雅思阅读 · The Greenland Shark's Century-Long Heartbeat

改编自 Scientific American 文章 "How Greenland sharks keep their hearts beating for centuries"。题型：判断题（True / False / Not Given）+ 选词填空。难度：中等偏上（Passage 2）。

正文 Passage

Everything about a Greenland shark's life is slow: its heart beats about once every 12 seconds; it swims at an average speed of just a foot per second; it grows at a sluggish rate of just one centimeter a year; and it does not reach sexual maturity until its 150th birthday. This sluggish living makes sense for steely behemoths that live comfortably into their 200s and possibly to 400 or more.

Recently, scientists found that the sharks keep their eyesight well into old age, revealing their vision remains functional in low light for more than a century. Understanding how these sharks keep all their parts working for so long offers insights into aging — which one day could help researchers extend the human life span. And now a new study shows how the sharks' heart can beat steadily for centuries without any apparent malfunction.

Long-lived animals are often equipped with age-defying traits, such as efficient DNA repair mechanisms, evolved protection from tumours and adept immune systems. The Greenland shark, which can grow to more than 16 feet long, is a prime example: its genome is full of genes linked to anti-inflammation, cancer suppression and resistance to cellular damage. But what about its most vital organ?

In the new study, Alessandro Cellerino of the Biology Laboratory at the Superior Normal School in Italy and his colleagues investigated whether the shark's heart was somehow protected against the wear and tear that comes with age. They analysed heart tissue from Greenland sharks for signs of aging and compared it with the hearts of the much smaller velvet belly lantern shark — a deep-sea shark with a far shorter life span — and the short-lived African turquoise killifish, a model organism used to study accelerated aging.

It turned out that the Greenland sharks, all estimated to be between 100 and 155 years of age, had a decrepit heart. The hearts showed severe fibrosis, which happens when scar tissue accumulates and causes stiffness that can impair pumping over time. Inside the sharks' cardiomyocytes — the cells that mechanically pump the heart — the team found massive amounts of lipofuscin, an age-related pigment produced when damaged cell machinery does not break down properly. And the analysis showed damage to the cardiac mitochondria, which power the cells, and oversize lysosomes, which help break down cellular material.

These same aging indicators did not appear in the comparison hearts.

"All in all, the analysed Greenland shark samples showed clearly recognisable signs of classic aging at the molecular and tissue level," Cellerino said in a statement. "This proves that aging processes also take place in the heart tissue of this species." The findings were published in the journal Aging Cell.

Despite their aging heart, the sharks seemed quite able to get around — some specimens in the study were collected by longline fishing in Greenland waters, suggesting the sharks could find bait and successfully capture it.

The team is not sure exactly how the hearts of the Greenland sharks seem to operate so smoothly. The sharks are known to have lower blood pressure compared with other species; that fact, along with the distinct structure of their ventral aorta, could keep their heart muscle elastic despite the damage caused by age, the researchers speculated.

The study results provide a window into how one of Earth's longest-lived vertebrates manages cellular and tissue aging in a vital organ. The sharks' resilience to aging could help scientists better understand longevity in vertebrates, including humans. "These findings may also inform translational approaches to mitigate age-related cardiac decline in humans," the study authors wrote.

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. Greenland sharks reach sexual maturity at around 15 years of age.

2. The Greenland shark's genome contains genes linked to cancer suppression.

3. The researchers compared Greenland sharks with two other animal species.

4. The hearts of the studied Greenland sharks showed no signs of aging.

5. The Greenland shark is the longest-lived vertebrate on Earth.

Questions 6-10: Complete the notes below.

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

• The Greenland shark grows just one (6) ____________ per year.
• The researchers analysed heart tissue for signs of (7) ____________.
• Scar tissue accumulation in the heart causes (8) ____________ that impairs pumping.
• Lipofuscin is an age-related (9) ____________ that builds up in heart cells.
• Lower (10) ____________ may help keep the shark's heart muscle elastic despite damage.

答案 Answers

核心词汇 Core Vocabulary