How Populations Evolve Chapter 13 How Populations Evolve

Clown, Fool, or Simply Well Adapted? Clown, Fool, or Simply Well Adapted? The blue-footed booby bird living in the Galápagos Islands

many “specialized characteristics”: evolutionary adaptations ... ??? http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/videos/BoobiesCourtship-V.html many “specialized characteristics”: evolutionary adaptations ... ??? inherited traits, enhance its ability to survive and reproduce in particular environment

DARWIN’S THEORY OF EVOLUTION 13.1 A sea voyage helped Darwin frame his theory of evolution Galápagos Islands many unique organisms Figure 13.1A

In century prior to Darwin study of fossils suggested: life forms change Geologists proposed a very old Earth changed by gradual processes

HMS Beagle, 1830s Darwin observed North America Europe Great Britain Africa Equator Asia Australia Tasmania New Zealand PACIFIC OCEAN ATLANTIC OCEAN The Galápagos Islands South America Tierra del Fuego Cape Horn Cape of Good Hope Andes Pinta Marchena Genovesa Santiago Isabela Fernandina Florenza Española San Cristobal Santa Cruz Santa Fe Pinzón Daphne Islands 40 miles 40 km Figure 13.1B HMS Beagle, 1830s Darwin observed similarities btwn living & fossil organisms diversity of life on Galápagos Islands

His experiences during the voyage His experiences during the voyage Helped him frame his ideas on evolution http://media.pearsoncmg.com/bc/bc_campbell_essentials_3/discvids/_html/index.htm?info_text=cc5_charles_darwin

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 heritable characteristics

Darwin reasoned that natural selection Results in favored traits being represented more and more and unfavored ones less and less in future generations of organisms

Hundreds to thousands of years of breeding (artificial selection) Artificial selection supports his ideas 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

Thousands to millions of years of natural selection Darwin proposed living species descended from earlier life forms natural selection is the mechanism of evolution Thousands to millions of years of natural selection Ancestral canine African wild dog Coyote Wolf Fox Jackal Figure 13.2C

13.3 fossils: strong evidence for evolution fossil record strongly supports theory of evolution A Skull of Homo erectus D Dinosaur tracks C Ammonite casts B Petrified tree E Fossilized organic matter of a leaf G “Ice Man” Figure 13.3A–G F Insect in amber

http://media. pearsoncmg. com/bc/bc_0media_bio/bioflix/bioflix. htm http://media.pearsoncmg.com/bc/bc_0media_bio/bioflix/bioflix.htm?cc5evolution

organisms have evolved in a historical sequence Fossil record organisms have evolved in a historical sequence Figure 13.3H

Many fossils link early extinct species with species living today Figure 13.3I

13.4 A mass of other evidence reinforces the evolutionary view of life

1. Biogeography geographic distribution of species Suggests (to Darwin): organisms evolve from common ancestors Darwin: Galápagos animals Resembled species of South American mainland more than animals on similar but distant islands

2. Comparative anatomy body structures, different species Homology Similarity, results from common ancestry

Homologous structures http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/interactivemedia/activityshared/ActivityLoader.html?c6e&22&06&13C%20Reconstructing%20Forelimbs Homologous structures features often w/different functions but structurally similar because of common ancestry Human Cat Whale Bat Figure 13.4A

3. Comparative Embryology early stages of development, different organisms

Many vertebrates -- common embryonic structures Post-anal tail Pharyngeal pouches Chick embryo Human embryo Figure 13.4B Many vertebrates -- common embryonic structures

4. Molecular Biology DNA, amino acid sequences between different organisms  evolutionary relationships Table 13.4

13.5 Scientists observe natural selection in action CONNECTION 13.5 Scientists observe natural selection in action Camouflage adaptations evolved in different environments A flower mantid in Malaysia A leaf mantid in Costa Rica Figure 13.5A

Development of pesticide resistance in insects 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

1.6 review...

1.6 Evolution explains the unity and diversity of life Charles Dar win Synthesized theory of evolution by natural selection Figure 1.6A

Natural selection is an editing mechanism occurs when populations/organisms, having inherited variations, exposed to environmental factors that favor the reproductive success of some individuals over others 1 2 3 Populations with varied inherited traits Elimination of individuals with certain traits Reproduction of survivors Figure 1.6B

All organisms have adaptations have evolved by means of natural selection Killer whale Pangolin Figure 1.6C

13.12 Mutation & sexual recombination generate variation changes in nucleotide sequence of DNA Can create new alleles

shuffling alleles during meiosis  variation! http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/interactivemedia/activityshared/ActivityLoader.html?c6e&23&02&13E%20Genetic%20Variation%20from%20Sexual%20Recombination Sexual recombination shuffling alleles during meiosis  variation! A1 A2 A3 and X Parents Meiosis Gametes Fertilization Offspring, with new combinations of alleles Figure 13.12

CONNECTION 13.13 The evolution of antibiotic resistance in bacteria is a serious public health concern excessive use of antibiotics evolution of antibiotic-resistant bacteria Colorized SEM 5,600 Figure 13.13

13.15 The perpetuation of genes defines evolutionary fitness An individual’s fitness ??? contribution it makes to gene pool of next generation

13.18 Natural selection cannot fashion perfect organisms At least 4 reasons why Organisms limited by historical constraints Adaptations often compromises Chance and natural selection interact Selection can only edit existing variations

Review ?s Articles Go over Quiz

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

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

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

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 Webbing No webbing Figure 13.7A

Hardy-Weinberg equilibrium 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 WW Ww ww Number of animals (total  500) 320 160 20 500 Genotype frequencies  0.64  0.32  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

We can follow alleles in a population 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 WW 0.32 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 p2  0.64 Ww pq  0.16 wW qp  0.16 ww q2  0.04 Figure 13.7C

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

13.8 The Hardy-Weinberg equation is useful in public health science 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 disease-causing alleles in the human population

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

Can cause the bottleneck effect or the founder effect Genetic drift Can cause the bottleneck effect or the founder effect Original population Bottlenecking event Surviving population Figure 13.9A Figure 13.9B

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

Natural selection Leads to differential reproductive success in a population Can alter allele frequencies in a population

13.10 Endangered species often have reduced variation 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

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

Populations may also exhibit geographic variation Variation of an inherited characteristic along a geographic continuum

13.14 Diploidy and balancing selection variation 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

Some variations may be neutral Some variations may be neutral Providing no apparent advantage or disadvantage Figure 13.14

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

Stabilizing selection Directional selection Three possible effects of natural selection Original population Stabilizing selection Evolved population Frequency of individuals Phenotypes (fur color) Directional selection Disruptive selection Figure 13.16

13.17 Sexual selection may produce sexual dimorphism 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 13.17B Figure 13.17A