Genetic Drift, Founder Effect,

Bottleneck Effect.

Genetic Drift

• Is a change in the allele frequencies of a population as a result of chance processes.

• It happens in small populations where chance alone can play a considerable role.

• Heterozygous gene pairs tend to become homozygous for one allele by chance rather than selection, so that the alternative can be lost.

Founder Effect

• If a few organisms move to a new area, they may only possess a few of the available genes from the original population.

• Because they only have some of the available alleles from the ‘gene pool’ of the ‘founder ancestors’ the new population can have different genes from the same species elsewhere.

The Founder Effect

The Bottleneck Effect

• Disasters such as fires or drought can reduce a population down to just a few individuals.

• These individuals may not necessarily be representative of the original population.

• Some alleles will be above the normal number and some may be lost forever.

• If one survivor has a rare gene, the new population may no longer be rare!

The Bottlenect Effect

Questions

• Genetic Drift– Questions in Booklet .

• (Answers in the back of Patterns of Life Workbook)• Page 346 BIOZONE

– The Founder Effect• Page 344 BIOZONE

– The Bottleneck Effect• Page 345 BIOZONE