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Chapter 13

Chapter 13. 0. How Populations Evolve. Figure 13.1A. DARWIN’S THEORY OF EVOLUTION. 0. Voyage of H.M.S. Beagle Galápagos Islands-Charles Darwin observed many unique organisms. 0. In the century prior to Darwin The study of fossils suggested that life forms change

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Chapter 13

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  1. Chapter 13 0 How Populations Evolve

  2. Figure 13.1A DARWIN’S THEORY OF EVOLUTION 0 • Voyage of H.M.S. Beagle • Galápagos Islands-Charles Darwin observed many unique organisms

  3. 0 • In the century prior to Darwin • The study of fossils suggested that life forms change • Geologists proposed that a very old Earth • Is changed by gradual processes

  4. 0 NorthAmerica GreatBritain Europe Asia ATLANTICOCEAN PACIFICOCEAN Africa PACIFICOCEAN Equator TheGalápagosIslands PACIFICOCEAN SouthAmerica Pinta Genovesa Australia Marchena Equator Andes Cape ofGood Hope Santiago DaphneIslands Pinzón Fernandina Tasmania NewZealand Cape Horn Isabela SantaCruz SantaFe SanCristobal Tierra del Fuego 40 km 0 Florenza Española Figure 13.1B 40 miles 0 • While on the voyage of the HMS Beagle in the 1830s- Charles Darwin observed similarities between living and fossil organisms and the diversity of life on the Galápagos Islands

  5. Charles Darwin

  6. 0 • 13.2 Natural selection as the mechanism of evolution • The selection of the environmental pressures on the population would choose best adapted organisms to survive and reproduce • Darwin observed: • Variety in many characteristics that can be inherited (height, intelligence, skin color, feet size, shell size) • Produce more offspring than the environment can support (social darwinism)

  7. 0 • Natural selection- Results in favored traits being represented more and more and unfavored ones less and less in ensuing generations of organisms

  8. Theory of Evolution Variation of individuals Variety of sizes How does meiosis have a role here? Natural Selection Survival of the Fittest

  9. Hundreds to thousandsof years of breeding(artificial selection) Ancestral dog (wolf) Figure 13.2B Figure 13.2A 0 Darwin found evidence for ideas in artificial selection The selective breeding of domesticated plants and animals

  10. Artificial Selection: choosing traits for parent of the next generation

  11. African wild dog Coyote Jackal Wolf Fox Thousands tomillions of yearsof natural selection Ancestral canine Figure 13.2C 0 • Darwin proposed that living species descended from earlier life forms and that natural selection is the mechanism of evolution

  12. A Skull of Homoerectus B Petrified tree C Ammonite casts D Dinosaur tracks F Insect in amber E Fossilized organicmatter of a leaf G “Ice Man” Figure 13.3A–G 0 • 13.3 The study of fossils provides strong evidence for evolution • Fossils and the fossil record are physical evidence that support evolution

  13. Figure 13.3H 0 • The fossil record • Reveals that organisms have evolved in a historical sequence

  14. Figure 13.3I 0 • Many fossils link early extinct species • With species living today

  15. 0 • 13.4 A mass of other evidence reinforces the evolutionary view of life

  16. 0 • Biogeography • Biogeography, the geographic distribution of species • Suggested to Darwin that organisms evolve from common ancestors • Darwin noted that Galápagos animals • Resembled species of the South American mainland more than animals on similar but distant islands

  17. 0 • Comparative anatomy • Comparative anatomy • Is the comparison of body structures in different species • Homology • Is the similarity in characteristics that result from common ancestry • http://www.pingrybiology.com/embryo.htm

  18. Cat Whale Bat Human Figure 13.4A 0 • Homologous structures • Are features that often have different functions but are structurally similar because of common ancestry

  19. 0 • Comparative Embryology • Comparative embryology • Is the comparison of early stages of development among different organisms

  20. 0 Pharyngealpouches Post-analtail Human embryo Chick embryo Figure 13.4B • Many vertebrates • Have common embryonic structures

  21. Table 13.4 0 • Molecular Biology • Comparisons of DNA and amino acid sequences between different organisms • Reveal evolutionary relationships

  22. A flower mantidin Malaysia A leaf mantid in Costa Rica Figure 13.5A CONNECTION 0 • 13.5 Scientists can observe natural selection in action • Camouflage adaptations that evolved in different environments • Are examples of the results of natural selection

  23. Chromosome with geneconferring resistanceto pesticide Pesticide application Survivor Additionalapplications of thesame pesticide willbe less effective, andthe frequency ofresistant insects inthe populationwill grow Figure 13.5B 0 • Development of pesticide resistance in insects • Is another example of natural selection in action

  24. POPULATION GENETICS AND THE MODERN SYNTHESIS 0 • 13.6 Populations are the units of evolution • A population • Is a group of individuals of the same species living in the same place at the same time • A species is a group of populations • Whose individuals can interbreed and produce fertile offspring

  25. 0 • Population genetics • Studies how populations change genetically over time • The modern synthesis • Connects Darwin’s theory with population genetics

  26. 0 • A gene pool • Is the total collection of genes in a population at any one time • Microevolution • Is a change in the relative frequencies of alleles in a gene pool

  27. Webbing No webbing Figure 13.7A 0 • 13.7 The gene pool of a nonevolving population remains constant over the generations • In a nonevolving population • The shuffling of alleles that accompanies sexual reproduction does not alter the genetic makeup of the population

  28. Phenotypes Genotypes WW Ww ww Number of animals(total  500) 320 160 20 160 500 20 500 320 500 Genotype frequencies  0.32  0.04  0.64 Number of allelesin gene pool(total  1,000) 640 W 160 W 160 w 40 w 800 1,000 200 1,000  0.8 W  0.2 w Allele frequencies Figure 13.7B 0 • Hardy-Weinberg equilibrium • States that the shuffling of genes during sexual reproduction does not alter the proportions of different alleles in a gene pool

  29. Recombinationof alleles fromparent generation SPERM W spermp 0.8 w spermq 0.2 Wwpq 0.16 WWp2 0.64 W eggp 0.8 EGGS wwq2 0.04 wWqp 0.16 w eggq 0.2 Next generation: 0.04 ww Genotype frequencies 0.64 WW 0.32 Ww 0.2 w Allele frequencies 0.8 W Figure 13.7C 0 • We can follow alleles in a population • To observe if Hardy-Weinberg equilibrium exists

  30. 0 • For a population to be in Hardy-Weinberg equilibrium, it must satisfy five main conditions • The population is very large • The population is isolated • Mutations do not alter the gene pool • Mating is random • All individuals are equal in reproductive success

  31. CONNECTION 0 • 13.8 The Hardy-Weinberg equation is useful in public health science • Public health scientists use the Hardy-Weinberg equation • To estimate frequencies of disease-causing alleles in the human population

  32. 0 • 13.9 In addition to natural selection, genetic drift and gene flow can contribute to evolution • Genetic drift • Is a change in the gene pool of a population due to chance • Can alter allele frequencies in a population

  33. Originalpopulation Bottleneckingevent Survivingpopulation Figure 13.9B Figure 13.9A 0 • Genetic drift • Can cause the bottleneck effect or the founder effect

  34. 0 • Gene flow • Is the movement of individuals or gametes between populations • Can alter allele frequencies in a population

  35. 0 • Natural selection • Leads to differential reproductive success in a population • Can alter allele frequencies in a population

  36. CONNECTION 0 • 13.10 Endangered species often have reduced variation • Low genetic variability • May reduce the capacity of endangered species to survive as humans continue to alter the environment Figure 13.10

  37. Figure 13.11 VARIATION AND NATURAL SELECTION 0 • 13.11 Variation is extensive in most populations • Many populations exhibit polymorphism • Different forms of phenotypic characteristics

  38. 0 • Populations may also exhibit geographic variation • Variation of an inherited characteristic along a geographic continuum

  39. 0 • 13.12 Mutation and sexual recombination generate variation • Mutations, or changes in the nucleotide sequence of DNA • Can create new alleles

  40. A1 A1 A2 A3 Parents X Meiosis A2 A1 A3 Gametes Fertilization A2 A1 Offspring,with newcombinationsof alleles A1 A3 and Figure 13.12 0 • Sexual recombination • Generates variation by shuffling alleles during meiosis

  41. CONNECTION 0 • 13.13 The evolution of antibiotic resistance in bacteria is a serious public health concern • The excessive use of antibiotics • Is leading to the evolution of antibiotic-resistant bacteria Colorized SEM 5,600 Figure 13.13

  42. 0 • 13.14 Diploidy and balancing selection variation • Diploidy preserves variation • By “hiding” recessive alleles • Balanced polymorphism • May result from the heterozygote advantage or frequency-dependent selection

  43. Figure 13.14 0 • Some variations may be neutral • Providing no apparent advantage or disadvantage

  44. 0 • 13.15 The perpetuation of genes defines evolutionary fitness • An individual’s fitness • Is the contribution it makes to the gene pool of the next generation

  45. 0 • 13.16 Natural selection can alter variation in a population in three ways • Stabilizing selection • Favors intermediate phenotypes • Directional selection • Acts against individuals at one of the phenotypic extremes • Disruptive selection • Favors individuals at both extremes of the phenotypic range

  46. Originalpopulation Frequency of individuals Phenotypes (fur color) Originalpopulation Evolvedpopulation Figure 13.16 Stabilizing selection Disruptive selection Directional selection 0 • Three possible effects of natural selection

  47. Figure 13.17B Figure 13.17A 0 • 13.17 Sexual selection may produce sexual dimorphism • Sexual selection leads to the evolution of secondary sexual characteristics • Which may give individuals an advantage in mating

  48. 0 • 13.18 Natural selection cannot fashion perfect organisms • There are at least four reasons why natural selection cannot produce perfection • Organisms are limited by historical constraints • Adaptations are often compromises • Chance and natural selection interact • Selection can only edit existing variations

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