Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 13 How Populations Evolve

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Clown, Fool, or Simply Well Adapted? The blue-footed booby –Is a type of bird living in the Galápagos Islands

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings This type of bird possesses many specialized characteristics, called evolutionary adaptations –Which are inherited traits that enhance its ability to survive and reproduce in its particular environment

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings DARWIN’S THEORY OF EVOLUTION 13.1 A sea voyage helped Darwin frame his theory of evolution On his visit to the Galápagos Islands –Charles Darwin observed many unique organisms Figure 13.1A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Darwin’s main ideas –Can be traced back to the ancient Greeks Aristotle and the Judeo-Christian culture –Believed that species are fixed

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 North America Europe Great Britain Africa Equator Asia Australia Tasmania New Zealand PACIFIC OCEAN ATLANTIC OCEAN PACIFIC OCEAN The Galápagos Islands South America Tierra del Fuego Cape Horn Cape of Good Hope Andes Pinta Marchena Genovesa Equator Santiago Isabela Fernandina Florenza Española San Cristobal Santa Cruz Santa Fe Pinzón Daphne Islands 40 miles 40 km 0 0 Figure 13.1B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Darwin’s experiences during the voyage of the Beagle –Helped him frame his ideas on evolution

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 13.2 Darwin proposed natural selection as the mechanism of evolution Darwin observed that organisms –Produce more offspring than the environment can support –Vary in many characteristics that can be inherited

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Darwin reasoned that natural selection –Results in favored traits being represented more and more and unfavored ones less and less in ensuing generations of organisms

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Darwin found convincing evidence for his ideas in the results of artificial selection –The selective breeding of domesticated plants and animals Figure 13.2A Hundreds to thousands of years of breeding (artificial selection) Ancestral dog (wolf) Figure 13.2B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Darwin proposed that living species –Are descended from earlier life forms and that natural selection is the mechanism of evolution Thousands to millions of years of natural selection Ancestral canine African wild dogCoyote Wolf Fox Jackal Figure 13.2C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 13.3 The study of fossils provides strong evidence for evolution Fossils and the fossil record –Strongly support the theory of evolution A Skull of Homo erectus D Dinosaur tracks C Ammonite castsB Petrified tree E Fossilized organic matter of a leaf G “Ice Man” Figure 13.3A–G F Insect in amber

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The fossil record –Reveals that organisms have evolved in a historical sequence Figure 13.3H

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Many fossils link early extinct species –With species living today Figure 13.3I

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 13.4 A mass of other evidence reinforces the evolutionary view of life

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Comparative anatomy –Is the comparison of body structures in different species Homology –Is the similarity in characteristics that result from common ancestry

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Homologous structures –Are features that often have different functions but are structurally similar because of common ancestry Human CatWhale Bat Figure 13.4A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Comparative Embryology Comparative embryology –Is the comparison of early stages of development among different organisms

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Many vertebrates –Have common embryonic structures Post-anal tail Pharyngeal pouches Chick embryo Human embryo Figure 13.4B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Molecular Biology Comparisons of DNA and amino acid sequences between different organisms –Reveal evolutionary relationships Table 13.4

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 13.5 Scientists can observe natural selection in action Camouflage adaptations that evolved in different environments –Are examples of the results of natural selection A flower mantid in Malaysia A leaf mantid in Costa Rica Figure 13.5A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Development of pesticide resistance in insects –Is another example of natural selection in action Pesticide application Survivor Chromosome with gene conferring resistance to pesticide Additional applications of the same pesticide will be less effective, and the frequency of resistant insects in the population will grow Figure 13.5B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 POPULATION GENETICS AND THE MODERN SYNTHESIS

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Population genetics –Studies how populations change genetically over time The modern synthesis –Connects Darwin’s theory with population genetics

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 WebbingNo webbing Figure 13.7A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Hardy-Weinberg equilibrium –States that the shuffling of genes during sexual reproduction does not alter the proportions of different alleles in a gene pool Phenotypes GenotypesWWWw ww Number of animals (total  500) Genotype frequencies    0.04 Number of alleles in gene pool (total  1,000) Allele frequencies 800 1,000  0.8 W  0.2 w 640 W 160 W  160 w 40 w Figure 13.7B 200 1,000

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings We can follow alleles in a population –To observe if Hardy-Weinberg equilibrium exists Recombination of alleles from parent generation EGGS Genotype frequencies Allele frequencies 0.64 WW0.32 Ww 0.04 ww 0.8 W 0.2 w Next generation: W egg p  0.8 w egg q  0.2 W sperm p  0.8 w sperm q  0.2 SPERM WW p 2  0.64 Ww pq  0.16 wW qp  0.16 ww q 2  0.04 Figure 13.7C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 CONNECTION

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Genetic drift –Can cause the bottleneck effect or the founder effect Original population Bottlenecking event Surviving population Figure 13.9A Figure 13.9B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Gene flow –Is the movement of individuals or gametes between populations –Can alter allele frequencies in a population

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Natural selection –Leads to differential reproductive success in a population –Can alter allele frequencies in a population

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 CONNECTION Figure 13.10

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Variation is extensive in most populations Many populations exhibit polymorphism –Different forms of phenotypic characteristics VARIATION AND NATURAL SELECTION Figure 13.11

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Populations may also exhibit geographic variation –Variation of an inherited characteristic along a geographic continuum

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mutation and sexual recombination generate variation Mutations, or changes in the nucleotide sequence of DNA –Can create new alleles

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Sexual recombination –Generates variation by shuffling alleles during meiosis A1A1 A2A2 A1A1 A3A3 A1A1 A1A1 A2A2 A3A3 A2A2 A1A1 A3A3 and X Parents Meiosis Gametes Fertilization Offspring, with new combinations of alleles Figure 13.12

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 CONNECTION Colorized SEM 5,600  Figure 13.13

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Diploidy and balancing selection variation Diploidy preserves variation –By “hiding” recessive alleles Balanced polymorphism –May result from the heterozygote advantage or frequency-dependent selection

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Some variations may be neutral –Providing no apparent advantage or disadvantage Figure 13.14

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The perpetuation of genes defines evolutionary fitness An individual’s fitness –Is the contribution it makes to the gene pool of the next generation

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Three possible effects of natural selection Original population Stabilizing selection Original population Evolved population Frequency of individuals Phenotypes (fur color) Directional selection Disruptive selection Figure 13.16

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Sexual selection may produce sexual dimorphism Sexual selection leads to the evolution of secondary sexual characteristics –Which may give individuals an advantage in mating Figure 13.17A Figure 13.17B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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