Genetic drift

• Is natural selection the only way that evolution can occur?

  No, there are other mechanisms
• What is a sampling error in genetic drift?

  Variation in allele frequencies from the population
• How does sample size affect genetic variation?

  Smaller samples have greater variation
• What happens to allele frequencies in a natural population?

  Only a small proportion result in new organisms
• How does the number of individuals produced each generation affect genetic drift?

  Fewer individuals increase random variation
• What is the amplitude of change in genetic drift?

  Greater in smaller populations
• Can the direction of change in genetic drift be predicted?

  No, it cannot be predicted
• What happens to alleles over time due to genetic drift?

  Alleles can go extinct
• How does genetic drift affect genetic diversity?

  It declines genetic diversity
• In what type of populations does genetic diversity decline more quickly?

  In smaller populations
• What is the founder effect?

  Small group founds a new population
• What is a bottleneck in genetic drift?

  A random event wipes out most of the population
• What is an example of the founder effect?

  Polydactyly in Eastern Pennsylvania Amish
• How did the Amish community contribute to polydactyly?

  Married strictly within their own community
• What syndrome is associated with the Amish population's polydactyly?

  Ellis-van Creveld syndrome
• What caused the high frequency of the polydactyly allele in the Amish population?

  Carried by one of the settlers
• What is an example of a bottleneck event?

  Typhoon in Pingalap
• What happened to the population of Pingalap after the typhoon?

  Only 30 people survived
• What allele became common in the Pingalap population?

  Allele for achromatopsia
• What is the current frequency of the achromatopsia allele in Pingalap?

  Approximately 0.32
• Why is genetic diversity important?

  Essential for natural selection and adaptation
• What does heterozygosity indicate?

  Likelihood of being heterozygous at a locus
• How is expected heterozygosity calculated?

  He = 1 - sum of homozygote frequencies
• What does a difference between observed and expected heterozygosity indicate?

  Indicates non-random mating
• What is allelic diversity?

  Number of alleles averaged across loci
• How does sample size affect allelic diversity?

  Very sensitive to sample size
• What is local adaptation?

  Mutation generates diversity within populations
• How does the local environment affect allele frequencies?

  It selects phenotypes best adapted
• What can cause reproductive isolation between populations?

  Genetic drift and local adaptation
• What are some traits that can cause reproductive isolation?

  Mate choice, chemical, visual traits
• What is an example of speciation in apple flies?

  Adaptation to feed on apples
• How are apple flies and hawthorn flies reproductively isolated?

  They never meet due to different emergence times
• What is the Biological Species Concept?

  Organisms can interbreed to produce fertile offspring
• What is a problem with the Biological Species Concept?

  Many species hybridize and don't reproduce sexually
• What is an example of a hybrid species?

  Italian sparrow
• How did the Italian sparrow originate?

  From hybrids between Spanish and house sparrows
• Where is the Italian sparrow native to?

  Originated from Central Asia
• How did the Italian sparrow spread?

  In association with introduced crops
• What is the relationship between Spanish and Italian sparrows?

  Italian sparrow likely hybridized with Spanish sparrows
• What makes the Italian sparrow genetically distinct?

  Originated from hybridization events