Mountaineers have noted that as they climb, for example, up to the 12,633­foot Humphreys Peak in Arizona, plant life changes greatly. In the Sonoran Desert, one climbs into a pine forest at 7,000 feet and a treeless tundra(冻土带) on the top of the mountain. It may seem that plants at a given altitude are associated in what can be called “communities” －groupings of species. The idea is that over time, plants that require particular climate and soil conditions come to live in the same places, and are frequently to be found together. Scientists study the history of plant life and build up a picture of how groups of plants have responded to climate changes and how ecosystems develop. But are these associations, which are real in the present, permanent?

    A great natural experiment took place on this planet between 25,000 and 10,000 years ago, when small changes in the earth's orbit caused great sheets of ice to spread from poles. These glaciers(冰川) covered much of North America and Europe to depths of up to two miles, and then, as the climate warmed, they retreated. During this retreat, they left behind newly uncovered land for living things to occupy, and as those living things moved in they laid down a record we can read now. As the ice retreated and plants started to grow near a lake, they release pollen(花粉). Some would fall into the lake, sink to the bottom and mix with the sand. By drilling into the lake bottom it is possible to read the record of the plant life around the lake. The fossil record seems clear; there is little or no evidence that entire groups of plants moved north together. Things that lived together in the past don't live together now, and things that live together now didn't live together in the past. Each individual living things moved at its own pace. The fossil record seems to be telling us that we should be thinking about preserving species by giving them room to move about－to respond to environmental changes.

    Like most July days, it was hot. I stepped into a tiny ice-cream shop to cool off with a chocolate ice-cream. It was an old-time store with little round tables and chairs.

    As I entered, I found a very old woman bent over a table near the door. Her back was so badly twisted by some sadness that her face nearly touched the table top. I sat down facing her several tables away.

    “Poor woman,” I thought. “What does she get out of life? Why God let people live so long past their prime?”

As I thought, another aged lady entered the shop and sat down with her. Soon the two of them were talking about childhood days. They talked of how little the shop had changed in 70 years… In minutes, the two of them were trembling with laughter.

    I looked again at the first woman, then in the mirror on a nearby wall, catching a picture of myself.

I was wearing a dirty shirt. She was well dressed in white, her hands shining with gold rings.

    I was gloomy(愁闷的). She was laughing, smiling.

    I was putting the pieces of my life together. She had millions of wonderful memories to recall.

    I sat alone. She was sharing the day with a good friend.

I was secretly worried about getting old. She was old, but it wasn't hurting her.

    As I left the shop, I thought of my foolish question about God letting people live past their prime. Why, that woman was more alive, more sensitive to life than I was. Age has not bent her spirit.

    An Italian company has created the world's first underwater farm. The station named Nemo's Garden consists of five biospheres(生物圈) fixed to the bottom of the sea off the coast of Savona, Italy. They're being used to grow strawberries, beans, garlic, and lettuce.

    “The main target of this project is to create other sources of plant production in areas where environmental conditions make it difficult to grow crops through traditional farming, including lack of fresh water, fertile soil, and extreme temperature changes,'' said project spokesperson Luca Gamberini.

    The five biospheres, currently floating between depths of 18 and 36 feet, are constantly watched by Ocean Reef Group —— a diving equipment company——from a control center on dry land. According to various news reports, the plants are watered by drips of water on the inner walls of the biospheres. With a constant temperature of 79 degrees day and night, and humidity(湿度) at around 83 percent, the conditions are ideal for plants to grow well. The high amount of carbon dioxide also encourages growth.

    Ocean Reef president Sergio Gamberini said he came up with the idea of growing plants underwater during a summer vacation in Italy. In his own words, he wanted to do something that's different and to show the beauty of the ocean. After two years of failed attempts, they finally were able to get these five biospheres working. Their success may lay the foundation for a new form of crop production that can be done without harming the environment.

    In fact, the biosphere seems to be attracting wildlife. Octopuses(章鱼) and endangered seahorses are taking shelter under the structure, while crabs(螃蟹) are climbing up the anchors and into the greenhouses. None of the creatures have damaged the plants so far. “It's so kind of science-fiction to see these two different forms of life interact,” Gamberini said.

    In October, I told the eight-year-olds in the class I teach in Pompton Lakes, New Jersey, about my plan. "Since all of you have done extra jobs around the house to earn some money," I said. "Then we'll buy food for a Thanksgiving dinner for someone who might not have a nice dinner otherwise."

    I watched them while they walked up and down the supermarket. "Flowers!" Kristine cried. The group rushed toward the holiday plants.

    "You can't eat flowers."——It was more sensible(明智的) to use any extra money to buy something that could be transformed(转换，转变) into meals.

    "But Mrs. Sherlock," came the begging voice, "we want flowers."

    Defeated finally, I put a pot of "funny" purple(紫色的) mums in the cart full of foods. "She'll like this one," the children agreed.

    An organization had given us the name and address of a needy grandmother who had lived alone for many years. We finally pulled up in front of a small house. A slightly built woman with a weary face came to the door to welcome us.

    My little group ran to get the food. As each box was carried in, the old woman kept on saying "Thanks"—much to her visitors' pleasure. When Amy put the mums on the counter, the woman seemed surprised. She's wishing it was a bag of flour(面粉), I thought.

    We returned to the car. As we fastened our seat belts, we could see the kitchen window. The woman inside waved goodbye, then turned and walked across the room, past the turkey, past the goods, straight to the mums. She put her face in their petal. When she raised her head, there was a smile on her lips. She was transformed before our eyes.

    The children were quiet. At that moment, they had seen for themselves the power they possessed(拥有) to make another's life better. The children had sensed(感到) that sometimes a person needs a bunch of funny purple flowers on a dark November day.

    It is not always a good thing to praise children because "empty" words may make them unhappy. Words such as "well done" may make them doubt their own abilities, a leading psychologist (心理学家) Stephen Grosz has warned. He says that words such as "you're so clever" or "you're such an artist" could also hinder their future development at school. He says that such empty praise causes children to be unhappy as they may say they can't live up to these expectations.

    Instead he advises parents and teachers to praise children less frequently and use words like "trying really hard," Mr. Grosz said, "Empty praise is as bad as thoughtless criticism (批评). People often pay no attention to children's feelings and thoughts." He also mentions research showing that children who are heavily praised probably perform worse at school.

    Some psychologists from Columbia University asked 128 pupils aged 10 and 11 to work out a number of math problems. Afterwards, some were told, "You did really well­—you're so clever." But the researchers told the other group, "You did really well­—you must have tried really hard." Both groups of children were then given more difficult questions and those who had been told they were clever did not do as well as the others.

    He says that when collecting his daughter from a school near their home in North London, he heard a teacher tell her, "You have drawn the most beautiful tree. Well done," Later, after she had done another drawing, the same teacher said, "Wow, you are really an artist." In his book, Mr. Grosz writes, "How could I explain to the teacher that I would prefer it if she did not praise my daughter?"

    As a parent of two children, I strongly agree with Mr. Grosz. I praise them when praising is proven right. I want them to know if I praise them, they have done something beyond my expectation, beyond what they are able to do.

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