2018-04-18 15:40:59 发布 来源：雷哥托福 阅读量：2874
1、How Soil is Formed
Soil formation is a dynamic process that takes place in different environments. It is strongly influenced by the parent material， climate （largely vegetation and temperature and water exchanges）， topography （the elevations， depressions， directions and angles of slopes， and other surface features of the landscape）， and time.
The parent material is the unconsolidated mass on which soil formation takes place. This material may or may not be derived from the on-site geological substrate or bedrock on which it rests. Parent materials can be transported by wind， water， glaciers， and gravity and deposited on top of bedrock. Because of the diversity of materials involved， soils derived from transported parent materials are commonly more fertile than soils from parent materials derived in place. Whatever the parent material， whether derived in place from bedrock or from transported material， it ultimately comes from geological materials， such as igneous， sedimentary， and metamorphic rocks， and the composition of the rocks largely determines the chemical composition of the soil.
Climate is most influential in determining the nature and intensity of weathering and the type of vegetation that further affects soil formation. The soil material experiences daily and seasonal variations in heating and cooling. Open surfaces exposed to thermal radiation undergo the greatest daily fluctuations in heating and cooling， soils covered with vegetation the least. Hill slopes facing the sun absorb more heat than those facing away from the sun. Radiant energy has a pronounced effect on the moisture regime， especially the evaporative process and dryness. Temperature can stimulate or inhibit biogeochemical reactions in soil material.
By the early 1900s the field of animal behavior had split into two major branches. One branch, ethology,developed primarily in Europe. To ethologists, what is striking about animal behaviors in that they are fixed and seemingly unchangeable? For example, kittens and puppies play in characteristic but different ways. Present a kitten with a ball of yarn and invariably it draws back its head and bats the yarn with claws extended. Kittens are generally silent as they play, and their tails twitch. Puppies, by contrast, are most likely to pounce flat-footed on a ball of yarn. They bit and bark and their tails wag. Ethologists came to believe that ultimately even the most complex animal behaviors could be broken down into a series of unchangeable stimulus/response reactions. They became convinced that the details of these patterns were as distinctive of a particular group of animals as were anatomical characteristics. For well over half a century, their search for and description of innate patterns of animal behavior continued.
Meanwhile, mainly in North America, the study of animal behavior took a different tack, developing into comparative behavior. Of interest to comparative behaviorists was where a particular came from, that is, its evolutionary history, how the nervous system controlled it, and the extent to which it could be modified. In 1894, C. Lloyd Morgan, an early comparative behaviorist, insisted that animal behavior be explained as simply as possible without reference to emotions or motivations since these could not be observed or measured. In Morgan’s research, animals were put in simple situations, presented with an easily described stimulus, and their resultant behavior described.
The extension to animals of behaviorism—the idea that the study of behavior should be restricted to only
those elements that can be directly observed—was an important development in comparative behavior. Studies of stimulus/response and the importance of simple rewards to enforce and modify animal behavior were stressed. Not surprisingly, comparative behaviorists worked most comfortably in the laboratory. Comparative behaviorists stressed the idea that animal behavior could be modified, while their ethologist colleagues thought it was innate and unchangeable. Inevitably, the two approaches led to major disagreements.
To early ethologists, the major driving force in behavior was instinct, behaviors that are inherited and unchangeable.
Moths move towards light because they inherit the mechanism to so respond to light. Although dogs have more options available to them, they bark at strangers for much the same reasons. The comparative behaviorists disagreed: learning and rewards are more important factors than instinct in animal behavior. Geese are not born with the ability to retrieve lost eggs when they roll out the nest, they learn to do so. If their behavior seems sometimes silly to humans because it fails to take new conditions into account, that is because the animal’s ability to learn is limited. There were too many examples of behaviors modified by experience for comparative behaviorists to put their faith in instincts
student & employee听力题目：
1. What does the woman hope to find out by going to the art museum？
A. What types of volunteer positions are available for students
B. How much she would be paid for working as a tour guide
C. Whether alternative arrangements can be made for becoming a tour guide D. Why a particular museum employee has not returned her phone calls
2. Why does the woman mention a test that she has to take？
A. To explain why she is unable to attend a training session
B. To let the man know that she will be late for the tour on Monday
C. To list one requirement she must fulfill to receive extra credit
D. To show that she is aware of what she must do to become a tour guide 3. Why does the woman want to start working at the art museum before the current semester ends？
A. To fulfill a graduation requirement
B. To improve her grade in a class
C. To earn money for the following semester
D. To conduct research for a paper
3. What does the man imply when he mentions Professor Tyler？
A. That he is familiar with the situation the woman is in
B. That the training session for new tour guides covers some of the same material covered in art history classes
C. That Professor Tyler recognizes which students would make good tour guides
D. That Professor Tyler may have given the woman incorrect information about the job
4. According to the man， why might the woman want to consider a data processing position ？
Click on 2 answers.
A. It is probably more exciting than working as a tour guide.
B. It would allow the woman to begin working immediately.
C. It would give the woman experience in her major.
D. It could eventually lead to a paying job.