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Evolution of Populations

Evolution of Populations. Marie Černá. Microevolution. Genetic drift in small population Gene flow by migration Mutation Nonrandom mating Natural selection. Genetic Drift. Genetic D rift - small populations. Genetic Drift - large populations. Genetic Drift - Bottle neck effect.

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Evolution of Populations

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  1. Evolution of Populations Marie Černá

  2. Microevolution • Genetic drift in small population • Gene flow by migration • Mutation • Nonrandom mating • Natural selection

  3. Genetic Drift

  4. Genetic Drift - small populations

  5. Genetic Drift - large populations

  6. Genetic Drift - Bottle neck effect

  7. Genetic Drift - Bottle neck effect northern elephant seals of the coast of Mexico During the 1890’s, their population was reduced due to hunting to about 20 individuals. (It is also likely that one male would have fathered the offspring of the entire group.)

  8. Genetic Drift - Founder principle Drosophila subobscura (fruit fly) European → American

  9. Genetic Drift - Founder principle

  10. Gene flow - migration

  11. Mutation

  12. inbreeding assortative mating Nonrandom mating

  13. Natural selection • the differential ability to survive and produce viable, fertile offspring • is likely to adapt a population to its environment (accumulates and maintains favorable genotypes)

  14. Genetic variation: the substrate for natural selection • within populations (polymorphism) • between populations (geographical variation)

  15. Polymorphism

  16. Geographic variation

  17. Geographic variation - Cline

  18. Sources of Genetic variation • Mutation (affection of function) • Sexual recombination

  19. Crossing over in meiosis

  20. Independent assortment

  21. Preservation of Genetic variation • Diploidy (heterozygote protection) • Balanced polymorphism

  22. Heterozygote advantage

  23. Frequency-dependent selection

  24. Modes of natural selection

  25. Directional selection is most common - during periods of environmental change - when members of a population migrate to some new habitat with different environmental conditions

  26. Directional selection Desert cactus population peccaries

  27. Diversifying selection

  28. Diversifying selection a species of finch lives in Cameroon, West Africa large-billed birds (hard seeds) small-billed birds (soft seeds)

  29. Stabilizing selection This mode of selection reduces variation and maintains the status quo for a particular phenotypic character. It keeps the majority of human birth weights In the 3 – 4 kg range. For babies much smaller or larger than this, infant mortality is greater.

  30. Stabilizing selection Desert cactus population

  31. Literature Biology, eighth edition, Campbell, Reece Unit four: Mechanisms of Evolution Chapter 23: The Evolution of Populations Pages 468 – 486

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