Natural Selection

Natural Selection is topic 7.2 of AP Biology, inside Natural Selection. This page works through three real practice questions on it, with the full reasoning behind each credited answer.

Practise this topic freeThe whole unit
52 questionsArgumentation81% with a figure
Worked examples

Three real natural selection questions

From the practice pool, not the mock papers — each with the reasoning that produces the answer.

81% of them come with a figure. Reading the graph or diagram correctly is most of the work here before any content knowledge applies.

71% test a single AP skill: Argumentation. That makes this topic unusually predictable to prepare for.

Argumentation

Male birds with longer songs attract more mates, and song length is partly heritable. Over several generations, average song length increases. Which explanation is best supported?

  1. AThe population stopped evolving because mating success differed.
  2. BDifferential mating success can change allele frequenciescorrect
  3. CThe pattern is best explained by genetic drift alone
  4. DSong length increased because heritable variation was absent.
Why B is correct

Differences in mating success can drive sexual selection. If song length is heritable, alleles associated with longer songs can increase.

The stem asks students to explain a specific mechanism, not just recall a unit term: "Male birds with longer songs attract more mates, and song length is partly heritable. Over several generations,...". The correct choice is supported by If song length is heritable, alleles associated with longer songs can increase. The tempting alternatives such as population stopped evolving because mating success differed or pattern is best explained by genetic drift alone, even though... fail because they do not produce the same outcome described in the stem.

Argumentation

A drought occurs in a plant population. Plants with deeper roots survive and produce more seeds than plants with shallow roots. Which claim is best supported?

  1. AThe trait distribution can shift within a population even if the trait is not heritable.
  2. BAlleles associated with deeper roots may increase in the population.correct
  3. CThe pattern is best explained by genetic drift alone, even though survival or reproduction differs among phenotypes.
  4. DEnvironment raises mutation in low-fitness individuals
Why B is correct

If deeper roots are heritable and increase survival and reproduction during drought, alleles associated with deeper roots can increase over generations.

The stem asks students to explain a specific mechanism, not just recall a unit term: "A drought occurs in a plant population. Plants with deeper roots survive and produce more seeds than plants with...". The correct choice is supported by If deeper roots are heritable and increase survival and reproduction during drought, alleles associated with deeper roots can increase over generations. The tempting alternatives such as trait distribution can shift within a population even if the trait... or pattern is best explained by genetic drift alone, even though... fail because they do not produce the same outcome described in the stem.

Representing and Describing Data · with figure

A population is monitored after a new predator arrives. Which statement best describes the trend in allele B? Use Figure 1 to answer the question.

  1. AAllele B disappears from the population by generation 15.
  2. BAllele B remains constant across all generations.
  3. CAllele B is present only in individual organisms, not populations.
  4. DAllele B increases in frequency over the observed generations.correct
Why D is correct

The frequency of allele B rises from 0.12 to 0.41 over 15 generations.

The evidence in the prompt matters before the topic label: "A population is monitored after a new predator arrives. Which statement best describes the trend in allele B". The supported answer is "Allele B increases in frequency over the observed generations" because The frequency of allele B rises from 0.12 to 0.41 over 15 generations. Distractors such as Allele B disappears from the population by generation 15 or Allele B remains constant across all generations either ignore the stated pattern or name a related concept without matching the evidence.

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Last reviewed 2026-08-28. Topic and unit names follow the College Board course framework. Question counts describe the PrepScore practice bank, not the exam.
Same unit
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Work natural selection until the reasoning is automatic.

Real AP questions with a full explanation on every answer, and a mistake bank that only clears when you get it right.

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