[Campbell Biology P.82] According to the provided graph and information, if a Neanderthal f... | Practice Question

According to the provided graph and information, if a Neanderthal fossil contains approximately 0.0078 of its original Carbon-14 14C , how many half-lives have passed since the Neanderthal died?

  • A: 5 half-lives
  • B: 6 half-lives
  • C: 7 half-lives
  • D: 8 half-lives

Explanation

The fraction of isotope remaining after 'n' half-lives is 1/2 ^n. We are given the fraction 0.0078. We need to find 'n' such that 1/2 ^n ≈ 0.0078. Let's calculate: 1/2 ^5 = 0.03125; 1/2 ^6 = 0.015625; 1/2 ^7 = 0.0078125. Therefore, 0.0078 is approximately 7 half-lives. This can also be visually confirmed on the graph by finding 0.0078 on the y-axis and tracing to the x-axis.