Unit 7: Natural Selection

AP Biology — 12 practice questions with detailed explanations. Use the links below to open each full question page (ideal for search indexing and deep study).

Unit summary

This unit covers core ideas tested on the AP exam. Each listed item links to a standalone page with the full stem, answer choices where applicable, a step-by-step explanation, and the correct answer. Difficulty labels help you prioritize review.

Questions in this unit

A species of plant produces a highly toxic chemical that deters most herbivorous insects. Over time, a species of caterpillar evolves an enzyme that safely metabolizes the toxin. In response, the plant population evolves to produce an even more potent variation of the toxin. This reciprocal adaptation is best described as:easy · mcq · 1 pt
A small group of beetles colonizes an isolated island. Over thousands of years, the beetle population divides into two distinct species living in different ecological niches—one in the island's forest canopy and one in the soil. No geographic barriers, such as rivers or mountains, separate them. Which mechanism of speciation most likely occurred?hard · mcq · 1 pt
Which of the following observations provides the strongest evidence that biological evolution is a continuous and ongoing process?easy · mcq · 1 pt
A population of bacteria is exposed to an antibiotic. Initially, most of the bacteria die, but a small fraction survives. Over several generations, the entire population is resistant to the antibiotic. Which mechanism best explains this phenomenon?easy · mcq · 1 pt
Scientists use DNA sequence data to construct a phylogenetic tree for several related species. In this tree, Species X and Species Y share a most recent common ancestor that is not shared by Species Z. Which of the following statements is true regarding the classification of Species X and Species Y?hard · mcq · 1 pt
In a population of insects, a single gene with two alleles (A and a) controls coloration. Insects with genotype AA or Aa are green, while insects with genotype aa are brown. An environmental shift introduces a new predator that easily spots green insects, but cannot see brown insects. Which statement best explains how natural selection will act on this population?easy · mcq · 1 pt
Which of the following processes is the ultimate source of new, heritable genetic variation within a population?medium · mcq · 1 pt
The forelimbs of humans, whales, and bats contain the same basic set of bones arranged in different patterns to perform distinct functions, such as grasping, swimming, and flying. Which evolutionary concept does this observation best support?easy · mcq · 1 pt
The process of speciation can occur through allopatric speciation, where a geographic barrier separates a population and prevents gene flow between the two groups. However, this is not the primary reason for the speciation of the African elephant and the Asian elephant. Which of the following is the primary reason?hard · mcq · 1 pt
A population of birds has a certain frequency of a gene that codes for a wing color trait. According to the Hardy-Weinberg principle, what will happen to the frequency of the gene if there is no gene flow, mutation, or genetic drift, and the population size remains constant?medium · mcq · 1 pt
A scientist studying the evolution of the finches on the Galapagos Islands finds that the beak shape and size are correlated with the type of food the birds eat. Based on this data, which of the following is the primary reason for the variation in beak shape and size?medium · mcq · 1 pt
The peppered moth in England provides evidence for natural selection becauseeasy · mcq · 1 pt

Sample prompts

Short previews of topics covered (not full question text).

A species of plant produces a highly toxic chemical that deters most herbivorous…
A small group of beetles colonizes an isolated island. Over thousands of years, …
Which of the following observations provides the strongest evidence that biologi…
A population of bacteria is exposed to an antibiotic. Initially, most of the bac…
Scientists use DNA sequence data to construct a phylogenetic tree for several re…
In a population of insects, a single gene with two alleles (A and a) controls co…
Which of the following processes is the ultimate source of new, heritable geneti…
The forelimbs of humans, whales, and bats contain the same basic set of bones ar…
The process of speciation can occur through allopatric speciation, where a geogr…
A population of birds has a certain frequency of a gene that codes for a wing co…
A scientist studying the evolution of the finches on the Galapagos Islands finds…
The peppered moth in England provides evidence for natural selection because…