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Chapter 16:

Chapter 16:. Population Genetics and Speciation. Chapter 16.1. Genetic Equilibrium. Evolution by Natural Selection. widely accepted by end 1800s Further genetics research supported it. What’s population genetics ?. Studying evolution of genes in a population Type of Microevolution

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Chapter 16:

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  1. Chapter 16: Population Genetics and Speciation

  2. Chapter 16.1 Genetic Equilibrium

  3. Evolution by Natural Selection • widely accepted by end 1800s • Further genetics research supported it

  4. What’s population genetics? • Studying evolution of genes in a population • Type of Microevolution • What’s an allele? • What’s a species? • Same genotypes? • Interbreed?

  5. Can an individual evolve? NO!!!!!

  6. What are causes of VARIATION? • Environmental factors • Heredity • Mutations • Recombination • Random pairing of gametes • Complex characters

  7. GENE POOL... • ALL ALLELES IN POPULATION • Allele Frequency Example: • 20 lions in population • ½ are heterozygous • ¼ are hom dom • ¼ are hom rec • Freq of A? • Freq of a?

  8. How’s allele frequency different from phenotype frequency?

  9. Hardy-Weinberg Equilibrium • Genotype frequencies usually stay ~same across generations UNLESS acted on by outside influences... • ????? • Important b/c... • Tells us what forces may disrupt genetic equilibrium & allow for evolution to take place

  10. How it can change the population:

  11. 5 Assumptions of Hardy-Weinberg Principle: • No net mutations; alleles remain same. • No immigration or emigration • Large population size • Random mating • No selection occurring

  12. 5 Factors that can lead to Evolution: • Genetic drift • Gene flow • Mutation • Sexual selection • Natural selection

  13. REVIEW... • What are 3 causes of genetic variation in a population? • What’s a GENE POOL? • How do you calculate genotype & phenotype frequency? • What are the assumptions of the H-W principle? • How does the pairing of gametes produce genotypic variation?

  14. Opener, Wednesday April 24th Allele Frequency Practice There are 100 Heffalumps in the population. 80 have an extra-long snout (homozygous dominant). 15 have a medium-sized snout (heterozygous). 5 have a short snout (homozygous recessive). Calculate the allele frequency for both alleles.

  15. Some tigers have a recessive allele that causes an absence of fur pigment in homozygous individuals (albino tigers). • Do you think the white phenotype in tigers is favored by natural selection? • Why or why not? • What does this mean for the occurrence of the allele in future generations (more, less)?

  16. List the 5 assumptions of Hardy-Weinberg Equilibrium… • ANY EXCEPTIONS  • CHANGE IN ALLELE FREQ  • EVOLUTION OF POPULATION OVER GENERATIONS

  17. 16-2: Disruption of Genetic EquilibriumLooking at those H-W assumptions…continuing on your chart.

  18. 1. Mutations • Mutagens increase mutation rates • Radiation, chemicals • New alleles • - / 0 / + effects

  19. 2. GeneFlow • Change in population size...how? • Immigration, emigration • Migration, seed dispersal • Male apes moving to new troops...gene flow?

  20. 3. GeneticDrift • Allele freq changes due to random event/chance • Small pop  bigger effects

  21. 4. Nonrandom Mating • Many species don’t mate randomly! • Geography, similar traits (assortative mating), sexualselection • SURVIVE & REPRODUCE!

  22. 5. Natural Selection • Ongoing in nature • SURVIVE & REPRODUCE! • 3 patterns/modes

  23. Campbell CD • Activity 13D

  24. REVIEW! • How can mutation lead to evolution? • What’s gene flow? • How’s it different from genetic drift? • Why does genetic drift affect small populations more dramatically? • Stabilizing selection? Example? • Disruptive? • Directional? • Example OTHER THAN A PEACOCK/BIRD for sexual selection?

  25. Practice! • Beads • Rat Islands • Or • Natural Selection/Camouflage

  26. Opener, Thurs. Jan 7th • Use the following terms in a sentence to summarize what you learned yesterday & LINK it to last night’s homework: • Genetic equilibrium • Gene pool • Speciation

  27. Opener, Thursday Jan. 7th Some tigers have a recessive allele that causes an absence of fur pigment in homozygous individuals (albino tigers). • Do you think the white phenotype in tigers is favored by natural selection? • Why or why not? • Will it be selected “for” or “against”? • What does this mean for the occurrence of the allele in future generations (more, less)?

  28. 16-3: Speciation

  29. How many species are on Earth? • BioBucks! Estimate w/reference…

  30. http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001127http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001127

  31. Reproductive Isolation: • Can be caused by... • 1. • 2. • 3. • Is the final stage of ...

  32. 1. Behavioral Isolation • Courtship/mating behavior • Prevents reproduction between populations • (Leads to evolution of new species) • Examples: bird songs, firefly lights

  33. 2. Geographical Isolation • Physical barriers divide a population into 2 or more groups • Prevents repro. b/w pops. • (Leads to evolution of new species) • Examples: 10,000 yrs ago—Colorado River…squirrels @ N. & S. rim of Grand Canyon • Mountains—salamanders • Islands—finches, tortoises!

  34. 3. Temporal Isolation • TIMING of reproductive or courtship events • prevents repro. b/w pops. • (Leads to evolution of new species) • Examples: flowers w/ diff. bloom times • Clams—different spawning times

  35. What’s speciation? • Common ancestor • Deviations • Similar ------- very different • How can some be similar and some so different? • Time!

  36. How do scientists determine if 2 organisms are the same species? • Morphology, anatomy • Molecular evidence • INTERBREED & PRODUCE FULLY FERTILE OFFSPRING http://evolution.berkeley.edu/evosite/evo101/VSpeciation.shtml

  37. How long does this take? • Depends on the species & conditions! • Gradualism: Punctuated equilibrium:

  38. Test Tomorrow… • Review Ch 17 also! • Ch 14, 15, 16 • Let’s go over your quiz so you can STUDY it • Test Corrections available … • Friday, Monday, Tuesday only. • Must have HW completed!

  39. Chapter 16 Activity: Data Analysis, Frequencies, & Natural Selection • Identifying patterns in data by studying graphs and charts is important in making future predictions and hypotheses. • Population Genetics • Swordtails are small freshwater fish. One section of the tail of the male fish is elongated and has a specific color pattern of two black lines running the outside length of the section, with yellow in the middle. Scientists conducted an experiment to determine which component of the color pattern may be most attractive to the female swordtail during mating. The females were exposed to three different stimuli: a normal male fish tail, an all-black male fish tail, and an all-yellow male f ish tale. The response of the females to each stimulus was recorded. The graph below shows the results of the research. • Groups of 3 • Read • Analyze Graph • Answer questions AS A GROUP • Write on your own paper

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