『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 66 Passage2阅读练习，TPO/Official 66 Passage2原文答案解析，TPO/Official 66 Passage2阅读原文练习音频翻译。

托福TPO/Official 66 Passage2阅读原文题目答案及解析-新东方托福官方网校手机版

珊瑚属于一类被称为刺胞动物的动物群体。

Corals belong to a group of animals called cnidarians.

这一群体包括硬珊瑚、软珊瑚、海扇、柳珊瑚、水螅、水母和海葵。

This group encompasses hard and soft corals, sea fans, gorgonians, hydroids, jellyfish, and sea anemones.

尽管这一群体极为多样，但所有成员都有一些共同特征。

Although the group is remarkably diverse, there are a few features shared by all.

它们具有自由游泳的幼虫阶段和简单的身体结构：一个中央口，物质通过它进出身体，以及一圈触手。

They have a free-swimming larval stage and a simple body plan: a central mouth, through which material passes in and out of the body, and a ring of tentacles.

刺胞动物的另一个显著特征是存在刺细胞（ stinging cells），用于捕捉猎物。

The other distinguishing feature of the cnidarians is the presence of nematocysts (stinging cells), which are used to catch prey.

单个珊瑚被称为珊瑚虫，每个都是一个单独的动物。

Individual corals are known as coral polyps; each is a single animal.

单独的珊瑚虫看起来与海葵非常相似，但与彼此分离生活的海葵不同，珊瑚会形成群体。

In isolation a coral polyp looks very similar to a sea anemone, but unlike sea anemones, which live separated from each other, corals form colonies.

少数种类保持独居，但大多数情况下，新的珊瑚虫从最初的创始珊瑚虫上萌芽，逐渐形成由数千甚至数百万珊瑚虫组成的群体，每个珊瑚虫通过活体组织与其邻居相连。

A few species remain solitary, but in most cases, new polyps bud off the initial founding polyp, and gradually colonies of thousands or even millions of polyps will grow, each connected to its neighbors by living tissue.

摆脱了独居的限制，群体可以生长到巨大的规模并存活很长时间。

Freed from the limitations of living alone, colonies can grow to immense sizes and live a very long time.

珊瑚有各种形状和大小，但基本结构相同；珊瑚虫作为表层生活在某种结构上，无论是坚硬且不可弯曲的，还是柔韧的。

Corals come in all shapes and sizes, but the basic plan is the same; polyps live as a surface layer on some sort of structure, be it hard and inflexible or rubbery.

硬珊瑚或真正的珊瑚，以珊瑚礁最为著名，它们在活体组织下构建石灰石骨骼。

The hard, or true corals, for which reefs are most famous, build limestone skeletons beneath the living tissue.

软珊瑚，顾名思义，不形成坚固的骨骼；相反，它们分泌称为骨针的石灰石晶体结构，这些结构嵌入珊瑚虫下方的胶状基质中。

Soft corals, as their name implies, do not form solid skeletons; instead they secrete limestone crystal structures called sclerites, which are embedded within a jellylike matrix beneath the polyps.

当它们死亡时，大多数软珊瑚几乎不留下什么，因为它们的石灰石成分很小且容易分解。

When they die, little is left of most soft corals as the limestone element of their makeup is so small and easily breaks up.

相比之下，一些海鞭、海扇，尤其是黑珊瑚，具有由石灰石、蛋白质和矿物质组成的密集骨骼，极为耐用，常被采集并抛光制成首饰。

By contrast, some sea whips and fans and, notably, the black corals, have such dense skeletons of limestone, protein, and minerals that they are highly durable and are collected and polished for jewelry.

黑珊瑚的骨骼生长越慢越密集，而在深处生长更慢。

The skeleton of black corals is more dense the slower it grows, and it grows more slowly at depth.

所以深而老的蚁群才是最珍贵的。

So it is the very deep, older colonies that are most highly prized.

如果没有珊瑚虫分泌石灰石或碳酸钙的能力，珊瑚礁就不会存在。

Coral reefs would not exist if it were not for the ability of coral polyps to secrete limestone or calcium carbonate.

珊瑚周围的海水富含溶解的碳酸钙，但珊瑚虫体内的液体无法保留大量碳酸钙，因此它以微观针状晶体的形式沉积在珊瑚虫下方和周围。

Sea water surrounding a coral is very rich in dissolved calcium carbonate, but the fluid inside the polyp cannot retain a large quantity of calcium carbonate, so it is laid down as microscopic needle-shaped crystals beneath and around the polyp.

当珊瑚虫在夜间用触手扩展觅食时，它会从骨骼上抬起，类似手套从手上一半脱落。

As the polyp expands to feed with its tentacles at night, it lifts off the skeleton, rather like a glove coming part way off a hand.

在这个阶段，碳酸钙晶体形成脊状结构。

At this stage, the calcium carbonate crystals form ridges.

在接下来的白天（当珊瑚虫收缩并躺在新结构上时），脊之间的谷地被更多的碳酸钙填充，骨骼呈现出更光滑的外观。

During the following day (when the coral polyp is retracted and lying on its new structure), the valleys between the ridges fill in with more calcium carbonate and the skeleton takes on a smoother appearance.

因为硬珊瑚的骨骼由石灰石或碳酸钙构成，它是纯白色的。

Because the skeleton of hard corals is made of limestone or calcium carbonate, it is pure white.

每个珊瑚物种以不同的方式沉积其骨骼。

Each coral species lays down its skeleton in a different way.

这导致了硬珊瑚呈现出极为多样的形状和形态。

This gives rise to the extraordinary range of shapes and forms that hard corals take.

一些形成大块岩石，珊瑚虫生活在骨骼上小的、孤立的凹陷或沟槽中。

Some form large boulders, where the polyps live in small, isolated depressions or grooves in the skeleton.

一些以分支形式生长，可以是短小粗壮的，而其他的是扩展的、树状结构。

Some grow in branches, which can be small and stubby, while others are spreading, treelike structures.

还有一些生长出精致的叶状薄板或平坦的桌面状结构。

Still others grow delicate, leaflike plates or flat tables.

形态范围极广，更复杂的是，同一物种会根据其所在地的物理特性以不同方式生长。

The range is huge, and to complicate the matter further, the same species will grow in a different way depending on the physical characteristics of the place in which it finds itself.

虽然珊瑚的遗传蓝图是决定其外观的基础，但其外形也受到波浪、洋流、光线和礁石上空间竞争的影响。

Although a coral's genetic blueprint is fundamental in determining what it looks like, its appearance is also affected by waves, currents, light, and competition for space on the reef.

多年来，珊瑚形态的这种变化使识别问题变得复杂。

Such variations in coral form have complicated the matter of identification over the years.

According to paragraph 1, which of the following is true about the group of animals called cnidarians?

According to paragraph 2, what do corals and sea anemones have in common?

Which of the following can be inferred about coral reefs from paragraph 3?

The author mentions sea whips, fans, and black corals in paragraph 4 as examples of

According to paragraphs 3 and 4, the corals considered to be the most valuable are those that

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

The author mentions a glove in paragraph 5 in order to explain

The phrase "gives rise to" in the passage is closest in meaning to

Look at the four squares  that indicate where the following sentence could be added to the passage. In fact, some of these colonies have been known to last for several centuries.  Where would the sentence best fit? Click on a squareto add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

What is Coral? Corals belong to a group of animals called cnidarians. This group encompasses hard and soft corals, sea fans, gorgonians, hydroids, jellyfish, and sea anemones. Although the group is remarkably diverse, there are a few features shared by all. They have a free-swimming larval stage and a simple body plan: a central mouth, through which material passes in and out of the body, and a ring of tentacles. The other distinguishing feature of the cnidarians is the presence of nematocysts (stinging cells), which are used to catch prey. Individual corals are known as coral polyps; each is a single animal. In isolation a coral polyp looks very similar to a sea anemone, but unlike sea anemones, which live separated from each other, corals form colonies. A few species remain solitary, but in most cases, new polyps bud off the initial founding polyp, and gradually colonies of thousands or even millions of polyps will grow, each connected to its neighbors by living tissue. Freed from the limitations of living alone, colonies can grow to immense sizes and live a very long time. Corals come in all shapes and sizes, but the basic plan is the same; polyps live as a surface layer on some sort of structure, be it hard and inflexible or rubbery. The hard, or true corals, for which reefs are most famous, build limestone skeletons beneath the living tissue. Soft corals, as their name implies, do not form solid skeletons; instead they secrete limestone crystal structures called sclerites, which are embedded within a jellylike matrix beneath the polyps. When they die, little is left of most soft corals as the limestone element of their makeup is so small and easily breaks up. By contrast, some sea whips and fans and, notably, the black corals, have such dense skeletons of limestone, protein, and minerals that they are highly durable and are collected and polished for jewelry. The skeleton of black corals is more dense the slower it grows, and it grows more slowly at depth. So it is the very deep, older colonies that are most highly prized. Coral reefs would not exist if it were not for the ability of coral polyps to secrete limestone or calcium carbonate. Sea water surrounding a coral is very rich in dissolved calcium carbonate, but the fluid inside the polyp cannot retain a large quantity of calcium carbonate, so it is laid down as microscopic needle-shaped crystals beneath and around the polyp. This process occurs in two stages. As the polyp expands to feed with its tentacles at night, it lifts off the skeleton, rather like a glove coming part way off a hand. At this stage, the calcium carbonate crystals form ridges. During the following day (when the coral polyp is retracted and lying on its new structure), the valleys between the ridges fill in with more calcium carbonate and the skeleton takes on a smoother appearance. Because the skeleton of hard corals is made of limestone or calcium carbonate, it is pure white. Each coral species lays down its skeleton in a different way. This gives rise to the extraordinary range of shapes and forms that hard corals take. Some form large boulders, where the polyps live in small, isolated depressions or grooves in the skeleton. Some grow in branches, which can be small and stubby, while others are spreading, treelike structures. Still others grow delicate, leaflike plates or flat tables. The range is huge, and to complicate the matter further, the same species will grow in a different way depending on the physical characteristics of the place in which it finds itself. Although a coral's genetic blueprint is fundamental in determining what it looks like, its appearance is also affected by waves, currents, light, and competition for space on the reef. Such variations in coral form have complicated the matter of identification over the years.