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Chapter 16

POPULATION GENETICS AND SPECIATION. Chapter 16. Population Genetics. The study of evolution from a genetic point of view. Microevolution. A change in the collective genetic material of a population.

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Chapter 16

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  1. POPULATION GENETICS AND SPECIATION Chapter 16

  2. Population Genetics • The study of evolution from a genetic point of view.

  3. Microevolution • A change in the collective genetic material of a population. • genetic material= the many alleles or variations of the many genes that code for various traits

  4. Population • A population consists of a group of individuals of the same species that routinely interbreed. Population of Giraffes in Calauit in the Philippines

  5. Populations and Evolution • Populations are important in the study of evolution because a population is the smallest unit in which evolution occurs

  6. Patterns in Quantitative Traits • Quantitative traits, such as height and weight, tend to follow a bell shaped curve.

  7. Variations in a Population 1. Environmental factors, such as the amount of food or quality of resources available to an organism. 2. Variations are also influenced by heredity/genetics.

  8. Variation in Genes 1. Mutation- a random change in gene that is passed on to offspring. This may change or add alleles within a population. 2. Recombination- the reshuffling of genes in a diploid individual. Independent Assortment/ Crossing Over 3. The random pairing of gametes during sexual reproduction.

  9. Shoulder Partners 1. What three things cause genes to vary? (A’s tell B’s your answer) 2. Why is it important to have variation within a population? (B’s tell A’s your answer)

  10. Gene Pool • The total genetic information in a population. • All of the alleles that can be passed to the next generation exist in an imaginary pool

  11. Allele Frequency • Allele Frequency – the measure of how common a specific allele is within a population.

  12. Phenotype Frequency • The measure of how common a specific phenotype is in a population.

  13. Genetic Equilibrium • The state within a population at which the frequency of alleles and genotypes does not change from generation to generation. • When a population is in genetic equilibrium it means no evolution occurs.

  14. Disruptions in Genetic Equilibrium 1. Mutations: A change in the DNA of an organism resulting in new alleles, which can cause a change in the population

  15. 2. Gene Flow Immigration- the movement of individuals are entering into a population. Emigration- the movement of individuals out of a population.

  16. 3. Non-Random Mating • Individuals pair by choice not by chance

  17. Genetic drift is the phenomenon by which allele frequencies in a population change as a result of random events, or chance. e.g. Northern elephant seals have lost genetic variability because they have been hunted to near extinction. 4. Genetic Drift

  18. Genetic drift occurs more rapidly and has a greater affect of small populations. Small populations = small gene pool =less genetic variation

  19. Check it… • Why is genetic variation so important??? Discuss this at your table and be prepared to share your answer. #2 is the spokesperson

  20. Genetic Bottleneck A genetic bottleneck occurs when environmental disturbances cause populations to become so small that inbreeding occurs which often leads to decreased genetic variability. Over evolutionary time, populations with low variability are less likely to adapt to changing environmental conditions. • e.g. Cheetahs and black footed ferrets.

  21. 5. Selection • One of the strongest evolutionary forces.

  22. Natural Selection • Darwin’s theory • The environment selects against individuals that cannot survive and reproduce. This acts on the phenotype of an organism.

  23. Sexual Selection • When one of the genders (male or female) chooses a mate based on the phenotype or certain traits. • e.g. Female peahens choose attractive peacocks

  24. Sexual Dimorphism • When the appearance of the female is different from the appearance of the male. • e.g. Male lions have a mane female lions don’t

  25. Sexual DimorphismAntelope

  26. Artificial Selection • When humans select a specific trait and breed for that specific trait. • Seen in dogs

  27. Speciation • The process of species formation which results in closely related species.

  28. Cause of Speciation • Geographical Isolation- the physical separation of members of a population. e.g. Death Valley pupfish Grand Canyon squirrels

  29. Cause of Speciation • Reproductive Isolation- results from barriers to successful breeding between population groups in the same area. e.g. Frogs

  30. Hardy-Weinberg Genetic Equilibrium • If no evolution is occurring then allele frequency will remain stable (in equilibrium) for each succeeding generation of sexually reproducing individuals. • This cannot truly exist in real life; there is always evolution occurring in some way.

  31. Hardy Weinberg The following formulas allow us to detect changes in allele frequency from generation to generation. • #1: p2 + 2pq + q2 = 1 • #2: p + q = 1

  32. Thought Question…. • What five things cause there to be a disruption in genetic equilibrium? In other words what five things cause there to be evolution? • Each table prepare an answer – #3 is the spokesperson

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