Genetic Drift and Effective Population Size · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Sampling error that evolves

Science · Genetics & Evolution · ages 18-19
Name ______________________   Date ____________

  1. Drift pushes allele frequencies steadily toward higher fitness.

    Circle one:   True   False

  2. What causes genetic drift?

    • Stronger predators each year
    • Sampling luck each generation
    • Mutations aiming at fitness

  3. A neutral allele in a small group over many generations may do what?

    • Always split fifty fifty
    • Turn harmful at once
    • Fix or vanish by luck alone

  4. A crash leaves five survivors whose alleles shape the future. What is this?

    • Natural selection
    • The bottleneck effect
    • Gene flow

  5. A herd of 1000 has one male fathering most offspring. What follows?

    • Effective size sits far below 1000
    • Drift stops entirely
    • Selection doubles in force

  6. How does drift differ from selection?

    • Drift acts faster in large groups
    • Selection strikes at random
    • Drift is directionless noise; selection pushes toward fitness

  7. A plan keeps headcount high but lets one male dominate. What is wrong?

    • Males eat too much
    • Effective size stays small, so drift still bites
    • Headcounts scare tourists

  8. Two groups each count 500. One breeds evenly, the other swings wildly. Which loses variation faster?

    • The even one
    • Both tie exactly
    • The chaotic one
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Sampling error that evolves W1-mt_lbB1GbKv_t-s1

  1. False · Drift has no preferred direction; that push belongs to selection.
  2. Sampling luck each generation · Drift is the wobble of random sampling, not adaptation.
  3. Fix or vanish by luck alone · With no selection, luck alone can fix or erase a neutral allele.
  4. The bottleneck effect · A crash that resamples the gene pool is a bottleneck.
  5. Effective size sits far below 1000 · Few gene contributors shrink the genetic size below the headcount.
  6. Drift is directionless noise; selection pushes toward fitness · Drift is statistics while selection is a steady push.
  7. Effective size stays small, so drift still bites · Dominance by one male keeps the genetic size small.
  8. The chaotic one · Wild family size swings shrink effective size, speeding drift.
Worksheet · LightMySky