1. Genetic Drift Random changes in allele frequency.
Will occur faster in small populations
NOT the same as Natural Selection (which is not random)
The bottleneck and founder effects commonly cause populations small enough for genetic drift to be significant

2. Genetic drift faster in small population
Large pool
Small pool AA Aa aa
Genetic drift faster in small population AA Aa aa AA Aa aa AA

3. Changes in allele frequencies
In small populations, genetic drift operates quite quickly and new alleles can increase in frequency by chance.
In larger populations, genetic drift is slower, and natural selection is more important in increasing the frequency of a new allele.

4. Founder Effect Bottleneck Effect
Small group of individuals move away from the main population. Eg a group of insects blown by wind to a small island
Bottleneck Effect
Catastrophic events wipe out many individuals. Eg avalanche, volcanic eruption

5. Original large population has equal proportions of blue and red
A small founder population may be separated from the parent population

6. Mutant has established in the new populationAA AA AA AA AA AA AA AA AA AA Aa AA AA Aa Aa AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA Aa AA Aa AA Aa Aa AA Aa AA AA AA AA AA AA AA AA Aa AA AA
Parent population has a single mutant AA Aa AA Aa AA AA AA AA AA
A catastrophe wipes out most of the parent population Aa Aa AA AA AA AA AA Aa

7. Genetic drift RANDOM CHANGES IN GENE POOL Occurs over time
Faster in small populations
Without other factors Genetic drift will eventually lead to the extinction of one allele
RESULT: Change in allele frequencies

8. Founder & Bottleneck effects
Founder effect – small population of pioneers
Bottleneck effect – small population due to catastrophe
Founder effect and bottleneck effect both cause an immediate change in allele frequency + small population is more prone to genetic drift
RESULT: Change in allele frequencies