Think of a seed buried in a pot. It’s dark down there in the potting soil. There’s no light, no sunshine. So how does it know which way is up and which way is down? It does know. Seeds send shoots up toward the sky, and roots the other way. Darkness doesn’t confuse them. Somehow, they get it right.
More surprisingly, if you turn a seedling (秧苗) or a whole bunch of seedlings upside down, as Thomas Andrew Knight of the Royal Society did around 200 years ago, the tips and roots of the plant will sense, “Hey, I’m upside down. Look! I will turn my way to the right direction and do a U-turn.”
How do they know? According to botanist Daniel Chamovitz, Thomas Knight about 200 years ago guessed that plants must sense gravity. Knight proved it with a crazy experiment involving a spinning plate.
He attached a bunch of plant seedlings onto a disc. The plate was then turned by a water wheel powered by a local stream at a speed of 150 revolutions (旋转) per minute for several days.
If you have been at an amusement park in a spinning teacup, you know that because of centrifugal force (离心力) you get pushed away from the center of the spinning object toward the outside.
Knight wondered, would the plants respond to the centrifugal pull of gravity and point their roots to the outside of the spinning plate? When he looked, that’s what they’d done. Every plant on the disc had responded to the pull of gravity, and pointed its roots to the outside. The roots pointed out, and the shoots pointed in. So Thomas Knight proved that plants can and do sense the pull.
1. How does the author write about the young seedling in Paragraph 2?A.By describing vividly. | B.By giving examples. |
C.By telling stones. | D.By asking questions. |
A.Soil. | B.Sunshine. |
C.Darkness. | D.Gravity. |
A.Plants have their own desires. | B.Plants can feel the pull. |
C.Speed influences plants’ growing. | D.Plants can grow quickly by doing a U-turn. |
A.In a book review. | B.In a lifestyle magazine. |
C.In a scientific report. | D.In an official document. |
相似题推荐
【推荐1】I go to school the youth to learn the future.
﹣Robert Frost
Harvard University Type:private Created Time:1636 Location:Cambridge.Massachusetts.USA | |
Harvard University's history,influence and wealth have made it one of the most famous universities in the world | |
University of Oxford Type:public Created Time:Not quite clear Location:Oxford,Britain | |
The University of Oxford is the second oldest university in the world and the oldest in the English﹣speaking world. | |
University of Cambridge Type:public Created Time:1209 Location:Cambridge,Britain | |
The University of Cambridge is the second oldest university in the English﹣speaking world and the sixth oldest in Europe. | |
Tsinghua University Type:public Created Time:1211 Location:Haidian District,Beijing.China | |
Tsinghua University was originally(起初)under the name “Tsinghua Xuetang” The school was renamed “Tsinghua School” in 1912.The university section was founded in 1925. |
1. What is Harvard University famous for?
A.People and wealth. | B.Subjects and country |
C.Professors and students. | D.History,influence and wealth. |
A.In 1211. | B.In 1912. |
C.In 1925. | D.Not quite clear |
A.Harvard University was set up in 1636. |
B.The University of Oxford is the oldest university in the world. |
C.The University of Cambridge is the sixth oldest university in Europe |
D.Tsinghua University is located in Beijing now. |
【推荐2】Spring is finally here, and it’s a great time to get outside and get dirty!
Gardening connects people. When you are gardening, you are outdoors. So it is a perfect time to socialize with your neighbors. Gardening can greatly strengthen a person’s sense of community and belonging, and thus loneliness is far away from you!
Benefit children
Gardening is a great activity to do with children. It gets families outdoors and off computers, televisions and other electronics.
A.Reduce loneliness |
B.Improve family relationships |
C.Gardening can be a great teacher |
D.Gardening is popular in many parts of the world |
E.Gardening may also help you feel calm and happy |
F.However, the decreases were stronger in the gardening group |
G.Gardening can also give you the feeling that you have done something good |
【推荐3】"Mummy, I don' t know what to play with." Steve interrupts his mother, who is talking to a friend, for the fourth time. "You've got a room full of toys!" his mother says, impatiently. In fact it is the jumble of toys which is to blame for four-year-old Steve's lack of interest in his dolls, cars and stuffed (packed) animals. Each morning he tips out three washing baskets of toys all over his floor, listlessly pulls out something and shortly after is standing at his mother's desk or following her into the kitchen saying: "Mummy, I am bored."
A family therapist ( 心理医生) explains why children lose interest when they have a whole "toy shop" at home: "According to their brain development, little children are not in a position to judge the quality of a variety of things at once. There is always just one favorite toy for the moment. All the rest is left lying about." What can parents do to stop their children from being oversupplied with toys? Under no conditions simply make something disappear without the child's knowledge. If he/she takes no more notice of a toy, a parent can ask if it can be stored or given away. Be warned though the child will always say he/she wants it then! A talk with relatives and friends may also help. Lyn is the mother of four-year-old Jessie, and we like her way. A small set of shelves in her child's room holds the toys and books that are the current (at present) favorites. When it seems to her that her daughter is tired of these toys, they put them away in a box together and select some other toys from a cupboard in another room. The box of "old" toys goes into the cupboard. When her child says she is "bored", they also get something from her cupboard - it may be something she has had for some time but because she hasn't seen it for a while it is almost like a new toy.
Some favorite toys stay out all the time, and there is collection of dolls which sits in the corner, but in this way Lyn has found that she has fewer toys to put away at the end of the day and her daughter always has something "fresh" to play with.
1. Steve interrupted his mother several times because _____.A.he felt uninterested in his toys |
B.he disliked his mother's guest |
C.he didn't have enough toys to play with |
D.he hoped his mother would play with him |
A.they can't play alone for a long time |
B.they are too young to play with so many toys |
C.they are too lazy to pick out their favorites |
D.they lack the ability to value too many things at a time |
A.Simple choice. | B.Mixture in disorder. |
C.Ordinary appearance. | D.Same shape. |
A.Buy fewer toys for their children. |
B.Form good habits for their children. |
C.Spare some time to play with their children. |
D.Put some toys away without telling their children. |
【推荐1】Scientists say they’ve developed a system using machine learning to predict when and where lightning will strike. The research was led by engineers from the Swiss Federal Institute of Technology in Switzerland.
European researchers have estimated between 6,000 and 24,000 people are killed by lightning worldwide each year. The strikes can also cause power outages (停电), destroyed property, damage electrical equipment and start forest fires. For these reasons, climate scientists have long sought to develop methods to predict and control lightning. But no system has been created to effectively predict lightning.
The system tested in the experiments used a combination of data from weather stations and machine learning methods. The researchers developed a prediction model that was trained to recognized weather conditions that were likely to cause lightning.
The model was created with data collected over 12-year period from 12 Swiss weather stations in cities and mountain areas. The data related to four main surface conditions: air pressure, air temperature, relative humidity (湿度) and wind speed.
The atmospheric data was placed into a machine learning algorithm (算法), which compared it to records of lightning strikes. Researchers say the algorithm was then able to learn the conditions under which lightning happens.
Amirhossein Mostajabi is a PhD student at the institute who led the development of the method. He said, “current systems for gathering such data are slow and complex and require costly collection equipment like radar or satellites.”
“Our method uses data that can be obtained from any weather station,” Mostajabi said. “This will improve data collection in very remote areas not covered by radar and satellites or in places where communication systems have been cut,” he added.
1. Why have climate scientists tried to predict and control lightning?A.To collect relative data. |
B.To create a scientific system. |
C.To do research in relation to machine learning. |
D.To reduce the destruction lightning has been caused. |
A.wind speed | B.air pollution |
C.relative humidity | D.air temperature |
A.Lightning. | B.The system being tested. |
C.The atmospheric data. | D.The machine learning algorithm. |
A.He developed the method and the system by himself. |
B.He thinks the current systems are too slow and simple. |
C.He is a professor at the Swiss Federal Institute of Technology. |
D.He believes their system does much better in data collection. |
【推荐2】In the 2022 Beijing Olympics process, hand-kitting (手工编织的) Chinese knot, a symbol of unity and happiness in Chinese context, is loved by friends from other countries. It has a complex graceful curve, but it can be reduced to the simple two-dimensional line. It displays fantasy and wisdom of the ancient Chinese civilization. It has elegant appeal which comes from the basic tools of human life in the beginning years.
Preparation of Chinese knot, roughly divided into three categories: the basic knot, varying knot and combinatorial knot. Its knitting techniques, in addition to all the basic techniques, agree with a common principle of knitting and can be summarized as the basic techniques and combinations techniques. But the basic techniques use a single line, double line or lines to knitting, or change the use of the parallel thread (线) to separate thread so as to make colorful knot or bow section; and a combination of techniques use the extend of head and extended ear flap (耳帽), and combine various knot flexibly, complete pack of ever-changing knot ornaments (装饰).
To design a set of beautiful decorative knot, the most important thing is to determine what the knot will be used for. Accordingly, determine its size and shape, taking into account of the appropriate use of color matching and accessories. The shape, color and ornaments should suit each other. Do attach your own artistic beauty and deep emotion to it, which will be able to fully demonstrate the beauty of Chinese traditional art.
Long cultural heritage makes the Han ethnic Chinese knot techniques unique, purely cultural essence, rich in cultural heritage. Chinese knot not only has shape and color beauty, but also gain its name because of its meaning, such as endless knot, caisson knot (藻井结) and double the money knot, reflecting the ancient Chinese cultural beliefs and strong religious meanings. It represents the pursuit of truth, goodness and beauty of good intentions.
1. What does Chinese knot represent in Chinese culture?A.Love and friendship. | B.Unity and happiness. |
C.Grace and simplicity. | D.Fantasy and wisdom. |
A.to explain basic rules for knitting | B.to introduce the knitting techniques |
C.to show how to make Chinese knot | D.to classify Chinese knot into categories |
A.Deciding its purpose. | B.Determining its shape. |
C.Matching with colors. | D.Attaching artistic beauty. |
A.Its inner beauty. | B.Its physical features. |
C.Its cultural meaning. | D.Its real pursuit. |
Ten years ago, no one thought that using computers could become a compulsive behavior that could affect the social and physical life of computer users. This obsessive behavior has affected teenagers and college students. They are likely to log on computers and spend long hours at different websites.
They become hooked on computers and gradually their social and school life is affected by this situation. They spend all free time surfing and don’t concentrate on homework, so this addiction influences their grades, and success at schools. Because they can find everything on the websites, they hang out there. Moreover, this addiction to websites influences their social life.
They spend more time in front of computers than with their friends. The relation with their friends changes. The virtual life becomes more important than their real life. They have a new language that they speak in the chat rooms and it causes cultural changes in society,
Because of the change in their behavior, they begin to isolate themselves from the society and live with their virtual friends. They share their emotions and feelings with friends who they have never met in their life.Although they feel confident on the computer, they are not confident with real life friends they have known all their life. It is a problem for the future. This addictive behavior is beginning to affect the whole world.
1. The passage is about ________.
A.the cause of weboholism | B.the advantage of weboholism |
C.the popularity of weboholism | D.the influence of weboholism |
A.attractive | B.addictive | C.professional | D.potential |
A.weboholism has the greatest effect on teenagers |
B.teenagers can hardly balance real and virtual life |
C.people are addicted to games on the Internet |
D.virtual life is more vivid and attractive anyway |
A.It contributes to the development of the web. |
B.The chat room language may change social culture. |
C.The problem will have a negative influence on our future. |
D.People addicted to the web often become inactive in real life. |
A.objective | B.positive | C.opposed | D.acceptable |