Question

Scientists have long puzzled over how iguanas, a group of lizards(蜥蜴) mostly found in the Americas, came to live in the isolated Pacific islands of Fiji and Tonga. Some scientists used to suppose that they must have traveled there on a raft, a journey of around 5,000 miles from South America to the islands. There are documented cases of iguanas reaching remote Caribbean islands and the Galapagos Islands on floating logs. But new research in January by Brice Noonan and Jack Sites suggested that iguanas may have simply walked to Fiji and Tonga when the islands were still a part of an ancient southern supercontinent.

The ancient supercontinent was made up of present-day Africa, Australia, Antarctica and parts of Asia. If that’s the case, the island species would need to be very old. Using “molecular (分子) clock” analysis of living iguanas’ DNA, Noonan and Sites found that, sure enough, the lineage of iguanas has been around for more than 60 million years—easily old enough to have been in the area when the islands were still connected by land bridges to Asia or Australia.

Fossils (化石) uncovered in Mongolia suggest that iguanid ancestors did once live in Asia. Though there’s currently no fossil evidence of iguanas in Australia, that doesn’t necessarily mean they were never there. “The fossil record of this continent is surprisingly poor and cannot be taken as evidence of true absence,” the authors write.

So if the iguanas simply walked to Fiji and Tonga from Asia or possibly Australia, why are they not also found on the rest of the Pacific islands? Noonan and Sites say fossil evidence suggests that iguana species did once inhabit other islands, but went extinct right around the time when humans settled in those islands. But Fiji and Tonga have a much shorter history of human presence, which may have helped the iguanas living there to escape extinction.

The researchers say that their study can’t completely rule out the rafting theory, but it does make the land bridge theory “far more reasonable than previously thought.”

1. What did some scientists previously believe about the iguanas?

   A. They were once discovered in America.     

B. They traveled by raft to Fiji and Tonga.

   C.  They could survive in poor living conditions.

D. They moved to Fiji and Tonga from Australia.

2.According to Noonan and Sites, 60 million years ago ____.  

A. the land of the world was a supercontinent  

B. Fiji and Tonga were connected to Asia or Australia

C. Africa, Australia and America were a continent

   D. iguanas walked to Fiji and Tonga from Africa

3.The underline word “l(fā)ineage” in Paragraph 2 probably refers to ____.

   A. conditions in which creatures can survive

B. the change in ancient plants and animals.

C. the line of generations of an ancestor

D. the habitat of a type of an ancient animal

4. What is the main topic of this passage?  

A. The life span of animals living on the ancient supercontinent.

B. The two islands being home to several iguana species in the Pacific region.

C. The fossil evidence suggesting iguanas’ ancestors’ swimming to Fiji and Tonga

D. By raft or by land — how did iguanas reach the tiny Pacific islands?

 

Answer 1

1.B

2.B

3.C

4.D

【解析】本文主要講述了lizards在世界上很多地方都可以找到。尤其是在一些與世隔絕的太平洋里的島嶼之上。文章中對(duì)于這個(gè)現(xiàn)象進(jìn)行了研究，分析了多種可能性。

1.B

【試題解析】細(xì)節(jié)題。根據(jù)第一段2,3,4行Some scientists used to suppose that they must have traveled there on a raft, a journey of around 5,000 miles from South America to the islands.可知以前科學(xué)家認(rèn)為蜥蜴是通過筏子等工具到達(dá)斐濟(jì)和湯加的。故B正確。

2.2】B

【試題解析】推理題。根據(jù)第二段最后2行more than 60 million years—easily old enough to have been in the area when the islands were still connected by land bridges to Asia or Australia.可知他們認(rèn)為在6千萬年前，蜥蜴居住的地方通過大陸橋和亞洲，澳大利亞是連接在一起的。故B正確。

3.3】C

【試題解析】推理題。根據(jù)本句Noonan and Sites found that, sure enough, the lineage of iguanas has been around for more than 60 million years—easily old enough to have been in the area when the islands were still connected by land bridges to Asia or Australia.可知他們認(rèn)為蜥蜴從6千萬年前一直存在了，就生存在通過大陸橋和亞洲或者澳大利亞相連接的地方。所以the lineage 指C項(xiàng)某一個(gè)動(dòng)物的祖先的血統(tǒng)。故C正確。

4.4】D

【試題解析】主旨大意題。本文主要講述了lizards在世界上很多地方都可以找到。尤其是在一些與世隔絕的太平洋里的島嶼之上。文章中對(duì)于這個(gè)現(xiàn)象進(jìn)行了研究，分析了多種可能性。故D正確。

【長(zhǎng)難句解析】

Scientists have long puzzled over how iguanas, a group of lizards(蜥蜴) mostly found in the Americas, came to live in the isolated Pacific islands of Fiji and Tonga.

【翻譯】很久以來科學(xué)家一直都很困惑一種通常在美洲被發(fā)現(xiàn)的蜥蜴如何來到與世隔絕的太平洋上的斐濟(jì)和湯加島上生活。

【分析】本句中介詞over的后面含有一個(gè)賓語從句how iguanas, a group of lizards(蜥蜴) mostly found in the Americas, came to live in the isolated Pacific islands of Fiji and Tonga.這個(gè)賓語從句里有一個(gè)過去分詞短語mostly found in the Americas用來修飾前面的名詞iguanas, a group of lizards。