20:I[817158,["/_next/static/immutable/chunks/3zlxnut_1-a4f.js","/_next/static/immutable/chunks/2xl513ed6g9yb.js","/_next/static/immutable/chunks/27e7gv0pu9t-6.js","/_next/static/immutable/chunks/2cgkg8zq8zix6.js"],"default"] 21:T16d3,

READING PASSAGE 2

You should spend about 20 minutes on Questions 14–26, which are based on Reading Passage 2 below.

The internal body clock

Each of our cells has an internal 'clock' which dictates our daily rhythms. But why?

From buffalo to bacteria, oaks to algae, all life follows the same relentless 24-hour cycle, which is driven by the rising and setting of the Sun. Or is it? Over 250 years ago, a French scientist performed a simple experiment that blew apart the idea that all life on Earth does the bidding of the Sun. Intrigued by the way some flowers open and close their leaves each day, Jean-Jacques de Mairan put a heliotrope in a darkened room and observed the effect. He was expecting the plant, robbed of sunlight, to cease its daily routine. To his astonishment, its leaves continued to open and close as if in response to some invisible timekeeper.

But what – and where – is this internal timekeeper? And how does it achieve such astonishing regularity? These are the mysteries at the forefront of chronobiology, the study of the effect of time in living organisms. The search for answers is about more than just tying up some scientific loose ends. Internal ‘clocks’ clearly cause a lot of hardship. When an individual’s ‘clock’ is knocked out of synchronization through having to work at night or go on long-haul flights, that person can be left utterly unable to think or act. Yet even when these ‘clocks’ work correctly, the natural rhythms of alertness they generate prove dangerous: traffic accident statistics show two deadly peaks, at 4 a.m. and again twelve hours later when people are at their least alert.

During the 1970s, best-selling books began to emerge claiming such phenomena were manifestations of so-called biorhythms, a set of three cycles governing physical, emotional and intellectual traits. Said to start from the moment of birth and repeat every 23, 28 and 33 days respectively, they were supposed to result in ‘critical days’ when one or more cycles led to sub-optimal performance, with unfortunate consequences.

Scientists have since dismissed biorhythms as pseudoscience, insisting the existence of the three cycles has no basis in fact. In 1998, Dr Terence Hines of Pace University, New York State published the most comprehensive study of the claims made for biorhythms, reviewing the results of over 130 investigations. He found that three-quarters of them failed to provide any support for biorhythms. Most of the remainder contained blunders ranging from faulty mathematics to basic errors in statistics, while the handful of positive studies were explicable as flukes.

But there is no doubting the existence of 24-hour biological cycles – or, rather, ones roughly 24 hours long. Following de Mairan’s pioneering work, other researchers found that when deprived of the cues provided by sunlight, organisms settle down to ‘free-running’ cycles that are close to, but rarely exactly, 24 hours long. In the case of humans, the cycle is typically around 24.5 hours long. This is the so-called ‘circadian’ cycle (from the Latin meaning ‘about a day’), the length of which is generated by the mysterious internal ‘clock’.

During the late 1960s, chronobiologists believed they had found the ‘clock’, in the form of the suprachiasmatic nucleus (SCN), a collection of nerves in a region of the brain known as the hypothalamus. Linked to photosensitive cells in the eye, the SCN senses daylight and triggers the release of hormones like melatonin, which keep body functions in synchronization with the time of day. For a few years the SCN was regarded as the ultimate pacemaker – at least in higher organisms such as ourselves. But in 1971, scientists at the California Institute of Technology working with fruit flies found evidence for something truly amazing. Fruit flies appeared to have genes affecting the daily rhythm of their behavior – suggesting that there are ‘clocks’ inside each of their cells. Further evidence for this emerged in 1995, when researchers at Massachusetts General Hospital isolated nerve cells from the SCN, and found they kept up a circadian cycle without help from daylight. Finally in 1997, scientists at Northwestern University, Illinois, found a gene that regulates the daily rhythms of cellular activity in mammals.

The details of how this gene, known as CLOCK, actually works are still being investigated, but they could culminate in better ways of coping with shift-work and jet-lag. Professor Takahashi, who led the research, says that now that we know that circadian clocks exist throughout our bodies, we will need new strategies and therapeutics to reset all of our cells. But how do all the biochemical ‘clocks’ inside their cells stay in synchronization and why did organisms bother to acquire a link with sunlight? So far, no-one knows, though there are several theories. For example, sunlight might be useful in keeping the myriad cellular ‘clocks’ in lockstep.

In the search for answers, researchers are studying the behavior of a microbe called cyanobacterium. In 2005, a team at Nagoya University, Japan, showed that chemical reactions between three proteins produced by this bacterium ebbed and flowed on a 24-hour cycle. Cyanobacterium is the oldest form of life on Earth, so this suggests that cellular ‘clocks’ have existed for over three billion years. All subsequent organisms have followed suit, says Professor Johnson of Vanderbilt University, Tennessee. ‘Bacteria, fungi, plants and animals all appear to have evolved clock systems independently from each other.’ Quite why is still unknown. But one thing is clear: the daily routine of life is certainly not a modern invention.

22:Tba8,

Questions 14–18

Reading Passage 2 has eight paragraphs, A–H.

Which paragraph contains the following information?

Write the correct letter, A–H, in boxes 14–18 on your answer sheet.

	A	B	C	D	E	F	G	H
14 support for an earlier finding from experiments on insects
15 criticism of the way some research data was analysed
16 reference to a basic test on a plant
17a statement that the length of natural cycles varies slightly between living things
18 reference to a theory that became popular with the public

23:T673,

Questions 19–22

Complete the summary below.

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

Write your answers in boxes 19–22 on your answer sheet.

An overview of research into the existence of the internal ‘clock’

Towards the end of the 1960s, research into the SCN, which is located in the hypothalamus, led chronobiologists to believe they had found the internal ‘clock’ at last. Their theory was based on the fact that certain hormones that regulate the timing of physical functions are controlled by the SCN. The SCN is able to perceive 19 as a result of connections to the eye.

Several years later, research involving 20 showed that the timing of their normal actions was regulated by certain 21 , or ‘clocks’, in their cells. Thus the internal ‘clock’ is not an individual mechanism, as previously thought, but exists within each cell. Other scientists went on to conduct experiments in the dark that proved that a 22 was maintained by individual SCN cells.

24:T505,

Questions 23 and 24

Choose TWO letters, A–E.

Write the correct letters in boxes 23 and 24 on your answer sheet.

Which TWO of the following problems are stated as being linked with the internal ‘clock’?

A a decrease in output in workplaces without windows to let in natural light

B a failure among workers on night-shifts to perform tasks

C an increase in casualties on the roads at specific times of day

D a decline in efficiency on certain days in a number of fixed cycles

E a rise in mood swings dependent on the appearance of the Sun

25:T570,

Questions 25 and 26

Choose TWO letters, A–E.

Write the correct letters in boxes 25 and 26 on your answer sheet.

Which TWO of the following issues relating to internal ‘clocks’ remain to be solved, according to information in the passage?

A the precise length of the free-running daily cycle in different animals

B the reason for ‘clocks’ being temporarily driven out of synchronisation

C the reason for living beings forming a connection with the Sun’s rhythms

D the way in which all ‘clocks’ in a single organism are able to stay in step with one another

E the location of the ‘clocks’ across the whole range of living organisms

17:["$","$L20",null,{"exam":{"id":"p2-medium-243","title":"The internal body clock","titleVi":"","part":"P2","frequency":"medium","questionCount":13,"kinds":["Ghép thông tin","Điền tóm tắt","Trắc nghiệm"],"hasExplanation":true,"questionOrder":["q1","q2","q3","q4","q5","q6","q7","q8","q9","q10","q11","q12","q13"],"displayMap":{"q1":"14","q2":"15","q3":"16","q4":"17","q5":"18","q6":"19","q7":"20","q8":"21","q9":"22","q10":"23","q11":"24","q12":"25","q13":"26"},"answerKey":{"q1":"F","q2":"D","q3":"A","q4":"E","q5":"C","q6":"daylight","q7":"fruit flies","q8":"genes","q9":"circadian cycle","q10":"B","q11":"C","q12":"C","q13":"D"},"questionIntroHtml":"","passageHtml":"$21","groups":[{"id":"group-1","kind":"matching","questionIds":["q1","q2","q3","q4","q5"],"leadHtml":"","html":"$22","allowOptionReuse":false},{"id":"group-2","kind":"summary_completion","questionIds":["q6","q7","q8","q9"],"leadHtml":"","html":"$23","allowOptionReuse":false},{"id":"group-3","kind":"multi_choice","questionIds":["q10","q11"],"leadHtml":"","html":"$24","allowOptionReuse":false},{"id":"group-4","kind":"multi_choice","questionIds":["q12","q13"],"leadHtml":"","html":"$25","allowOptionReuse":false}],"explanations":{"passageNotes":[],"questionExplanations":[{"sectionTitle":"Lời giải từng câu","items":[{"questionNumber":14,"text":"(1) Câu 14: support for an earlier finding from experiments on insects\nDịch đề: Cung cấp ủng hộ cho phát hiện trước đó từ các thí nghiệm trên côn trùng.\nĐáp án: F\nĐịnh vị: bài chính đoạn F, nửa sau\nBản gốc: Further evidence for this emerged in 1995, when researchers at Massachusetts General Hospital isolated nerve cells from the SCN, and found they kept up a circadian cycle without help from daylight.\nBản dịch: Năm 1995 xuất hiện thêm bằng chứng: các nhà nghiên cứu tách tế bào thần kinh SCN, phát hiện chúng không cần ánh sáng ban ngày vẫn duy trì chu kỳ ngày đêm.\n\nGiải thích: Further evidence tương ứng support, this chỉ phát hiện ở thí nghiệm ruồi giấm ở trên cho thấy trong tế bào có “đồng hồ” nội tại, nên chọn F."},{"questionNumber":15,"text":"(2) Câu 15: criticism of the way some research data was analysed\nDịch đề: Phê bình cách phân tích dữ liệu nghiên cứu nào đó.\nĐáp án: D\nĐịnh vị: bài chính đoạn D, câu 3\nBản gốc: Most of the remainder contained blunders ranging from faulty mathematics to basic errors in statistics\nBản dịch: Phần lớn các nghiên cứu còn lại có sai sót từ tính toán toán học sai đến lỗi thống kê cơ bản.\n\nGiải thích: faulty mathematics và errors in statistics đều là lỗi về phương pháp phân tích dữ liệu, nên chọn D."},{"questionNumber":16,"text":"(3) Câu 16: reference to a basic test on a plant\nDịch đề: Nhắc đến một thí nghiệm đơn giản trên thực vật.\nĐáp án: A\nĐịnh vị: bài chính đoạn A, phần giữa\nBản gốc: Jean-Jacques de Mairan put a heliotrope in a darkened room and observed the effect.\nBản dịch: Jean-Jacques de Mairan đặt một cây hướng nhật vào phòng tối và quan sát kết quả.\n\nGiải thích: Đặt thực vật vào phòng tối để quan sát lá đóng mở là basic test on a plant mà đề nói, nên chọn A."},{"questionNumber":17,"text":"(4) Câu 17: a statement that the length of natural cycles varies slightly between living things\nDịch đề: Nói rõ độ dài chu kỳ tự nhiên của các sinh vật khác nhau hơi khác nhau.\nĐáp án: E\nĐịnh vị: bài chính đoạn E, câu 2 đến 3\nBản gốc: organisms settle down to ‘free-running’ cycles that are close to, but rarely exactly, 24 hours long. In the case of humans, the cycle is typically around 24.5 hours long.\nBản dịch: Sinh vật ổn định ở chu kỳ “tự chạy” gần nhưng hiếm khi đúng 24 giờ; với con người, chu kỳ thường khoảng 24,5 giờ.\n\nGiải thích: rarely exactly 24 hours và ví dụ con người khoảng 24,5 giờ cho thấy chu kỳ của các sinh vật khác nhau có chênh lệch nhỏ, nên chọn E."},{"questionNumber":18,"text":"(5) Câu 18: reference to a theory that became popular with the public\nDịch đề: Nhắc đến một lý thuyết từng phổ biến trong công chúng.\nĐáp án: C\nĐịnh vị: bài chính đoạn C, câu 1\nBản gốc: During the 1970s, best-selling books began to emerge claiming such phenomena were manifestations of so-called biorhythms\nBản dịch: Thập niên 1970, bắt đầu xuất hiện những cuốn sách bán chạy tuyên bố các hiện tượng này là biểu hiện của cái gọi là “nhịp sinh học”.\n\nGiải thích: best-selling books cho thấy lý thuyết này được công chúng ưa chuộng, tên lý thuyết là biorhythms, nên chọn C."},{"questionNumber":19,"text":"(1) Câu 19: Towards the end of the 1960s, research into the SCN, which is located in the hypothalamus, led chronobiologists to believe they had found the internal ‘clock’ at last. Their theory was based on the fact that certain hormones that regulate the timing of physical functions are controlled by the SCN. The SCN is able to perceive ________ as a result of connections to the eye.\nDịch đề: SCN nối với mắt, nên có thể cảm nhận ________.\nĐáp án: daylight\nĐịnh vị: bài chính đoạn F, câu 2\nBản gốc: Linked to photosensitive cells in the eye, the SCN senses daylight\nBản dịch: SCN nối với tế bào cảm quang trong mắt, cảm nhận được ánh sáng ban ngày.\n\nGiải thích: perceive tương ứng senses, connections to the eye tương ứng linked to photosensitive cells in the eye, nên điền daylight."},{"questionNumber":20,"text":"(2) Câu 20: Several years later, research involving ________ showed that the timing of their normal actions was regulated by certain ________, or ‘clocks’, in their cells. Thus the internal ‘clock’ is not an individual mechanism, as previously thought, but exists within each cell. Other scientists went on to conduct experiments in the dark that proved that a ________ was maintained by individual SCN cells.\nDịch đề: Sau đó nghiên cứu trên ________ cho thấy nhịp hành vi hằng ngày của chúng được điều chỉnh bởi một số cơ chế trong tế bào.\nĐáp án: fruit flies\nĐịnh vị: bài chính đoạn F, câu 4\nBản gốc: scientists at the California Institute of Technology working with fruit flies found evidence for something truly amazing.\nBản dịch: Các nhà khoa học của Học viện Công nghệ California nghiên cứu ruồi giấm phát hiện bằng chứng đáng ngạc nhiên.\n\nGiải thích: research involving tương ứng working with, đối tượng thí nghiệm là fruit flies; hai từ và đều là cụm liên tiếp trong bài."},{"questionNumber":21,"text":"(3) Câu 21: Several years later, research involving ________ showed that the timing of their normal actions was regulated by certain ________, or ‘clocks’, in their cells. Thus the internal ‘clock’ is not an individual mechanism, as previously thought, but exists within each cell. Other scientists went on to conduct experiments in the dark that proved that a ________ was maintained by individual SCN cells.\nDịch đề: Nhịp hành vi hằng ngày của ruồi giấm được điều chỉnh bởi một số ________ trong tế bào, tức “đồng hồ”.\nĐáp án: genes\nĐịnh vị: bài chính đoạn F, câu 5\nBản gốc: Fruit flies appeared to have genes affecting the daily rhythm of their behavior – suggesting that there are ‘clocks’ inside each of their cells.\nBản dịch: Ruồi giấm dường như có các gen ảnh hưởng đến nhịp hành vi hằng ngày — gợi ý trong mỗi tế bào đều có “đồng hồ”.\n\nGiải thích: regulated by trong đề tương ứng affecting, or clocks tương ứng việc bài liên hệ các genes này với “đồng hồ” trong tế bào, nên điền genes."},{"questionNumber":22,"text":"(4) Câu 22: Several years later, research involving ________ showed that the timing of their normal actions was regulated by certain ________, or ‘clocks’, in their cells. Thus the internal ‘clock’ is not an individual mechanism, as previously thought, but exists within each cell. Other scientists went on to conduct experiments in the dark that proved that a ________ was maintained by individual SCN cells.\nDịch đề: Thí nghiệm trong bóng tối cho thấy từng tế bào SCN vẫn duy trì một ________.\nĐáp án: circadian cycle\nĐịnh vị: bài chính đoạn F, câu 6\nBản gốc: isolated nerve cells from the SCN, and found they kept up a circadian cycle without help from daylight.\nBản dịch: Các nhà nghiên cứu tách tế bào thần kinh SCN, phát hiện chúng không cần ánh sáng ban ngày vẫn duy trì chu kỳ ngày đêm.\n\nGiải thích: maintained tương ứng kept up, individual SCN cells tương ứng isolated nerve cells from the SCN, nên điền cụm liên tiếp trong bài circadian cycle."},{"questionNumber":23,"text":"(1) Câu 23: (Đề bài xem ở phần đề)\nDịch đề: Hai điều nào sau đây được bài nêu rõ là vấn đề liên quan đến đồng hồ nội tại của cơ thể?\nĐáp án: B（a failure among workers on night-shifts to perform tasks）\nĐịnh vị: bài chính đoạn B, câu 4\nBản gốc: When an individual’s ‘clock’ is knocked out of synchronization through having to work at night or go on long-haul flights, that person can be left utterly unable to think or act.\nBản dịch: Khi “đồng hồ” của một người mất đồng bộ do phải làm đêm hoặc đi chuyến bay đường dài, người đó có thể hoàn toàn không thể suy nghĩ hay hành động.\n\nGiải thích: work at night tương ứng workers on night-shifts, utterly unable to think or act tương ứng failure to perform tasks, nên chọn B."},{"questionNumber":24,"text":"(2) Câu 24: (Đề bài xem ở phần đề)\nDịch đề: Hai điều nào sau đây được bài nêu rõ là vấn đề liên quan đến đồng hồ nội tại của cơ thể?\nĐáp án: C（an increase in casualties on the roads at specific times of day）\nĐịnh vị: bài chính đoạn B, câu cuối\nBản gốc: traffic accident statistics show two deadly peaks, at 4 a.m. and again twelve hours later when people are at their least alert.\nBản dịch: Thống kê tai nạn giao thông cho thấy hai đỉnh chết người: bốn giờ sáng, và mười hai giờ sau khi người ta ít tỉnh táo nhất.\n\nGiải thích: traffic accident statistics và deadly peaks tương ứng thương vong đường bộ tăng, hai thời điểm 4 a.m. và mười hai giờ sau tương ứng specific times of day, nên chọn C."},{"questionNumber":25,"text":"(1) Câu 25: (Đề bài xem ở phần đề)\nDịch đề: Theo bài, hai vấn đề nào về đồng hồ nội tại vẫn chưa được giải quyết?\nĐáp án: C（the reason for living beings forming a connection with the Sun’s rhythms）\nĐịnh vị: bài chính đoạn G, câu 3 đến 4\nBản gốc: why did organisms bother to acquire a link with sunlight? So far, no-one knows\nBản dịch: Vì sao sinh vật phải tốn công hình thành liên hệ với ánh sáng mặt trời? Cho đến nay không ai biết.\n\nGiải thích: organisms tương ứng living beings, a link with sunlight tương ứng a connection with the Sun’s rhythms; So far, no-one knows nêu rõ nguyên nhân vẫn chưa được giải quyết, nên chọn C."},{"questionNumber":26,"text":"(2) Câu 26: (Đề bài xem ở phần đề)\nDịch đề: Theo bài, hai vấn đề nào về đồng hồ nội tại vẫn chưa được giải quyết?\nĐáp án: D（the way in which all ‘clocks’ in a single organism are able to stay in step with one another）\nĐịnh vị: bài chính đoạn G, câu 3 đến 4\nBản gốc: But how do all the biochemical ‘clocks’ inside their cells stay in synchronization and why did organisms bother to acquire a link with sunlight? So far, no-one knows\nBản dịch: Nhưng làm sao mọi “đồng hồ” sinh hóa trong tế bào của chúng giữ được đồng bộ? Và vì sao sinh vật phải tốn công hình thành liên hệ với ánh sáng mặt trời? Cho đến nay không ai biết.\n\nGiải thích: all the biochemical ‘clocks’ inside their cells tương ứng all ‘clocks’ in a single organism, stay in synchronization tương ứng stay in step with one another; no-one knows cho thấy cơ chế này vẫn chưa được giải quyết, nên chọn D."}]}]}}}]