1. © 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Chapter 13 How Populations Evolve

2. Biology and Society: Persistent Pests Mosquitoes and malaria –In the 1960s, the World Health Organization (WHO) began a campaign to eradicate the mosquitoes that transmit malaria. –It used DDT, to which some mosquitoes have evolved resistance. © 2010 Pearson Education, Inc.

3. The evolution of pesticide-resistant insects is just one of the ways that evolution affects our lives. An understanding of evolution informs every field of biology, for example: –Agriculture –Medicine –Biotechnology –Conservation biology

4. © 2010 Pearson Education, Inc. CHARLES DARWIN AND THE ORIGIN OF SPECIES Charles Darwin published On the Origin of Species by Means of Natural Selection, November 24, 1859. Darwin presented two main concepts: –Life evolves –Change occurs as a result of “descent with modification,” with natural selection as the mechanism

5. © 2010 Pearson Education, Inc. Natural selection is a process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are individuals with other characteristics.

6. A Trinidad tree mantid that mimics dead leaves Figure 13.1a

7. A leaf mantid in Costa Rica Figure 13.1b

8. A flower mantid in Malaysia Figure 13.1c

9. © 2010 Pearson Education, Inc. Natural selection leads to: –A population (a group of individuals of the same species living in the same place at the same time) changing over generations –Evolutionary adaptation In one modern definition of evolution, the genetic composition of a population changes over time.

10. 1809 Lamarck publishes his theory of evolution. 1830 Lyell publishes Principles of Geology. 1837 Darwin begins analyzing his specimens and writing his notebooks on the origin of species. 1844 Darwin writes his essay on the origin of species. 1865 Mendel publishes papers on genetics. 1858 Wallace sends an account of his theory to Darwin. 1859 Darwin publishes The Origin of Species. 1809 Charles Darwin is born. 1831–36 Darwin travels around the world on the HMS Beagle. Green sea turtle in the Galápagos Islands 1800 1870 Figure 13.2

11. Green sea turtle in the Galápagos Islands Figure 13.2a

12. Figure 13.2b

13. Figure 13.2c

14. Figure 13.2d

15. © 2010 Pearson Education, Inc. Darwin’s Cultural and Scientific Context The Origin of Species challenged the notion that the Earth was: –Relatively young –Populated by unrelated species

16. © 2010 Pearson Education, Inc. The Idea of Fixed Species The Greek philosopher Aristotle held the belief that species are fixed and do not evolve. The Judeo-Christian culture fortified this idea with a literal interpretation of the Bible and suggested the Earth may only be 6,000 years old.

17. © 2010 Pearson Education, Inc. Lamarck and Evolutionary Adaptations In the mid-1700s, the study of fossils began to take form as a branch of science. Naturalist Georges Buffon noted that: –The Earth may be more than 6,000 years old –There are similarities between fossils and living species –Fossil forms might be ancient versions of similar living species

18. © 2010 Pearson Education, Inc. Jean Baptiste Lamarck suggested that organisms evolved by the process of adaptation by the inheritance of acquired characteristics, now known to be incorrect.

19. © 2010 Pearson Education, Inc. The Voyage of the Beagle Darwin was born on February 12, 1809, the same day that Abraham Lincoln was born. In December 1831 Darwin left Great Britain on the HMS Beagle on a five-year voyage around the world.

20. Darwin in 1840 Figure 13.3a

21. HMS Beagle Figure 13.3b

22. Galápagos Islands PACIFIC OCEAN Pinta 40 miles 40 km 0 Florenza 0 Fernandina Marchena Genovesa Equator Santiago Daphne Islands Pinzón Española Isabela Santa Cruz Santa Fe San Cristobal Figure 13.3c

23. © 2010 Pearson Education, Inc. On his journey on the Beagle, Darwin: –Collected thousands of specimens –Observed various adaptations in organisms

24. © 2010 Pearson Education, Inc. Darwin was intrigued by: –The geographic distribution of organisms on the Galápagos Islands –Similarities between organisms in the Galápagos and those in South America

25. Figure 13.4a

26. Figure 13.4b

27. © 2010 Pearson Education, Inc. Darwin was strongly influenced by the writings of geologist Charles Lyell. Lyell suggested that the Earth: –Is very old –Was sculpted by gradual geological processes that continue today Darwin applied Lyell’s principle of gradualism to the evolution of life on Earth.

28. © 2010 Pearson Education, Inc. Descent with Modification Darwin made two main points in The Origin of Species: –Organisms inhabiting Earth today descended from ancestral species –Natural selection was the mechanism for descent with modification

29. © 2010 Pearson Education, Inc. EVIDENCE OF EVOLUTION Biological evolution leaves observable signs. We will examine five of the many lines of evidence in support of evolution: –The fossil record –Biogeography –Comparative anatomy –Comparative embryology –Molecular biology

30. © 2010 Pearson Education, Inc. The Fossil Record Fossils are: –Imprints or remains of organisms that lived in the past –Often found in sedimentary rocks

31. © 2010 Pearson Education, Inc. The fossil record: –Is the ordered sequence of fossils as they appear in rock layers –Reveals the appearance of organisms in a historical sequence –Fits the molecular and cellular evidence that prokaryotes are the ancestors of all life

32. Figure 13.5

33. © 2010 Pearson Education, Inc. Paleontologists: –Are scientists that study fossils –Have discovered many transitional forms that link past and present

34. Figure 13.6-3

35. © 2010 Pearson Education, Inc. Biogeography Biogeography is the study of the geographic distribution of species that first suggested to Darwin that today’s organisms evolved from ancestral forms.

36. © 2010 Pearson Education, Inc. Many examples from biogeography would be difficult to understand, except from an evolutionary perspective. One example is the distribution of marsupial mammals in Australia.

37. Common ringtail possum Red kangaroo Common wombat Australia Koala Figure 13.7

38. © 2010 Pearson Education, Inc. Comparative Anatomy Comparative anatomy –Is the comparison of body structure between different species –Confirms that evolution is a remodeling process

39. © 2010 Pearson Education, Inc. Homology is: –The similarity in structures due to common ancestry –Illustrated by the remodeling of the pattern of bones forming the forelimbs of mammals

40. HumanCatWhale Bat Figure 13.8

41. © 2010 Pearson Education, Inc. Vestigial structures: –Are remnants of features that served important functions in an organism’s ancestors –Now have only marginal, if any, importance

42. © 2010 Pearson Education, Inc. Comparative Embryology Early stages of development in different animal species reveal additional homologous relationships. –For example, pharyngeal pouches appear on the side of the embryo’s throat, which: –Develop into gill structures in fish –Form parts of the ear and throat in humans –Comparative embryology of vertebrates supports evolutionary theory.

43. Post-anal tail Human embryo Chicken embryo Pharyngeal pouches Figure 13.9

44. © 2010 Pearson Education, Inc. Molecular Biology The hereditary background of an organism is documented in: –Its DNA –The proteins encoded by the DNA Evolutionary relationships among species can be determined by comparing: –Genes –Proteins of different organisms

45. Percent of selected DNA sequences that match a chimpanzee’s DNA Chimpanzee 100%96%92% Human Gibbon Orangutan Gorilla Primate Old World monkey Figure 13.10

46. © 2010 Pearson Education, Inc. NATURAL SELECTION Darwin noted the close relationship between adaptation to the environment and the origin of new species. The evolution of finches on the Galápagos Islands is an excellent example.

47. (a) The large ground finch (b) The small tree finch(c) The woodpecker finch Figure 13.11

48. © 2010 Pearson Education, Inc. Darwin’s Theory of Natural Selection Darwin based his theory of natural selection on two key observations: –All species tend to produce excessive numbers of offspring –Organisms vary, and much of this variation is heritable

49. © 2010 Pearson Education, Inc. Observation 1: Overproduction –All species tend to produce excessive numbers. –This leads to a struggle for existence.

50. Spore cloud Figure 13.12

51. © 2010 Pearson Education, Inc. Observation 2: Individual variation –Variation exists among individuals in a population. –Much of this variation is heritable.

52. Figure 13.13

53. © 2010 Pearson Education, Inc. Inference: Differential reproductive success (natural selection) –Those individuals with traits best suited to the local environment generally leave a larger share of surviving, fertile offspring.

54. © 2010 Pearson Education, Inc. Natural Selection in Action Examples of natural selection include: –Pesticide-resistant insects –Antibiotic-resistant bacteria –Drug-resistant strains of HIV

55. Chromosome with gene conferring resistance to pesticide Reproduction Survivors Insecticide application Figure 13.14-3

56. Observation: Flat-tailed horned lizards defend against attack by: –Thrusting their heads backward –Stabbing a shrike with the spiked horns on the rear of their skull Question: Are longer horns a survival advantage? Hypothesis: Longer horns are a survival advantage. The Process of Science: Does Predation Drive the Evolution of Lizard Horn Length? © 2010 Pearson Education, Inc.

57. Side horns (tip to tip) Killed Live Killed Live Rear horns 0 10 20 Length (mm) (c) Results of measurement of lizard horns (b) The remains of a lizard impaled by a shrike (a) A flat-tailed horned lizard Figure 13.15

58. © 2010 Pearson Education, Inc. Prediction: Live horned lizards have longer horn lengths than dead ones. Experiment: Measure the horn lengths of dead and living lizards. Results: The average horn length of live lizards is about 10% longer than that of dead lizards.

59. Side horns (tip to tip) Killed Live Killed Live Rear horns 0 10 20 Length (mm) (c) Results of measurement of lizard horns Figure 13.15c

60. EVOLUTIONARY TREES Darwin saw the history of life as analogous to a tree: –The first forms of life on Earth form the common trunk –At each fork is the last common ancestor to all the branches extending from that fork © 2010 Pearson Education, Inc.

61. Tetrapod limbs Amnion Feathers Lungfishes Mammals Amphibians Lizards and snakes Crocodiles Hawks and other birds Ostriches Amniotes Tetrapods Birds Figure 13.16

62. The Modern Synthesis: Darwinism Meets Genetics The modern synthesis is the fusion of genetics with evolutionary biology. © 2010 Pearson Education, Inc.

63. Populations as the Units of Evolution A population is: –A group of individuals of the same species, living in the same place, at the same time –The smallest biological unit that can evolve

64. (a) Two dense populations of trees separated by a lake Figure 13.17a

65. (b) A nighttime satellite view of North America Figure 13.17b

66. © 2010 Pearson Education, Inc. The total collection of alleles in a population at any one time is the gene pool. When the relative frequency of alleles changes over a number of generations, evolution is occurring on its smallest scale, which is sometimes called microevolution.

67. © 2010 Pearson Education, Inc. Genetic Variation in Populations Individual variation abounds in populations. –Not all variation in a population is heritable. –Only the genetic component of variation is relevant to natural selection.

68. © 2010 Pearson Education, Inc. Variable traits in a population may be: –Polygenic, resulting from the combined effects of several genes or –Determined by a single gene Polygenic traits tend to produce phenotypes that vary more or less continuously. Single gene traits tend to produce only a few distinct phenotypes.

69. Figure 13.18

70. © 2010 Pearson Education, Inc. Sources of Genetic Variation Genetic variation results from: –Mutations, changes in the DNA of an organism –Sexual recombination, the shuffling of alleles during meiosis

71. © 2010 Pearson Education, Inc. For any one gene, mutation alone has little effect on a large population in a single generation. Organisms with very short generation spans, such as bacteria, can evolve rapidly with mutations as the only source of genetic variation.

72. © 2010 Pearson Education, Inc. Analyzing Gene Pools The gene pool is a reservoir from which the next generation draws its genes. Alleles in a gene pool occur in certain frequencies.

73. © 2010 Pearson Education, Inc. Alleles can be symbolized by: –p for the relative frequency of the dominant allele in the population –q for the frequency of the recessive allele in the population

74. © 2010 Pearson Education, Inc. Genotype frequencies: –Can be calculated from allele frequencies –Are symbolized by the expressions p 2, 2pq, and q 2

75. Figure 13.19

76. Allele frequencies Genotype frequencies Sperm Eggs p  0.8 (R) q  0.2 (r) p  0.8 R q  0.2 r RR p  0.8 R q  0.2 r p 2  0.64 rR qp  0.16 q 2  0.04 rr pq  0.16 Rr (RR) p 2  0.64 q 2  0.04 (rr) 2pq  0.32 (Rr) Figure 13.20

77. © 2010 Pearson Education, Inc. The Hardy-Weinberg formula can be used to calculate the frequencies of genotypes in a gene pool from the frequencies of alleles.

78. © 2010 Pearson Education, Inc. Population Genetics and Health Science The Hardy-Weinberg formula can be used to calculate the percentage of a human population that carries the allele for a particular inherited disease.

79. © 2010 Pearson Education, Inc. PKU: –Is a recessive allele that prevents the breakdown of the amino acid phenylalanine –Occurs in about one out of every 10,000 babies born in the United States

80. INGREDIENTS: SORBITOL, MAGNESIUM STEARATE, ARTIFICIAL FLAVOR, ASPARTAME † (SWEETENER), ARTIFICIAL COLOR (YELLOW 5 LAKE, BLUE 1 LAKE), ZINC GLUCONATE. † PHENYLKETONURICS: CONTAINS PHENYLALANINE Figure 13.21

81. © 2010 Pearson Education, Inc. Microevolution as Change in a Gene Pool How can we tell if a population is evolving? A non-evolving population is in genetic equilibrium, called the Hardy-Weinberg equilibrium, in which the population gene pool remains constant over time.

82. © 2010 Pearson Education, Inc. From a genetic perspective evolution can be defined as a generation-to-generation change in a population’s frequencies of alleles, sometimes called microevolution.

83. © 2010 Pearson Education, Inc. MECHANISMS OF EVOLUTION The main causes of evolutionary change are: –Genetic drift –Gene flow –Natural selection

84. © 2010 Pearson Education, Inc. Genetic Drift Genetic drift is: –A change in the gene pool of a small population –Due to chance

85. Only 5 of 10 plants leave offspring RR rr Rr RR Rr RR Rr Only 2 of 10 plants leave offspring RR rr RR Rr rr RR Rr rr RR Generation 1 p (frequency of R)  0.7 q (frequency of r)  0.3 Generation 2 p  0.5 q  0.5 Generation 3 p  1.0 q  0.0 Figure 13.22-3

86. © 2010 Pearson Education, Inc. The Bottleneck Effect The bottleneck effect: –Is an example of genetic drift –Results from a drastic reduction in population size

87. Original population Bottlenecking event Surviving population Figure 13.23-3

88. © 2010 Pearson Education, Inc. Bottlenecking in a population usually reduces genetic variation because at least some alleles are likely to be lost from the gene pool. Cheetahs appear to have experienced at least two genetic bottlenecks in the past 10,000 years.

89. Figure 13.24

90. © 2010 Pearson Education, Inc. The Founder Effect The founder effect is likely when a few individuals colonize an isolated habitat and represent genetic drift in a new colony.

91. The founder effect explains the relatively high frequency of certain inherited disorders among some small human populations. © 2010 Pearson Education, Inc.

92. South America Tristan da Cunha Africa Figure 13.25

93. © 2010 Pearson Education, Inc. Gene Flow Gene flow: –Is genetic exchange with another population –Tends to reduce genetic differences between populations

94. Figure 13.26

95. © 2010 Pearson Education, Inc. Natural Selection: A Closer Look Of all causes of microevolution, only natural selection promotes adaptation.

96. © 2010 Pearson Education, Inc. Darwinian Fitness Fitness is the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.

97. Figure 13.27

98. © 2010 Pearson Education, Inc. Three General Outcomes of Natural Selection Directional selection: –Shifts the phenotypic “curve” of a population –Selects in favor of some extreme phenotype Disruptive selection can lead to a balance between two or more contrasting phenotypic forms in a population.

99. © 2010 Pearson Education, Inc. Stabilizing selection: –Favors intermediate phenotypes –Is the most common

100. Original population Evolved population Phenotypes (fur color) Frequency of individuals Original population (a) Directional selection (b) Disruptive selection (c) Stabilizing selection Figure 13.28

101. © 2010 Pearson Education, Inc. Sexual Selection Sexual dimorphism is: –A distinction in appearance between males and females –Not directly associated with reproduction or survival

102. © 2010 Pearson Education, Inc. Sexual selection is a form of natural selection in which inherited characteristics determine mating preferences.

103. (a) Sexual dimorphism in a finch species Figure 13.29a

104. (b) Competing for mates Figure 13.29b

105. Evolution Connection: The Genetics of the Sickle-Cell Allele Sickle-cell disease: –Is a genetic disorder –Affects about one out of every 400 African-Americans Abnormally shaped red blood cells cause painful and life- threatening complications. © 2010 Pearson Education, Inc.

106. Heterozygous individuals for the sickle-cell allele: –Do not develop sickle-cell anemia –Are more resistant to malaria In the African tropics, where malaria is most common, the frequency of the sickle-cell allele is highest.

107. Areas with high incidence of malaria Frequencies of the sickle-cell allele 0–2.5% 10.0–12.5% 2.5–5.0% 5.0–7.5% 7.5–10.0%  12.5% Figure 13.30a

108. Colorized SEM Figure 13.30b