AP Biology Unit 7 Practice Test: Natural Selection
Master AP Biology Unit 7 with practice tests on natural selection, Hardy-Weinberg equilibrium, phylogenetics, speciation, and evidence for evolution.
What Unit 7 Covers in AP Biology
Unit 7 examines the mechanisms that drive evolutionary change and the tools biologists use to document and analyse it. AP Biology tests both the conceptual framework of evolution and quantitative skills like Hardy-Weinberg calculations and phylogenetic tree interpretation.
Core Topics in Unit 7
Mechanisms of Evolution
Five mechanisms drive allele frequency change in populations:
- Natural selection — differential survival and reproduction based on heritable traits
- Genetic drift — random allele frequency changes, especially significant in small populations (bottleneck and founder effects)
- Gene flow — movement of alleles between populations via migration
- Mutation — the ultimate source of new genetic variation
- Sexual selection — selection driven by mate choice or competition for mates
Hardy-Weinberg Equilibrium
Hardy-Weinberg equilibrium describes a non-evolving population. The equations p + q = 1 and p² + 2pq + q² = 1 allow you to calculate allele and genotype frequencies. AP FRQs require you to apply these equations, identify which assumptions are violated, and explain what that violation implies about evolutionary forces at work.
Phylogenetics and Cladograms
Cladograms and phylogenetic trees represent evolutionary relationships based on shared derived characteristics (synapomorphies). AP questions test your ability to read trees, identify common ancestors, determine relative relatedness, and interpret molecular or morphological data used to construct them.
Speciation
Allopatric speciation occurs when geographic barriers isolate populations. Sympatric speciation occurs without geographic isolation, often through polyploidy or disruptive selection. AP Biology tests the mechanisms and conditions required for each type.
Evidence for Evolution
Fossil records, comparative anatomy (homologous and analogous structures, vestigial organs), biogeography, and molecular evidence (DNA sequence comparisons) all provide lines of evidence for evolution testable on the AP exam.
AP Science Practice Skills for Unit 7
- Quantitative reasoning: Hardy-Weinberg frequency calculations and interpreting population genetics data
- Data analysis: Reading and constructing cladograms from character matrices
- Scientific argumentation: Using multiple lines of evidence to support evolutionary claims