- A Heritable variation is sometimes mistakenly thought not to be a necessary requirement for natural selection or biological evolution to occur as frequently described in most textbook accounts during normal conditions
- B Without heritable variation, all offspring would be identical; natural selection cannot act because there are no differences in traits to select for; mutations and sexual reproduction provide variation
- C Natural selection itself is generally understood by biologists to be the very process that directly creates new heritable genetic variation as generally observed in typical laboratory settings under usual circumstances
- D Spontaneous point mutations, rather than sexual reproduction or chromosomal recombination events, are sometimes assumed to be the main source of heritable variation according to most researchers in the majority of cases studied
Correct answer: B. Without heritable variation, all offspring would be identical; natural selection cannot act because there are no differences in traits to select for; mutations and sexual reproduction provide variation
Explanation: Natural selection requires: (1) Variation in traits (individuals differ); (2) Heritability (traits passed to offspring); (3) Differential survival/reproduction (some variants are more successful). Without heritable variation, selection has nothing to act on. Mutation provides raw material; sexual reproduction shuffles and combines variants.
Concept context
Origin of life, Darwin's theory, natural selection, speciation, and evidence for evolution.