Owl Secrets IELTS Reading Passage Academic
Reading Passage 3
You should spend about 20 minutes on Questions 27-40 which are based on Reading Passage 3
Owl Secrets
A.
It always appeared to fly in the face of logic. But now, the biological secrets that allow owls to rotate their heads without cutting off their blood supply have finally been unravelled. Scientists have discovered four major adaptations in owls designed to prevent injury when the animals rotate their overly large heads by up to 270 degrees.
B.
The study found that the birds’ unique bone structures and vascular systems let them move with increased flexibility. Scientists at John Hopkins University School of Medicine in the US studied snowy, barred and great horned owls after their deaths from natural causes. They found that the vertebral artery enters the neck higher than in other birds, creating more slack. Unlike humans, owls were found to have small vessel connections between the carotid and vertebral arteries, allowing the blood to be exchanged between the two blood vessels. This creates an uninterrupted blood flow to the brain, even if one route is blocked during extreme neck rotation.
C.
The adaptation gives the birds a huge range of vision without having to move their bodies and arouse detection by prey. The lack of similar adaptations in humans could explain why humans are more vulnerable to neck injury, the experts concluded. When humans attempt sudden and violent twists of their neck they risk damaging the lining of their blood vessels, which can result in a fatal blockage or stroke. Study senior investigator Doctor Philippe Gailloud, said: ‘Until now, brain imaging specialists like me who deal with human injuries caused by trauma to arteries in the head and neck have always been puzzled as to why rapid, twisting neck movements did not leave
thousands of owls lying dead on the forest floor from stroke. ‘The carotid and vertebral arteries in the neck of most animals – including owls and humans – are very fragile and highly susceptible to even minor tears of the vessel lining.’
D.
To solve the puzzle, the researchers studied the bone and blood vessel structures in the heads and necks of the birds. An injectable contrast dye was used to highlight the birds’ blood vessels, which were then dissected, drawn and scanned to allow detailed analysis.
E.
The most striking finding came after researchers injected dye into the owls’ arteries, mimicking blood flow, and manually turned the animals’ heads. They found that when they turned the heads, the blood vessels below the jaw bone expanded as more dye entered, creating pools of blood capable of maintaining the energy supply to the brain and eyes. They showed that the big carotid arteries, instead of being on the side of the neck as in humans, are carried close to the centre of rotation just in front of the spine. As a consequence, these arteries experience much less twisting and turning. The potential for damage is therefore greatly reduced. This contrasted starkly with human anatomical ability, where arteries generally tend to get smaller and smaller, and do not balloon out as they branch out. This creates the risk of clotting after sudden neck movements such as whiplash.
F.
Researchers say these contractile blood reservoirs act as a trade-off, allowing birds to pool blood to meet the energy needs of their large brains and eyes, while they rotate their heads. The supporting vascular network, with its many interconnections and adaptations,
helps minimise any interruption in blood flow. The study results demonstrate what physical properties are needed to allow such extreme head movements, and explain why injuries sustained from treatments that involve manipulating bones with the hands such as chiropractic therapy can have such serious consequences for humans. Dr Gailloud added: ‘Our new study results show precisely what morphological adaptations are needed to handle such head gyrations and why humans are so vulnerable to bone injury from chiropractic therapy. Extreme manipulations of the human head are really dangerous because we lack so many of the vessel-protecting features seen in owls.’
G.
Medical illustrator Fabian de Kok-Mercado said: ‘In humans, the vertebral artery really hugs the brains and eyes, while they rotate their heads. The supporting vascular network, with its many interconnections and adaptations, helps minimise any interruption in blood
flow. The study results demonstrate what physical properties are needed to allow such extreme head movements, and explain why injuries sustained from treatments that involve manipulating bones with the hands such as chiropractic therapy can have such serious consequences for humans. Dr Gailloud added: ‘Our new study results show precisely what morphological adaptations are needed to handle such head gyrations and why humans are hollow cavities in the neck. But this is not the case in owls, whose structures are specially adapted to allow for greater arterial flexibility and movement.’ It is a powerful adaptive trait, but it is not unique. Plenty of birds have a similar ability to look behind them. Red tailed hawks for example are almost as flexible as their nocturnal cousins. ‘There are lots of advantages to being able to look over your shoulder and see something coming – if you’re trying to avoid predators or detect prey’, he added.
Question 27-34
Complete the summary using the list of words and phrases A-M below.
Write the correct letter, A-Min boxes 27-34 on your answer sheet.
NB You may use any letter more than once.
How can owls rotate their heads by 27 _________ 270 degrees? The many small bones that make up the neck and spine enable them to achieve 28 _________ movement.A research team has discovered that in 29 _________ ,their vascular network has adapted to make the rotation possible. Owls’ carotid arteries are 30 _________ the spine, at the centre of rotation. This means the arteries endure 31 _________ strain when the head is turned. In addition, the vessels 32 _________ their heads can expand, creating reservoirs of blood to supply the brain when the head is turned. And the cavities in the neck vertebrae, through which the vessels pass, are extremely 33 _________ , giving the vessels space to move around when twisted. All this is necessary because their eyes can’t move: owls can only look 34 _________ ahead.
| A flexible | B as much as |
| C at the base of | D in front of |
| E intense | F limited |
| G far less | H multiple |
| I in excess of | J to the side of |
| K various ways | L large |
| M straight |
Questions 35-40
Complete each sentence with the correct ending, A-H below.
Write the correct letter, A-H in boxes 35-40 on your answer sheet.
35. The bone structure and circulatory system of owls has evolved in order to
36. Humans’ arteries tend to
37. Scientists injected dye into the blood vessels of dead owls in order to
38. When humans attempt sudden twists of their neck they are more likely to
39. The back;up arteries of owls are designed to
40. Owls have a huge range of vision which enables them to
A collect any excess blood created in the process of turning.
B cope with their very large heads.
C damage the lining of their blood vessels.
D decrease in size.
E make them lighter.
F mimic natural blood flow.
G offer a fresh supply of nutrients when blood vessels get closed off.
H avoid detection by predators or to find prey.
Owl Secrets IELTS Reading Passage Answers
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27 B
28 A
29 K
30 D
31 G
32 C
33 L
34 M
35 B
36 D
37 F
38 C
39 G
40 H
Owl Secrets IELTS Reading Answers Explanation
Answer 27: B. as much as
Supporting Sentence: Scientists have discovered owls rotate their overly large heads by up to 270 degrees.
Keyword: Scientists, owls, rotate, overly large heads, 270 degrees.
Keyword Location: Paragraph A, Line 3
Explanation: According to the scientists, the owls can spin their heads by at least 270 degrees without any sort of injury.
Answer 28: A. flexible
Supporting Sentence: The study found that the bird’s unique bone structures and vascular systems let them move with increased flexibility.
Keywords: Study, bird’s, bone structure, vascular systems, increased flexibility.
Keyword Location: Paragraph B, Line 1 ielts xpress
Explanation: According to the scientists, the owls have adapted their body parts in such a way that it allows flexible movement.
Answer 29: K. various ways
Supporting Sentence: Scientists studied owls. They found that the vertebral artery enters the neck higher than in other birds, creating more slack. Owls were found to have small vessel connections between carotid and vertebral arteries, allowing blood to be exchanged between two blood vessels.
Keyword: Scientists, owls, vertebral artery, neck, slack, vessel connections, carotid, vertebral, arteries, blood, exchange
Keyword Location: Paragraph B, Line 2-4
Explanation: According to the US scientists, adaptations like a higher vertebral artery and several compact connections among blood vessels allow owls to rotate their heads. ielts x pre s ss
Answer 30: D. in front of
Supporting Sentence: They showed that the big carotid arteries are carried close to the center of rotation just in front of the spine.
Keyword: Bid, carotid, arteries, center of rotation, spine
Keyword Location: Paragraph E, Line 3
Explanation: The researchers discovered that the secret to owls’ flexible neck movement is the presence of carotid arteries near the center of rotation and before the vertebral column.
Answer 31: G. far less
Supporting Sentence: As a consequence, these arteries experience much less twisting and turning.
Keyword: Consequence, arteries, experience, twisting, turning
Keyword Location: Paragraph E, Line 4
Explanation: The researchers discovered that the owls have adapted themselves in such a manner that their arteries hardly undergo any sort of rotation while they turn their large heads. ielts xpress
Answer 32: C. at the base of
Supporting Sentence: They found that when they turned their heads, the blood vessels below the jaw bone expanded, creating pools of blood capable of maintaining the energy supply to the brain and eyes.
Keywords: Turned their heads, blood vessels, jaw bone, expanded, pools of blood, energy supply, brain, eyes
Keyword Location: Paragraph E, Line 2
Explanation: The researchers found that the owls were capable of expanding the blood vessels below their heads which, in turn, helped to conserve the supply of energy to their brain and eyes during their neck rotation.
Answer 33: L. large
Supporting Sentence: Owls’ structures are specially adapted to allow for greater arterial flexibility and movement.
Keyword: Structures, owls, adapted, arterial flexibility, movement.
Keyword Location: Paragraph G, Line 1-2
Explanation: Unlike humans, the owls have large cavities in their necks that allow an increased arterial flexibility and movement.
Answer 34: M. straight
Supporting Sentence: The adaptation gives the birds a huge range of vision without having to move their bodies and arouses detection by prey.
Keyword: vision
Keyword Location: Paragraph 3, 1st line
Explanation: The main reason for the presence of various kinds of adaptation in owls is their complete incapability to move their eyeballs.
35. The bone structure and circulatory system of owls has evolved in order to
Answer: B. cope with their very large heads
Supporting Sentence: The biological secrets that allow owls to rotate their heads without cutting off their blood supply; Scientists have discovered adaptations in owls to prevent injury when the animals rotate their
overly large heads.
Keywords: Owls, rotate, heads, blood supply, adaptations, injury, overly large heads.
Keyword Location: Paragraph A, Line 2-3
Explanation: According to the scientists, the owls have evolved themselves in such a way that they are able to turn their oversized heads by at least 270 degrees without any bruises.
36. Human’s arteries tend to
Answer: D. decrease in size.
Supporting Sentence: This contrasted starkly with human anatomical ability where arteries generally tend to get smaller and smaller.
Keyword: Human, anatomical ability, arteries, smaller
Keyword Location: Paragraph E, Line 6
Explanation: Unlike owls, the arteries in human beings always have a tendency to become smaller. ielts x pre s s
37. Scientists injected dye into the blood vessels of dead owls in order to
Answer: F. mimic natural blood flow.
Supporting Sentence: Researchers injected dye into the owls’ arteries, mimicking blood flow.
Keyword: Researchers, injected dye, owls, arteries, mimicking, blood flow.
Keyword Location: Paragraph E, Line 1
Explanation: The scientists tried to imitate the blood flow in the arteries of owls by administering dye into the same.
38. When humans attempt sudden twists of their neck they are more likely to
Answer: C. damage the lining of their blood vessels.
Supporting Sentence: When humans attempt a sudden and violent twist of their neck they risk damaging the lining of their blood vessels.
Keywords: Humans, sudden, violent, twist, neck, damaging, lining, blood vessels
Keyword Location: Paragraph C, Line 3
Explanation: Unlike owls, any aggressive neck movement by human beings can cause injury to the vessel lining.
39. The backup arteries of owls are designed to
Answer: G. offer a fresh supply of nutrients when blood vessels get closed off.
Supporting Sentence: Owls were found to have small vessel connections between carotid and vertebral arteries; This creates an uninterrupted flow to the brain, even if one route is blocked during extreme neck rotation.
Keyword: Owls, small, vessel connections, carotid, vertebral, arteries, uninterrupted flow, brain, extreme, neck rotation
Keyword Location: Paragraph B, Line 4-5
Explanation: The US scientists discovered how owls maintain an undisturbed blood flow to their brain through a tiny network of blood vessels, even during acute cases of neck rotation.
40. Owls have a huge range of vision which enables them to
Answer: H. avoid detection by predators or to find prey.
Supporting Sentence: There are lots of advantages to being able to look over your shoulder and see something coming – if you’re trying to avoid predators or detect prey.
Keyword: Advantages, look, shoulder, avoid, predators, detect prey
Keyword Location: Paragraph G, Line 6
Explanation: The flexible neck movement of owls give them wide vision and thus, allows them to elude predators and discover prey.
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