第九篇AnEssential Scientific ProcessAll life on the earth depends upon green ing sunlight, the plants produce their own food. Then animals feed upon theplants. They take in the nutrients the plants have made and stored. But that‟snot all. Sunlight also helps a plant produce oxygen. Some of the oxygen is usedby the plant, but a plant usually produces more oxygen than it uses. The excess oxygen is necessary for animalsand other organisms to live.The process of changing light into food and oxygenis called photosynthesis. Besides light energy from the sun, plants also usewater and carbon dioxide. The water gets to the plant through its roots. Thecarbon dioxide enters the leaves through tiny openings called stomata. Thecarbon dioxide travels to chloroplasts, special cells in the bodies of greenplants. This is where photosynthesis takes place. Chloroplasts contain the chlorophyllsthat give plants their green color. The chlorophylls are the molecules thattrap light energy. The trapped light energy changes water and carbon dioxide toproduce oxygen and a simple sugar called glucose.Carbon dioxide and oxygen move into and out of thestomata. Water vapor also moves out of the stomata. More than 90 percent ofwater a plant takes in through its roots escapes through the stomata. Duringthe daytime, the stomata of most plants are open. This allows carbon dioxide toenter the leaves for photosynthesis. As night falls, carbon dioxide is notneeded. The stomata of most plants close. Water loss stops.If photosynthesis ceased, there would be littlefood or other organic matter on the earth. Most organisms would disappear. Theearth‟s atmosphere would no longer contain oxygen. Photosynthesis is essentialfor life on our planet.An Essential Scientific Process参考译文：一个至关重要的科学过程1. All life on the earth depends upon green plants.参考译文：地球上所有的生命都依靠绿色植物生存。

2. Using sunlight, the plants produce their ownfood.参考译文：植物利用阳光制造自己的食物。

3. Then animals feed upon the plants.参考译文：而动物则以植物为食。

4. They take in the nutrients the plants have madeand stored.参考译文：它们吸收植物制造和储存的营养物质。

5. But that's not all.参考译文：但是植物能做的不仅仅是这些。

6. Sunlight also helps a plant produce oxygen.参考译文：植物还能利用阳光制造氧气。

7. Some of the oxygen is used by the plant, but a plant usually produces more oxygen thanit uses.参考译文：这些氧气的一部分被植物自身消耗了，但植物制造的氧气远多于它们消耗的氧气。

8. The excess oxygen is necessary for animals andother organisms to live.参考译文：这些额外的氧气对于动物以及其他生物体的生存是至关重要的。

9. The process of changing light into food andoxygen is called photosynthesis.参考译文：植物将光转化为食物和氧气的过程叫做光合作用。

10. Besides light energy from the sun, plants alsouse water and carbon dioxide.参考译文：植物不仅吸收阳光中的能量，还吸收水和二氧化碳。

11. The water gets to the plant through its roots.参考译文：水通过根系进入植物体内。

12. The carbon dioxide enters the leaves throughtinyopeningscalled stomata.参考译文：二氧化碳通过小孔进入叶子，这些小孔叫做气孔。

13. The carbon dioxide travels to chloroplastsspecial cells in the bodies of green plants.参考译文：二氧化碳到达叶绿体，叶绿体是绿色植物体内的一种特殊细胞。

14. This is where photosynthesis takes place.参考译文：光合作用就是在这里发生的。

15. Chloroplasts contain the chlorophylls that giveplants their green color.参考译文：叶绿体内含有叶绿素，这种物质使得叶子呈现绿色。

16. The chlorophylls are the molecules that traplight energy.参考译文：叶绿素是能够收集光能的分子。

17. The trapped light energy changes water andcarbon dioxide to produce oxygen anda simple sugar called glucose.参考译文：收集来的光能将水和二氧化碳转化，产生氧气和一种单糖——葡萄糖。

18. Carbon dioxide and oxygen move into and out ofthe stomata.参考译文：二氧化碳和氧气通过气孔进出。

19. Water vapor also moves out of the stomata.参考译文：水蒸气也是从气孔逸出。

20. More than 90 percent of water a plant takes inthrough its roots escapes through the stomata.参考译文：植物体通过根系吸收的水分中，超过90%都是从气孔逸出的。

21. During the daytime, the stomata of most plantsare open.参考译文：白天，大多数植物的气孔都是张开的。

22. This allows carbon dioxide to enter the leavesfor photosynthesis.参考译文：这使得二氧化碳能进入叶子参与光合作用。

23. As night falls, carbon dioxide is not needed.参考译文：到了夜晚，植物不再需要二氧化碳。

24. The stomata of most plants close.参考译文：大多数植物的气孔就关闭了。

25. Water loss stops.参考译文：水分散失也停止了。

26. If photosynthesis ceased, there would be little（表否定）food or other organic matter onthe earth.参考译文：如果光合作用停止，地球上将不会再有食物或其他有机物质。

27. Mostorganisms would disappear.参考译文：大多数生物体都会消失。

28. The earth's atmosphere would no longer containoxygen.参考译文：地球的大气中将不再有氧气。

29. Photosynthesis is essential for life on ourplanet.参考译文：光合作用对于地球上的生命来说是至关重要的。

第二十二篇Real WorldRobotsWhen you think of a robot, do you envision a shiny,metallic device having the same general shape as a human being, performinghumanlike functions, and responding to your questions in a monotone voiceaccentuated by high-pitched tones and beeps? This is the way many of us imaginea robot, but in the real world, a robot is not humanoid at all. Instead a robotoften is a voiceless, box-shaped machine that efficiently carries outrepetitive or dangerous functions usually performed by humans. Today‟s robot ismore than an automatic machine that performs one task again and again. A modernrobot is programmed with varying degrees of artificial intelligence—that is, arobot contains a computer program that tells it how to perform tasks associatedwith human intelligence, such as reasoning, drawing conclusions, and learningfrom past experience.A robot does not possess a human shape for thesimple reason that a two-legged robot has great difficulty remaining balanced.A robot does, however, move from place to place on wheels and axles that rolland rotate. A robot even has limbs that swivel and move in combination withjoints and motors. To find its way in its surroundings1, a robotutilizes various built-in sensors. Antennae attached to the robot‟s base detectanything they bump into. If the robot starts to teeter as it moves on anincline, a gyroscope or a pendulum inside it senses the vertical differential.To determine its distance from an object and how quickly it will reach theobject，the robotbounces beams of laser light and ultrasonic sound waves off obstructions in itspath2. These and other sensors constantly feed information to thecomputer, which then analyzes the information and corrects or adjusts therobot‟s actions. As science and technology advance, the robot too will progressin its functions and use of artificial-intelligence programs.Real World Robots参考译文：现实世界中的机器人1. When you think of a robot, do you envision ashiny, metallic device having the same general shape as a human being,performing humanlike functions, and responding to your questions in a monotonevoice accentuated by high-pitched tones and beeps.参考译文：当你想到机器人的时候，你脑海中浮现的是不是一个有着大致人类轮廊的、能够发挥像人类一样的功能，并且能用夹杂着高音的单调音调回答你的问题的有光泽的金属装置？2. This is the way many of us imagine a robot, butin the real world, a robot is not humanoid at all.参考译文：很多人想象中的机器人都是这个样子的，但是，在现实世界中，机器人和人类长得一点都不像。