The African elephant, the largest land animal remaining on earth , is of great importance to African ecosystem(生态系统). Unlike other animals, the African elephant is to a great extent the builder of its environment. As a big plant-eater, it largely shapes the forest-and-savanna(大草原)surroundings in which it lives, therefore setting the terms of existence for millions of other animals that live in its habitat(栖息地).

    It is the elephant's great desire for food that makes it a disturber of the environment and an important builder of its habitat. In its continuous search for the 300 pounds of plants it must have every day, it kills small trees and underbushes, and pulls branches off big trees. This results in numerous open spaces in both deep tropical forests and in the woodlands that cover part of the African savannas. In these open spaces are numerous plants in various stages of growth that attract a variety of other plant-eaters.

    Take the rain forests for example. In their natural state, the spreading branches overhead shut out sunlight and prevent the growth of plants on the forest floor. By pulling down trees and eating plants, elephants make open spaces, allowing new plants to grow on the forest floor. In such situations, the forests become suitable for large hoofed plant-eaters to move around and for small plant-eaters to get their food as well.

    What worries scientists now is that the African elephant has become an endangered species. If the elephant disappears, scientists say, many other animals will also disappear from vast areas of forest and savanna, greatly changing and worsening the whole ecosystem.

    You're in a department store and you see a couple of attractive young women looking at a sweater．You listen to their conversation：

    “I can't believe it－Lorenzo Bertolla! They are almost impossible to find．Isn't it beautiful? And it's a lot cheaper than the one Sara bought in Rome．”

    They leave and you go over to see this incredible sweater．It's nice and the price is right．You've never heard of Lorenzo Bertolla, but those girls looked really stylish．They must know．So, you buy it．You never realize that those young women are employees of an advertising agency．They are actually paid to go from store to store, talking loudly about Lorenzo Bertolla clothes．

    Every day we notice what people are wearing, driving and eating．If the person looks cool, the product seems cool, too．This is the secret of undercover marketing．Companies from Ford to Nike are starting to use it．

    Undercover marketing is important because it reaches people that don't pay attention to traditional advertising．This is particularly true of the MTV generation－consumers between the age of 18 and （3）It's a golden group．They have a lot of money to spend, but they don't trust ads．

    So advertising agencies hire young actors to “perform” in bars and other places where young adults go．Some people might call this practice misleading, but marketing executive Jonathan Ressler calls it creative．“Look at traditional advertising．Its effectiveness is decreasing．”It is true, because everyone knows an ad is trying to persuade you to buy something．However, you don't know when a conversation you overhear is just a performance．

    Thomas Edison received a patent(专利) for his kinetoscope(电影放映机) on August31, 1887. It was a machine for viewing moving pictures. Edison had hoped to combine his no invention with the phonograph(留声机), which he had invented 10 years earlier. He thought that people would like to watch moving pictures that went along with the sound. He was not able to make them work together. The kinetoscope, however, was a popular attraction by itself. A person looked through small holes in a box-like machine and saw pictures in action. One of the first films made showed a man sneezing.

    A problem with this invention was that only one person could view the moving pictures at a time. By 1891, Edison had invented a projector that showed the film on a screen. Many people could watch together.

    In 1893, Edison built a motion-picture studio. He made over 300 silent films. Most of them were short. That was because the pictures flashed, or shook a lot. It was hard for people to watch more than 10 minutes at a time.

    The first films were mostly of real events. They would show famous people walking somewhere, cars on a street, burning houses, and other news stories. Then comedies and short dramas were made.

    Edison's movie studio closed in 1918. By then other companies were also making films. Better cameras were made. Sound was added. Then color came along. Today, movies are among the most popular forms of entertainment.

    The "Give It Up for Earth Day" encourages people to commit to giving up actions that are harmful to the environment, such as using poisonous cleaners.

    Throughout the month of April, Canadians are being asked to "Give It Up for Earth Day!" Earth Day has been celebrated every year on April 22 since 1970. Earth Day Canada president Jed Goldberg says that as people become more environmentally aware, they want to find ways to reduce their environmental influence, not just celebrate one special event.

    "Earth Day is a great launching pad for thinking about environmental action every day," said Goldberg. "Choosing healthier options, even for the short term, can lead to thinking about the influence of our decisions for a lifetime."

    That's the reason behind the "Give It Up for Earth Day" campaign. It's designed to encourage healthy habits that benefit people and the planet. It challenges everyone to help create a healthier world by making changes in their daily routine.

    "We wanted to plan an action—targeted campaign that will give people a chance to act on their concern for the environment in a positive way," said Goldberg.

    The campaign has identified four daily actions that can add up to huge environmental savings. They include pledging (保证) to turn off the TV, give up the use of poisonous cleaners, reduce consumption of consumer products and cut out meat.

    At the end of April, all of the pledges will be recorded and converted (转化) into the number of TV hours not watched, dollars not spent on unnecessary items, electricity saved, greenhouse gas emissions (排放) avoided by cutting out meat, and poisonous chemicals produced from homes and landfills.

    "What we're trying to achieve this year for Earth Day is to give people a chance to do something that is meaningful and measurable," said Goldberg.

    Li Hua is currently studying at Cambridge, UK. She has bought a bicycle and is worried about security. Her friend, Kate, found this article and sent it to her.

    Introduction

    A lot of crime is against bicycles. About 150, 000 bicycles are stolen every year and most are never found. You can prevent this happening by following a few careful steps.

    Basic Security

    Do not leave your bicycle in out-of-the-way places. Always lock your bicycle when youleave. Secure it to lampposts or trees. Take off smaller parts and take them with you, for example lights and saddlesleave（车座）.

    Locks

    Get a good lock. There are many different types in the shops. Buy one that has been tested against attack. Ask for a recommendation from a bike shop.

    Marking

    Security marking your bike can act as a deterrent to a thief. It can also help the police find your bicycle. It should be clearly written and include your postcode and your house or flat number. This will provide a simple way to identify your bicycle.

    Registration (登记)

    There are a number of security companies who will help mark your bicycle for you. They will then put your registration number and personal details on their computer database. Then if your bicycle is found it will be easy to contact you.

    Finally

    Keep a record of the bicycle yourself: its maker, model and registration number. You can even take a photograph of it. This will prove the bicycle belongs to you.

Ivan Pavlov was a Russian physiologist (生理学家) best known for his discovery of classical conditioning (经典条件反射). During his studies on the digestive systems of dogs, Pavlov found that the animals salivated (流口水) naturally upon the presentation of food. However, he also noticed that the animals began to salivate whenever they saw the white lab coat of an experimental assistant. By associating the presentation of food with the lab assistant, he finally found that a dog would salivate to the presence of a stimulus (刺激物) other than food. He called this response a conditional reflex.

Ivan Pavlov was born in a small village in Ryazan. Russia, where his father was the village minister. His earliest studies were focused on theology (神学), but reading Charles Darwin's On the Origin of Species had a powerful influence on his future interests. He soon stopped his religious studies and devoted himself to the study of science at the University of Saint Petersburg. Pavlov's interests were the study of physiology and natural sciences. He helped found the Department of Physiology at the Institute of Experimental Medicine and continued to manage the program for the next 45 years.

Pavlov received much praise for his work. He worked in the Russian Academy of Science and won the 1904 Nobel Prize in Physiology. The Soviet government also offered lots of support for Pavlov's work, and the Soviet Union soon became a leading center of research on physiology. While Ivan Pavlov was not a psychologist, and reportedly disliked the field of psychology, his work had a major influence on the field, particularly on the development of behaviorism. His discovery and research on reflexes influenced the growing behaviorist movement. and Pavlov's discovery had a major influence on many thinkers, such as John B. Watson.