Patterns of Evolution

1. Patterns of Evolution Essential Questions: 1. What are the mechanisms that lead to evolutionary change over time? 2. How do different species evolve? 3. Does evolutionary change occur in our lifetime?

2. A. Mechanisms of Change • Genetic Variation • Mutations • Sex  Gene shuffling • Gene Flow (Migration) • Genetic Drift • Bottleneck Effect • Founder Effect • Natural Selection • Stabilizing Selection • Directional Selection • Stabilizing Selection

3. I. Genetic Variation How might variation occur in a single population?

4. I. Genetic Variation • Mutations • Sex  Gene shuffling

5. I. Genetic Variation1. Mutations Mutation: A change in our DNA sequence • Some mutations are not inherited (do not get passed on) Example: color of an individual apple • Some mutations areinherited (do get passed on) Example: Lice, Sickle cell anemia

6. I. Genetic Variation1. Mutations Example: Lice The louse that has a mutation that makes it resistant to the lice-killing shampoo can produce offspring that also have that mutation

7. I. Genetic Variation1. Mutations Example: Lice Example: sickle cell anemia The louse that has a mutation that makes it resistant to the lice-killing shampoo can produce offspring that also have that mutation

8. I. Genetic Variation2. Sex (gene shuffling) How did this young wildebeest get so much variation in her DNA?

9. A herd of wildebeests?

10. A herd of DNA (the genetic information that makes us who we are, and wildebeests who they are)!

11. Sex is an elaborate way to maintain genetic diversity in a population by shuffling our genetic information around!

12. How can genetic variation occur between different populations?

13. How can genetic variation occur between different populations? What happens when the wind blows the pollen off of these oak catkins?

14. II. Gene Flow (Migration) Gene flow: any movement of genes (genetic info) from one population to another How might gene flow happen?

15. II. Gene Flow (Migration) Gene flow: any movement of genes (genetic info) from one population to another How might gene flow happen? Examples: Corn, milkweed

16. Is there such thing as luck in evolution? Does anything happen by chance? Do the “best fit” always survive?

17. Is there such thing as luck in evolution? Does anything happen by chance? Do the “best fit” always survive? What if the seed of a “fit” plant is eaten by a bird, but then pooped out in a parking lot instead of fertile soil? Will that “fit” plant successfully reproduce?

18. III. Genetic Drift Genetic drift: individuals in a population survive and reproduce due to random chance, NOT because they are more “fit,” as in natural selection.

19. III. Genetic Drift Genetic drift: individuals in a population survive and reproduce due to random chance, NOT because they are more “fit,” as in natural selection. • Genetic drift decreases diversity within a population • Genetic drift impacts the diversity of small populations • Genetic drift can create a “bottleneck effect” or “founder effect”

20. III. Genetic Drift 1. Bottleneck Effect Bottleneck effect: A random event dramatically decreases the population size (and, therefore, genetic diversity) for at least one generation.

21. III. Genetic Drift 1. Bottleneck Effect Bottleneck effect: A random event dramatically decreases the population size (and, therefore, genetic diversity) for at least one generation. Examples: Northern elephant seals, Cheetahs

22. What if the few individuals that colonized a new habitat carried DNA that only coded for proteins that produced blonde hair? What would the future population look like?

23. What if the few individuals that colonized a new habitat carried DNA that only coded for proteins that produced blonde hair? What would the future population look like? What if the few individuals that colonized a new habitat carried a mutation in their DNA that caused a disorder or disease? What would the future population be like?

24. III. Genetic Drift 2. Founder Effect Founder effect: a few members of an original population colonize a new population. • The founders may not accurately represent the genetic makeup of the original population • Genetic diversity may decrease

25. III. Genetic Drift 2. Founder Effect Founder effect: a few members of an original population start a new separate colony. • The founders may not accurately represent the genetic makeup of the original population • Genetic diversity may decrease Examples: Huntington’s disease among Afrikaners, polydactyly among Amish

26. IV. Natural Selection

27. Is bigger always better? Can being “average” be optimal? When is it advantageous to be extreme?

28. IV. Natural Selection Types of Selection • Stabilizing Selection • Directional Selection • Disruptive Selection

29. IV. Natural Selection1. Stabilizing Selection Example: birth weight, # eggs

30. IV. Natural Selection2. Directional Selection Examples: peppered moth, antibiotic resistant bacteria

31. IV. Natural Selection3. Disruptive Selection Example: beak size

32. Exit Ticket – hand in before you leave! • Name one concept of evolution that you may have heard about before today, but understand better now after class. Explain that concept in your own words. • Name one concept or real-world example of a concept that was completely new: • Write down a question about something that you do not completely understand or are curious about.