Evolution as a change in the allele frequencies in a population
Evolution means the allele frequencies in a population shift over generations. An allele is one version of a gene, and its frequency is how common it is in the population.
Formula
Allele frequency = (number of copies of that allele) ÷ (total number of alleles at that locus in the population)
Real World
The frequency of the lactase-persistence allele rose from near zero to over 90% in Northern European populations over roughly 7,000 years as dairy farming gave carriers a nutritional survival advantage.
Exam Focus
Define evolution as a change in allele frequency, not as 'organisms changing' — imprecise wording is a common lost-mark error.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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