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READING PASSAGE 1

You should spend about 20 minutes on Questions 1-12, which are based on Reading Passage 1 below.

FLIGHT OF THE HONEYBEE

  • Honeybees are characterised by their ability to produce liquefied sugar (honey) and a propensity to construct colonial nests using wax, two tasks that necessitate a significant level of social integration among members. As a result, they maintain strict divisions of labour, based on sex, with all males functioning as drones to fertilize and care for the eggs, and all females, with the exception of the single fertile queen, responsible for fetching nectar for the colony’s progeny. In addition, honeybees have devised a sophisticated system of communication to relay important information from member to member.
  • Perhaps the most intriguing feature of honeybee communication is a series of flight moves only performed by a female worker bee that has returned to the nest with nectar and needs to tell the rest of her colony that she has discovered food supplies and where they can be found. This so-called honeybee dance was first interpreted by German zoologist Karl von Frisch in the early 1970s. To facilitate observation, von Frisch and his students built several glass walled hives and marked a collection of worker bees, or foragers, with paint. He then trained those foragers to find nectar at designated sources at various distances from the hives, and when the bees returned he carefully recorded their movements, the angle and direction of their flight, and any additional visual cues offered to the colony. What von Frisch discovered was that each aspect of the dance indicated certain details about the location of the nectar reserves and recruited others to return to the site.
  • The first piece of information conveyed by dancing bees is the distance of the field to the hive, and they do this in one of three ways. If it is less than 50 meters from the colony’s nest the bee will fly around in narrow circles, and then suddenly fly in the opposite direction. She will repeat this pattern, which von Frisch’s team called the round dance, until she has recruited several other workers to return with her to the field. When the distance is greater than 50 meters, but less than 150 meters, she will perform a sickle dance, a crescent shaped flight course. If the field is farther than 150 meters, the forager will act out a waggle dance in which she will run straight ahead briefly before returning to her original position in a semi-circular movement. Then, she will run forward again and return from the opposite side. The length of the forward run coincides with the distance of the food supplies; for example, a 2.5 second run indicates that the nectar was found about 2500 meters way.
  • Recruits also need to know the direction in which they should fly to arrive at the appropriate foraging location, and this information is communicated via the bee’s angular orientation to the hive. It, however, is not a direct connection to the position of the food supplies from the hive, but its location relative to the sun. Therefore if the food is situated directly opposite from the sun, the bee will fly a straight run vertically downward; if it is in the same direction as the sun, it will fly directly upward from the colony nest. A position 60 degrees to the right of the sun will prompt the bee to fly downwards at a 60 degrees angle toward the right of the nest. Moreover, because the sun is in constant motion throughout the day, the bee’s orientation will shift depending on the time at which the dance is performed. Sceptics of von Frisch’s findings, however, claim that visual cues are not enough to provide all the clues necessary to convey the location of a food resource. Several scientists, among them Adrian Wenner, believe that the dance is only one component of honeybee communications; odour is the second key element. Using robotic bees to perform the same dances, Wenner was unable to attract new recruits to the foraging activities; however, when he added a bit of nectar to the robot, workers quickly followed. He also discovered that the odors must be representative of the actual flowers containing the food source; otherwise the bees will arrive at the site, but not know which ones will be profitable.
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