【小站出品】雅思阅读机经真题解析-Finches on Islands

A

Today, the quest continues. On Daphne Major-one of the most desolate of the Galipagos Islands, an uninhabited volcanic cone where cacti and shrubs seldom grow higher than a researcher's knee-Peter and Rosemary Grant have spent more than three decades watching Darwin's finch respond to the challenges of storms, drought and competition for food Biologists at Princeton University, the Grants know and recognize many of the individual birds on the island and can trace the birds' lineages hack through time. They have witnessed Darwin's principle in action again and again, over many generations of finches.

B

The Grants' most dramatic insights have come from watching the evolving bill of the medium ground finch. The plumage of this sparrow-sized bird ranges from dull brown to jet black. At first glance, it may not seem particularly striking, but among scientists who study evolutionary biology, the medium ground finch is a superstar. Its bill is a middling example in the array of shapes and sizes found among Galapagos finches: heftier than that of the small ground finch, which specializes in eating small, soft seeds, but petite compared to that of the large ground finch, an expert at cracking and devouring big, hard seeds.

C

When the Grants began their study in the 1970s, only two species of finch lived on Daphne Major, the medium ground finch and the cactus finch. The island is so small that the researchers were able to count and catalogue every bird. When a severe drought hit in 1977, the birds soon devoured the last of the small, easily eaten seeds. Smaller members of the medium ground finch population, lacking the bill strength to crack large seeds, died out.

D

Bill and body size are inherited traits, and the next generation had a high proportion of big-billed individuals. The Grants had documented natural selection at work-the same process that, over many millennia, directed the evolution of the Galapagos' 14 unique finch species, all descended from a common ancestor that reached the islands a few million years ago.

E

Eight years later, heavy rains brought by an El Nino transformed the normally meager vegetation on Daphne Major. Vines and other plants that in most years struggle for survival suddenly flourished, choking out the plants that provide large seeds to the finches. Small seeds came to dominate the food supply, and big birds with big bills died out at a higher rate than smaller ones. 'Natural selection is observable,’ Rosemary Grant says. 'It happens when the environment changes. When local conditions reverse themselves, so does the direction of adaptation.

F

Recently, the Grants witnessed another form of natural selection acting on the medium ground finch: competition from bigger, stronger cousins. In 1982, a third finch, the large ground finch, came to live on Daphne Major. The stout bills of these birds resemble the business end of a crescent wrench. Their arrival was the first such colonization recorded on the Galapagos in nearly a century of scientific observation. 'We realized,' Peter Grant says, 'we had a very unusual and potentially important event to follow.' For 20 years, the large ground finch coexisted with the medium ground finch, which shared the supply of large seeds with its bigger-billed relative. Then, in 2002 and 2003, another drought struck. None of the birds nested that year, and many died out. Medium ground finches with large bills, crowded out of feeding areas by the more powerful large ground finches, were hit particularly hard.

G

When wetter weather returned in 2004, and the finches nested again, the new generation of the medium ground finch was dominated by smaller birds with smaller bills, able to survive on smaller seeds. This situation, says Peter Grant, marked the first time that biologists have been able to follow the complete process of an evolutionary change due to competition between species and the strongest response to natural selection that he had seen in 33 years of tracking Galapagos finches.

H

On the inhabited island of Santa Cruz, just south of Daphne Major, Andrew Hendry of McGill University and Jeffrey Podos of the University of Massachusetts at Amherst have discovered a new, man-made twist in finch evolution. Their study focused on birds living near the Academy Bay research station, on the fringe of the town of Puerto Ayora. The human population of the area has been growing fast-from 900 people in 1974 to 9,582 in 2001. Today Puerto Ayora is full of hotels and mai tai bars,' Hendry says. 'People have taken this extremely arid place and tried to turn it into a Caribbean resort.’

I

Academy Bay records dating back to the early 1960s show that medium ground finches captured there had either small or large bills. Very few of the birds had mid-size bills. The finches appeared to be in the early stages of a new adaptive radiation: If the trend continued, the medium ground finch on Santa Cruz could split into two distinct subspecies, specializing in different types of seeds. But in the late 1960s and early 70s, medium ground finches with medium-sized bills began to thrive at Academy Bay along with small and large-billed birds. The booming human population had introduced new food sources, including exotic plants and bird feeding stations stocked with rice. Billsize, once critical to the finches' survival, no longer made any difference. 'Now an intermediate bill can do fine,’ Hendry says.

J

At a control site distant from Puerto Ayora, and relatively untouched by humans, the medium ground finch population remains split between large- and small-billed birds. On undisturbed parts of Santa Cruz, there is no ecological niche for a middling medium ground finch, and the birds continue to diversify. In town, though there are still many finches, once-distinct populations are merging.

K

The finches of Santa Cruz demonstrate a subtle process in which human meddling can stop evolution in its tracks, ending the formation of new species. In a time when global biodiversity continues its downhill slide, Darwin's finches have yet another unexpected lesson to teach. 'If we hope to regain some of the diversity that's already been lost/ Hendry says, 'we need to protect not just existing creatures, but also the processes that drive the origin of new species.

Year

Climate

Finch’s condition

1977

1

Small-beak birds failing to survive, without the power to open 2

1985

3 brought by El Nino

big-beak birds dying out, with 4 as the main food resource

题号

定位词

文中对应点

题目解析

1

1977

C段第三句

C段中有提到在1977年的气候和发生的事情，本题题目直接问1977年的climate，那可以直接在文中定位1977年，然后再看发生的气候，所以severe drought就是本题答案。

2

Smaller members of the medium

ground finch

C段第四句

C段中有提到在1977年的气候和小型雀鸟发生的状况，那本题目正好问到1977年small-beak birds 发生的状况，那么可以先定位1977年，然后找small-beak birds或类似意思内容，C段第四句出现 Smaller members of the medium ground finch lack the bill strength to crack large seeds,所以本题答案就是large seeds。

3

El Nino

E段第一句

E段中有提到El Nino带来的天气和影响，所以可以定位E段开头内容，本题答案为heavy rains。

4

Small seeds

E段第三句

E段中开头提到El Nino带来的大雨影响了为雀鸟提供大个种子作为食物的植物的生长空间，进而使得小个的种子成为雀鸟食物的主要来源，导致大型雀鸟比小型雀鸟以更高的速度消亡，所以该题答案为 small seeds、

5

Andrew

Hendry of McGill University and Jeffrey Podos

H段第一句

在H段开头有提到Andrew Hendry和 Jeffrey Podos 在雀鸟的进化过程中发现一个情况。所以finch evolution 就是本题答案。

6

in the late 1960s and early 70s

I段第四句

在I 段的开头有提到早在1960年代，岛上的中型地雀的鸟嘴不是小的就是大的，很少有中等大小的鸟嘴，但是到了1960年代末和70年代初，有着中等大小鸟嘴的中型地雀开始在Academy Bay出现在繁荣，所以本题答案为medium-sized

Bills.

7

introduced new food sources, including

exotic plants and bird feeding stations stocked with rice

I段第五句

I段后面内容开始讲到迅速增长的人口给雀鸟带来了新的食物来源，包括异国的食物。new food sources, including exotic plants and bird feeding stations stocked with rice与本题题目中问到的 brought in alien plants 有相同意思，所以答案应为前面的human population。

8

new food sources，

Survival

I段第六句

I段后面内容开始讲到迅速增长的人口给雀鸟带来了新的食物来源，包括异国的食物和在雀鸟喂食站堆积的大米，后面提示中等雀鸟也可以很好的生存，说明他们是以rice为食的。

9

Darwin theory

A段最后一句

本题目中有提到 Darwin theory，而在文章中第一段最后有提到Grants 已经一次次目睹了达尔文的理论在实际中的应用，说明他是支持达尔文的理论的。

10

Cactus finches,

Medium ground finch

C段前两句

文中只有C段开头有提到 Cactus finches和Medium ground finch，但是本段并没有提到两者收到食物影响大小的比较。

11

In 2002 and 2003

F段第六句

F段有提到在2002年和2003年的drought中对于finch的影响,文中指出那一年没有一直雀鸟有筑巢，很多都死了，说明题目给出的内容是正确的。

12

human

meddling

K段第一二句

K段的开始有提到Andrew Hendry和Jeffrey Podos的研究与现在全球生物多样化不断减少的现状是令人出乎意料的，表明其研究结果与之前的发现有所不同。

13

another unexpected lesson to teach

K段第二，三句

K段有提到Andrew Hendry和Jeffrey Podos的研究与现在全球生物多样化不断减少的现状是不同的，令人无处意料的，说明如果我们希望重新获得原本已经失去的生物多样性，那么我们不仅需要保护现状存在的物种，而且也要保护这种可以产生新物种的原始驱动力。所以本题答案是对的。

A

直到今天，相关雀鸟的研究仍在继续。Galapagos群岛中的最荒芜的一个小岛Daphne Major，是一个没有人居住的火山锥，在那里连仙人掌和灌木丛都很少能长得比一个研究者的双膝高，Peter和Rosemary Grant在那里已经花了超过30年的时间观察达尔文所提到的雀鸟，观察它们是如何对抗暴风雨，干旱和对食物的竞争的，普林斯顿大学的生物学家Grants可以认出小岛上许多单个的雀鸟，还可以追溯出雀鸟的血统。他们已经一次次目睹了达尔文的理论在实际中的应用，其中包括很多代的雀鸟。

B

Grants的最具戏剧性的观察是关于中型地雀的鸟嘴的进化。这种像麻雀大小的鸟的羽毛变化从暗棕到乌黑。乍一看，这个变化似乎没有什么特别的，但是对于研究生物进化论的科学家来说，这种中型地雀可是超级明星，它的鸟嘴是在Galapagos群岛上的雀鸟从形状和大小上处于中等的典范：比小型地雀要笨重些，主要是用来吃小的种子，但是比大型地雀又要小些，使其成为啄开和吞吃又大又硬的种子的能手。

C

当Grants在1970年代开始他们的研究时，在Daphne Major岛上只有两种雀鸟，中型地雀和仙人掌雀。该岛十分得小，以至于研究人员可以将每一只鸟都进行洁点和分类。1977年，该岛发生了一次严重的干旱，这些雀鸟 随即吞食了最后剩下的一些小个的易吃的种子。中型地雀中的相对鸟嘴 些的成员因为没有足够强壮的鸟嘴来吞吃大个些的种子而消亡。

D

雀鸟的鸟嘴和身体大小是遗传的，并且下一代往往有高比例的大鸟嘴的个体。Grants已经记录下丁自然选择的作用一一这也是几千年中指导Galapagos群岛上其它14种独有雀鸟的进化过程的，这些雀鸟都是从几百万年前到达这个群岛的同一个祖先进化来的。

E

8年后，由于厄尔尼诺现象带来的大雨改变了Dapne Major岛上原本只有很少植被生长的情况。原本在很多年中都要靠挣扎才能勉强生存下来的藤本植物和其它植物突然开始茂盛起来，抢夺了原本为雀鸟提供大个种子作为食物的植物的生长空间，小个的种子成为了雀鸟食物的主要来源，所以长着大嘴的大型雀鸟比小型雀鸟以更高的速度消亡。Rosemary Grant说道：“当环境改变时自然选择显而易见，当当地环境对雀鸟本身不利的时候， 适应的方向也发生了改变。”

F

近期，Grants目击了发生在中型雀鸟身上的另一种形式的自然选择：在更大更强壮的有血缘关系的雀鸟之间。在1982年，第三种地雀也就是大型地雀开始在Daphne Major岛上生活，它的鸟嘴和月牙形的扳手锋利的一面有点相似。它们的到来是Galapagos群岛近一个世纪以来，第一次科学记录如此大规模的殖民化。Peter Grant说道：“我们认为将会有一个很平常但将是很重要的事件需要我们去跟进。”在20年间，大型地雀和中型地雀共同生存，和它的大嘴亲戚一起分享大个的种子，但是到了2002年和2003 年，另一次干旱席卷了该岛。那一年，没有一只雀鸟有筑巢，许多都死了， 有着大个鸟嘴的中型地雀被大型地雀用更强有力的鸟嘴挤采食区，数量受到了重创。

G

当2004年天气变回潮湿一些，雀鸟又开始筑巢，新一代的中型地雀的栖息地被小嘴的小型地雀统治，所以它们只能通过食用更小个的种子来生存。Peter Grant认为这种情况标志着第一次生物学家可以通过物种间的竞争和对自然选择的反应来观察一个已经在Galapagos群岛上观察了33年的雀鸟的完整的进化史。

H

当在Daphne Major南面的Santa Cruz岛上，McGill大学的Andrew Hendry和位于Amherst的麻省理工学院的Podos发现在雀鸟的进化过程中一个新产生的认为造成的扭曲。他们的研究着眼于Academy Bay研究Puerto Ayora镇的边上。该地区的人口增长很快，从1974年的900人增长到2001年的9582人。Henry说道：“现如今在Puerto Ayora建满了酒店和Mai Tai吧，人们想要把这个极度贫瘠的土地变成一个度假胜地。”

I

Academy Bay研究站的记录显示，早在1960年代，在那里捕捉到的中型地雀的鸟嘴不是小的就是大的，很少有中等大小的鸟嘴。雀鸟似乎属于一个适应性辐射的早期：如果这种趋势继续下去，Santa Cruz岛上的中型地雀会变成两种完全不同的亚种，尤其是在食用的种子方面。但是到了 1960年代末和70年代初，有着中等大小鸟嘴的中型地雀开始在Academy Bay与其它有着或大或小鸟嘴的其它雀鸟一起繁荣，迅速增长的人口给雀鸟带来了新的食物来源，包括异国的植物和在雀鸟喂食站堆满的大米，鸟嘴的大小曾经一度对于雀鸟的生存至关重要，但是从此不再会带来不同的影响了。Henry说：“如今即使是中等大小的鸟嘴也可以让雀鸟很好地生存。”

J

在Puerto Ayora可控制范围内的一个观察站，很少有人到访，在那里中型地雀的还是主要分为大鸟嘴和小鸟嘴两种。在Santa Cruz此岛上没有人干扰 的地方，没有中等鸟嘴的中型地雀，并且雀鸟还在不停地发生着多样性的 变化。在那里尽管还有很多的雀鸟，但是明显不同的种群正在出现融合。

K

Santa Cruz的雀鸟表明了人类的干涉会改变原本进化的方向，最终导致新物种的出现。在全球生物多样性不断减少的时代，达尔文的雀鸟却给人们上了出人意料的一课。Hendry说道：“如果我们希望重新获得原本己经失去的生物多样性，那么我们不仅需要保护现在存在的物种，而且也要保护这种可以产生新物种的原始驱动力。”

Version 22203 主题 岛上的雀鸟

1

drought

2

large seeds

3

heavy rains

4

small seeds

5

finch evolution

6

medium-sized bills

7

human population

8

rice

9

FALSE

10

NOT GIVEN

11

TRUE

12

FALSE

13

TRUE