托福阅读生物类背景知识及真题

托福阅读生物类背景知识及真题

珊瑚礁

珊瑚礁(coral reef)是指造礁石珊瑚群体死后其遗骸(remains)构成的岩体。珊瑚礁的主体是由珊瑚虫(polyp)组成的。珊瑚虫是海洋中的一种腔肠动物在生长过程中能吸收海水中的钙和二氧化碳，然后分泌出石灰石(limestone)，变为自己生存的外壳。每一个单体的珊瑚虫只有米粒那样大小，它们一群一群地聚居在一起，一代代地新陈代谢(metabolism)，生长繁衍，同时不断分泌出石灰石，并粘合在一起。这些石灰石经过以后的压实、石化，形成岛屿和礁石，也就是所谓的珊瑚礁(coral reef)。

达尔文根据礁体与岸线的关系，划分出岸礁(fringing reef)、堡礁(barrier reef)和环礁(atoll)。

fringing reef

暗礁

沿大陆(mainland)或岛屿(island)岸边(shore)生长发育，亦称裙礁或边缘礁。现代最长的岸礁沿红海沿岸发育，绵延约2700多公里，分布水深约36米。中国台湾恒春半岛和海南岛沿岸也有岸礁发育。barrier reef

堡礁

又称堤礁，是离岸有一定距离的堤状礁体，它与陆地隔以泻湖(环礁湖)(lagoon)。现代规模最大的堡礁是澳大利亚昆士兰大堡礁，全长

约2000公里，分布水深约30米。

atoll

环礁

礁体呈环带状围绕泻湖(lagoon)，有的与外海有水道相通。环礁直径在几百米至几十公里，形态多样。已知的环礁有330个之多,主要分布在西太平洋的信风带和印度洋热带海域。环礁多坐落在大洋火山锥上，孤立于汪洋大海之中，展布受洋底火山(volcano)作用的控制，某些也可在大陆架(continental shelf)上见到。环礁礁坪上常有灰砂(砾)岛或礁岩岛，统称为珊瑚岛。

马绍尔群岛上的夸贾林环礁和马尔代夫群岛的苏瓦迪瓦环礁，面积都在1800平方公里以上，是世界上最大的两个环礁。南海发育的环礁颇具特色，有泻湖全被封闭的玉琢礁;有泻湖与外海有3个通道的华光礁;还有多通道开放式的永乐环礁，半月形全开放式的宣德环礁。永乐环礁和宣德环礁均发育有灰砂岛和礁岩岛，其中最大的灰砂岛是永兴岛，面积1.85平方公里。

托福阅读真题练习：蝴蝶

托福阅读文本：

Butterflies are among the most extensively studied insects —it is estimated that 90 percent of the worlds species have scientific names. As a consequence, they are perhaps the best group of insects for examining patterns of terrestrial biotic diversity and distribution. Butterflies also have a favorable

image with the general public. Hence, they are an excellent group for communicating information on science and conservation issues such as diversity.

Perhaps the aspect of butterfly diversity that has received the most attention over the past century is the striking difference in species richness between tropical and temperate regions. For example, in 1875 one biologist pointed out the diversity of butterflies in the Amazon when he mentioned that about 700 species were found within an hours walk, whereas the total number found on the British islands did not exceed 66, and the whole of Europe supported only 321. This early comparison of tropical and temperate butterfly richness has been well confirmed.

A general theory of diversity would have to predict not only this difference between temperate and tropical zones, but also patterns within each region, and how these patterns vary among different animal and plant groups. However, for butterflies, variation of species richness within temperate or tropical regions, rather man between them, is poorly understood. Indeed, comparisons of numbers of species among the Amazon basin, tropical Asia, and Africa are still mostly personal communication citations, even for vertebrates.

In other words, unlike comparison between temperate and tropical areas, these patterns are still in the documentation phase.

In documenting geographical variation in butterfly diversity, some arbitrary, practical decisions are made. Diversity, number of species, and species richness are used synonymously;little is known about the evenness of butterfly distribution. The New World butterflies make up the preponderance of examples because they are the most familiar species. It is hoped that by focusing on them, the errors generated by imperfect and incomplete taxonomy will be minimized.

托福阅读题目：

1. Which aspect of butterflies does the passage mainly discuss?

(A) Their physical characteristics

(B) Their names

(C) Their adaptation to different habitats

(D) Their variety

2. The word consequence in line 2 is closest in meaning to

(A) result

(B) explanation

(C) analysis

(D) requirement