IB Biology HL A2.1.8 Dating First Cells and Luca Questions

Practise IB Biology HL A2.1.8 by explaining carbon-14 and potassium-40 dating methods and selecting radioisotopes for fossil ages.

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Explain carbon-14 dating by relating isotope decay and changing ¹⁴C:¹²C ratios to the age of a fossil.
Explain potassium-40 dating by relating ⁴⁰K decay, argon accumulation and isotope ratios to rock or fossil age.
Select suitable radioisotopes for dating fossils of different age ranges.

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Study A2.1.8—Dating first cells and LUCA conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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Outline the methods used for dating fossils and rocks using ${ }^{40} \mathrm{~K}$ .

${ }^{40} \mathrm{~K}$ decays into ${ }^{40} \mathrm{Ar}$ ;
ratio/proportion of ${ }^{40} \mathrm{~K}$ to ${ }^{40} \mathrm{Ar}$ indicates the age of the rock/fossil;
half-life of ${ }^{40} \mathrm{~K}$ is 1250 million/ 1.25 billion years;
${ }^{40} \mathrm{~K}$ can (only) be used to date very old samples/older than 100 000 years;

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IB Biology HL A2.1.8 Dating First Cells and Luca Questions question 1