题目
Section B. Multiple choice. (2%*10=20%)Directions:There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C, and D. You should decide on the best choice.Passage OnePOLAR bears have patrolled the planet’s icy regions for millions of years longer than previously thought--riding outseveral episodes of global warming in that time. While this suggests their future might not be so bleak, it is no guarantee they will survive the melting occurring in the polar regions today.Charlotte Lindqvist of the University at Buffalo, New York, and an international team of researchers have just completed the most comprehensive analysis yet of the polar bear genome (基因组). The team looked at DNA from 23 living polar bears and a 110,000-year-old polar bear jawbone. Aided by comparisons with the genomes of brown and black bears, they found that polar bears first emerged as a separate species between four and five million years ago. Previous studies had suggested the species didn’t diverge (分化) from brown bears until much later-- perhaps just 600,000 years ago.The analysis also showed that polar and brown bears have sometimes interbred (杂交) since their initial divergence, and that populations of polar bears have been changing over the past million years in accordance with the climate. Polar bear numbers dropped during warm periods but bounced back with prolonged ice ages – most noticeably during a period of cooling between 800,000 and 600,000 years ago. The population looks set to fall again as melting pack ice forces polar bears back to the land-based habitats (栖息地) of brown bears, where interbreeding has recently been observed. Should extensive interbreeding occur, both polar and brown bear populations could decline with the emergence of a new hybrid (杂交的) species.Lindqvist says that the analysis reveals that polar bear DNA has lost diversity as population has decreased, drifted apart and become genetically isolated, suggesting today’s bears have less adaptability to the environmental change, habitat loss, pollution and diseases they now face.Earlier this year, Frank Hailer of the Biodiversity and Climate Research Centre in Frankfurt, Germany, and colleagues estimated that polar bears diverged from brown bears 600,000 years ago--a result that itself pushed back the evolutionary record of polar bears by about 450,000 years. However, Hailer says that the new results broadly are consistent with his team’s findings, which also suggested that polar bears may have evolved much earlier than the 600,000 year mark.(1) (单选题)What is the closest meaning of the phrase “riding out” (Para.1)?A.Skyrocketing.B.Seesawing.C.Surviving.D.Substituting.(2) (单选题)What was found in the research of polar bear genome according to the passage?A.Polar bears appeared as a separate species much earlier than we had thought.B.The DNA of living polar bears is very similar to that of a 110,000-year-old polar bear.C.Polar bears have survived the icy ages and will also survive the melting today.D.Polar bears diverged from brown bears perhaps just 600,000 years ago.(3) (单选题)When would populations of polar bears drop over the past million years according to the passage?A.When the climate became colder.B.After the initial divergence between polar and brown bears.C.During a period between 800,000 and 600,000 years ago.D.When polar bears were forced back to the land-based habitats.(4) (单选题)Why are the polar bears today less able to adapt themselves to the environment according to the passage?A.Because polar bears are isolated and cannot find new habitats.B.ecause polar bears are facing more difficulties nowadays.C.Because the DNA of polar bears has lost diversity.D.Because the interbreeding with brown bears has produced a new hybrid species.(5) (单选题)What can be inferred from this passage?A.Brown bear populations may increase, while polar bear populations decline.B.We are not sure that polar bears will survive the melting of polar regions.C.A new hybrid species of polar bears will have more adaptability to the environmental changes.D.The polar bear populations would increase when they began to interbreed with brown bears.
Section B. Multiple choice. (2%*10=20%)Directions:There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C, and D. You should decide on the best choice.Passage OnePOLAR bears have patrolled the planet’s icy regions for millions of years longer than previously thought--riding outseveral episodes of global warming in that time. While this suggests their future might not be so bleak, it is no guarantee they will survive the melting occurring in the polar regions today.Charlotte Lindqvist of the University at Buffalo, New York, and an international team of researchers have just completed the most comprehensive analysis yet of the polar bear genome (基因组). The team looked at DNA from 23 living polar bears and a 110,000-year-old polar bear jawbone. Aided by comparisons with the genomes of brown and black bears, they found that polar bears first emerged as a separate species between four and five million years ago. Previous studies had suggested the species didn’t diverge (分化) from brown bears until much later-- perhaps just 600,000 years ago.The analysis also showed that polar and brown bears have sometimes interbred (杂交) since their initial divergence, and that populations of polar bears have been changing over the past million years in accordance with the climate. Polar bear numbers dropped during warm periods but bounced back with prolonged ice ages – most noticeably during a period of cooling between 800,000 and 600,000 years ago. The population looks set to fall again as melting pack ice forces polar bears back to the land-based habitats (栖息地) of brown bears, where interbreeding has recently been observed. Should extensive interbreeding occur, both polar and brown bear populations could decline with the emergence of a new hybrid (杂交的) species.Lindqvist says that the analysis reveals that polar bear DNA has lost diversity as population has decreased, drifted apart and become genetically isolated, suggesting today’s bears have less adaptability to the environmental change, habitat loss, pollution and diseases they now face.Earlier this year, Frank Hailer of the Biodiversity and Climate Research Centre in Frankfurt, Germany, and colleagues estimated that polar bears diverged from brown bears 600,000 years ago--a result that itself pushed back the evolutionary record of polar bears by about 450,000 years. However, Hailer says that the new results broadly are consistent with his team’s findings, which also suggested that polar bears may have evolved much earlier than the 600,000 year mark.(1) (单选题)What is the closest meaning of the phrase “riding out” (Para.1)?A.Skyrocketing.B.Seesawing.C.Surviving.D.Substituting.(2) (单选题)What was found in the research of polar bear genome according to the passage?A.Polar bears appeared as a separate species much earlier than we had thought.B.The DNA of living polar bears is very similar to that of a 110,000-year-old polar bear.C.Polar bears have survived the icy ages and will also survive the melting today.D.Polar bears diverged from brown bears perhaps just 600,000 years ago.(3) (单选题)When would populations of polar bears drop over the past million years according to the passage?A.When the climate became colder.B.After the initial divergence between polar and brown bears.C.During a period between 800,000 and 600,000 years ago.D.When polar bears were forced back to the land-based habitats.(4) (单选题)Why are the polar bears today less able to adapt themselves to the environment according to the passage?A.Because polar bears are isolated and cannot find new habitats.B.ecause polar bears are facing more difficulties nowadays.C.Because the DNA of polar bears has lost diversity.D.Because the interbreeding with brown bears has produced a new hybrid species.(5) (单选题)What can be inferred from this passage?A.Brown bear populations may increase, while polar bear populations decline.B.We are not sure that polar bears will survive the melting of polar regions.C.A new hybrid species of polar bears will have more adaptability to the environmental changes.D.The polar bear populations would increase when they began to interbreed with brown bears.
题目解答
答案
1、C2、A3、D4、C5、C
解析
Passage One 题目解析
1. 词义猜测题：“riding out”的近义词
文章第一段提到“POLAR bears have patrolled the planet’s icy regions for millions millions of years longer than previously thought--riding out several episodes of global warming”，结合上下文，北极熊在更久之前就存在，并经历了多次全球变暖，此处“riding out”应表示“挺过、生存下来”。选项C（Surviving）符合此意，A（Skyrocketing激增）、B（Seesawing摇摆）、D（Substituting替代）均不符。
2. 基因组研究发现
文章第二段指出“polar bears first emerged as a separate species between four and five million years ago. Previous studies had suggested... until much later--perhaps just 600,0000 years ago”，即新研究发现北极熊作为独立物种出现的时间比之前认为的早得多（四到五百万年前 vs 六十万年前）。选项A正确；B（现代北极熊DNA与11万年前北极熊极相似）未提及；C（北极熊会挺过今日融化）与第一段“no guarantee they will survive”矛盾；D（分化于60万年前）是之前的研究结论，非新发现。
3. 北极熊数量下降的时期
第三段提到“Polar bear numbers dropped during warm periods but bounced back with prolonged ice ages”，而“melting pack ice forces polar bears back to the land-based habitats... Should extensive interbreeding occur... both populations could decline”，且过去数量在温暖期下降。选项D（被迫回到陆地栖息地时）符合，因为融化导致回到陆地，进而可能数量下降；A（气候变冷时）数量回升，相反；B（初始分化后）未直接关联；C（80-60万年前）是数量回升期，相反。
4. 现代北极熊适应力下降的原因
第四段明确“polar bear DNA has lost diversity... suggesting today’s bears have less adaptability”，即DNA多样性丧失导致适应力下降。选项C正确；A（孤立无新栖息地）是多样性丧失的原因之一，非直接原因；B（面临更多困难）是结果非原因；D（杂交产生新物种）是可能的未来结果，非当前适应力下降的原因。
5. 推论题
第三段提到“Should extensive interbreeding occur, both polar and brown bear populations could decline with the emergence of a new hybrid species”，但未提及棕熊数量增加（A错）；第一段“no guarantee they will survive”说明B（不确定能否存活）是直接陈述，非推论；D（杂交导致数量增加）与“both populations could decline”矛盾；C（新杂交物种可能更适应环境）虽未明确，但根据进化逻辑，杂交可能带来基因多样性，提升适应力，且其他选项均错误，故C为合理推论。