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题型:阅读理解-阅读单选 难度:0.65 引用次数:571 题号:364580

A recent study of ancient and modern elephants has come up with the unexpected conclusion that the African elephant is divided into two distinct species.

The discovery was made by researchers at York and Harvard universities when they were examining the genetic relationship between the ancient woolly mammoth and mastodon to modern elephants — the Asian elephant, African forest elephant and African savanna elephant.

Once they obtained DNA sequences from two fossils, mammoths and mastodons the team compared them with DNA from modern elephants. They found to their amazement that modern forest and savanna elephants are as distinct from each other as Asian elephants and mammoths.

The scientists used detailed genetic analysis to prove that the African savanna elephants and the African forest elephants have been distinct species for several million years. The divergence of the two species took place around the time of the divergence of Asian elephants and woolly mammoths. This result amazed all the scientists.

There has long been debate in the scientific community that the two might be separate species but this is the most convincing scientific evidence so far that they are indeed different species.

Previously, many naturalists believed that African savanna elephants and African forest elephants were two populations of the same species despite the elephants’ significant size differences. The savanna elephant has an average shoulder height of 3.5metres while the forest elephant has an average shoulder height of 2.5metres. The savanna elephant weighs between six and seven tons, roughly double the weight of the forest elephant. But the fact that they look so different does not necessarily mean they are different species. However, the proof lay in the analysis of the DNA.

Alfred Roca, assistant professor in the department of Animal Sciences at the University of Minois, said, “We now have to treat the forest and savanna elephants as two different units for conservation purpose. Since 1950 all African elephants have been conserved as one species. Now that we know the forest and savanna elephants are two very distinct animals, the forest elephant should become a bigger priority for conservation purpose.”

1. One of the fossils studied by the researchers is that of ________.
A.the Asian elephantB.the forest elephant
C.the savanna elephantD.the mastodon elephant
2. The underlined word “divergence” in paragraph 4means “________”
A.evolutionB.exhibitionC.separationD.examination
3. The researcher’s conclusion was based on a study of the African elephant’s ____________
A.DNAB.heightC.weightD.population
4. What were Alfred Roca’s words mainly about?
A.The conservation of African elephants.
B.The purpose of studying African elephants
C.The way to divide African elephants into two units
D.The reason for the distinction of African elephants
5. Which of the following can be the best title for the passage?
A.Naturalist’s Belief about Elephants.B.Amazing Experiment about Elephants
C.An Unexpected Finding about ElephantsD.A Long scientific Debate about Elephants
2011·湖南·高考真题 查看更多[3]
【知识点】 动物 科普知识 说明文

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【推荐1】Bald eagles are a breathtaking sight, no matter where you see them. Bald eagles are making headlines again, as proven by NPR’s story about the birds’ amazing recovery in Chesapeake Bay.

“Forty years ago, we probably would not have seen a single bald eagle here,” says Bryan Watts, a conservation biologist. This is a familiar story across a nation where pollution and pesticides(杀虫剂) nearly wiped out the species in the United States. The bald eagle was on the endangered species list for decades, and considerable recovery efforts were put into place to bring the national symbol back.

It was delisted in 2007, and stories of its recovery have continued to be a source of celebration from Glenwood, Iowa to Chicago to Sandy Island Eagle Sanctuary in Missouri. The fascination with watching this species come back with vigor(活力) has been equally as wonderful as witnessing the recovery itself. Some efforts to help endangered species recover can be controversial, but the recovery of the bald eagle has been a story everyone can get behind. A bald eagle nest in Decorah, Iowa brings in millions of viewers every season as the parents hatch their chicks. It’s not often a livestream angled on a bird’s nest gets that kind of viewership!

The conservation effort has not been easy and in some areas, such as the Channel Islands off the California coast, it is really tough to carry out. Bald eagles once called these islands home but disappeared with the emergence of the pesticide DDT. In addition, humans changed the ecosystem there by introducing invasive species. Restoration efforts have included removing the alien species and helping native species. A program for reintroducing bald eagles starting in 2002 has been a success, with 2010 seeing a record-setting 15 wild chicks hatched.

At present, while there are many dangers that still face the bald eagle, the incredibly successful recovery over the last several decades is a conservation story to champion - and one to feed hope for other endangered species whose recovery is still underway.

1. What were bald eagles faced with four decades ago?
A.They were at risk of extinction.
B.They were nearly killed by pesticides.
C.They were facing hunted by human beings.
D.They were saved through some recovery efforts.
2. Which word can best describe the recovery efforts?
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3. What does the fourth paragraph mainly concern?
A.The concepts and difficulties.
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D.The methods and achievements.
4. What idea does the author convey in the last paragraph?
A.Not all hopes were lost in protecting nature.
B.Ups and downs are common in the ecosystem.
C.There is still a long way to protect wild animals.
D.Dangers in the wild advance the growth of wildlife.
2021-04-19更新 | 55次组卷
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【推荐2】The air is thin and we have to rest several times on the shore hike from camp. To our left, snow-covered mountains disappear into clouds that seem almost close enough to touch. On the plain in front of us, we can just make out a herd of graceful animals. This is why we stay here.

Tibetan antelopes live mainly on the plains of Tibet. Watching them move slowly across the green grass, I'm struck by their beauty. I'm also reminded of the danger they are in. They are being hunted illegally for their valuable fur.

My guide is Zhaxi, a villager from Changtang. He works at the Changtang National Nature Reserve. The reserve is a safe place for the animals and plants of northwestern Tibet. To Zhaxi, protecting the wildlife is a way of life. “We're not trying to save the animals,” he says. “Actually, we're trying to save ourselves.”

In the 1980s and 1990s the population of Tibetan antelopes dropped by more than 50 percent. Hunters were shooting antelopes to make money. Their living places were becoming smaller as new roads and railways were built.

In order to save Tibetan antelopes, the Chinese government placed them under national protection. Zhaxi and volunteers watched over the antelopes day and night to keep them safe from attacks. Bridges and gates were added to let the antelopes move easily and keep them safe from cars and trains.

The measures were effective. The antelope population has recovered and in June 2015, the Tibetan antelope was removed from the endangered species list. The government, however, does not intend to stop the protection program since the threat to the Tibetan antelope has not yet disappeared. Only when we learn to exist in harmony with nature can we stop being a threat to wildlife and to our planet.

1. What can we learn from Zhaxi's words in paragraph 3?
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【推荐3】In nature, smaller animals often “take a ride” on larger ones to save energy on long-distance movements. In paper published in the journal Current Biology, researchers show how fine Caenorhabditis worms can use electric fields to “jump” across Petri plates or onto insects, allowing them to go through the air and attach themselves, for example, onto naturally charged bumblebees (大黄蜂).

“Pollinators(传粉昆虫), such as insects and hummingbirds, are known to be electrically charged, and it is believed that pollen (花粉) is attracted by the electric field formed by the pollinator and the plant,” says Takuma Sugi, a co-senior author on the study. “However, it was not completely clear whether electric fields are used for communications between different land animals.”

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Next, the researchers rubbed flower pollen on a bumblebee. Once close to these bees, worms stood on their tails, then jumped aboard. Some worms even piled on top of each other and jumped in a single post, moving 80 worms at once across the gap.

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