How does the biological clock tick?: reading answers and analysis
The passage argues that living things don't age like machines wearing out, because organisms constantly renew their material. Death still exists because evolution needs room for new types, life span is fixed for each species, and an internal clock linked to metabolic rate seems to control ageing, so using energy sparingly may lengthen life.
The headings (27-32) cover B to G in order, with A given as the example. The notes (33-36) come from B and C. The YES / NO / NOT GIVEN statements (37-40) jump between B, D and G.
Answer key and self-check
Type what you wrote and hit mark. Hide the key first if you haven't done the passage yet. Every question number jumps to its explanation.
How to attack this block: The paragraphs build an argument, so each heading is one step: objects versus organisms, why death helps, fixed life spans, the internal clock, energy use, then advice. Don't be pulled by single words: genetic material, men and women and metabolic rate all appear in paragraphs where they aren't the main idea.
Question 27
Answer: ixParagraph B
Which heading fits paragraph B?
Our 'dead' products are 'static', closed systems… an organism is an open, dynamic system through which new material continuously flows.
Question says → Passage says
objectsOur 'dead' products are 'static', closed systems
organismsan organism is an open, dynamic system
fundamental differences in ageingthe result of this law is not inexorable in the same way
Why: B sets objects and living things side by side: objects are closed and simply wear down, while organisms are open and keep renewing their material. That basic contrast in how they age is heading ix.
The trap: x, 'Repair of genetic material', picks up on renewal and new material. But B is about exchanging old substance for new, not repairing genes, and repair mechanisms only get a mention in C.
Question 28
Answer: iiParagraph C, last three sentences
Which heading goes with paragraph C?
Immortality would disturb this system - it needs room for new and better life.
Question says → Passage says
why dying is beneficiala restricted life span, ageing, and then death are basic characteristics of life. The reason for this is easy to recognise
beneficialit needs room for new and better life
Why: C explains the reason organisms die even though they don't have to: death makes room for new, better-adapted types. That's the benefit of dying, heading ii.
The trap: x, 'Repair of genetic material', is tempting because C mentions both 'mechanisms for repair' and 'genetic material'. They're in different sentences and neither is the main point.
Question 29
Answer: viiParagraph D, third and fourth sentences
Which heading matches paragraph D?
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
Question says → Passage says
a stable life spanhas hardly changed in thousands of years / within one species the parameter is relatively constant
despite improvementsAlthough… developments in medical care and better nutrition
Why: D says each species has a fairly constant life span, and the human limit is still about 80 years even with better medicine and food. 'Despite improvements' matches the 'Although' clause. vii.
The trap: v, 'Limitations of life span', also fits the idea of an upper limit, but it's the example heading for A. vii adds the key point: the limit hasn't moved.
Question 30
Answer: iParagraph E, first sentence
Which heading suits paragraph E?
it is logically necessary to propose the existence of an internal clock, which in some way measures and controls the ageing process
Question says → Passage says
the biological clockan internal clock
Why: E's main claim is that if life span is genetic, there must be an internal clock controlling ageing. The rest of E backs it up with metabolic rate and body mass. Heading i.
The trap: viii, 'Energy consumption', is tempting because E introduces metabolic rate. But E only links it to body size. The full discussion of using energy comes in F.
Question 31
Answer: viiiParagraph F
Which heading fits paragraph F?
Animals which behave 'frugally' with energy become particularly old
Question says → Passage says
energy consumptionbehave 'frugally' with energy / save energy by hibernation / The metabolic rate of mice can be reduced
Why: Every example in F is about how much energy an animal uses: crocodiles, hibernating bats, underfed mice, and men versus women. Lower energy use goes with a longer life. viii.
The trap: iii, 'The ageing process of men and women', fits only the last few sentences. Men and women are one example of the energy point, not the whole paragraph.
Question 32
Answer: ivParagraph G, first sentence
Which heading goes with paragraph G?
It follows from the above that sparing use of energy reserves should tend to extend life.
Question says → Passage says
prolonging your lifeextend life / increases the life span
your (the reader)Each of us can develop his or her own 'energy saving programme'
Why: G turns the science into advice: relax, sleep well, avoid extreme sport, and build your own energy-saving programme to live longer. Practical advice for the reader is iv.
The trap: viii, 'Energy consumption', is about F. G uses energy as the means, but its point is what you can do to live longer.
Note completion (NO MORE THAN TWO WORDS)
Questions 33-36
How to attack this block: Q33 and Q34 can be in either order and come from one sentence. Q35 needs a verb after 'can', so take the verb form, not the noun. Q36 starts a sentence and needs a noun subject.
Question 33
Answer: physical chemistryParagraph B, third sentence
Also accepted: thermodynamics
Objects age according to the principles of which field?
Ageing in this case must occur according to the laws of physical chemistry and of thermodynamics.
Question says → Passage says
Objects ageAgeing in this case
in accordance with principles ofaccording to the laws of
Why: 'In this case' refers to dead, man-made products. The notes copy the sentence's structure (_ and of _), and the first field is physical chemistry. Q33 and Q34 can be in either order.
The trap: Don't write just 'chemistry'. The passage says 'physical chemistry', and both words count.
Question 34
Answer: thermodynamicsParagraph B, third sentence
Also accepted: physical chemistry
What is the second set of principles objects age by?
Ageing in this case must occur according to the laws of physical chemistry and of thermodynamics.
Question says → Passage says
and ofand of thermodynamics
Why: The second field after 'and of' is thermodynamics. It's a long word, so check the spelling. This answer and Q33 can be swapped.
The trap: 'Wear and tear' is the everyday description of ageing in A, but it isn't a set of laws or principles, so it doesn't fit after 'principles of'.
Question 35
Answer: adaptParagraph C, middle
What can mutations help organisms do better to their environment?
in nature, the existent organisms either adapt or are regularly replaced by new types. Because of changes in the genetic material (mutations) these have new characteristics
Question says → Passage says
Through mutationsBecause of changes in the genetic material (mutations)
better to the environmentbetter adaptation to the environmental conditions
Why: The gap follows 'can', so it needs a base verb. The passage uses 'adapt' as a verb and 'adaptation… to the environmental conditions' a sentence later. Write 'adapt', not the noun.
The trap: 'Adaptation' is the word closest to 'better to the environment', but it's a noun and won't work after 'can'.
Question 36
Answer: immortalityParagraph C, last two sentences
What would cause a serious problem for evolution?
Immortality would disturb this system - it needs room for new and better life. This is the basic problem of evolution.
Question says → Passage says
would pose a serious problemwould disturb this system
the theory of evolutionthe basic problem of evolution
Why: The note starts with the gap, so it needs a noun subject. Immortality would disturb evolution, because evolution needs room for new life. One word: immortality.
The trap: 'Death' is the wrong way round. Death helps evolution. It's living for ever that would be the problem.
YES / NO / NOT GIVEN
Questions 37-40
How to attack this block: These ask for the writer's views. The writer explicitly argues against wear and tear for living things and recommends saving energy. Numbers that aren't in the passage, like percentages and years, signal NOT GIVEN.
Question 37
Answer: NOParagraph B, fourth sentence; Paragraph D, last sentence
Does wear and tear theory apply to both man-made objects and living things?
Although the same law holds for a living organism, the result of this law is not inexorable in the same way… A further argument against the simple wear and tear theory
Question says → Passage says
applies to boththe result of this law is not inexorable in the same way
the wear and tear theorythe simple wear and tear theory
Why: The writer says organisms can renew themselves and become older without ageing, and D calls a point 'a further argument against' the wear and tear theory. The writer rejects applying it to living things, so NO.
The trap: 'The same law holds for a living organism' sounds like YES. Keep reading: the law applies, but its result for organisms is different, so wear and tear doesn't describe how they age.
Question 38
Answer: YESParagraph B, fifth sentence
Is it possible, in theory, for a living system to get older without ageing?
At least as long as a biological system has the ability to renew itself it could actually become older without ageing
Question says → Passage says
in principle, it is possiblecould actually
become older without ageingbecome older without ageing
Why: The statement repeats the passage almost word for word, with the condition that the system can still renew itself. C adds 'It is not, in principle, necessary for a biological system to age and die'. YES.
Question 39
Answer: NOT GIVENParagraph B, last two sentences
Is about 90 per cent of the body replaced every seven years?
Thus our bodies continuously exchange old substance for new, just like a spring
Question says → Passage says
replaced as newcontinuously exchange old substance for new
Why: The passage says our bodies keep swapping old material for new, but gives no time span and no percentage. Seven years and 90 per cent aren't there. NOT GIVEN.
The trap: The idea of replacement is clearly in B, so people say YES. The numbers are the test: if the passage doesn't give them, you can't confirm them.
Question 40
Answer: YESParagraph G, first sentence
Might saving energy help people live longer?
It follows from the above that sparing use of energy reserves should tend to extend life.
Question says → Passage says
conserving energysparing use of energy reserves
may help to extend a human's lifeshould tend to extend life
Why: 'Sparing use of energy' is conserving it, and 'should tend to extend life' matches 'may help to extend'. The writer goes on to give an 'energy saving programme' for people. YES.
Renewal of material in B can look like 'repair of genetic material', but B's main point is the contrast between closed objects and open organisms (ix).
'The same law holds for a living organism' sounds like YES, but the writer adds that the result is different and later argues against the wear and tear theory: NO.
'Adaptation' is the closest word, but the gap follows 'can', so you need the verb 'adapt'.
Words from this passage worth keeping
inexorable(B)
impossible to stop or prevent
equilibrium(B)
a balanced state
inevitable(C)
certain to happen
attain(D)
reach or achieve
frugally(F)
carefully, without using much
lethargy(F)
a state of very low activity
prolong(G)
make something last longer
equable(G)
calm and even-tempered
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The full Cambridge 8 Test 3 reading paper: all three passages, 60 minutes, marked the second you finish with a review of every answer. Already done it? Take it again and see if the same traps still get you.
Cambridge IELTS 8, Test 3, Reading Passage 3. The passage and questions belong to Cambridge University Press and are not reproduced here. We quote short extracts only as evidence for our own commentary, and the answers are published for self-marking. Get the book for the full text, or sit the test on Langujet.
