Table 1 Coverage of key concepts and misconceptions about genetic drift in the GeDI and the Ferrets module
Key concepts | GeDI Item | Ferrets workbook | Ferrets simulations |
|---|---|---|---|
1. Random sampling error happens every generation, which can result in random changes in allele frequency that is called genetic drift | |||
a. Genetic drift results from random sampling error | ✓ | ✓ | |
b. Random sampling occurs each generation in all finite populations | 16 | ✓ | |
c. Random sampling can result in random changes in allelic, phenotypic, and/or genotypic frequency | ✓ | ✓ | |
2. Random sampling error tends to cause a loss of genetic variation within populations, which in turn increases the level of genetic differentiation among populations | |||
a. The processes leading to genetic drift tend to cause a loss of genetic variation within populations over many generations | 3, 13 | ✓ | ✓ |
b. Decreasing genetic variation within populations usually increases genetic differentiation among populations | ✓ | ||
3. The magnitude of the effect of random sampling error from one generation to the next depends on the population size. The effect is greater when populations have a small effective size, but generally small or undetectable when effective population size is large | |||
a. The effects of genetic drift are larger when the population is smaller | 1 | ✓ | ✓ |
b. Founding and bottlenecking events are two situations in which the effects of genetic drift are greater because the effective population size is rapidly reduced | 10 | ✓ | ✓ |
4. In populations with small effective sizes, genetic drift can overwhelm the effects of natural selection, mutation, and migration; therefore, an allele that is increasing in frequency due to selection might decrease in frequency some generations due to genetic drift | |||
a. Other evolutionary mechanisms, such as natural selection, mutation, and migration act simultaneously with genetic drift | |||
b. The processes leading to genetic drift can overwhelm the effects of other evolutionary mechanisms | 15 | ||
c. Random sampling error can result in populations that perpetuate deleterious alleles or traits | 4 | ||
Misconceptions | |||
About sampling error | |||
1. Random sampling error only results in fixation or loss | |||
2. Genetic drift is unpredictable because it has a random component | 7 | ✓ | |
3. Genetic drift only occurs in small populations, because random sampling error does not occur in large populations | ✓ | ✓ | |
Confusing genetic drift with natural selection | |||
4. Genetic drift is natural selection/adaptation/acclimation to the environment that may result from a need to survive | 5, 6, 8 | ✓ | |
5. Genetic drift only occurs when natural selection cannot or is not occurring | |||
6. Genetic drift is not evolution because it does not lead to directional change that increases fitness | 2 | ✓ | |
7. Natural selection is always most powerful mechanism of evolution, and it is the primary agent of evolutionary change | 9, 12, 17, 20 | ||
Confusing genetic drift with evolutionary processes other than natural selection | |||
8. Genetic drift is random mutation | 14, 19, 22 | ||
9. Genetic drift is speciation | |||
10. Genetic drift is gene flow or migration | 11, 18, 21 | ||
Limiting when genetic drift occurs | |||
11. Genetic drift results only from an isolated event, often a catastrophe | ✓ | ||