Why this chapter matters
Evolution by natural selection is a central framework that unifies biological diversity and adaptation.
What you will learn
- Distinguish evolution as population change from acclimation in an individual organism.
- Explain how mutation, gene flow, genetic drift, and selection can shift allele frequencies.
- Evaluate evolutionary claims using data from fossils, comparative anatomy, molecular evidence, and population studies.
Lessons in this chapter
- Population genetics foundationsDefine allele frequency and conditions for Hardy-Weinberg equilibrium.
- Mechanisms of evolutionary changeCompare directional effects of selection with stochastic effects of drift.
- Evidence for common ancestryIntegrate anatomical, molecular, and fossil evidence into coherent evolutionary explanations.
- Speciation and macroevolution patternsConnect reproductive isolation and divergence to new species formation.
Study task
Interpret a data table of allele frequencies over multiple generations and argue which evolutionary mechanism is most strongly supported.
Chapter checkpoint
Why is natural selection described as population-level change?
Selection acts on individual phenotypes, but evolution is measured as changes in allele frequencies across generations within a population.