Biology  by Bradford
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7.4 Population Genetics: revision map

The subtopic in the middle and five tasks round it: label a diagram, complete two tables and fill 10 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.

Unit 7 practice questionsThe whole Unit 7 map

Topic 7.4

Population Genetics

AP Biology ยท Unit 7 Natural SelectionName

7.4.AForces that change allele frequencies

ForceWhat it doesEffect on a population
favors alleles that raise fitnessadapts the population
random change in allele frequency by chancestrongest in small populations; can remove alleles
movement of alleles between populations by migrantsmakes populations more alike
Mutationcreates new allelesa slow source of new variation

7.4.CChance or choice?

ObservationMore likely
An allele rises in every environment tested, whatever the conditionsdrift or gene flow
An allele rises only where a certain predator lives

7.4.AEvolution as a count

Evolution is change in the of a population over generations. The set of all alleles in a population is its gene pool. In a small population, chance events can change the makeup of the gene pool a lot: this is genetic drift. A population that has been through a bottleneck, such as a few northern elephant seals surviving hunting, has lost much of its genetic variation, and so has a population founded by a few migrants, the founder effect.

Topic 7.4Population Genetics

7.4.A, 7.4.B, 7.4.CA bottleneck

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  1. 1
  2. 2
  3. 3
  4. 4

7.4.B, 7.4.CSmall populations

Genetic drift changes allele frequencies at random, so unlike selection it does not favor the . A rare allele can be lost altogether by chance, or become common. Small populations are more at risk, since they lose variation and inbreeding raises the number of homozygous individuals. Gene flow between populations adds alleles and works against differences, so reducing migration lets populations diverge.

Word bank allele frequenciesbottleneckfittestGene flowGenetic driftNatural selectionoriginal populationrare alleleselectionsurviving population

Answer key

Every box on the sheet with its gaps filled in, as the subtopic reads in full.

  1. LabelA bottleneck

    1. original population
    2. bottleneck
    3. surviving population
    4. rare allele

  2. TableForces that change allele frequencies

    ForceWhat it doesEffect on a population
    Natural selectionfavors alleles that raise fitnessadapts the population
    Genetic driftrandom change in allele frequency by chancestrongest in small populations; can remove alleles
    Gene flowmovement of alleles between populations by migrantsmakes populations more alike
    Mutationcreates new allelesa slow source of new variation

  3. GapsEvolution as a count

    Evolution is change in the allele frequencies of a population over generations. The set of all alleles in a population is its gene pool. In a small population, chance events can change the makeup of the gene pool a lot: this is genetic drift. A population that has been through a bottleneck, such as a few northern elephant seals surviving hunting, has lost much of its genetic variation, and so has a population founded by a few migrants, the founder effect.

  4. GapsSmall populations

    Genetic drift changes allele frequencies at random, so unlike selection it does not favor the fittest. A rare allele can be lost altogether by chance, or become common. Small populations are more at risk, since they lose variation and inbreeding raises the number of homozygous individuals. Gene flow between populations adds alleles and works against differences, so reducing migration lets populations diverge.

  5. TableChance or choice?

    ObservationMore likely
    An allele rises in every environment tested, whatever the conditionsdrift or gene flow
    An allele rises only where a certain predator livesselection