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Bio 100 Chapter 13

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This document is a lecture outline on Charles Darwin and the theory of evolution. It covers Darwin's voyage on the HMS Beagle where he made observations of animals in different parts of the world. It discusses how Darwin was influenced by earlier scientists like Cuvier and Lamarck and how he developed the theory of natural selection based on his observations of variations between individuals and how certain traits could provide advantages for survival and reproduction. The document outlines Darwin's key ideas of natural selection and variation within populations. It also notes that Alfred Wallace independently developed a similar theory of natural selection.

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Chapter 13 Darwin and Evolution Lecture Outline See PowerPoint Image 際際滷s for all figures and tables pre-inserted into PowerPoint without notes. To run the animations you must be in 際際滷show View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please note: once you have used any of the animation functions (such as Play or Pause), you must first click in the white background before you advance the next slide. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Darwin Developed a Natural Selection Hypothesis 13-2
Darwin made a trip around the world Georges Cuvier knew that fossils showed a succession of different life-forms through time Paleontology the study of fossils Jean-Baptiste de Lamarck concluded on the basis of fossil evidence that more complex organisms are descended from less complex organisms 13-3
Figure 13.1A One of the animals that Cuvier reconstructed from fossils was the mastodon 13-4
Figure 13.1B Lamarck thought the long neck of a giraffe was due to continued stretching in each generation 13-5
December 1831 a 22-year-old naturalist named Charles Darwin (18091882) set sail on the British naval vessel HMS Beagle Primary mission to expand navys knowledge of natural resources in foreign lands Darwin made many observations about similarities and differences among animals in different parts of the world 13-6
Darwin also collected fossils Sediments deposited in strata Darwin was convinced that the Earths massive geologic changes are the result of slow processes and that, therefore, in contrast to thought at that time, the Earth was old enough to have allowed evolution to occur 13-7
Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Rhea Patagonian desert Earths strata contain fossils Great Britain Europe North America ATLANTIC OCEAN PACIFIC Africa OCEAN Gal叩pagos South INDIAN Islands America OCEAN Australia Charles Darwin, age 31 HMS Beagle Tropical rain forest Woodpecker finch Marine iguana 13-8 (rhea): 息 Nicole Duplaix/National Geographic/Getty Images; (desert): 息 C. Luiz Claudio Marigo/Peter Arnold/Photolibrary; (rain forest): 息 Chad Ehlers/Getty Images; (Darwin): 息 Carolina Biological/Visuals Unlimited; (iguana): 息 Sami Sarkis/Getty RF; (finch): 息 D. Parer & E. Parer-Cook/Ardea; (strata): 息 Anthony L. Solis/Getty RF
Artificial selection mimics natural selection Darwin made a study of artificial selection Process by which humans choose, on the basis of certain traits, the animals and plants that will reproduce Example: Foxes are very shy and normally shun people, but Russian scientists have produced silver foxes that are pets Example: Several varieties of vegetables can be traced to a single ancestor that exhibits various characteristics 13-9
Figure 13.2A Artificial selection has produced domesticated foxes 13-10
Figure 13.2B These three plants came from the wild mustard plant through artificial selection Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chinese cabbage Brussels sprouts Kohlrabi Wild mustard 13-11 (cabbage, brussel sprouts, kohlrabi): Courtesy W. Atlee Burpee Company; (wild mustard): 息 Medioimages/Punchstock
Darwin formulated natural selection as a mechanism for evolution Thomas Malthus who had proposed that death and famine are inevitable because the human population tends to increase faster than the supply of food Darwin hypothesized there is a constant struggle for existence, and only certain members of a population survive and reproduce in each generation Those members that have some advantage are best able to compete successfully for limited resources 13-12
Darwin called the process by which organisms with an advantage reproduce more than others of their kind natural selection Some aspect of the environment acts as a selective agent and chooses the members of the population with the advantageous phenotype to reproduce more than the other members 13-13
Essential components of Natural Selection The members of a population have inheritable variations A population is able to produce more offspring than the environment can support Only certain members of the population survive and reproduce Natural selection results in a population adapted to the local environment Evolution Changes in a population over time due to the accumulation of inherited differences 13-14
FIGURE 13.3 The brightly colored tree frog can hide among tropical plants where the large red eyes confuse predators. The frog climbs trees and other plants assisted by toes with suction cups 13-15
13.4 Wallace independently formulated a natural selection hypothesis Alfred Russel Wallace (18231913) was also a British naturalist Wallaces travels took him to the Amazon and Malay Archipeligo He too had read Malthuss essay, and in 1858 had the idea of survival of the fittest as well Darwin suggested that Wallaces paper be published immediately Lyell and others suggested that a joint paper be read to the Linnean Society 13-16
HOW SCIENCE PROGRESSES 13A Natural selection can be witnessed Darwin formed his idea of natural selection by observing tortoises and finches on the Gal叩pagos Islands Example: Finches Heavy beak of large, ground-dwelling finch suited to seeds Beak of warbler-finch suited to feeding on insects Longer, de-curved beak and split tongue of cactus-finch suited for probing cactus flowers for nectar Peter and Rosemary Grant are actually watching natural selection as it occurs in the finches 13-17
Figure 13A.1 Finches on the Gal叩pagos Islands Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A ground-dwelling finch A cactus-finch probes flowers feeds on seeds. for nectar. A warbber-finch feeds on insects. 13-18 (ground finch, cactus finch): 息 Laura L. Fellows; (warbler finch): 息 Greg W. Lasley
Figure 13A.2 The beak depth of a ground finch varies from generation to generation, according to the weather Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. wet year dry year dry year dry year Beak Depth medium ground finch 1977 1980 1982 1984 13-19
The Evidence for Evolution Is Strong 13-20
13.5 Fossils provide a record of the past Best evidence for evolution comes from fossils Traces of past life, such as trails, footprints, burrows, worm casts, or preserved droppings Sedimentation Weathering and erosion of rocks produces an accumulation of particles that vary in size and nature Sediment becomes a stratum, a recognizable layer in several layers Fossil record History of life recorded by fossils and the most direct evidence we have that evolution has occurred 13-21
Figure 13.5A a. Paleontologists carefully remove and study fossils b. The deeper the stratum, the older are the fossils found there 13-22
Figure 13.5B Fossils are carefully cleaned, and organisms are reconstructed 13-23
13.6 Fossils are evidence for common descent Darwin used the phrase descent with modification to explain evolution You and your cousins have a common ancestor in your grandparents, so one couple can give rise to many descendants Transitional fossil is either the common ancestor for the two different groups or is closely related to the common ancestor Allow us to trace the descent of organisms Ex: Archaeopteryx lithographica 13-24
Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. head tail wing Figure 13.6AFossil of Archaeopteryx and an artists representation feet wing Archaeopteryx fossil reptile characteristics bird characteristics feathers teeth tail with vertebrae claws 13-25 (fossil): 息 Jason Edwards/Getty RF; (art): 息 Joe Tucciarone
Figure 13.6B Ambulocetus natans, an ancestor of the modern toothed whale, and its fossil remains 13-26
13.7 Anatomic evidence supports common descent Anatomic similarities exist between fossils and between living organisms Homologous structures those that are anatomically similar because they are inherited from a recent common ancestor Analogous structures those that serve the same function, but they are not constructed similarly, nor do they share a recent common ancestry 13-27
13.7 Anatomic evidence supports common descent Comparative anatomy Vertebrate forelimbs are used for flight, orientation during swimming, running, climbing, or swinging from tree branches Yet all vertebrate forelimbs contain the same sets of bones organized in similar ways despite their dissimilar functions Vestigial structures Fully developed in one group of organisms but reduced and possibly nonfunctional in similar groups Pelvic girdle in whales and snakes 13-28
Figure 13.7A Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Despite differences in bird humerus function, vertebrate ulna forelimbs have the radius metacarpals same bones phalanges bat whale cat horse human 13-29
13.7 Anatomic evidence supports common descent Embryological evidence Homology shared by vertebrates extends to their embryologic development At some time during development, all vertebrates have a postanal tail and paired pharyngeal pouches Terrestrial vertebrates can trace their ancestry to amphibians and then to fishes 13-30
Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pig embryo Figure 13.7B Vertebrate embryos have features in common, despite different appearances as adults pharyngeal postanal pouches tail Chick embryo 13-31 (both): 息 Carolina Biological Supply/Phototake
13.8 Biogeographic evidence supports common descent Biogeography is the study of the distribution of plants and animals in different places throughout the world Such distributions are consistent with the hypothesis that life-forms evolved in a particular locale Example: Both cactuses and euphorbia are succulent, spiny, flowering plants adapted to a hot, dry environment, but cactuses grow in North American deserts and euphorbia grow in African deserts It seems they just happened to evolve on their respective continents 13-32
13.9 Molecular evidence supports common descent Almost all organisms use the same basic biochemical molecules, including DNA, ATP, and many enzymes All organisms use the same DNA triplet code and the same 20 amino acids in their proteins Humans share a large number of genes with much simpler organisms Lifes vast diversity has come about by only a slight difference in the regulation of genes 13-33
Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Species Figure 13.9 Biochemical 51 differences indicate yeast degrees of relatedness among organisms 30 moth 20 fish 18 Cytochrome c is a small protein that plays an important role in turtle the electron transport chain within mitochondria of all cells. 11 duck 9 pig 2 monkey 0 5 10 15 20 25 30 35 40 45 50 55 60 Number of amino acid differences 13-34 compared to human cytochrome c.
Population Genetics Tells Us When Microevolution Occurs 13-35
13.10 The human population is diverse Population Members of a single species occupying a particular area at the same time All humans are the same species Much of the genomic diversity of humans is due to microvariations such as single nucleotide polymorphisms (differences) or SNPs Humans inherit patterns of base-pair differences now called haplotypes 13-36
FIGURE 13.10 The HapMap project compares DNA sequences among African, Asian, and European populations to discover unique base-pair differences 13-37
A Hardy-Weinberg equilibrium is not expected Gene pool of a population is composed of all the alleles in all the individuals making up the population When the allele frequencies for a population change, microevolution has occurred Peppered moth example Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. genotypes DD Dd dd frequency of genotypes 0.04 0.32 0.64 in the population 0.04 + 0.16 0.16 + 0.64 frequency of alleles and gametes in the population 13-38 0.20 D 0.80 d
Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. F1 generation Genotypes: DD Dd dd Genotype frequencies: 0.04 0.32 0.64 Allele and gamete frequencies: D = 0.20 d = 0.80 eggs F2 generation 0.20 D 0.80 d 0.20 D sperm 0.04 DD 0.16 Dd 0.80 d 0.16 Dd 0.64 dd Offspring Genotype frequencies: 0.04 DD + 0.32 Dd + 0.64 dd = 1 p2 + 2pq + q 2 = 1 p2 = frequency of DD genotype (dark-colored) = (0.20)2 = 0.04 2pq = frequency of Dd genotype (dark-colored) = 2(0.20)(0.80) = 0.32 q2 = frequency of dd genotype (light-colored) = (0.80)2 = 0.64 1.00 Figure 13.11 Calculating gene pool frequencies for F1 and F2 13-39
The Hardy-Weinberg Principle Potential constancy, or equilibrium state, of gene pool frequencies was independently recognized by G. H. Hardy and W. Weinberg Binomial equation (p2 + 2pq + q2 = 1) to calculate the genotype and allele frequencies of a population Formulated Hardy-Weinberg principle 13-40
5 conditions for Hardy-Weinberg equilibrium 1. No mutations 2. No gene flow 3. Random mating 4. No genetic drift 5. No natural selection 13-41
Mutations & sexual recombination produce variations Mutations permanent genetic changes Without mutations, there could be no inheritable phenotypic variations 13-42
Mutations are the primary source of genetic differences among asexual prokaryotes In sexually reproducing organisms, sexual recombination is as important as mutation in creating phenotypic differences Sexual recombination creates new combinations of alleles 13-43
Nonrandom mating occurs when only certain genotypes or phenotypes mate with one another Gene flow (gene migration) the movement of alleles between populations Continued gene flow tends to make the gene pools similar and reduce the possibility of allele frequency differences between populations 13-44
Figure 13.13A The anatomy of Figure 13.13B Occasional cross- the garden pea (Pisum sativum) pollination between a population of ensures self-pollination and Pisum sativum and a population of nonrandom mating Pisum arvense is an example of gene flow Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. gene flow self- pollination Pisum arvense stamen stigma Pisum sativam Pisum sativum 13-45
13.14 The effects of genetic drift are unpredictable Genetic drift changes in the allele frequencies of a gene pool due to chance rather than selection by the environment 2 mechanisms 1. Bottleneck effect 2. Founder effect 13-46
Small Versus Large Populations Although genetic drift occurs in populations of all sizes, a smaller population is more likely to show the effects of drift Bottleneck and Founder Effects Bottleneck effect prevents the majority of genotypes from participating in the next generation Founder effect is an example of genetic drift in which rare alleles, or combinations of alleles, occur at a higher frequency in a population isolated from the general population 13-47
Figure 13.14A Chance events can cause allele frequency changes and genetic drift Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10% of natural disaster kills population five green frogs 20% of population 13-48
Figure 13.14B A rare form of dwarfism that is linked to polydactylism is seen among the Amish in Pennsylvania (1/1,000 in general population, 1/14 in Amish community) 13-49
13.15 Natural selection can be stabilizing, directional, or disruptive Stabilizing selection Occurs when an intermediate phenotype is favored Improves adaptation of the population to those aspects of the environment that remain constant Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20 100 Percent of Births in Population 70 Percent Infant Mortality 15 50 30 Figure 13.15B Stabilizing 20 selection as exemplified by 10 10 human birth weight 7 5 5 3 2 2 3 4 5 6 7 8 9 10 13-50 Birth Weight (in pounds)
Directional selection Occurs when an extreme phenotype is favored, and the distribution curve shifts in that direction Such a shift can occur when a population is adapting to a changing environment Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. No All guppies predation are drab and small Amount of Color Low above waterfall predation High predation below waterfall 0 4 8 12 Months a. Experimental site b. Result (a): 息 Helen Rodd Figure 13.15C Directional selection in guppies 13-51
Disruptive selection Two or more extreme phenotypes are favored over any intermediate phenotype Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Forested Low-lying areas vegetation 息 Bob Evans/Peter Arnold/Photolibrary 13-52 Figure 13.15D Disruptive selection in snails
Figure 13.15A Phenotype ranges before and after three types of selection Blue represents favored phenotype(s) Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Number of Individuals Phenotype Range Phenotype Range Phenotype Range a. stabilizing selection b. directional selection c. disruptive selection Number of Individuals Peak narrows. Peak shifts. Two peaks result. Phenotype Range Phenotype Range Phenotype Range 13-53
13.16 Stabilizing selection can help maintain the heterozygote Variations are maintained in a population for any number of reasons Mutations, gene flow, genetic drift and disruptive selection can maintain or increase variations in a population Cystic Fibrosis Recessive allele codes for defective membrane protein Northwestern European descent Typhoid fever agent can use normal version of this protein, but not the defective one to enter cells 13-54 Heterozygote superiority
Sickle-Cell Disease Condition due to abnormal form of hemoglobin (Hb) People who are heterozygous (HbA HbS) have an advantage because they dont die from sickle-cell disease and they dont die from malaria Frequency of the HbS allele is declining among African Americans because the heterozygote has no particular advantage in US with low to no malaria 13-55
Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Genotype Phenotype Result Dies due to HbA HbA Normal malarial infection Lives due to HbA Hbs Sickle-cell trait protection from both Hbs Hbs Sickle-cell Dies due to disease sickle-cell disease 13-56
Figure 13.16 Sickle-cell disease is more prevalent in areas of Africa where malaria is more common Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. malaria sickle-cell overlap of both 13-57
Connecting the Concepts: Chapter 13 Darwin developed theory of natural selection based on his own observations and the work of others Evolution explains the unity and diversity of life Life is unified because of common descent, and it is diverse because of adaptations to particular environments Application of principles of genetics to evolution Hardy-Weinberg equilibrium Natural selection is the only agent of evolution that results in adaptation to the environment 13-58

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Bio 100 Chapter 13

  • 1. Chapter 13 Darwin and Evolution Lecture Outline See PowerPoint Image 際際滷s for all figures and tables pre-inserted into PowerPoint without notes. To run the animations you must be in 際際滷show View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please note: once you have used any of the animation functions (such as Play or Pause), you must first click in the white background before you advance the next slide. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  • 2. Darwin Developed a Natural Selection Hypothesis 13-2
  • 3. Darwin made a trip around the world Georges Cuvier knew that fossils showed a succession of different life-forms through time Paleontology the study of fossils Jean-Baptiste de Lamarck concluded on the basis of fossil evidence that more complex organisms are descended from less complex organisms 13-3
  • 4. Figure 13.1A One of the animals that Cuvier reconstructed from fossils was the mastodon 13-4
  • 5. Figure 13.1B Lamarck thought the long neck of a giraffe was due to continued stretching in each generation 13-5
  • 6. December 1831 a 22-year-old naturalist named Charles Darwin (18091882) set sail on the British naval vessel HMS Beagle Primary mission to expand navys knowledge of natural resources in foreign lands Darwin made many observations about similarities and differences among animals in different parts of the world 13-6
  • 7. Darwin also collected fossils Sediments deposited in strata Darwin was convinced that the Earths massive geologic changes are the result of slow processes and that, therefore, in contrast to thought at that time, the Earth was old enough to have allowed evolution to occur 13-7
  • 8. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Rhea Patagonian desert Earths strata contain fossils Great Britain Europe North America ATLANTIC OCEAN PACIFIC Africa OCEAN Gal叩pagos South INDIAN Islands America OCEAN Australia Charles Darwin, age 31 HMS Beagle Tropical rain forest Woodpecker finch Marine iguana 13-8 (rhea): 息 Nicole Duplaix/National Geographic/Getty Images; (desert): 息 C. Luiz Claudio Marigo/Peter Arnold/Photolibrary; (rain forest): 息 Chad Ehlers/Getty Images; (Darwin): 息 Carolina Biological/Visuals Unlimited; (iguana): 息 Sami Sarkis/Getty RF; (finch): 息 D. Parer & E. Parer-Cook/Ardea; (strata): 息 Anthony L. Solis/Getty RF
  • 9. Artificial selection mimics natural selection Darwin made a study of artificial selection Process by which humans choose, on the basis of certain traits, the animals and plants that will reproduce Example: Foxes are very shy and normally shun people, but Russian scientists have produced silver foxes that are pets Example: Several varieties of vegetables can be traced to a single ancestor that exhibits various characteristics 13-9
  • 10. Figure 13.2A Artificial selection has produced domesticated foxes 13-10
  • 11. Figure 13.2B These three plants came from the wild mustard plant through artificial selection Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chinese cabbage Brussels sprouts Kohlrabi Wild mustard 13-11 (cabbage, brussel sprouts, kohlrabi): Courtesy W. Atlee Burpee Company; (wild mustard): 息 Medioimages/Punchstock
  • 12. Darwin formulated natural selection as a mechanism for evolution Thomas Malthus who had proposed that death and famine are inevitable because the human population tends to increase faster than the supply of food Darwin hypothesized there is a constant struggle for existence, and only certain members of a population survive and reproduce in each generation Those members that have some advantage are best able to compete successfully for limited resources 13-12
  • 13. Darwin called the process by which organisms with an advantage reproduce more than others of their kind natural selection Some aspect of the environment acts as a selective agent and chooses the members of the population with the advantageous phenotype to reproduce more than the other members 13-13
  • 14. Essential components of Natural Selection The members of a population have inheritable variations A population is able to produce more offspring than the environment can support Only certain members of the population survive and reproduce Natural selection results in a population adapted to the local environment Evolution Changes in a population over time due to the accumulation of inherited differences 13-14
  • 15. FIGURE 13.3 The brightly colored tree frog can hide among tropical plants where the large red eyes confuse predators. The frog climbs trees and other plants assisted by toes with suction cups 13-15
  • 16. 13.4 Wallace independently formulated a natural selection hypothesis Alfred Russel Wallace (18231913) was also a British naturalist Wallaces travels took him to the Amazon and Malay Archipeligo He too had read Malthuss essay, and in 1858 had the idea of survival of the fittest as well Darwin suggested that Wallaces paper be published immediately Lyell and others suggested that a joint paper be read to the Linnean Society 13-16
  • 17. HOW SCIENCE PROGRESSES 13A Natural selection can be witnessed Darwin formed his idea of natural selection by observing tortoises and finches on the Gal叩pagos Islands Example: Finches Heavy beak of large, ground-dwelling finch suited to seeds Beak of warbler-finch suited to feeding on insects Longer, de-curved beak and split tongue of cactus-finch suited for probing cactus flowers for nectar Peter and Rosemary Grant are actually watching natural selection as it occurs in the finches 13-17
  • 18. Figure 13A.1 Finches on the Gal叩pagos Islands Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A ground-dwelling finch A cactus-finch probes flowers feeds on seeds. for nectar. A warbber-finch feeds on insects. 13-18 (ground finch, cactus finch): 息 Laura L. Fellows; (warbler finch): 息 Greg W. Lasley
  • 19. Figure 13A.2 The beak depth of a ground finch varies from generation to generation, according to the weather Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. wet year dry year dry year dry year Beak Depth medium ground finch 1977 1980 1982 1984 13-19
  • 20. The Evidence for Evolution Is Strong 13-20
  • 21. 13.5 Fossils provide a record of the past Best evidence for evolution comes from fossils Traces of past life, such as trails, footprints, burrows, worm casts, or preserved droppings Sedimentation Weathering and erosion of rocks produces an accumulation of particles that vary in size and nature Sediment becomes a stratum, a recognizable layer in several layers Fossil record History of life recorded by fossils and the most direct evidence we have that evolution has occurred 13-21
  • 22. Figure 13.5A a. Paleontologists carefully remove and study fossils b. The deeper the stratum, the older are the fossils found there 13-22
  • 23. Figure 13.5B Fossils are carefully cleaned, and organisms are reconstructed 13-23
  • 24. 13.6 Fossils are evidence for common descent Darwin used the phrase descent with modification to explain evolution You and your cousins have a common ancestor in your grandparents, so one couple can give rise to many descendants Transitional fossil is either the common ancestor for the two different groups or is closely related to the common ancestor Allow us to trace the descent of organisms Ex: Archaeopteryx lithographica 13-24
  • 25. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. head tail wing Figure 13.6AFossil of Archaeopteryx and an artists representation feet wing Archaeopteryx fossil reptile characteristics bird characteristics feathers teeth tail with vertebrae claws 13-25 (fossil): 息 Jason Edwards/Getty RF; (art): 息 Joe Tucciarone
  • 26. Figure 13.6B Ambulocetus natans, an ancestor of the modern toothed whale, and its fossil remains 13-26
  • 27. 13.7 Anatomic evidence supports common descent Anatomic similarities exist between fossils and between living organisms Homologous structures those that are anatomically similar because they are inherited from a recent common ancestor Analogous structures those that serve the same function, but they are not constructed similarly, nor do they share a recent common ancestry 13-27
  • 28. 13.7 Anatomic evidence supports common descent Comparative anatomy Vertebrate forelimbs are used for flight, orientation during swimming, running, climbing, or swinging from tree branches Yet all vertebrate forelimbs contain the same sets of bones organized in similar ways despite their dissimilar functions Vestigial structures Fully developed in one group of organisms but reduced and possibly nonfunctional in similar groups Pelvic girdle in whales and snakes 13-28
  • 29. Figure 13.7A Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Despite differences in bird humerus function, vertebrate ulna forelimbs have the radius metacarpals same bones phalanges bat whale cat horse human 13-29
  • 30. 13.7 Anatomic evidence supports common descent Embryological evidence Homology shared by vertebrates extends to their embryologic development At some time during development, all vertebrates have a postanal tail and paired pharyngeal pouches Terrestrial vertebrates can trace their ancestry to amphibians and then to fishes 13-30
  • 31. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pig embryo Figure 13.7B Vertebrate embryos have features in common, despite different appearances as adults pharyngeal postanal pouches tail Chick embryo 13-31 (both): 息 Carolina Biological Supply/Phototake
  • 32. 13.8 Biogeographic evidence supports common descent Biogeography is the study of the distribution of plants and animals in different places throughout the world Such distributions are consistent with the hypothesis that life-forms evolved in a particular locale Example: Both cactuses and euphorbia are succulent, spiny, flowering plants adapted to a hot, dry environment, but cactuses grow in North American deserts and euphorbia grow in African deserts It seems they just happened to evolve on their respective continents 13-32
  • 33. 13.9 Molecular evidence supports common descent Almost all organisms use the same basic biochemical molecules, including DNA, ATP, and many enzymes All organisms use the same DNA triplet code and the same 20 amino acids in their proteins Humans share a large number of genes with much simpler organisms Lifes vast diversity has come about by only a slight difference in the regulation of genes 13-33
  • 34. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Species Figure 13.9 Biochemical 51 differences indicate yeast degrees of relatedness among organisms 30 moth 20 fish 18 Cytochrome c is a small protein that plays an important role in turtle the electron transport chain within mitochondria of all cells. 11 duck 9 pig 2 monkey 0 5 10 15 20 25 30 35 40 45 50 55 60 Number of amino acid differences 13-34 compared to human cytochrome c.
  • 35. Population Genetics Tells Us When Microevolution Occurs 13-35
  • 36. 13.10 The human population is diverse Population Members of a single species occupying a particular area at the same time All humans are the same species Much of the genomic diversity of humans is due to microvariations such as single nucleotide polymorphisms (differences) or SNPs Humans inherit patterns of base-pair differences now called haplotypes 13-36
  • 37. FIGURE 13.10 The HapMap project compares DNA sequences among African, Asian, and European populations to discover unique base-pair differences 13-37
  • 38. A Hardy-Weinberg equilibrium is not expected Gene pool of a population is composed of all the alleles in all the individuals making up the population When the allele frequencies for a population change, microevolution has occurred Peppered moth example Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. genotypes DD Dd dd frequency of genotypes 0.04 0.32 0.64 in the population 0.04 + 0.16 0.16 + 0.64 frequency of alleles and gametes in the population 13-38 0.20 D 0.80 d
  • 39. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. F1 generation Genotypes: DD Dd dd Genotype frequencies: 0.04 0.32 0.64 Allele and gamete frequencies: D = 0.20 d = 0.80 eggs F2 generation 0.20 D 0.80 d 0.20 D sperm 0.04 DD 0.16 Dd 0.80 d 0.16 Dd 0.64 dd Offspring Genotype frequencies: 0.04 DD + 0.32 Dd + 0.64 dd = 1 p2 + 2pq + q 2 = 1 p2 = frequency of DD genotype (dark-colored) = (0.20)2 = 0.04 2pq = frequency of Dd genotype (dark-colored) = 2(0.20)(0.80) = 0.32 q2 = frequency of dd genotype (light-colored) = (0.80)2 = 0.64 1.00 Figure 13.11 Calculating gene pool frequencies for F1 and F2 13-39
  • 40. The Hardy-Weinberg Principle Potential constancy, or equilibrium state, of gene pool frequencies was independently recognized by G. H. Hardy and W. Weinberg Binomial equation (p2 + 2pq + q2 = 1) to calculate the genotype and allele frequencies of a population Formulated Hardy-Weinberg principle 13-40
  • 41. 5 conditions for Hardy-Weinberg equilibrium 1. No mutations 2. No gene flow 3. Random mating 4. No genetic drift 5. No natural selection 13-41
  • 42. Mutations & sexual recombination produce variations Mutations permanent genetic changes Without mutations, there could be no inheritable phenotypic variations 13-42
  • 43. Mutations are the primary source of genetic differences among asexual prokaryotes In sexually reproducing organisms, sexual recombination is as important as mutation in creating phenotypic differences Sexual recombination creates new combinations of alleles 13-43
  • 44. Nonrandom mating occurs when only certain genotypes or phenotypes mate with one another Gene flow (gene migration) the movement of alleles between populations Continued gene flow tends to make the gene pools similar and reduce the possibility of allele frequency differences between populations 13-44
  • 45. Figure 13.13A The anatomy of Figure 13.13B Occasional cross- the garden pea (Pisum sativum) pollination between a population of ensures self-pollination and Pisum sativum and a population of nonrandom mating Pisum arvense is an example of gene flow Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. gene flow self- pollination Pisum arvense stamen stigma Pisum sativam Pisum sativum 13-45
  • 46. 13.14 The effects of genetic drift are unpredictable Genetic drift changes in the allele frequencies of a gene pool due to chance rather than selection by the environment 2 mechanisms 1. Bottleneck effect 2. Founder effect 13-46
  • 47. Small Versus Large Populations Although genetic drift occurs in populations of all sizes, a smaller population is more likely to show the effects of drift Bottleneck and Founder Effects Bottleneck effect prevents the majority of genotypes from participating in the next generation Founder effect is an example of genetic drift in which rare alleles, or combinations of alleles, occur at a higher frequency in a population isolated from the general population 13-47
  • 48. Figure 13.14A Chance events can cause allele frequency changes and genetic drift Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10% of natural disaster kills population five green frogs 20% of population 13-48
  • 49. Figure 13.14B A rare form of dwarfism that is linked to polydactylism is seen among the Amish in Pennsylvania (1/1,000 in general population, 1/14 in Amish community) 13-49
  • 50. 13.15 Natural selection can be stabilizing, directional, or disruptive Stabilizing selection Occurs when an intermediate phenotype is favored Improves adaptation of the population to those aspects of the environment that remain constant Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20 100 Percent of Births in Population 70 Percent Infant Mortality 15 50 30 Figure 13.15B Stabilizing 20 selection as exemplified by 10 10 human birth weight 7 5 5 3 2 2 3 4 5 6 7 8 9 10 13-50 Birth Weight (in pounds)
  • 51. Directional selection Occurs when an extreme phenotype is favored, and the distribution curve shifts in that direction Such a shift can occur when a population is adapting to a changing environment Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. No All guppies predation are drab and small Amount of Color Low above waterfall predation High predation below waterfall 0 4 8 12 Months a. Experimental site b. Result (a): 息 Helen Rodd Figure 13.15C Directional selection in guppies 13-51
  • 52. Disruptive selection Two or more extreme phenotypes are favored over any intermediate phenotype Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Forested Low-lying areas vegetation 息 Bob Evans/Peter Arnold/Photolibrary 13-52 Figure 13.15D Disruptive selection in snails
  • 53. Figure 13.15A Phenotype ranges before and after three types of selection Blue represents favored phenotype(s) Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Number of Individuals Phenotype Range Phenotype Range Phenotype Range a. stabilizing selection b. directional selection c. disruptive selection Number of Individuals Peak narrows. Peak shifts. Two peaks result. Phenotype Range Phenotype Range Phenotype Range 13-53
  • 54. 13.16 Stabilizing selection can help maintain the heterozygote Variations are maintained in a population for any number of reasons Mutations, gene flow, genetic drift and disruptive selection can maintain or increase variations in a population Cystic Fibrosis Recessive allele codes for defective membrane protein Northwestern European descent Typhoid fever agent can use normal version of this protein, but not the defective one to enter cells 13-54 Heterozygote superiority
  • 55. Sickle-Cell Disease Condition due to abnormal form of hemoglobin (Hb) People who are heterozygous (HbA HbS) have an advantage because they dont die from sickle-cell disease and they dont die from malaria Frequency of the HbS allele is declining among African Americans because the heterozygote has no particular advantage in US with low to no malaria 13-55
  • 56. Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Genotype Phenotype Result Dies due to HbA HbA Normal malarial infection Lives due to HbA Hbs Sickle-cell trait protection from both Hbs Hbs Sickle-cell Dies due to disease sickle-cell disease 13-56
  • 57. Figure 13.16 Sickle-cell disease is more prevalent in areas of Africa where malaria is more common Copyright 息 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. malaria sickle-cell overlap of both 13-57
  • 58. Connecting the Concepts: Chapter 13 Darwin developed theory of natural selection based on his own observations and the work of others Evolution explains the unity and diversity of life Life is unified because of common descent, and it is diverse because of adaptations to particular environments Application of principles of genetics to evolution Hardy-Weinberg equilibrium Natural selection is the only agent of evolution that results in adaptation to the environment 13-58