Chapter 13 How Populations Evolve Power Point Lectures

Chapter 13 How Populations Evolve Power. Point Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero 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. 1 A 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 1830 s – Charles Darwin observed similarities between living and fossil organisms and the diversity of life on the Galápagos Islands North America Great Britain Europe Asia ATLANTIC OCEAN PACIFIC OCEAN Africa PACIFIC OCEAN Equator PACIFIC OCEAN Pinta Marchena Genovesa Equator Santiago Pinzón Fernandina Isabela Figure 13. 1 B 0 0 40 km Daphne Islands Australia Cape of Good Hope Tasmania Santa Cruz Fe Florenza 40 miles South America Andes The Galápagos Islands Cape Horn San Cristobal Tierra del Fuego Española Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings New Zealand

• 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 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 Hundreds to thousands of years of breeding (artificial selection) Ancestral dog (wolf) Figure 13. 2 A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Figure 13. 2 B

• Darwin proposed that living species – Are descended from earlier life forms and that natural selection is the mechanism of evolution African wild dog Coyote Wolf Thousands to millions of years of natural selection Figure 13. 2 C Ancestral canine Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Fox Jackal

13. 3 The study of fossils provides strong evidence for evolution • Fossils and the fossil record – Strongly support theory of evolution A Skull of Homo erectus B Petrified tree E Fossilized organic matter of a leaf Figure 13. 3 A–G Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings C Ammonite casts D Dinosaur tracks F Insect in amber G “Ice Man”

• The fossil record – Reveals that organisms have evolved in a historical sequence Figure 13. 3 H Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Many fossils link early extinct species – With species living today Figure 13. 3 I 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 • 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 Figure 13. 4 A Human Cat Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Whale Bat

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 Pharyngeal pouches Post-anal tail Human embryo Chick embryo Figure 13. 4 B 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. 5 A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

• Development of pesticide resistance in insects – Is another example of natural selection in action Chromosome with gene conferring resistance to pesticide Pesticide application Survivor Figure 13. 5 B Additional applications of the same pesticide will be less effective, and the frequency of resistant insects in the population will grow Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

POPULATION GENETICS AND THE MODERN SYNTHESIS • 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 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 Figure 13. 7 A Webbing Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings No webbing

• 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 Genotypes Number of animals (total 500) Genotype frequencies Number of alleles in gene pool (total 1, 000) Allele frequencies Figure 13. 7 B Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings WW 320 0. 64 500 640 W 800 0. 8 W 1, 000 Ww ww 160 20 160 0. 32 500 160 W 160 w 20 0. 04 500 40 w 200 0. 2 w 1, 000

• We can follow alleles in a population – To observe if Hardy-Weinberg equilibrium exists Recombination of alleles from parent generation SPERM W sperm w sperm p 0. 8 q 0. 2 WW p 2 0. 64 Ww pq 0. 16 w. W qp 0. 16 ww q 2 0. 04 W egg p 0. 8 EGGS w egg q 0. 2 Next generation: Genotype frequencies Allele frequencies Figure 13. 7 C Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 0. 64 WW 0. 8 W 0. 32 Ww 0. 04 ww 0. 2 w

• 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

CONNECTION 13. 8 The Hardy-Weinberg equation is useful in public health science • Public health scientists use the Hardy-Weinberg equation – To estimate frequencies of diseasecausing alleles in the human population 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. 9 A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Figure 13. 9 B

• 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

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

VARIATION AND NATURAL SELECTION 13. 11 Variation is extensive in most populations • Many populations exhibit polymorphism – Different forms of phenotypic characteristics 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

13. 12 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 Parents A 1 X A 2 A 3 Meiosis Gametes A 2 A 1 A 3 Fertilization Figure 13. 12 Offspring, with new combinations of alleles Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A 1 A 2 A 1 and A 3

CONNECTION 13. 13 The evolution of antibiotic resistance in bacteria is a serious public health concern • The excessive use of antibiotics Colorized SEM 5, 600 – Is leading to the evolution of antibioticresistant bacteria Figure 13. 13 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

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 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

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

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

Frequency of individuals • Three possible effects of natural selection Original population Figure 13. 16 Evolved population Stabilizing selection Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Original population Phenotypes (fur color) Directional selection Disruptive selection

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 Figure 13. 17 A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Figure 13. 17 B

13. 18 Natural selection cannot fashion perfect organisms • There 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 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings