colony matures,the tasks the worker performs change,following a predictable progression.
Prose Summary Questions概要小结题
Select 3 answers
AExperiments show that in honeybees,the change of tasks with age is regulated by juvenile hormone levels,which increase as bees get older.
BChanges in the levels of juvenile hormone lead to changes in the brain that enable workers to do more advanced information processing.
CEvidence from starved hives indicates that for honeybees to synthesize juvenile hormone at normal rates,they must have ample food and be part of a well-functioning colony.
DThe speed with which individual bees reach behavioral maturity varies depending on the sensitivity of the individual’s corpora allata to juvenile hormone.
ETreating young workers with a chemical that blocks the synthesis of juvenile hormone prevents them from developing the brain capacity needed for successful foraging.
FAlthough the age-based division of labor in honeybees is regulated by juvenile hormone levels,it is flexible enough to allow adjustments in response to changes in colony needs.
