雅思阅读 · Giant Armored Crustaceans and the Stolen Gene

改编自 Scientific American 文章 "Giant armored crustaceans survive thanks to a gene stolen from bacteria"。题型：判断题（True / False / Not Given）+ 选词填空。难度：中等偏上（Passage 2-3 之间）。

正文 Passage

When scientists refer to the deep sea as alien, they are not exaggerating. Among the cast of bizarre characters are enormous armor-covered crustaceans with large triangular compound eyes and long antennae. Researchers have long wondered how these strange creatures pull off one extreme feat: surviving more than five years without food.

It turns out that millions of years ago these deep-sea isopods most likely co-opted a gene from bacteria that — paired with a large stomach — lets them gorge on rare meals and slow their metabolism to endure long-term starvation in the ocean depths. "This is surprising because bacteria and animals are very different, and such gene transfers are rare," says Jianbo Yuan, a marine biologist at the Chinese Academy of Sciences' Institute of Oceanology and co-author on the new research published in Cell.

Giant marine isopods, which are related to garden pill bugs, live across a wide range of ocean depths, from a comparatively shallow 170 meters to the deep, dark sea around 2,100 meters down, where food and light are scarce. Some deep-sea isopods are supergiant, reaching up to half a meter in length. To understand what separates the deep-sea species from their shallower cousins, the researchers sequenced full genomes from specimens found at 300 and 800 meters and compared their energy demands, enzyme activity and oxygen use.

They found a key gene called ND1 expressed much more strongly in the deep-sea isopods. The gene looked more like one found in bacteria than in an animal: it lacked filler genetic segments called introns and produced very tiny proteins, both signs of a bacterial origin. The researchers theorize that more than 16 million years ago, genes from bacteria living in an isopod's stomach may have been incorporated into its genome in a way that was then passed along to future generations.

The many copies now in deep-sea isopods' genomes seem to slow down energy production when the creatures are in cold conditions. Inserting the gene into zebrafish, nematode worms and human cells, the researchers found, lowered those organisms' metabolic rates, too.

The finding "opens a completely new window to study the evolution of deep-sea gigantism and the role of the microbiome in deep-sea adaptation," says Torben Riehl, a marine biologist at the Senckenberg Ocean Species Alliance in Frankfurt, Germany, who was not involved in the study. Deep-sea ecosystems cover more than 50 percent of Earth's surface and are vital to the planet — so every little bit we learn, Riehl adds, may help us understand the benefits these ecosystems provide and how to preserve them.

题目 Questions

Questions 1-5: Do the following statements agree with the information given in the passage?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

1. Deep-sea isopods can survive without eating for over five years.

2. The gene ND1 originally came from the isopod's own ancestors.

3. The researchers studied isopods living at depths between 300 and 800 meters.

4. The ND1 gene was found only in deep-sea isopods, not in any other animals.

5. Torben Riehl was one of the lead authors of the study.

Questions 6-10: Complete the notes below.

Choose NO MORE THAN TWO WORDS from the passage for each answer.

• Deep-sea isopods are related to garden (6) ____________.
• The ND1 gene lacks filler segments called (7) ____________.
• The gene was incorporated into the isopod genome more than (8) ____________ years ago.
• When inserted into other organisms, ND1 lowered their (9) ____________.
• Deep-sea ecosystems cover over (10) ____________ of Earth's surface.

答案 Answers

核心词汇 Core Vocabulary

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