Bottlenecks and Founder Effects

1. Bottlenecks and Founder Effects By: BeccaLencz, Ashley English, Nick Couto, Hillary Thorpe

2. Genetic Bottleneck

3. Definition • A dramatic, often temporary, reduction in population size, usually resulting in significant genetic drift.

4. How It Works A dramatic reduction in population size (usually due to a natural disaster) New population’s genetic make up is not the same as the original population’s When population recovers, generations are limited to alleles carried by surviving individuals

5. Causes of Population Reduction Natural disaster such as: • fire • hurricane • earthquake • tsunami • volcano • tornado Population could also go through a dramatic reduction due to over hunting, poaching, disease, or a new predator.

6. Results • A significant genetic drift • Eliminated rare alleles from original population • Rare alleles from original population become common • Little genetic variation in population

7. Diagram

8. Examples • Cheetahs have very little genetic variability. It is believed that they once belonged to a species that went through a dramatic genetic bottleneck event, where only seven individuals survived about 10 000 years ago. • Northern elephant seals passed through a genetic bottleneck event caused by hunting, its reduced their population size to as few as 20 individuals. There population has since rebounded to 30,000 but there traits still reflect the effects of the bottleneck event

9. Founder Effect

10. Definition • Genetic drift that results when small number of individuals separate from their original population and establish a new population.

11. How It Works New Colony is formed by few members of the original population New population is then created

12. Causes of the New Colony • A group of individuals from the original population get separated and start a new colony • Mainly happens when individuals from a species travel to a new island or continent

13. Results • Reduced genetic variation from original population • A new population created (new species) • Rare Alleles become common

14. Diagram

15. Examples • A large population of Dutch settlers in South Africa descended from only a few colonists. Much of this population has Huntington’s Disease because those few colonists happened to have an unusually high frequency of the disease.

16. Why Are They Classified Differently? The reason why these two types of genetic drifts are classified differently is because of the events leading to the reduction of the original population • Genetic Bottleneck – a dramatic, temporary reduction in population • Founder Effect – the separation of a small amount of individuals creating a new population

17. How Are They Different From Natural Selection? • In natural selection the genes with the best survival qualities are the ones that get passed on to the next generation. • In the founder effect or genetic bottleneck, the genes that get passed on aren't necessarily any better than the ones that got eliminated, they were just passed on by chance.

18. The End