[Campbell Biology P.688] Based on the provided data and formula, which of the three ancient ... | Practice Question

Based on the provided data and formula, which of the three ancient date palm seeds is the oldest, and what is the most plausible explanation for why the germinated seed Seed 3 retained a higher fraction of Carbon-14 compared to the non-germinated seeds?

  • A: Seed 1 is the oldest; the germinated seed was exposed to more recent carbon that contaminated the sample.
  • B: Seed 2 is the oldest; the germinated seed metabolized its older carbon-14 during growth, leading to a higher remaining fraction.
  • C: Seed 3 is the oldest; germinated seeds naturally contain more carbon-14 due to increased photosynthetic activity.
  • D: Seed 1 is the oldest; the germinated seed (Seed 3) probably incorporated some modern carbon from the environment during its germination and growth as a seedling.

Explanation

To determine the age, we use the formula t = - ln F / k, where k = 0.00012097. For Seed 1 F=0.7656 , t ≈ 2207 years. For Seed 2 F=0.7752 , t ≈ 2105 years. For Seed 3 F=0.7977 , t ≈ 1868 years. Therefore, Seed 1 is the oldest. The text mentions that Seed 3 germinated and grew into a seedling. Living organisms continuously exchange carbon with their environment. An ancient seed, upon germinating and growing, would incorporate modern carbon which has a higher carbon-14 fraction into its tissues, thus appearing 'younger' or having a higher fraction of carbon-14 than expected for its true ancient origin.