Genetic drift

Gene flow

movement of alleles from one population to another and the exchange of genes between two populations as a result of immigration and emigration

Immigration

Genotypes will INCREASE in frequency

Emigration

Genotypes will DECREASE in frequency

Genetic drift

Change in allele frequency as a result of CHANCE

• More likely to happen if population is SMALL

Law of large numbers

As the size of random sample increases, the realized frequencies approach truer frequencies

Examples of chance events

1. Some mating pairings happen more or less offspring than expected

2. Some genotypes produce more or less offspring than expected

3. Some genotypes survive more or less than expected

What are the two processes that reduce population size?

1. Population bottleneck

2. Founder’s effect

Population bottleneck

A change in allele frequency following a dramatic reduction in population size

• Caused by any disaster

• Conservations are utilized to preserve the population BUT it reduces genetic diversity

Founder’s effect

Change in allele frequencies that occur when a small number of individuals from a large population COLONIZE an area and found a NEW population

• Genetic diversity is reduced

Order of evolutionary mechanisms from least to most effective

1. Mutation

2. Gene flow

3. Non random mating

4. Genetic drift

5. Selection

What is the difference between genetic drift and natural selection

entirely RANDOM → NOT random

Alleles change RANDOMLY over time → Traits with greater fitness thrive over time

Does NOT work to produce adaptations →Produces adaptations