IB Biology SL A4.1 Evolution and speciation questions

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Question 1

Multiple choiceHard1 mark

In a beetle population, 20% of adults have dark shells before the substrate darkens. After the change, 70% of the same adults have dark shells. Adults of both shades contribute equally to an offspring cohort, of which 20% have dark shells when raised on the original substrate. Which interpretation applies the definition of evolution to shell shade?

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Answer: C. Evolution is a change in the heritable characteristics of a population, not a change acquired by individuals during their lives. The proportion of dark-shelled adults rises from 20% to 70%, but their offspring, raised on the original substrate, have the initial 20% frequency. Thus, no inherited shift in shell shade is demonstrated. A: treats a change in adult appearance as an evolutionary change in heritable population characteristics. B: applies Lamarckian inheritance, but the offspring do not retain the increase in dark shells. D: confuses some offspring having a characteristic with the frequency of that characteristic changing across generations. Remember: evolution requires a change in heritable population characteristics across generations.

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