In Experiment 2, you calculated the rate at which the percentage of fish with a complete pelvis decreased in an ancient lake. Which statement best reflects applying that rate to modern fish populations?

• A. The same rate would definitely apply to modern populations.
• B. It is possible that the same rate of change observed in the fossil record applies to modern populations.
• C. The rate cannot be applied to modern populations under any circumstances.
• D. The rate applies to modern populations but only in identical ecosystems.

Answer: (B)

Rates inferred from the fossil record can inform expectations about modern populations, but with caveats. The rate you calculated shows how quickly the trait changed under historical conditions. Applying that same pace to today’s fish assumes similar selective pressures and environments, which is possible but not guaranteed. Modern ecosystems, genetic variation, population dynamics, and other factors can alter the rate of change. So saying it’s possible the same rate applies to modern populations captures the reasonable, testable expectation without overcommitting. The other options are too absolute or too restrictive: the fossil rate isn’t guaranteed to be identical today, and it doesn’t require identical ecosystems to be relevant, though similarity helps.