BEST IELTS Academic Reading Test 499

BEST IELTS Academic Reading Test 499

IELTS Academic Reading Test

Koalas

Their food is poisonous!

A. The koala, or Phascolarctos cinereus, is a herbivorous marsupial, native to Australia that only lives in eucalyptus trees and survives on an exclusive diet of their leaves. Apart from the fact that the leaves are highly fibrous and low in nutrition, due to the content of eucalyptus oil in the leaves, they would be toxic for most other animals, but not the koala. Recent research on the animal’s DNA has revealed how they are able to consume such a poisonous diet and how they decide which leaves to eat.

B. Animal geneticist Anna Barlow was constantly receiving calls asking for her advice on the best way to preserve healthy, genetically diverse koala populations around the country. She knew that the way to understand genetic diversity in a species is to have access to their genome. So she put together a team of specialists from around the world and they slowly assembled the pieces of the genetic puzzle for other scientists to use. Shona Mitchell, an American geneticist on the team and whose regular job concerns the human genome and pollution, said she thought most of the group jumped at the chance because koalas are so cute.

IELTS Academic Reading Test

C. Adorable they may be but they are also fascinating to study. To minimize the poisonous effects of the leaves, their digestive system has evolved to enable them to eliminate toxins very efficiently. This way, they can eat up to half a kilo of leaves every day without getting sick. The leaves are very low in calories, so to preserve energy, they need to spend around 18 to 22 hours a day sleeping or resting.

D. Barlow, whose work now only focuses on this unique animal, discovered that the section of its DNA related to detoxifying proteins is about double the length of other mammals, including humans. It seems that this was an accidental mutation where that genomic section repeated itself. After this duplication, it seems that survival of the fittest meant that those animals with the mutation were better able to live in the eucalypt environment, and the process became even more efficient.

IELTS Academic Reading Test

‘It’s all about co-evolution, explains Margaret Farnham, a researcher at the College of Technology, Melbourne who specializes in studying how the koala’s gut microbiome helps process eucalyptus. The eucalyptus has developed toxicity to stop being eaten, and the emergence of this ability to consume them has given koalas an environment with food that is exclusive to their species.

E. It is fascinating to know that koalas smell the leaves before eating them to make selections based on their toxicity. They have extra copies of genes that give them a strong sense of smell which helps them identify the toxic compounds in the leaves. They choose and eat leaves which are less toxic.

However, the very efficient system that enables them to digest toxic chemicals, means any drugs they are given are also eliminated from the body at a similar pace, a great deal faster than the systems of other animals. Antibacterial medication also disrupts the level of good bacteria in their digestive systems, blocking their ability to flush out toxins, and as a result they suffer from malnutrition. This makes it very difficult for them to be treated when they are ill.

IELTS Academic Reading Test

F. Many researchers have been trying to develop a vaccine that could prevent koala chlamydia, which is a bacterial infection that causes infertility. The whole koala research community is desperately trying to develop a vaccine to keep the birth rate up, but we just don’t know enough about their immune system yet, says microbiologist Angela Foreman, from the Institute of Technology, Sydney who is an expert at producing vaccines for many animal species. ‘Hopefully, now that we have sequenced the koala genome, we can better investigate their immune response to develop a vaccine!

G. Many koalas have a retrovirus similar to the human AIDS virus. As it compromises their immune systems, they are less able to combat chlamydia and cancer. Retroviruses have been known to insert themselves into genetic codes. The researchers found that this has long been the case with the koala, and by observing the genome, a history of retroviruses can be seen recurring dozens of times over the koala’s evolution. Conservation geneticist Robert Weeks says it is important for koalas to be genetically diverse in order to overcome the various threats to their lives. Of all the animals he studies, the koala is the most at risk.

IELTS Academic Reading Test

An animal that spends 18 to 22 hours a day sleeping in a tree is hardly going to travel far to find a genetically diverse mate. This is not helped by the fact that most of the habitats that remain are isolated from each other by farmland and cities. Many thousands of koalas were killed in the 2020 bushfires that directly hit almost every koala community in Australia. To survive into the future, koalas are probably going to need our help.

Reading Passage 2 has seven paragraphs, A-G.

Which paragraph relates to the following?

Write the correct letter, A-G.

NB You may use any letter more than once.

14. A part of the genome which controls the removal of poisonous substances.

15. Koalas use one of their senses to select their food.

16. The attractive physical appearance of the koala was a benefit.

17. Koalas have suffered from versions of a disease for a very long time.

18. Some drugs can upset the digestive system of the koala.

19. Genetic research may be used to improve the koala’s ability to reproduce.

IELTS Academic Reading Test

Choose TWO letters, A-E.

Which TWO scientists only work with koalas?

A. Anna Barlow

B. Shona Mitchell

C. Margaret Farnham

D. Angela Foreman

E. Robert Weeks

IELTS Academic Reading Test

Choose TWO letters, A-E.

Which TWO features relating to koalas are not mentioned in the text?

A. evolution

B. habitat

C. lifespan

D. nutrition

E. pollution

IELTS Academic Reading Test

Choose NO MORE THAN ONE WORD from the passage for each answer.

Koalas

• Koalas are able to eat toxic 24………. leaves because they have developed a genetically unique detoxifying ability.

• This ability also means that medicines tends not to be effective on koalas because the body flushes it out before it can begin to work, much 25……….. than in other mammal species.

• Koalas can also starve if medication disrupts the gut biome and they cannot digest the leaves.

• By studying the genome of koalas, scientists hope to develop a 26……….. for both chlamydia and retrovirus.

IELTS Academic Reading Test

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IELTS Academic Reading Test

14. D

15. E

16. B

17. G

18. E

19. F

20. A

21. C

22. C

23. E

24. EUCALYPTUS

25. FASTER

26. VACCINE

IELTS Academic Reading Test

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