Multiple Choice
What did the discovery of Tiktaalik reveal about vertebrate evolution that was previously unknown?
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21. Evolution
Introduction to Evolution and Natural Selection
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Why is there more carbon-14 (\(^{14}\)C) in living bones than in once-living ancient bones of the same mass?
A
Living bones have a higher density, which allows them to store more \(^{14}\)C.
B
Living organisms continually exchange carbon with the environment, replenishing \(^{14}\)C, while ancient bones no longer do so and their \(^{14}\)C decays over time.
C
The process of fossilization increases the amount of \(^{14}\)C in ancient bones.
D
Ancient bones absorb more \(^{14}\)C from the soil, increasing their \(^{14}\)C content over time.
Verified step by step guidance1
Step 1: Understand the role of carbon-14 (\(^{14}\)C) in living organisms. Carbon-14 is a radioactive isotope of carbon that is naturally present in the environment. Living organisms constantly exchange carbon with their surroundings through processes like respiration and feeding, which replenishes their \(^{14}\)C levels.
Step 2: Recognize what happens to \(^{14}\)C after an organism dies. Once an organism dies, it stops exchanging carbon with the environment. As a result, the \(^{14}\)C in its tissues begins to decay into nitrogen-14 (\(^{14}\)N) through radioactive decay, and no new \(^{14}\)C is replenished.
Step 3: Compare living bones to ancient bones. Living bones are part of an active organism that is continuously replenishing \(^{14}\)C through carbon exchange with the environment. Ancient bones, on the other hand, are no longer part of a living organism, so their \(^{14}\)C content decreases over time due to radioactive decay.
Step 4: Address misconceptions about \(^{14}\)C in ancient bones. Fossilization does not increase the amount of \(^{14}\)C in ancient bones, nor do ancient bones absorb \(^{14}\)C from the soil. Instead, the \(^{14}\)C content in ancient bones decreases steadily over time.
Step 5: Conclude that the difference in \(^{14}\)C levels between living and ancient bones is due to the continuous replenishment of \(^{14}\)C in living organisms and the decay of \(^{14}\)C in ancient bones after death.
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