英語語言學(xué)習(xí)：古老的腳印
And I’m Christopher Cruise.
Today we tell how some extremely small organisms may help meet our food needs in the future. Then, we report on an American project to save endangered orchids. Finally, we tell about the discovery of what British scientists are calling the oldest human footprints found outside of Africa.
Small Organisms May Help Meet Food Needs of the Future
Experts say farmers will need to produce about 70 percent more food by the middle of the century. They predict that nine billion people will need to be fed worldwide by 2050.
The prediction means experts will need to develop more-effective farming methods that cause less harm to the environment. Experts say living things called “microbes” could help meet that need. A microbe is an organism so small it can be seen only with a microscope.
Jeff Dangl is a biology professor at the University of North Carolina. He says researchers are finding extremely small organisms in the ground.
“This soil was teeming with life.”
Jeff Dangl says one gram of soil contains between 100 million and one billion microbes.
He says microbes are taking part in a healthy exchange with the plants that share the soil. Around plant roots, microbes change chemicals in the air and soil into food for the plants. The microbes include bacteria and material known as “fungi.”
Some microbes act as bodyguards. They produce anti-bodies and other chemicals to fight harmful germs.
Plants make sugar through a process called “photosynthesis.” This happens when a plant receiving light changes water and carbon dioxide into food.
Professor Dangl says much of the sugar is pumped down through the roots. There, it is turned into sugar-based microbe food and released into the soil. He says that is done to get microbes to help the plants grow better. Some of the organisms turn chemicals in the air and soil into food that the plants can eat.
The microbes produce antibiotics and other chemicals to fight the harmful germs. Professor Dangl said bacterial and fungal parts of the plant organism must be considered to understand how plant organisms operate.
The biosciences company Novozymes already sells one kind of fungi that helps plants get phosphorous from the soil.
Shawn Semones is the head of product research for the company. At an experimental greenhouse in Virginia, he is treating the roots of corn plants with a microscopic fungus.
He holds a small plastic cup which has a dead insect inside. The insect is developing a fine white coat of mold -- a substance that grows on living organisms. That mold killed the insect. The white covering is producing spores that will blow in the wind to infect another insect.
Shawn Semones says the microbe develops naturally. He says Novozymes has found a way to produce it in very large amounts and offer it to farmers as a bio-pesticide. A bio-pesticide protects crops from animals, microbes, bacteria and fungi.
Novozymes recently signed a $300 million deal with Monsanto, a company best known for producing seeds and chemicals. The goal is to help bring discoveries about microbes to farmers’ fields.
You are listening to the VOA Learning English program Science in the News. With Christopher Cruise, I’m Anna Matteo in Washington.
Project to Save Endangered Orchids Growing in Florida
Our planet is home to 20,000 kinds of orchids. Orchids exist on almost every continent. But the beautiful and valuable flowers live mainly in warm, moist climates like that found in the southern part of Florida.
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America’s “sunshine state” has about 50 native species of orchid. But many are in danger of dying out. This threat has led scientists to launch a five-year project to save them.
Carl Lewis directs Miami’s Fairchild Tropical Botanical Garden. He says many orchid species native to Florida have become rare.
“Most of those orchids are very difficult to find now. They’ve, they’ve been hunted almost to extinction in the wild. So, really, we launched this project just as an effort to bring those orchids back.”
The project to grow and plant one million orchid seedlings began two years ago. Orchids grow mostly on trees. But their seedlings are extremely small, delicate and weak. So they start their life in a laboratory.
The seeds grow in clean bottles with required nutrients. After that, the young plants are moved to a warming device with LED lights. Next, they go to a nursery -- an area where plants are grown. Two years may pass before the plants are strong enough to be connected to -- or fixed onto -- trees.
Volunteers help Carl Lewis to transplant -- or move -- the orchid plants. He says it is important to transplant enough older orchids so they can continue to reproduce without that help.
“This is supposed to be an infusion, just to get so many out there that they start to reproduce on their own.”
After these plants are moved to areas where other orchids grow, scientists hope insects and tiny organisms will find the orchids.
The campaign to save native orchids also depends on help from local students. They have been asked to watch the transplanted orchids in their neighborhoods. A number of plants will also be given away to try to reduce the chance that people will steal them off the trees.
The Center for Plant Conservation guides the conservation and study of threatened plants across the United States. The center is based in the city of St. Louis, Missouri.
Britain’s Oldest Human Footprints Found on Coastline
Finally, British scientists have found what they believe are the oldest human footprints ever discovered outside of Africa. The footprints of what appears to be ancient humans were found in the seaside community of Norfolk, in eastern Britain. The scientists estimate the markings are between 800,000 and almost one million years old. They may be about 500,000 years older than the earliest footprints ever found in the country. If so, that could provide the oldest evidence of human beings in northern Europe.
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Images and a model of one of the footprints were recently shown to reporters at the British Museum in London. A team of scientists found the footprints in May, 2013. The scientists work for the British Museum, Britain’s Natural History Museum, and Queen Mary University of London. The researchers say ocean water from incoming tidal waves made it impossible to remove the prints from the coast.
The area appears to have 50 footprints of both adults and children. They were found near the village of Happisburg. The British Museum says the Happisburg area has what it calls a “remarkable concentration” of early Stone Age archeological sites. All were found since 2000.
Archeologist Nick Ashton described how he felt when he recognized the footprints came from prehistoric humans. At the time, he was looking at e-mails on his computer.
“It was only when the, this overhead views e-mailed through to me back in my office I suddenly looked at it and opened up the file and I thought, ‘This is absolutely amazing, you know -- there, there is no doubt this is really is human footprints.”
He says the discovery will change the understanding of early human history in Europe.
The researchers estimate the height of the early humans at between about .93 and 1.73 meters. The difference in the heights suggests a group of mixed ages.
Isabelle de Groote is with Liverpool John Moores University in the city of Liverpool. She examined the footprints. She says the markings help to tell about the humans who may have made them.
“The spread of the footprint size gives us an indication that we have children, a number of children and then probably some adults there with at least one, you know with probably one, male.”
One footprint appears to show the mark of toes.
Scientists say Britain was joined to continental Europe about a million years ago. It is not known how the early humans survived in the cold climate of northern Europe. Scientists believe the creatures who left the footprints were related to Pioneer Man, an ancestor of Homo sapiens. Pioneer Man was known to have lived in a warmer climate.
Researchers continue looking for human fossil remains in the Happisburg area. A report on the footprint discovery and its meaning was published in the journal PLOS ONE.
This Science in the News was written by Jerilyn Watson. It was based on stories from VOA reporters Steve Baragona and George Putic. Christopher Cruise produced the program.
I’m Anna Matteo.
And I’m Christopher Cruise.
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