SHOULD WE TRY TO BRING EXTINCT SPECIES BACK TO LIFE?
A
The passenger pigeon was a legendary species. Flying in vast numbers across North America, with potentially many millions within a single flock, their migration was once one of nature’s great spectacles. Sadly, the passenger pigeon’s existence came to an end on 1 September 1914, when the last living specimen died at Cincinnati Zoo. Geneticist Ben Novak is lead researcher on an ambitious project which now aims to bring the bird back to life through a process known as ‘de-extinction’. The basic premise involves using cloning technology to turn the DNA of extinct animals into a fertilised embryo, which is carried by the nearest relative still in existence – in this case, the abundant band-tailed pigeon – before being born as a living, breathing animal. Passenger pigeons are one of the pioneering species in this field, but they are far from the only ones on which this cutting-edge technology is being trialled.
B
In Australia, the thylacine, more commonly known as the Tasmanian tiger, is another extinct creature which genetic scientists are striving to bring back to life. ‘There is no carnivore now in Tasmania that fills the niche which thylacines once occupied,’ explains Michael Archer of the University of New South Wales. He points out that in the decades since the thylacine went extinct, there has been a spread in a ‘dangerously debilitating’ facial tumour syndrome which threatens the existence of the Tasmanian devils, the island’s other notorious resident. Thylacines would have prevented this spread because they would have killed significant numbers of Tasmanian devils. ‘If that contagious cancer had popped up previously, it would have burned out in whatever region it started. The return of thylacines to Tasmania could help to ensure that devils are never again subjected to risks of this kind.’
C
If extinct species can be brought back to life, can humanity begin to correct the damage it has caused to the natural world over the past few millennia? ‘The idea of de-extinction is that we can reverse this process, bringing species that no longer exist back to life,’ says Beth Shapiro of University of California Santa Cruz’s Genomics Institute. ‘I don’t think that we can do this. There is no way to bring back something that is 100 per cent identical to a species that went extinct a long time ago.’ A more practical approach for long-extinct species is to take the DNA of existing species as a template, ready for the insertion of strands of extinct animal DNA to create something new; a hybrid, based on the living species, but which looks and/or acts like the animal which died out.
D
This complicated process and questionable outcome begs the question: what is the actual point of this technology? ‘For us, the goal has always been replacing the extinct species with a suitable replacement,’ explains Novak. ‘When it comes to breeding, band-tailed pigeons scatter and make maybe one or two nests per hectare, whereas passenger pigeons were very social and would make 10,000 or more nests in one hectare.’ Since the disappearance of this key species, ecosystems in the eastern US have suffered, as the lack of disturbance caused by thousands of passenger pigeons wrecking trees and branches means there has been minimal need for regrowth. This has left forests stagnant and therefore unwelcoming to the plants and animals which evolved to help regenerate the forest after a disturbance. According to Novak, a hybridized band-tailed pigeon, with the added nesting habits of a passenger pigeon, could, in theory, re-establish that forest disturbance, thereby creating a habitat necessary for a great many other native species to thrive.
E
Another popular candidate for this technology is the woolly mammoth. George Church, professor at Harvard Medical School and leader of the Woolly Mammoth Revival Project, has been focusing on cold resistance, the main way in which the extinct woolly mammoth and its nearest living relative, the Asian elephant, differ. By pinpointing which genetic traits made it possible for mammoths to survive the icy climate of the tundra, the project’s goal is to return mammoths, or a mammoth-like species, to the area. ‘My highest priority would be preserving the endangered Asian elephant,’ says Church, ‘expanding their range to the huge ecosystem of the tundra. Necessary adaptations would include smaller ears, thicker hair, and extra insulating fat, all for the purpose of reducing heat loss in the tundra, and all traits found in the now extinct woolly mammoth.’ This repopulation of the tundra and boreal forests of Eurasia and North America with large mammals could also be a useful factor in reducing carbon emissions – elephants punch holes through snow and knock down trees, which encourages grass growth. This grass growth would reduce temperature, and mitigate emissions from melting permafrost.
F
While the prospect of bringing extinct animals back to life might capture imaginations, it is, of course, far easier to try to save an existing species which is merely threatened with extinction. ‘Many of the technologies that people have in mind when they think about de-extinction can be used as a form of “genetic rescue”,’ explains Shapiro. She prefers to focus the debate on how this emerging technology could be used to fully understand why various species went extinct in the first place, and therefore how we could use it to make genetic modifications which could prevent mass extinctions in the future. ‘I would also say there’s an incredible moral hazard to not do anything at all,’ she continues. ‘We know that what we are doing today is not enough, and we have to be willing to take some calculated and measured risks.’
Questions 14-17
Reading Passage 2 has six paragraphs, A-F.
Which paragraph contains the following information?
Write the correct letter, A-F, in boxes 14-17 on your answer sheet.
NB You may use any letter more than once.
14. a reference to how further disappearance of multiple species could be avoided.
15. explanation of a way of reproducing an extinct animal using the DNA of only that species
16. reference to a habitat which has suffered following the extinction of a species
17. mention of the exact point at which a particular species became extinct
Questions 18-22
Complete the summary below.
Choose NO MORE THAN TWO WORDS from the passage for each answer.
Write your answers in boxes 18-22 on your answer sheet.
The woolly mammoth revival project
Professor George Church and his team are trying to identify the 18…………………… which enabled mammoths to live in the tundra. The findings could help preserve the mammoth’s close relative, the endangered Asian elephant.
According to Church, introducing Asian elephants to the tundra would involve certain physical adaptations to minimise 19…………………… To survive in the tundra, the species would need to have the mammoth-like features of thicker hair, 20………………….. of a reduced size and more 21……………………..
Repopulating the tundra with mammoths or Asian elephant/mammoth hybrids would also have an impact on the environment, which could help to reduce temperatures and decrease 22……………………
Questions 23-26
Look at the following statements (Questions 23-26) and the list of people below.
Match each statement with the correct person, A, B or C.
Write the correct letter, A, B or C, in boxes 23-26 on your answer sheet.
NB You may use any letter more than once.
23. Reintroducing an extinct species to its original habitat could improve the health of a particular species living there.
24. It is important to concentrate on the causes of an animal’s extinction.
25. A species brought back from extinction could have an important beneficial impact on the vegetation of its habitat.
26. Our current efforts at preserving biodiversity are insufficient.
List of People
A Ben Novak
B Michael Archer
C Beth Shapiro
LỜI GIẢI CHI TIẾT
14.
Key words: disappearance, avoided
While most paragraphs are about bringing back extinct species, only paragraph F mentions how extinction could be avoided in the first place. It is stated that it is “far easier to save an existing species which is merely threatened with extinction”, and this could be achieved specifically by making “genetic modifications which could prevent mass extinctions in the future”. In this sentence, “prevent” could be understood as “avoid”. In mass extinctions, many/multiple species disappear/become extinct. Therefore, paragraph F contains the message that matches this statement, so F is the answer.
avoid = prevent
→ Answer: F
15.
Key words: explanation, reproducing, using DNA
By using the scanning and skimming technique, in paragraph A we could find the details of how DNA could be used to reproduce extinct animals. Specifically, it is stated that “the basic premise involves using cloning technology to turn the DNA of extinct animals into a fertilised embryo, which is carried by the nearest relative still in existence …”, meaning that this is an explanation of the mechanism of the technology. Therefore, A is the answer.
reproduce = clone
→ Answer: A
16.
Key words: habitat, suffered, following the extinction
The purposes of bringing back extinct species are mentioned in paragraph D, where one of the reasons is to repair damage to ecosystems. Specifically, it is stated that “Since the disappearance of this key species (passenger pigeons), ecosystems in the eastern US have suffered….”, in which “ecosystems” refers to “habitat”. Therefore, D is the answer.
habitat = ecosystems
→ Answer: D
17.
Key words: exact point, particular species, extinct
As the “exact point” might refer to an exact time or date, we could use the skimming and scanning technique and find in paragraph A the particular date for the extinction of the passenger pigeon, which “came to an end on 1 September 1914, when the last living specimen died…” As “come to an end” is the same as “become extinct”, it is confirmed that A is the answer.
become extinct = come to an end
→ Answer: A
QUESTIONS 18 – 22: COMPLETE THE SUMMARY BELOW.
18.
Key words: George Church, mammoths, tundra
In paragraph E, the team is focusing on reaching its goal by “pinpointing which genetic traits made it possible for mammoths to survive the icy climate of the tundra”.
- identify = pinpoint
- enable = make it possible
- live = survive
Therefore, the subject that Professor George Church and his team are trying to identify ís the “genetic traits”, which should be filled in gap 18.
→ Answer: genetic traits
19.
Key words: Church, Asian elephants, physical adaptations, minimise
In the same paragraph, it is stated that in order to expand the range of Asian elephants to the tundra, there would be multiple necessary physical adaptations that are “all for the purpose of reducing heat loss in the tundra”.
- minimise = reduce
Therefore, certain physical adaptations are aimed at minimising “heat loss”, which are the missing words in gap 19.
→ Answer: heat loss
20.
Key words: mammoth-like features
As mentioned earlier, multiple adaptations are necessary for the elephant to survive in the tundra, including “smaller ears, thicker hair, and extra insulation fat”, which are traits found in the woolly mammoth.
- reduced size = smaller
- more = extra
Therefore, the adaptations can be rewritten as “ears” of reduced size and more “insulation fat”. Thus, “ears” and “insulation fat” are respectively filled in gaps 20 and 21.
→ Answer: ears – (insulating) fat
21.
Key words: mammoth-like features
As mentioned earlier, multiple adaptations are necessary for the elephant to survive in the tundra, including “smaller ears, thicker hair, and extra insulation fat”, which are traits found in the woolly mammoth.
- reduced size = smaller
- more = extra
Therefore, the adaptations can be rewritten as “ears” of reduced size and more “insulation fat”. Thus, “ears” and “insulation fat” are respectively filled in gaps 20 and 21.
→ Answer: ears – (insulating) fat
22.
Key words: repopulating, environment
In paragraph E, the repopulation of the tundra with large mammals (which refers to mammoths and Asian elephants) might encourage grass growth, which would “reduce temperatures, and mitigate emissions from melting permafrost”.
Thus, it means that repopulating the tundra could help decrease “emissions”, or specifically “carbon emissions” in the preceding sentence. Therefore, “(carbon) emissions” is the answer.
- decrease = mitigate
→ Answer: (carbon) emissions
QUESTIONS 23 – 26: LOOK AT THE FOLLOWING STATEMENTS (QUESTIONS 23-26) AND THE LIST OF PEOPLE BELOW.
23.
Key words: reproducing an extinct species, improve, particular species
Among multiple benefits from reintroducing an extinct species, one of them, which is improving the health of a particular species living in a certain area (the island of Tasmania) is mentioned in paragraph B. Specifically, Michael Archer refers to the example of how the reintroduction of the thylacine would have helped the Tasmanian devils avoid the threats from the facial tumour syndrome, which dangerously affects their health. Therefore, B is the answer here,
→ Answer: B
24.
Key words: concentrate, causes
By skimming and scanning, we can find the emphasis on finding the causes of an animal’s extinction in paragraph F. Particularly, Beth Shapiro prefers to “fully understand why various species went extinct in the first place”, where “understand why” could be understood as “concentrate on the causes”. Therefore, C is the answer.
→ Answer: C
25.
Key words: beneficial impact, vegetation
By looking for keywords that relate to “vegetation”, we could find the idea of this statement in paragraph D. Since the extinction of a species – the passenger pigeon – the forests where they used to live have become “stagnant”. Ben Novak explains how the return of the passenger pigeons to their forest habitat, with their nesting habits, would help “re-establish that forest disturbance, thereby creating a habitat necessary for a great many other native species to thrive”. As the “forest disturbance” conveys the same meaning as “impact on the vegetation”, it is once again confirmed that this statement is the idea of Ben Novak. Therefore, A is the answer.
- brought back = return(ed)
→ Answer: A
26.
Key words: efforts, preserving biodiversity, insufficient
“Preserving biodiversity” could be understood as preventing extinction in the first place, which is the idea of paragraph F, so we would look in this one. In this paragraph, Shapiro expresses how it is “far easier to try to save an existing species …”, and commented that “we know that what we are doing today is not enough” for this act of preserving biodiversity.
- current = today
- insufficient = not enough
Therefore, this is the statement of Beth Shapiro, so C is the answer.
→ Answer: C
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