2019年10月12、13日托福阅读机经预测

来源:智课教育 时间:2019-10-09 13:11:49

   大家在备考托福阅读时,可以通过机经进行练习。因为机经内容里有更多的背景知识,这些内容有利于大家更好的理解文章,对于考试成绩提升也有很大的帮助。今天小编为大家带来了2019年10月12、13日托福阅读机经预测,下面一起来看看吧。

  Honeybee

  Foragers communicate their floral findings in order to recruit other worker bees of the hive to forage in the same area. The factors that determine recruiting success are not completely known but probably include evaluations of the quality of nectar and/or pollen brought in.

  There are two main hypotheses to explain how foragers recruit other workers—the "waggle dance" or "dance language" theory and the "odor plume" theory. The dance language theory is far more widely accepted, and has far more empirical support. The theories also differ in that the former allows for an important role of odor in recruitment (i.e., effective recruitment relies on dance plus odor), while the latter claims that the dance is essentially irrelevant (recruitment relies on odor alone). The academic debate between these two theories is extremely polarized and often hostile.[7]

  Dance communication

  Figure-Eight-Shaped waggle dance of the honeybee (Apis mellifera). A waggle run oriented 45° to the right of ‘up' on the vertical comb indicates a food source 45° to the right of the direction of the sun outside the hive. The abdomen of the dancer appears blurred because of the rapid motion from side to side.

  It has long been known that successfully foraging Western honey bees perform a dance on their return to the hive, known as waggle dance, indicating that food is farther away, while the round dance is a short version of the waggle dance, indicating that food is nearby. The laden forager dances on the comb in a circular pattern, occasionally crossing the circle in a zig-zag or waggle pattern. Aristotle described this behaviour in his Historia Animalium.[8] It was thought to attract the attention of other bees.

  In 1947,[citation needed] Karl von Frisch correlated the runs and turns of the dance to the distance and direction of the food source from the hive. The orientation of the dance correlates to the relative position of the sun to the food source, and the length of the waggle portion of the run is correlated to the distance from the hive. Also, the more vigorous the display is, the better the food. There is no evidence that this form of communication depends on individual learning. Honeybees detect the dances of conspecifics by sensing near field sound and electric fields using the Johnston's organ.

  Von Frisch performed a series of experiments to validate his theory.[9] He was awarded the Nobel Prize in Physiology or Medicine in 1973 for his discoveries.

  One of the most important lines of evidence on the origin and utility of the dance is that all of the known species and races of honey bees exhibit the behavior, but details of its execution vary among the different species. For example, in Apis florea and Apis andreniformis (the "dwarf honeybees") the dance is performed on the dorsal, horizontal portion of the nest, which is exposed. The runs and dances point directly toward the resource in these species. Each honey bee species has a characteristically different correlation of "waggling" to distance, as well.[10] Such species-specific behavior suggests that this form of communication does not depend on learning but is rather determined genetically. It also suggests how the dance may have evolved.

  Various experiments document that changes in the conditions under which the dance is performed lead to characteristic changes in recruitment to external resources,[11] in a manner consistent with von Frisch's original conclusions. Experiments with robotic dummies were indeed to induce some recruitment,[12] which should not have been possible if the dance contains no information. Various experimental results demonstrate that the dance does convey information, but the use of this information may be context-dependent,[13] and this may explain why the results of earlier studies were inconsistent. Researchers have also discovered other forms of honeybee dance communication, such as the tremble dance.

  Odor plume

  While many researchers believe that bee dances give enough information to locate resources, proponents of the odor plume theory argue that the dance gives little, or no actual guidance to a nectar source. They argue that bees instead are primarily recruited by odor. The purpose of the dance is simply to gain attention to the returning worker bee so she can share the odor of the nectar with other workers who will then follow the odor trail to the source. Most scientists agree that odor is used in recruitment to resources, but they differ strongly in opinion as to the information content of the dance.[citation needed]

  The primary lines of evidence used by the odor plume advocates are experiments with odorless sugar sources which show that worker bees are unable to recruit to those sources[14] and logical difficulties of a small-scale dance (a few centimeters across) giving directions precise enough to hold the other bees on course during a flight that could be several kilometers long. Misreading by even a few degrees would lead the bee off course by hundreds of meters at the far end.[citation needed]

  Neither of these points invalidate the dance theory, but simply suggest that odor might be involved, which is indeed conceded by all proponents of dance theory.[citation needed] Critics of the odor plume theory counter that most natural nectar sources are relatively large—orchards or entire fields— so, precision may not be necessary or even desirable. They have also challenged the reproducibility of the odorless source experiment.

  Odor learning in bees is usually tested by the proboscis extension reflex. Significant to the argument are the experiments of William F. Towne, of the Kutztown University in Pennsylvania,[15] in which hives are moved to "mirror image" terrain settings, and the bees are thereby fooled into dancing about the wrong location for a nectar source. Foragers were successfully recruited to the wrong location, but only when the sun was obscured by clouds, forcing them to rely on terrain-based navigation rather than "solar ephemeris"-based navigation. As the cloud cover broke up, more and more bees corrected their dances to indicate the actual location of nectar, and forager visits shifted to the correct location.

  Odor is an essential and even necessary at various stages of the recruitment process, including once a recruited forager reaches the vicinity of the resource[16] while some scientists think that dancing may be a simple idiothetic movement that conveys no information.[17] Others see the dance as conveying information, but doing it poorly compared to other means and potentially used backup approach.

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