when honeybees become foragers
Many species of insect, including the familiar honeybee, exhibit considerable flexibility in their behavioral development. Honeybee colonies usually contain tens of thousands of sterile female worker bees laboring on behalf of a single queen, who lays most or all of the eggs in her hive. At first, the young workers feed the larvae that hatch from the queen’s eggs (most of which will become new workers), but after about three weeks of nurse duty, they graduate to the job of collecting pollen and nectar outside the hive.
Research indicates that the age-related transition between nursing and foraging (collecting food) is regulated by hormonal changes. Young nurse workers have very low concentrations of juvenile hormone in their blood, whereas older foragers have much higher concentrations of this hormone. If young bees are treated with juvenile hormone, they become early foragers. In contrast, the onset of foraging behavior is delayed by removal of the corpora allata, the glands that produce juvenile hormone; furthermore, bees without corpora allata that receive hormone treatment regain normal timing of the switch to foraging. Bees that collect pollen and nectar also have bigger mushroom bodies, an anatomical feature of the honeybee brain. Neither juvenile hormone nor foraging experience appears to be necessary for this change in brain structure to occur, although both factors influence the rate at which the mushroom bodies grow. The expansion of the mushroom bodies takes place in anticipation of the needs of foragers, as they must be able to recognize spatial landmarks so they can travel back and forth between the hive and distant patches of flowers.
As it turns out, the changes in juvenile hormone concentrations that take place within the bodies of honeybee workers are not absolutely fixed with worker age. This conclusion is based on experiments with colonies that have been manipulated so that all the workers are the same, relatively young, age. Under these conditions, a division of labor still manifests itself, with some individuals remaining nurses much longer than usual while others start foraging as much as two weeks sooner than average. As a result, the larvae are cared for continuously while the colony also receives food supplies.
What enables bees to make these developmental adjustments? One hypothesis is that a deficit in social encounters with older foragers may stimulate the developmental transition from nurse to forager behavior. This possibility has been tested by studies in which groups of older foragers were added to experimental colonies made up of only young workers. The higher the proportion of older bees, the lower the proportion of young nurse bees that undergo an early transformation into foragers. The behavioral interactions between the young residents and the older transplants must inhibit the development of foraging behavior.Transplants of young workers have no such effect on young workers already at the site. Thus, the social environment of young honeybee workers influences their behavioral development by regulating the release of a key hormone. When released, the hormone becomes part of a bee’s cellular environment and modifies the properties of the brain’s nerve cells. After these hormonally induced changes in brain structure have occurred, workers change their behavior to match the special needs of their hive.
The interaction between genetic information and the environmental causes of task-switching in the honeybee has been highlighted by a study of how genetic variation affects the rate of behavioral development in this insect. If one keeps genetically different lineages of honeybees in identical conditions, some genotypes (genetic makeups) respond to exactly the same hive environment differently by making the transition from nurse to forager more quickly than others. If the physiological cause of task-switching is the increase in juvenile-hormone concentrations caused by changes in the social environment, then the genes of fast- developing lineages can be predicted to influence things like the production schedule for juvenile hormone or the sensitivity of individuals to the age composition of their colony. As it turns out, some genotypes do tend to make more juvenile hormone sooner than usual, while other genotypes are especially sensitive to increases in the numbers of older workers in their hives. Thus, several different physiological routes can lead to fast (or slow) behavioral development in the honeybee, each dependent on a particular mix of genetic and environmental factors.
1
Many species of insect, including the familiar honeybee, exhibit considerable flexibility in their behavioral development. Honeybee colonies usually contain tens of thousands of sterile female worker bees laboring on behalf of a single queen, who lays most or all of the eggs in her hive. At first, the young workers feed the larvae that hatch from the queen’s eggs (most of which will become new workers), but after about three weeks of nurse duty, they graduate to the job of collecting pollen and nectar outside the hive.
According to paragraph 1, what is the typical job of the youngest female honeybee workers?
Factual Information Questions事实信息题
ACaring for the hive’s queen
BProtecting the queen’s unhatched eggs
CFeeding hatched larvae
DCollecting pollen and nectar
2
Research indicates that the age-related transition between nursing and foraging (collecting food) is regulated by hormonal changes. Young nurse workers have very low concentrations of juvenile hormone in their blood, whereas older foragers have much higher concentrations of this hormone. If young bees are treated with juvenile hormone, they become early foragers. In contrast, the onset of foraging behavior is delayed by removal of the corpora allata, the glands that produce juvenile hormone; furthermore, bees without corpora allata that receive hormone treatment regain normal timing of the switch to foraging. Bees that collect pollen and nectar also have bigger mushroom bodies, an anatomical feature of the honeybee brain. Neither juvenile hormone nor foraging experience appears to be necessary for this change in brain structure to occur, although both factors influence the rate at which the mushroom bodies grow. The expansion of the mushroom bodies takes place in anticipation of the needs of foragers, as they must be able to recognize spatial landmarks so they can travel back and forth between the hive and distant patches of flowers.
The phrase “in anticipation of” in the passage is closest in meaning to
Vocabulary Questions词汇题
Ain expectation of
Bas a result of
Cin satisfaction of
Din proportion to
3
Research indicates that the age-related transition between nursing and foraging (collecting food) is regulated by hormonal changes. Young nurse workers have very low concentrations of juvenile hormone in their blood, whereas older foragers have much higher concentrations of this hormone. If young bees are treated with juvenile hormone, they become early foragers. In contrast, the onset of foraging behavior is delayed by removal of the corpora allata, the glands that produce juvenile hormone; furthermore, bees without corpora allata that receive hormone treatment regain normal timing of the switch to foraging. Bees that collect pollen and nectar also have bigger mushroom bodies, an anatomical feature of the honeybee brain. Neither juvenile hormone nor foraging experience appears to be necessary for this change in brain structure to occur, although both factors influence the rate at which the mushroom bodies grow. The expansion of the mushroom bodies takes place in anticipation of the needs of foragers, as they must be able to recognize spatial landmarks so they can travel back and forth between the hive and distant patches of flowers.
According to paragraph 2, one way nurse workers differ from foragers is that nurse workers
Factual Information Questions事实信息题
Aare larger
Bhave corpora allata glands that are more active
Cdo not yet have any juvenile hormone in their blood
Dhave smaller mushroom bodies in their brains
4
Research indicates that the age-related transition between nursing and foraging (collecting food) is regulated by hormonal changes. Young nurse workers have very low concentrations of juvenile hormone in their blood, whereas older foragers have much higher concentrations of this hormone. If young bees are treated with juvenile hormone, they become early foragers. In contrast, the onset of foraging behavior is delayed by removal of the corpora allata, the glands that produce juvenile hormone; furthermore, bees without corpora allata that receive hormone treatment regain normal timing of the switch to foraging. Bees that collect pollen and nectar also have bigger mushroom bodies, an anatomical feature of the honeybee brain. Neither juvenile hormone nor foraging experience appears to be necessary for this change in brain structure to occur, although both factors influence the rate at which the mushroom bodies grow. The expansion of the mushroom bodies takes place in anticipation of the needs of foragers, as they must be able to recognize spatial landmarks so they can travel back and forth between the hive and distant patches of flowers.
Paragraph 2 suggests that an important function of the mushroom bodies in the brains of honeybees is
Inference Questions推理题
Ahelping regulate the production of juvenile hormone
Benabling the bees to recognize landmarks
Cenabling the bees to tell whether a patch of flowers is suitable for foraging
Dactivating the switch to foraging
5
As it turns out, the changes in juvenile hormone concentrations that take place within the bodies of honeybee workers are not absolutely fixed with worker age. This conclusion is based on experiments with colonies that have been manipulated so that all the workers are the same, relatively young, age. Under these conditions, a division of labor still manifests itself, with some individuals remaining nurses much longer than usual while others start foraging as much as two weeks sooner than average. As a result, the larvae are cared for continuously while the colony also receives food supplies.
How did workers react when they were placed in colonies manipulated so that the workers were all the “same, relatively young, age”?
Rhetorical Purpose Questions修辞目的题
ASome began spending unusually long periods of time out gathering food supplies.
BSome switched back and forth between acting as nurses and acting as foragers.
CSome never transitioned to foraging and instead cared for larvae continuously.
DSome continued nursing longer than usual while others became foragers sooner than usual.
6
What enables bees to make these developmental adjustments? One hypothesis is that a deficit in social encounters with older foragers may stimulate the developmental transition from nurse to forager behavior. This possibility has been tested by studies in which groups of older foragers were added to experimental colonies made up of only young workers. The higher the proportion of older bees, the lower the proportion of young nurse bees that undergo an early transformation into foragers. The behavioral interactions between the young residents and the older transplants must inhibit the development of foraging behavior.Transplants of young workers have no such effect on young workers already at the site. Thus, the social environment of young honeybee workers influences their behavioral development by regulating the release of a key hormone. When released, the hormone becomes part of a bee’s cellular environment and modifies the properties of the brain’s nerve cells. After these hormonally induced changes in brain structure have occurred, workers change their behavior to match the special needs of their hive.
The phrase “deficit in” in the passage is closest in meaning to
Vocabulary Questions词汇题
Aincrease in
Binterference with
Cshortage of
Dpreference for
7
What enables bees to make these developmental adjustments? One hypothesis is that a deficit in social encounters with older foragers may stimulate the developmental transition from nurse to forager behavior. This possibility has been tested by studies in which groups of older foragers were added to experimental colonies made up of only young workers. The higher the proportion of older bees, the lower the proportion of young nurse bees that undergo an early transformation into foragers. The behavioral interactions between the young residents and the older transplants must inhibit the development of foraging behavior.Transplants of young workers have no such effect on young workers already at the site. Thus, the social environment of young honeybee workers influences their behavioral development by regulating the release of a key hormone. When released, the hormone becomes part of a bee’s cellular environment and modifies the properties of the brain’s nerve cells. After these hormonally induced changes in brain structure have occurred, workers change their behavior to match the special needs of their hive.
What is the purpose of the sentence “Transplants of young workers have no such effect on young workers already at the site”？
Rhetorical Purpose Questions修辞目的题
ATo explain why researchers added older foragers to experimental colonies made up of only younger workers
BTo add evidence supporting the idea that the social environment of young honeybees influences their behavioral development
CTo provide evidence that the release of a key hormone induces changes in the brain structure of young worker bees
DTo identify the observation that first led to interest in studying the factors that inhibit the development of foraging behavior
8
The interaction between genetic information and the environmental causes of task-switching in the honeybee has been highlighted by a study of how genetic variation affects the rate of behavioral development in this insect. If one keeps genetically different lineages of honeybees in identical conditions, some genotypes (genetic makeups) respond to exactly the same hive environment differently by making the transition from nurse to forager more quickly than others. If the physiological cause of task-switching is the increase in juvenile-hormone concentrations caused by changes in the social environment, then the genes of fast- developing lineages can be predicted to influence things like the production schedule for juvenile hormone or the sensitivity of individuals to the age composition of their colony. As it turns out, some genotypes do tend to make more juvenile hormone sooner than usual, while other genotypes are especially sensitive to increases in the numbers of older workers in their hives. Thus, several different physiological routes can lead to fast (or slow) behavioral development in the honeybee, each dependent on a particular mix of genetic and environmental factors.
According to paragraph 5, genetic variation affects honeybee development in part by causing some honeybees to become
Factual Information Questions事实信息题
Aless dependent on juvenile-hormone concentrations for task-switching
Bespecially sensitive to having a large proportion of older bees in their colony
Cable to detect differences in the genotypes of other bees in their hive
Dunable to interact successfully with bees of other genetic lineages
9
What enables bees to make these developmental adjustments? [■]One hypothesis is that a deficit in social encounters with older foragers may stimulate the developmental transition from nurse to forager behavior. [■]This possibility has been tested by studies in which groups of older foragers were added to experimental colonies made up of only young workers. [■]The higher the proportion of older bees, the lower the proportion of young nurse bees that undergo an early transformation into foragers. [■]The behavioral interactions between the young residents and the older transplants must inhibit the development of foraging behavior.Transplants of young workers have no such effect on young workers already at the site. Thus, the social environment of young honeybee workers influences their behavioral development by regulating the release of a key hormone. When released, the hormone becomes part of a bee’s cellular environment and modifies the properties of the brain’s nerve cells. After these hormonally induced changes in brain structure have occurred, workers change their behavior to match the special needs of their hive.
Look at the four squaresthat indicate where the following sentence could be added to the passage
There must be some kind of cue that causes the bees to alter their behavior in order to meet the current needs of the hive.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Like many other insects, honeybees are flexible in their behavioral development.
Prose Summary Questions概要小结题
Select 3 answers
AThe proportion of forager bees in a hive depends on factors like the number of hatching larvae and the amount of food available near the hive.
BWhen workers lack the glands that produce juvenile hormone,their mushroom bodies do not grow, preventing these workers from becoming foragers.
CA combination of factors determines when task-switching occurs, with some bees making more juvenile hormones earlier and others reacting to the age composition of their colony.
DYoung workers have far lower concentrations of juvenile hormone in their blood than older workers do, and the switch from nurse to forager seems to occur as a result of this increase in hormone levels.
EThe exact age at which individual bees within a colony begin to forage varies somewhat because task-switching depends partly on the social conditions within a hive.
FStudies of the effects of genetic variation on behavioral development in honeybees indicate that the genes of fast-developing lineages also influence the speed with which spatial landmarks are recognized.
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