AP Biology: Evolution Practice Questions
Test yourself on AP Biology: Evolution with 12 original AP Exams practice questions. Pick an answer to see instant feedback and a full explanation.
Free original practice questions for study purposes. Open Exam Prep is an independent study resource and is not affiliated with, endorsed by, or sponsored by the makers of AP Exams.
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1. A population of beetles contains green and brown color variants. After several generations in a habitat with dark soil, the brown variant becomes more common because birds more often spot the green beetles. Which process best explains this change?
Explanation. Natural selection occurs when heritable traits affect survival or reproduction. In this example, brown coloration is favored in the dark-soil environment, so alleles linked to that phenotype can increase in frequency over generations.
2. Which observation would provide the strongest evidence that two species share a recent common ancestor?
Explanation. Similarity across many DNA sequences is strong evidence of common ancestry because genomes are inherited and modified through descent. Shared habitat or general life processes can occur in distantly related organisms.
3. A small group of birds is blown from a mainland population to an island and starts a new population. Years later, allele frequencies on the island differ greatly from the mainland. Which evolutionary mechanism is most directly involved?
Explanation. The founder effect is a form of genetic drift that occurs when a new population begins from a small, nonrepresentative sample of the original population. Random allele frequency differences can become large in the isolated group.
4. In a population at Hardy-Weinberg equilibrium, the frequency of the recessive allele is q = 0.3. What is the expected frequency of heterozygotes?
Explanation. If q = 0.3, then p = 1 - q = 0.7. The expected heterozygote frequency is 2pq, so 2(0.7)(0.3) = 0.42.
5. Which condition is required for a population to remain in Hardy-Weinberg equilibrium?
Explanation. Hardy-Weinberg equilibrium is a null model that assumes random mating, a very large population, no natural selection, no mutation, and no gene flow. Violating those assumptions can change allele or genotype frequencies.
6. Two populations of frogs are separated by a mountain range. Over time they accumulate genetic differences and no longer produce viable offspring when brought together. What has occurred?
Explanation. Allopatric speciation occurs when geographic isolation reduces gene flow and separated populations diverge. If reproductive isolation evolves, the populations can become separate species.
7. Which example best illustrates stabilizing selection?
Explanation. Stabilizing selection favors intermediate phenotypes and selects against extremes. Directional selection favors one end of a range, disruptive selection favors both extremes, and random death is not selection by phenotype.
8. A population of bacteria is exposed to an antibiotic. A few cells already carry a resistance allele and survive, while susceptible cells die. What is the best evolutionary interpretation?
Explanation. Selection acts on variation that is already present or that arises by mutation. Antibiotic exposure increases the relative success of resistant cells, so resistance alleles can become more common in the population.
9. Which statement correctly distinguishes homologous structures from analogous structures?
Explanation. Homologous structures are similar because they were inherited from a common ancestor, even if their functions differ. Analogous structures can have similar functions because of convergent evolution, not recent shared ancestry.
10. A sudden environmental change leaves only 20 individuals from a population of 10,000. The surviving group has much lower genetic variation than the original population. Which term best describes this event?
Explanation. A population bottleneck is a sharp reduction in population size that can randomly remove alleles and reduce genetic diversity. The surviving allele frequencies may not represent the original population.
11. Why can gene flow slow divergence between two populations?
Explanation. Gene flow is the movement of alleles between populations through migration or gamete exchange. This exchange can make populations more genetically similar and counteract divergence caused by selection or drift.
12. A phylogenetic tree shows species X and species Y sharing a node that no other species on the tree shares. What does that node represent?
Explanation. A node on a phylogenetic tree represents a common ancestor. If X and Y share a node not shared by other listed species, that node is their most recent common ancestor in the tree model.
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FAQ
What evolution topics are most important for AP Biology?
Focus on natural selection, genetic drift, gene flow, mutation, Hardy-Weinberg calculations, speciation, phylogenetic trees, evidence for common ancestry, and different patterns of selection.
How should I solve Hardy-Weinberg questions?
Identify whether the problem gives an allele frequency or a genotype frequency. Use p + q = 1 and p^2 + 2pq + q^2 = 1, then check whether the question asks for homozygotes, heterozygotes, or allele frequency.
What mistakes should I avoid on AP Biology evolution questions?
Do not say individuals evolve during their lifetime. Populations evolve as allele frequencies change across generations, and selection acts on phenotypes produced by heritable variation.