Cambridge IELTS 8 · Academic · Test 3 · Passage 3
How Does the Biological Clock Tick? — IELTS Reading Answers
All 14 answers for How Does the Biological Clock Tick?, Cambridge IELTS 8 Academic Reading Test 3 Passage 3, with the passage evidence and an explanation for each.
← All Cambridge 8 Test 3 answers
How Does the Biological Clock Tick? answer key at a glance
Questions 27–40. Tap an answer to see the evidence.
What this passage tests
This passage is tested with Matching Headings (Q27–32), Note Completion (Q33–36), Yes / No / Not Given (Q37–40). Each section below gives the strategy for that question type, the answers, and the sentence that proves them.
Questions 27–32: Matching Headings
Strategy: Read the paragraph first and summarise its main idea in five words. Choose the heading that matches the whole paragraph, not a repeated keyword.
Paragraph B
“Our ‘dead’ products are ‘static’, closed systems. It is always the basic material which constitutes the object and which, in the natural course of things, is worn down and becomes ‘older’. Ageing in this case must occur according to the laws of physical chemistry and of thermodynamics.”
Paragraph B contrasts 'static' dead products that wear down by physical chemistry with living organisms, where the same law is 'not inexorable' — the heading on the problem of ageing.
Paragraph C
“Immortality would disturb this system – it needs room for new and better life. This is the basic problem of evolution”
Paragraph C argues 'immortality would disturb this system – it needs room for new and better life', so death benefits evolution: the heading explaining why dying is beneficial.
Paragraph D
“For example, the average duration of human life has hardly changed in thousands of years. Although more and more people attain an advanced age as a result of developments in medical care and better nutrition, the characteristic upper limit for most remains 80 years”
Paragraph D stresses that 'the characteristic upper limit for most remains 80 years' despite better medicine, showing a fixed lifespan rather than an extendable one.
Paragraph E
“If a life span is a genetically determined biological characteristic, it is logically necessary to propose the existence of an internal clock, which in some way measures and controls the ageing process and which finally determines death as the last step in a fixed programme”
Paragraph E reasons that if lifespan is genetically determined there must be an 'internal clock' measuring and controlling ageing — the heading about the biological clock.
Paragraph F
“Animals which behave ‘frugally’ with energy become particularly old, for example, crocodiles and tortoises. Parrots and birds of prey are often held chained up. Thus they are not able to ‘experience life’ and so they attain a high life span in captivity. Animals which save energy by hibernation or lethargy (e.g.”
Paragraph F links long life to frugal energy use — crocodiles, tortoises, hibernating bats — so its heading concerns energy consumption and ageing.
Paragraph G
“It follows from the above that sparing use of energy reserves should tend to extend life. Extreme high performance sports may lead to optimal cardiovascular performance, but they quite certainly do not prolong life”
Paragraph G concludes that 'sparing use of energy reserves should tend to extend life', while extreme sport does not, pointing to the heading on prolonging the human lifespan.
Questions 33–36: Note Completion
Strategy: Predict the word class from the note, find the paraphrase of the note's keyword in the passage, then copy the answer exactly within the word limit.
“Ageing in this case must occur according to the laws of physical chemistry and of thermodynamics”
The gap needs the first of two named laws: ageing 'must occur according to the laws of physical chemistry and of thermodynamics', so 'physical chemistry' precedes 'thermodynamics'.
“Ageing in this case must occur according to the laws of physical chemistry and of thermodynamics”
The second law completing the pair is 'thermodynamics', named directly after physical chemistry in the same sentence about how dead objects age.
“in nature, the existent organisms either adapt or are regularly replaced by new types”
The gap needs a verb: 'the existent organisms either adapt or are regularly replaced by new types', so 'adapt' fits the either/or structure.
“Immortality would disturb this system – it needs room for new and better life. This is the basic problem of evolution”
The note needs the noun naming what would disrupt the system: 'Immortality would disturb this system', and it requires room for new life.
Questions 37–40: Yes / No / Not Given
Strategy: These test the writer's opinions, not facts. Look for evaluative language, and treat 'may' or 'could' as weaker than the question's claim.
The wear and tear theory applies to both artificial objects and biological systems.
“A further argument against the simple wear and tear theory is the observation that the time within which organisms age lies between a few days (even a few hours for unicellular organisms) and several thousand years, as with mammoth trees”
The writer argues against wear and tear applying to living things: organisms age anywhere from a few days to several thousand years, unlike objects, so it does not cover both.
In principle, it is possible for a biological system to become older without ageing.
“At least as long as a biological system has the ability to renew itself it could actually become older without ageing; an organism is an open, dynamic system through which new material continuously flows It is not, in principle, necessary for a biological system to age and die”
'Could actually become older without ageing' and 'not, in principle, necessary... to age and die' directly support the statement.
Within seven years, about 90 per cent of a human body is replaced as new.
“Thus our bodies continuously exchange old substance for new, just like a spring which more or less maintains its form and movement, but in which the water molecules are always different”
The text only says our bodies 'continuously exchange old substance for new', like flowing spring water; it gives no seven-year period and no 90 per cent figure.
Conserving energy may help to extend a human's life.
“It follows from the above that sparing use of energy reserves should tend to extend life”
'Sparing use of energy reserves should tend to extend life' states exactly that conserving energy may lengthen life, so the answer is YES.
Learn the question types in this passage
Frequently asked questions
Where does the How Does the Biological Clock Tick? passage come from?
It is Passage 3 of Cambridge IELTS 8 Academic Reading Test 3, and it covers Questions 27–40.
What question types appear in How Does the Biological Clock Tick??
The passage is tested with Matching Headings, Note Completion, Yes / No / Not Given. Each type is explained on this page, alongside the answers.
Are these reading answers reliable?
Every answer is paired with the sentence that proves it, so you can check each one against the passage yourself. Use the page after a timed attempt, not instead of one.
Cambridge IELTS is published by Cambridge University Press & Assessment. Band9Prep is not affiliated with Cambridge. This page is an independent study aid: it gives the answer key, the passage evidence and an explanation so you can review an attempt you have already made.