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The grass minerals in the Indian dung fossils are of oldest minerals on record,
A．Y
B．N
C．NG
答案
更多“The grass minerals in the Indian dung fossils are of oldest minerals on record,A．YB．NC．NG”相關(guān)的問題
第1題
Dung Fossils Suggest Dinosaurs Ate Grass
Ancient pieces of plant minerals have offered up the first evidence that dinosaurs ate grass and grasses actually exist earlier than people have imagined, a new study says.
The proof was found in what might seem to be an unlikely location: fossilized dung left by titanosaurs (無(wú)法龍).
The coprolites -- the technical, and polite, term for dung fossils -- were found in India and this could date to about 65 million years ago.
Evidence of ancient plants is often found in fossils that contain outlines of easily visible leaves and stems. Such fossils of grasses have been dated to about 55 million years ago but no older. This gives people an impression that there is no grass in existence 55 million years ago.
The plant evidence found in coprolites, however, is based on microscopic bits of minerals that form. in plants. When plants are eaten or decay, the mineral bits are released and pass through an animal's digestive system. And this has become the very precious evidence for the study nowadays. By carefully examining the contents in the dung, the scientists or researcher can have a general idea of what these animals ate millions of years ago and also possibly their living habits.
Researchers were able to examine and date minerals from ancient grasses found in the fossilized dinosaur dung. The scientists will describe the fossils in tomorrow's issue of the journal Science.
Their work "is the first unambiguous evidence that grasses originated and had already diversified during the Cretaceous (白堊紀(jì)時(shí)代) ," Dolores Piperno and Hans-Dieter Sues of the Smithsonian Institution's National Museum of Natural History wrote in a review accompanying the journal paper.
And we must keep in mind that the Cretaceous period extends from 145.5 to 65.5 million years ago, a period much earlier than 55 million years ago.
Grassy Dino Diets？
The fossils containing the plant minerals were found close to Pisdura in central India and date within the late Cretaceous.
Coprolites are very common in the area and are often found in rocks that have been worn down by weather. Based on their common association with titanosaur bones, many of the dung fossils probably come from the massive plant-eating reptiles(爬蟲類).
The finding is the first indication that grasses evolved before the dinosaurs went extinct. This finding is contradictory to the previous thinking that there is no grass existing at the time when dinosaurs lived. Just as what Caroline A. E. Str0mberg, a co-author of the paper and a researcher at the Swedish Museum of Natural History in Stockholm, said that until now "it has been assumed that dinosaurs lived in virtually grass-free ecosystems."
Grasses exist today on every continent except Antarctica. It has become very important in today's life in that not only many animal, but also human beings themselves depend on them for food to a great extend.
Scientists have long believed that the now ubiquitous plants first began to spread and diversify some 70 to 60 million years ago.
However, fossil evidence had suggested that grasses evolved along with early plant-eating mammals. For example, the Hoofed animals with high-crowned teeth suitable for chewing grass first began to appear about 25 million years ago.
But the grass minerals in the Indian coprolites were much older than the hoofed mammals and were at that time already diversified. According to the latest findings by the researchers, five different species were evident, which means that grasses likely diversified substantially before the end of the late Cretaceous.
The researchers believe that various species of grass had spread before India became geographically isolated from other continents about 125 million years ago.
Tooth Ev
A．Y
B．N
C．NG
第2題
Why does the author mention "herbs," "shrubs," and "trees"？
A．To provide examples of plant types that cannot tolerate high levels of harmful minerals
B．To show why so many plants are hyperaccumulators
C．To help explain why hyperaccumulators can be found in so many different places
D．To emphasize that hyperaccumulators occur in a wide range of plant types
第3題
A.weed, weed
B.weeds, weed
C.grass, grass
D.grasses, grass
第4題
A.It’s very kind of you
B.No, I wouldn’t
C.Yes, please
D.Here you are
第5題
Which of the following works established Doris Lessing as a prominent writer？
A．The Grass is Singing.
B．Children of Violence.
C．The Golden Notebook.
D．The Fifth Child.
第6題
聽力原文：M: Why do park keepers always prohibit people from walking on the grass？
W: I think you should go to ask the officials over there.
The two speakers are probably
A．in a park.
B．in a parking lot.
C．in an office.
D．in a store.
第7題
聽力原文：M: Have you seen Lee recently？ Last I saw him he was on the grass by the pool.
W: He must be home by now. I saw him leave on his bike half an hour ago.
Where does the woman think Lee is？
A．On the grass.
B．Near the pool.
C．At home.
D．On his bike.
第8題
聽力原文：It hasn't rained in weeks.
(A) No, I haven't seen him either.
(B) I know, and all the grass is dying.
(C) It takes six to eight weeks to ship.
(40)
A．
B．
C．
第9題
W: I'd rather stay here if you don't mind. It's awfully sunny down there and I always avoid sitting in the sun wherever I can.
Q: Where did the woman want to sit？
(14)
A．On the grass under the trees.
B．In the sunshine.
C．Near the river bank.
D．Wherever she can.
第10題
M: I prefer autumn myself. The colors of leaves changing are so beautiful.
In what season does this conversation take place？
A．Spring.
B．Summer.
C．Autumn.
D．Winter.
