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One form of dating the age of a fossil is by radioactive carbon dating - VCE - SSCE Biology - Question 6 - 2012 - Paper 1
Question 6
One form of dating the age of a fossil is by radioactive carbon dating. The ratio of carbon-14 to nitrogen-14 ($C_{14} : N_{14}$) in the fossil is analysed and compa... show full transcript
Worked Solution & Example Answer:One form of dating the age of a fossil is by radioactive carbon dating - VCE - SSCE Biology - Question 6 - 2012 - Paper 1
Step 1
a. i. Place an X on the curve to show the fossil's $C_{14} : N_{14}$ ratio.
Answer
To indicate the fossil's ratio on the graph, we note it has only one-quarter of the carbon-14. This corresponds to a ratio of . Therefore, the X should be placed on the graph at the coordinates on the radioactive decay curve for .
Step 2
a. ii. Given the half-life of carbon is approximately 6000 years, what is the approximate age, in years, of the kangaroo skull?
Answer
Since the fossil has one-quarter of the original carbon-14, we can determine the number of half-lives that have passed. One-quarter corresponds to two half-lives because:
rac{1}{2} \rightarrow \frac{1}{4}
Thus, the approximate age of the kangaroo skull can be calculated as:
Step 3
b. i. Why is carbon-dating analysis not always possible?
Answer
Carbon-dating analysis is not always possible due to several reasons:
- The fossil may be too old, exceeding the effective range of carbon dating (around 50,000 years).
- Carbon-14 may not be present in sufficient amounts if the organic material has decomposed extensively or is contaminated.
- The environment where the fossil is discovered may have conditions that affect carbon retention, making accurate dating challenging.
Step 4
b. ii. Name another absolute dating technique that can determine the age of the rock surrounding a fossil.
Answer
Another absolute dating technique that can be used is Potassium-Argon (K-Ar) dating, which measures the decay of potassium-40 to argon-40, useful for dating igneous rocks and identifying the age of fossils contained within.