问题 单项选择题

下列哪一观点缺乏科学依据()。

A.由于存在生殖隔离,转基因植物很难与其他植物杂交

B.许多农作物花粉的传播距离有限,绝对不会造成其他生物的安全问题

C.植物花粉的存活时间有限,一般不会对其他生物造成危害

D.转基因农作物若缺乏配套的种植技术,也会造成减产

答案

参考答案:B

解析:尽管农作物花粉传播的距离有限,花粉存活时间有限,但转基因植物的花粉还是有可能通过花粉传播而进入杂草中,使杂草具有某些特殊性状。考点:本题主要考查生殖隔离和转基因技术等知识,意在考查考生理解所学知识的要点,综合分析的能力。

阅读理解

Development of a widely accepted chronology for the arrival of humans has been equally difficult, and it was only with the development of optically stimulated luminescence dating that a human presence in Australia was confirmed at 53,000 to 60,000 years ago. Older dates for a human presence in Australia have now been shown to be erroneous .

The importance of Australia as a separate natural laboratory in which to test extinction theories lies in the fact that humans arrived there much earlier than they arrived in the other continental areas (the Americas and northern Eurasia) that experienced substantial megafaunal extinction. What Miller et al. have shown is that the extinction of Genyornis occurred simultaneously across southeastern Australia (indeed probably right across the continent) about 50,000 years ago. This is very close to the presently accepted time of arrival of humans in Australia. It was also a period of modest climate change, well before the dramatic climatic fluctuations of the terminal Pleistocene. The data of Miller et al., therefore, support those who see human hunting rather than climate as causing the extinction of the megafauna.

Genyornis was a ponderous bird, around 80 to 100 kg in weight, about twice as heavy as the living emu and cassowary. It was an inhabitant of Australias inland plains and some coastal regions, but its legs were relatively short and thick, suggestion that it was a slower runner than the emu. Proponents of humancaused extinction suggest that it is just such characteristics that made the megafauna vulnerable to human hunting.

A new school of thought has recently established itself in the extinction debate. It advocates the idea that a combination of human impact and climate change was responsible for the extinction of the worlds megafauna. The new Genyornis data also weaken that argument, for the following reason. Fifty thousand years ago, Australia was experiencing mild cooling; 11,000 to 12,000 years ago, the Americas were experiencing rapid warming. These disparate climatic conditions, all coincident with megafaunal extinction, suggest that whatever was happening with climate, it was bad for the big animals. Under these conditions, the hybrid model becomes indistinguishable from the humancaused extinction model for the influence of climate becomes extremely weak, and only the arrival of humans is important in predicting extinction.

小题1: The last word “megafauna” in Paragraph 2 most probably means

A  birds.  B  plants.

C  big animals.  D  small animals.

小题2: Genyornis was vulnerable to human hunting because it was

A  a delicacy.  B  very weak.

C  very small in size.  D  clumsy.

小题3:  How many models have been put forward for the extinction of Genyoris?

A  One.  B  Two.

C  Three.  D  Four.

小题4: That Australia experienced mild cooling and the Americas rapid warming suggests that

A  the climatic conditions were unfit for Genyornis to live.

B  Genyornis were highly adaptable to different climatic conditions.

C  The two climatic conditions were both bad for Genyornis.

D  The climatic conditions had nothing to do with the extinction of Genyoris.

小题5: The selection is mainly about

A  the debate over the time of the human presence in Australia.

B  the relationship between the human presence and magafaunal extinction.

C  the relationship between human activities and climatic changes.

D  the debate over factors causing megafaunal extinction.

单项选择题