# HOW DOES THE BIOLOGICAL CLOCK TICK?: answers and explanations

Cambridge IELTS 8, Test 3, Reading Passage 3

Source: Passage, questions and answer key from Cambridge IELTS 8, Test 3, Reading Passage 3. © Cambridge University Press & Assessment. Used for educational practice. Explanations and evidence notes are written by Testmigo.

## Answer key

| Q | Answer | Proof |
| --- | --- | --- |
| 27 | ix | Our 'dead' products are 'static', closed systems. ... an organism is an open, dynamic system through which new material continuously flows |
| 28 | ii | Immortality would disturb this system - it needs room for new and better life. |
| 29 | vii | the average duration of human life has hardly changed in thousands of years ... the characteristic upper limit for most remains 80 years |
| 30 | i | it is logically necessary to propose the existence of an internal clock |
| 31 | viii | Animals which behave 'frugally' with energy become particularly old |
| 32 | iv | Each of us can develop his or her own 'energy saving programme' ... to live in this way not only increases the life span but is also very healthy |
| 33 | physical chemistry | Ageing in this case must occur according to the laws of physical chemistry |
| 34 | thermodynamics | laws of physical chemistry and of thermodynamics |
| 35 | adapt | the existent organisms either adapt or are regularly replaced by new types |
| 36 | immortality | Immortality would disturb this system ... This is the basic problem of evolution. |
| 37 | NO | 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 |
| 38 | YES | it could actually become older without ageing |
| 39 | NOT GIVEN | Thus our bodies continuously exchange old substance for new |
| 40 | YES | sparing use of energy reserves should tend to extend life |

## Why these answers are right

**27. ix.** Paragraph B contrasts man-made objects, which are static closed systems that wear down, with organisms, which are open dynamic systems that constantly renew their material. This basic contrast in how each one ages matches heading ix.

**28. ii.** Paragraph C explains why organisms die even though they could repair themselves: new types with mutations must replace old ones, and immortality would leave no room for better-adapted life. Death serves evolution, so heading ii, why dying is beneficial, fits.

**29. vii.** Paragraph D says each species has a typical life span, and human life has hardly changed in thousands of years. Better medical care and nutrition help more people grow old, yet the upper limit stays at 80, which is heading vii.

The why and the trap for questions 30 onwards are free with an account on the [answers page](https://testmigo.com/ielts/reading/how-does-the-biological-clock-tick/answers).

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