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 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 frequency is 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

38. Reproductive isolation: Monkeyflower

39. Reproductive isolation - sympatric

40. Rates of Speciation Gradualism Punctuated equilibrium
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.