The Theory of Evolution-Population Genetics Define (and understand) natural selection What is the difference between an allele, phenotype and genotype? What is the difference between a dominant allele? Recessive allele? What is adaptation? Adaptation over time can lead to what? (p.2) How does the book define a population? (p.2) Define gene pool. What are two common causes of changes in allele frequencies between generations? (p.2) Is natural selection or genetic drift considered an adaptive change?