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MICROEVOLUTION VS. MACROEVOLUTION

MICROEVOLUTION VS. MACROEVOLUTION. Microevolution : survival through the inheritance of favorable characteristics mutations selection Macroevolution : progression of biodiversity through geological time speciation extinction. MICROEVOLUTION. Evolutionary Mechanisms

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MICROEVOLUTION VS. MACROEVOLUTION

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  1. MICROEVOLUTION VS. MACROEVOLUTION Microevolution: survival through the inheritance of favorable characteristics mutations selection Macroevolution: progression of biodiversity through geological time speciation extinction

  2. MICROEVOLUTION Evolutionary Mechanisms Types of Natural Selection Hardy-Weinberg Equilibrium

  3. WHAT IS MICROEVOLUTION? Traces generational changes in a population of organisms Changes eh? Allelic frequency changes within a gene pool!

  4. WHAT LEADS TO CHANGES IN THE GENE POOL OF A POPULATION? SMALL POPULATION SIZE (small pop  frequencies) toss a coin to prove it.

  5. MECHANISMS OF EVOLUTION GENETIC DRIFT (random/chance events that change the gene pool of a small population) examples: natural disasters

  6. 2 TYPES OF GENETIC DRIFT MECHANISMS Genetic Bottleneck dramatic decrease in pop size due to : catastrophes predation disease, etc.

  7. Founder Effect migration leads to changes in allele frequencies from population of origin

  8. WHAT ELSE CAUSES GENE POOL CHANGES ? GENE FLOW immigration emigration

  9. EX OF GENE FLOW IN HUMANS Frequency of Rh- allele among Africans: 63% Frequency of Rh- allele among African-Americans 45% Frequency of Rh- allele among White European population 3%

  10. MUTATIONS may produce a selective advantage may produce deleterious effects may be harmless

  11. NATURAL SELECTION! increases/decreases allele frequencies due to environmental impact. Ex: English Peppered Moths

  12. NON-RANDOM MATING individuals choose based upon traits (vertebrates) individuals “choose” based upon physical proximity (invertebrates)

  13. OTHER FORMS OF NON-RANDOM MATING: INBREEDING Proximity issues SEXUAL SELECTION: Male competition: # offspring  fitness Female choice: quality offspring  fitness

  14. SEXUAL SELECTION Picky females, show-off males…

  15. MICROEVOLUTION REVIEW Changes in the GENE POOL! Caused by: Gene Flow Natural Selection Mutations Non-Random Mating Sexual Selection Inbreeding

  16. THE SIGNIFICANCE OF SELECTION Selection increases the adaptive qualities of a population for the environment in which it lives. Types of Selection: Natural Selection determined by phenotype selection toward phenotypes that improve fitness

  17. SUBDIVISIONS OF NATURAL SELECTION… Stabilizing Selection Eliminates individuals with extreme traits. Results in decreased variation

  18. Directional Selection Favors traits at ONE extreme ex: resistance to insecticides

  19. DIRECTIONAL SELECTION

  20. Disruptive Selection Selection toward BOTH extremes. Extreme traits are favored, common traits are NOT! Results in major divisions in population! What might result?

  21. DISRUPTIVE SELECTION

  22. ARTIFICIAL SELECTION Directional selection determined by humans

  23. CAUSES OF VARIATION Mutation is the ultimate source of variation Two major types of mutations: Gene mutations Chromosome mutations

  24. GENE MUTATIONS Addition / Insertion Deletion Substitution Inversion

  25. SPECIFIC EXAMPLES OF MUTATIONS Gene mutations PKU (phenylketonuria) CF (cystic fibrosis) Chromosome mutation Klinefelter syndrome (male with 47,XXY karyotype)

  26. ONCE MUTATIONS HAVE ARISEN, FURTHER VARIATION RESULTS FROM: Recombination of alleles during meiosis Recombination of alleles during fertilization

  27. ONCE GENETIC VARIATION HAS ARISEN, THERE IS ALSO PHENOTYPIC VARIATION. Recall that, according to Darwin’s Theory, due to competition within populations, there is … Differential Reproduction of Selected Phenotypes

  28. GREAT EXAMPLE OF DIFFERENTIAL REPRODUCTION OF SELECTED PHENOTYPES:

  29. ULTIMATE RESULT OF EVOLUTION Change in the genetic composition (gene pool) of a population.

  30. RELATED CAUSES OF GENETIC VARIATION Sexual Reproduction! Diploidy Outbreeding

  31. MINORITY ADVANTAGE… 50/50 Sex Ratio Predation (more common phenotype preferred by predator) The Lefty Hypothesis 10-15 % general population >50% contact sports (esp. males)

  32. REPRODUCTIVE ISOLATION Prezygotic Temporal isolation Behavioral isolation Mechanical isolation Ecological isolation Gametic isolation Postzygotic Hybrid inviability Hybrid sterility Hybrid breakdown

  33. ALLOPATRIC SPECIATION

  34. SYMPATRIC SPECIATION

  35. GRADUALISM Species A evolves to become species B. LONG, GRADUAL process!

  36. PUNCTUATED EQUILIBRIUM Evolution is Slow with brief periods of rapid development of new species.

  37. THE HARDY WEINBERG LAW If allele frequencies for a population do not change… NO EVOLUTION IS OCCURRING! Genetic Equilibrium Hardy Weinberg Equilibrium

  38. GENETIC EQUILIBRIUM OCCURS ONLY IF THERE IS… A large breeding population Random mating No change in allelic frequency due to mutation No immigration or emigration No natural selection

  39. EQUILIBRIUM REQUIRES… Large Population Size (laws of probability must apply) Isolation of Population (no immigration/emigration to/from other populations) NO MUTATIONS ALLOWED! NO NATURAL SELECTION ! all traits must be selectively neutral Mating Must Be RANDOM equal probabilities of mating btwn genotypes

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