Why is genetic variation within a population important for its survival?
Topic 7.12 Variations in Populations: explain why genetic variation within a population is important for survival and the response to environmental change.
A focused answer to AP Biology Topic 7.12, covering the sources and importance of genetic diversity, how variation buffers populations against change, the risks of low diversity, and the role of variation in evolution, with a worked example.
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What this topic is asking
The College Board (Topic 7.12) wants you to explain why genetic variation within a population matters for survival and the response to environmental change, including the sources of variation and the risks of low diversity.
Where variation comes from
Why variation matters
Variation and conservation
Diversity at the population level also scales up to the ecosystem level: genetically diverse populations are more resilient, and ecosystems built from resilient populations are more stable, which connects this topic to biodiversity in Unit 8.
Try this
Q1. State the two main sources of genetic variation in a sexually reproducing population. [2 points]
- Cue. Mutation (new alleles) and recombination (crossing over, independent assortment and random fertilization shuffling alleles).
Q2. Explain why a genetically diverse population is more likely to survive a new disease. [2 points]
- Cue. Diversity makes it more likely that some individuals carry resistance alleles, so they survive and reproduce, and resistance spreads, whereas a uniform population may have no resistant individuals.
Exam-style practice questions
Practice questions written in the style of College Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AP 2021 (style)4 marksSection II (long FRQ excerpt). Two populations of the same crop are grown: population A is genetically uniform, and population B is genetically diverse. A new fungal disease arrives. (a) Predict which population is more likely to survive the disease and explain why. (b) Explain how the diverse population could become resistant to the disease over generations.Show worked answer →
A 4-point predict-and-explain FRQ on the value of variation.
(a) Predict and explain (2 points): (1 point) population B (the diverse one) is more likely to survive; (1 point) because genetic diversity means some individuals are more likely to carry alleles for disease resistance, whereas a uniform population may have none and could be wiped out.
(b) Explain (2 points): (1 point) the resistant individuals in population B survive the disease and reproduce, while susceptible ones die; (1 point) the resistance alleles increase in frequency over generations, so the population becomes more resistant (natural selection acting on existing variation).
Markers reward predicting the diverse population survives and explaining how selection on existing variation builds resistance.
AP 2018 (style)1 marksSection I (multiple choice). Genetic variation within a population is ultimately generated by: (A) natural selection. (B) mutation and the recombination of alleles. (C) genetic drift. (D) the environment directing useful changes.Show worked answer →
The correct answer is (B).
Mutation creates new alleles, and recombination (crossing over, independent assortment, random fertilization in sexual reproduction) shuffles them into new combinations, generating variation. Natural selection (A) and drift (C) sort existing variation; the environment does not direct useful changes (D).
Related dot points
- Topic 7.1 Introduction to Natural Selection: explain the conditions required for natural selection and how it leads to changes in a population.
A focused answer to AP Biology Topic 7.1, covering Darwin's reasoning, the conditions for natural selection (variation, heritability, overproduction, differential reproduction), fitness, and how selection changes allele frequencies, with a worked example.
- Topic 7.4 Population Genetics: explain how natural selection, mutation, gene flow, genetic drift and non-random mating change allele frequencies.
A focused answer to AP Biology Topic 7.4, covering the gene pool, allele frequencies, and the five mechanisms of microevolution (selection, mutation, gene flow, genetic drift, non-random mating), including bottleneck and founder effects, with a worked allele-frequency calculation.
- Topic 5.2 Meiosis and Genetic Diversity: explain how crossing over, independent assortment and random fertilization produce genetic variation.
A focused answer to AP Biology Topic 5.2, covering crossing over, independent assortment and random fertilization as the three sources of genetic variation, with a worked calculation of gamete combinations.
- Topic 7.11 Extinction: explain the causes of extinction, including mass extinctions, and its role in shaping biodiversity.
A focused answer to AP Biology Topic 7.11, covering the causes of extinction, background versus mass extinction, the five mass extinctions, adaptive radiation after extinction, and the current human-driven loss, with a worked example.
- Topic 6.7 Mutations: explain the types of mutations and how they affect gene products, phenotype and the variation available to a population.
A focused answer to AP Biology Topic 6.7, covering point mutations (silent, missense, nonsense), frameshift mutations, chromosomal mutations, their effects on proteins and phenotype, and their role as the source of new variation, with a worked example.
Sources & how we know this
- AP Biology Course and Exam Description — College Board (2020)