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- IELTS Reading Summary Completion
- IELTS Reading Multiple Choice Questions
- IELTS Reading Sentence Completion
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IELTS reading passage – Owl Secrets
Owl Secrets
It always seemed to defy common sense. However, researchers have now finally uncovered the underlying mechanisms that allow owls to spin their heads without cutting off their blood supply. Owls’ four main adaptations to protect themselves from harm as they rotate their oversized heads by up to 270 degrees have been uncovered by scientists. The study discovered that the birds’ distinctive circulatory and bone systems allowed them to move with greater flexibility. Following the deaths of these owls from natural causes, researchers at the John Hopkins University School of Medicine in the US analyzed snowy, barred, and great-horned owls in several ways. They discovered that more slack exists in the neck because the vertebral artery enters it higher than it does in other birds. In contrast to humans, owls were discovered to have tiny vascular connections that allowed blood to flow back and forth between the carotid and vertebral arteries. This ensures that blood continues to flow to the brain even when one pathway is blocked due to excessive neck movement.
The adaption allows the birds to see a wide area without moving their bodies and alerts prey to their presence. The specialists came to the conclusion that humans may be more prone to neck injuries because they lack similar adaptations. Humans run the danger of injuring the blood vessel lining when they undertake sudden, severe neck twists, which can cause a fatal obstruction or stroke. “Until now, neuroscientific specialists dealing with injuries caused by trauma to arteries in the head and neck have always been confused as to why swift, twisting neck movements did not leave thousands of owls lying dead on the forest floor from a stroke,” said study senior investigator Doctor Philippe Gailloud. Most animals, including owls and humans, have very delicate carotid and vertebral arteries in their necks that are highly sensitive to even tiny lining tears.
To answer the puzzle, researchers investigated avian heads and necks for bone and blood vascular structures. Injectable contrast dye highlighted the birds’ blood arteries, which were then dissected, drawn, and scanned. The most dramatic discovery was made after scientists manually moved the owls’ heads while injecting dye into their arteries to simulate blood flow. When the heads were tilted, scientists discovered that the blood channels just under the jaw bone grew as more pigment entered, forming pools of blood that could maintain the brain and eye’s energy supply. They demonstrated that the large carotid arteries are carried near the center of rotation right in front of the spine rather than on the other side of the neck as in humans. These arteries consequently undergo substantially less twisting and turning. As a result, the risk of harm is considerably diminished. Contrasting sharply with human anatomy, arteries typically tend to get progressively smaller as they branch out rather than balloon out. As a result, there is a chance that blood will clot following abrupt neck motions like whiplash.
These viscoelastic blood reservoirs act as a trade-off and allow birds to collect blood for their enormous brains and eyes while rotating their heads, explain researchers. The interconnected and adaptable vascular network minimizes blood flow interruptions. The study results show what physical qualities are required for such significant head motions and explain why injuries from bone-manipulating therapies like chiropractic therapy can be so catastrophic. Dr. Gailloud said, ‘Our new study results demonstrate what morphological modifications are needed to withstand head gyrations and why people are so prone to bone fracture from chiropractic therapy.’ Extreme head manipulations are harmful because humans lack owls’ vessel-protecting characteristics.
In humans, the vertebra artery really hugs the brain and eyes when the head rotates, according to medical cartoonist Fabian de Kok-Mercado. The interconnected and adaptable vascular network minimizes blood flow interruptions. The study results show what physical qualities are needed to allow such significant head motions and explain why injuries from bone-manipulating therapies like chiropractic therapy can be so catastrophic. Dr. Gailloud said, ‘Our new study results demonstrate what morphological adaptations are needed to tolerate head gyrations and why humans have hollow neck cavities.’ But owls anatomy allows for greater vascular flexibility and movement. It’s adaptive, but not unique. Many birds can gaze back. Red-tailed hawks are flexible like their nocturnal cousins. ‘There are lots of advantages to being able to glance over your shoulder and notice anything approaching,’ he said.
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Owl Secrets Reading Questions
Questions 1 – 7
Complete the summary using the list of words and phrases A-M below.
Write the correct letter, A-M in boxes 1-7 on your answer sheet.
How can owls rotate their heads by 1 _______270 degrees? The many small bones that make up the neck and spine enable them to achieve 2 ________ movements. A research team has discovered that in 3________, their vascular network has adapted to make the rotation possible. Owls’ carotid arteries are 4 ________ the spine, at the center of rotation. This means the arteries endure 5 _________ the strain when the head is turned. In addition, the vessels 6_______ 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 7 ________ giving the vessels space to move around when twisted.
List of words/ phrases:
- flexible
- as much as
- at the base of
- in front of
- intense
- limited
- far less
- in excess of
- to the side of
- various ways
- large
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Questions 8 – 10
Choose the correct letters A, B, C or D
Write the correct letters in boxes 8 – 10 on your answer sheet.
8. Blood flow interruptions are decreased by
- Interconnections
- Arteries
- Vascular network
- neurons
9. What do contractile blood reservoirs act as to support the movement system?
- Adaptor
- Trade-off
- Blood pool
- Vessel
10. What Gailloud does NOT claim?
- Twisting neck was not harmful to owls
- Working of morphological adaptions
- Theory of hollow cavities
- Explanation of owl’s flying pace
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Questions 11 – 14
Complete the sentences with the correct ending, A – F below.
Write the correct letter, A – F in boxes 11 – 14 on your answer sheet.
11. The bone structure and circulatory system of owls have evolved in order to
12. Humans’ arteries tend to
13. Scientists injected dye into the blood vessels of dead owls in order to
14. When humans attempt sudden twists of their neck they are more likely 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 offers a fresh supply of nutrients when blood vessels get closed off.
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Owl Secrets Reading Answers
1. B
2. A
3. K
4. D
5. G
6. C
7. L
8. C
9. B
10. D
11. B
12. D
13. F
14. C
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