Individuals in a population may evolve.

1. Individuals in a population may evolve. • True • False False! Individuals do NOT evolve; POPULATIONS do!

2. Populations evolve, not individuals! • Natural selection acts on individuals. • Some individuals are better adapted. • Some individuals will bear more offspring than others. • Populations evolve. • The genetic makeup of populations change over time. • Favorable traits (greater fitness) become more common. In other words, NS determines which alleles give individuals a higher fitness, but it is the population as a WHOLE that evolves!

3. Bent Grass on Toxic Mine Site Populations of Bent Grass that live on the mine site have a higher copper tolerance than populations that live further from the mine. Only individuals tolerant of toxic heavy metals will grow from the seeds blown in from the nearby field!

4. Individuals don’t evolve! Individuals survive or don’t… Individuals reproduce or don’t… Individuals are selected… Populations evolve!

5. Evolution of Populations • Populations evolve when they undergo genetic change.

6. What causes populations to evolve? Natural selection is not always the cause of evolution! • There are 5 things that could cause a genetic change in a population: • Mutation • Gene Flow • Non-random Mating • Natural Selection • Genetic Drift

7. 5 Agents of Evolutionary Change What’s this?!

8. Genetic Drift

9. Genetic Drift • Change in allele frequencies due to chance • 2 types: • Bottleneck Effect: some factor (disaster) reduces the population to a small number & those that survive may not be representative of the original gene pool • Founder Effect: small group splinters off & starts a new colony

10. The Bottleneck Effect can greatly reduce genetic variability! Has this population changed over time?

11. The Founder Effect There is very little genetic variety in the gene pool, because not all genes from the original population are represented. Has this population changed over time?

12. A. Founder Effect B. Bottleneck Effect South & Central American Indians were nearly 100% blood type O. It’s likely that most of these people are descendants of a small band of closely related “founders” also had type O blood.

13. A. Founder Effect B. Bottleneck Effect • All cheetahs share a small number of alleles; there is less than 1% diversity! • It’s as if all cheetahs are identical twins. WHY? • In the history of the cheetah, there have been 2 major reductions in their populations: • Ice Age 10,000 years ago • Poaching & habitat loss in the last 100 years • Those few that survived reproduced & made the population that exists today.

14. Polydactyly (extra fingers/toes) is unusually common in the Amish populations in Pennsylvania. WHY? Polydactyly is a symptom of Ellis-van Creveld Syndrome. The original settlers of the Amish population were carriers of this disease. Since the Amish tend to marry within the community, it’s more likely that a child will inherit this disease & have extra fingers/toes. A. Founder Effect B. Bottleneck Effect

15. How could the bottleneck or founder effect negatively impact a forming population? It could lead to a loss of genetic variation! Reduced genetic variation means that the population may not be able to adapt to new selective pressures like climate change or disease. In 1982, captive cheetahs at a wildlife safari in Oregon were exposed to a deadly virus. 90% of the cheetahs fell ill & half of them died.

16. Loss of Genetic Variation • The potato, Solanumtuberosum, originated in South America. It was carried to Europe in the 1500s, & by the 1800s it was a staple food in Ireland. • Because the potatoes in Ireland originated from the small number that were introduced, there was little genetic diversity. • In 1845, a disease called potato blight swept through Ireland. None of the potatoes were resistant to the disease, so nearly every potato was killed. • Since the Irish heavily depended on the potato as a food source, this led to a mass starvation & decimated 25% of the Irish population. A. Founder Effect B. Bottleneck Effect