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1、 An Essential Scientific ProcessAll life on the earth depends upon green plants. Using sunlight, the plants produce their own food. Then animals feed upon the plants. They take in the nutrients the plants have made and stored. But thats not all. Sunlight also helps a plant produce oxygen. Some of th
2、e oxygen is used by the plant, but a plant usually produces more oxygen than it uses. The excess oxygen is necessary for animals and other organisms to live.The process of changing light into food and oxygen is called photosynthesis. Besides light energy from the sun, plants also use water and carbo
3、n dioxide. The water gets to the plant through its roots. The carbon dioxide enters the leaves through tiny openings called stomata. The carbon dioxide travels to chloroplasts, special cells in the bodies of green plants. This is where photosynthesis takes place. Chloroplasts contain the chlorophyll
4、s that give plants their green color. The chlorophylls are the molecules that trap light energy. The trapped light energy changes water and carbon dioxide to produce oxygen and a simple sugar called glucose.Carbon dioxide and oxygen move into and out of the stomata. Water vapor also moves out of the
5、 stomata. More than 90 percent of water a plant takes in through its roots escapes through the stomata. During the daytime, the stomata of most plants are open. This allows carbon dioxide to enter the leaves for photosynthesis. As night falls, carbon dioxide is not needed. The stomata of most plants
6、 close. Water loss stops.If photosynthesis ceased, there would be little food or other organic matter on the earth. Most organisms would disappear. The earths atmosphere would no longer contain oxygen. Photosynthesis is essential for life on our planet.1Then animals feed upon the plants.动物以植物为食。练习：1
7、In the first paragraph，the word “excess” meansAheavy.Bextra.Cgreen.Dliquid.2Which of the following does not move through a plants stomata?ACarbon dioxide.BWater vapor.COxygen.DFood.3In the title, the term Essential Scientific Process refers toAphotosynthesis.Bthe formation of glucose.Cglobal warming
8、.Dwater getting to the roots of plants.4This passage is primarily developed byAexplaining a process.Btelling a story.Ccomparing and contrasting.Dconvincing the reader of plants importance.5Another good title for this passage would beAOxygen and Carbon Dioxide.BPlants and Their Roots.CHow Photosynthe
9、sis Works.DWhy Our Earth Needs Water. A Record-Breaking RoverNASAs Mars rover Opportunity has boldly gone where no rover has gone beforeat least in terms of distance. _1F_On July 27, after years of moving about on Martian ground, the golf-cart-sized Opportunity had driven more than 24 miles, beating
10、 the previous record holdera Soviet rover sent to the moon in 1973.“This is so remarkable considering Opportunity was intended to drive about 1 kilometer and was never designed for distance,” says John Callas, the Mars Exploration Rover Project Manager._2B_ “But what is really importantly is not how
11、 many miles the rover has racked up, but how much exploration and discovery we have accomplished over that distance.”OPPORTUNITYThe solar-powered Opportunity and its twin rover, Spirit, landed on Mars 10 years ago on a mission expected to last 3 months. _3E_Spirit stopped communicating with Earth in
12、 March 2010, a few months after it got stuck in a sand pit. But Opportunity has continued to collect and analyze Martian soil and rocks.During its mission, Opportunity has captured, and sent back to Earth, some 187,000 panoramic and microscopic images of Mars with its cameras. _4A_MARATHON ROVERThe
13、rover doesnt seem to be ready to stop just yet. If Opportunity can continue on, it will reach another major investigation site when its odometer hits 26.2 miles. _5C_Researchers believe that clay minerals exposed near Marathon Valley could hold clues to Marss ancient environment1. Opportunitys conti
14、nuing travels will also help researchers as they plan for an eventual human mission to the Red Planet.注释：1could hold clues to Marss ancient environment：含有与火星早期环境有关的线索。练习：AIt has also provided scientists with data on the planets atmosphere, soil, rocks, and terrain.BHe works at NASAs Jet Propulsion L
15、aboratory in Pasadena, California.CScientists call this site Marathon Valley, because when the rover reaches the area, it will have traveled the same distance as the length of a marathon since its arrival on Mars.DOpportunity has been working on Mars since January 2004.EThe objective of the rovers was to help scientists learn more about the planet and to search for signs of life，such as the possible presence of water.FSince arriving on the Red Planet in 2004, Opportunity has traveled 25.01 miles, more than any other wheeled vehicle has on another
