Bell Work

1. Bell Work Pick up plickers card Pick up notes page for today (population genetics) Turn in Natural Selection worksheet #2 to basket

2. Chapter 16 Population Genetics and Speciation Mrs. Stewart Advanced Honors / Honors Biology

3. Standard • CLE 3210.5.3 Explain how genetic variation in a population and changing environmental conditions are associated with adaptation and the emergence of new species.

4. Objective • Define evolution in terms of alleles • Be able to calculate the allele frequency of a population • Determine how the 5 Hardy Weinberg factors affect allele frequencies

5. Goldfish Lab • Each group should obtain the following items: • 1 Paper towel (this will be your “pond”) • 10 pretzel goldfish • 10 regular goldfish • 10 parmesan goldfish • Keep goldfish on paper towel

6. Population Genetics • The study of evolution from a genetic point of view • Microevolution: change in the allele frequencies of a population

7. Variation Within a Population • All populations show variations in their traits • Different shaped beaks • Different colors • Different athletic abilities • Different immune system responses

8. Sources of Variation Within a Population • Variations in the genotypes of a population arise by: • mutation – changes in genes that occur either naturally or influenced by environment • Passed to offspring if occurs in gametes • Recombination– the law of independent assortment (chromosomes) and crossing over during meiosis • random pairing of gametes (sexual reproduction) – organisms produce large numbers of gametes, so the union of a particular pair is strictly by chance.

9. The Gene Pool • The total genetic information available in a population is called the gene pool. • In other words: All of the possible alleles (variations) that are present, for each gene, within a population • Frogs in a pond • Trees in the forest • People in a town **This is not a real place – it’s an abstract idea – an imaginary collection

10. Allele Frequency • Allele frequencyis the number of times an allele occurs in the gene pool • This is in comparison to how often the other alleles occur too

11. Relative Allele Frequencies • determined by dividing the total number of a certain allele by the total number of alleles of all types in the population • Total number of a certain allele___ total number of all alleles in a population • Expressed as a percentage or a decimal.

12. Activity • Discover the allele frequency for brown (pretzel) fish. • Add up the total number of all alleles in your population of fish • Brown fish (pretzel) = BB • Orange fish (regular) = Bb • Yellow fish (parmesan) = bb • Divide the number of “brown” alleles by the total number of alleles.

13. Evolution is any change in the relative frequency of alleles in a population. • Remember: Populations, not individual organisms, evolve over time. • Allele frequencies in the gene pool do not change unless acted upon by certain forces.

14. Five conditions that affect the relative frequency of alleles • Genetic mutations • Gene flow • Genetic drift • Nonrandom mating • Natural selection • This is known as the Hardy Weinberg Genetic Equilibrium model • used to determine and understand the forces that act upon genetic equilibrium

15. 1. Mutations • Mutations are changes in the DNA.

16. 2. Gene Flow • The flow of genes between populations • Emigration and immigration cause gene flow between populations and can thus affect gene frequencies.

17. Immigration vs. Emigration • Immigration: Gene flow INTO a population • Emigration: Gene flow OUT of a population

18. Activity • Immigrate: 10 yellow fish move in from a neighboring pond • Emigrate: 5 brown fish move out to another pond • Recalculate the brown allele frequency • Question: How does immigration or emigration affect allele frequencies in a gene pool?

19. Human Evolution from Gene Flow

20. 3. Genetic Drift • Genetic drift is a change in allele frequencies due to random events. • Genetic drift operates most strongly in small populations.

21. Think – pair - share • What are some other random events that could affect allele frequencies in a population?

22. Activity • Genetic Drift:Perform a random act to your population • Recalculate the brown allele frequency • Question: How does genetic drift affect allele frequencies in a gene pool?

23. Random Mating • Do humans randomly mate? • No. • Random mating: happens more by chance and not by choice (has less effect on allele frequencies)

24. 4. Nonrandom Mating: Sexual Selection • Mating is nonrandom whenever individuals may choose partners. • Sexual selection occurs when certain traits increase an individual’s success at mating. • Sexual selection affects the allele frequencies of a population. • Courtship ritual

25. Activity • What if every fish in your “pond” only wants to mate with an brown fish? • What would that do to your allele frequencies?

26. 5. Natural Selection • The ongoing process in nature where the presence or absence of certain factors in the environment “select” which traits/variations within a population are most successful • Most traits are polygenic = many variations

27. Without Natural Selection, polygenic traits maintain a bell curve

28. With Natural Selection… • Three general patterns • Stabilizing Selection • favors the formation of average traits. • Disruptive Selection • favors extreme traits rather than average traits. • Directional Selection • favors the formation of one of the extreme traits.

30. Exit Ticket • How does evolution by natural selection depend on variation within a population?

31. Complete Types of Natural Selection practice sheet

32. JELLY BELLICUS LAB • COMPLETE JELLY BELLICUS ACTIVITY AND CREATE GRAPHS

33. Exit Ticket: (for jellybellicus lab) • I gave you 3 examples of natural selection patterns in this lab. The environmental factors in nature determine “fitness” in natural selection. • Come up with an example using the jelly bellicus species and the crew members to show artificial selection occurring.

34. Bellwork – which natural selection pattern is represented?

35. The Concept of Species • Biological species concept • a species is a population of organisms that can successfully interbreed but cannot breed with other groups

36. Isolation and Speciation • Geographic Isolation • Results from the separation of population subgroups by geographic barriers. • Allopatric Speciation • Speciation due to separation of subgroups of a population – geographic isolation • Reproductive Isolation • Results from the separation of population subgroups by barriers to successful breeding. • Sympatric Speciation • Reproductive isolation within the same geographic area

37. Allopatry vs Sympatry http://deltabiology.com/wp-content/uploads/2012/02/Sympatry.jpg http://scienceblogs.com/evolvingthoughts/allopatry.jpg

38. Reproductive isolation: Monkeyflower http://faculty.washington.edu/toby/images/mim29%20Nature.jpg

39. Reproductive isolation - sympatric http://evolution.berkeley.edu/evolibrary/images/evo/drosophila_scene7.gif

40. Rates of Speciation • Gradualism • species undergo small changes at a constant rate. • Punctuated equilibrium • new species arise abruptly, differ greatly from their ancestors, and then change little over long periods.