Principles Evolution APBioCh13-14

Chapter 14Chapter 14

Principles of Principles of EvolutionEvolution

Chapter 14 2

Evolution of Evolutionary ThoughtEvolution of Evolutionary ThoughtDevelop time line of historical eventsDevelop time line of historical events• 427-347 B.C. Plato’s divinely inspired “ideal form” 427-347 B.C. Plato’s divinely inspired “ideal form” • 384-322 B.C. Aristotle’s “Ladder of Nature”384-322 B.C. Aristotle’s “Ladder of Nature”• until 1700s Creationismuntil 1700s Creationism

– Each species was created individually by GodEach species was created individually by God– Earth was the center of the universeEarth was the center of the universe– Man stood atop creationMan stood atop creation

Exploration of New LandsExploration of New Lands• Number of species was greater than expectedNumber of species was greater than expected• Some species closely resembled one anotherSome species closely resembled one another• Some naturalists concluded that similar species Some naturalists concluded that similar species

may have developed from a common ancestormay have developed from a common ancestor

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Evolution of Evolutionary Thought IEvolution of Evolutionary Thought I

1707-1788 George LeClerc (Comte of Buffon);1707-1788 George LeClerc (Comte of Buffon); creation provided a relatively small creation provided a relatively small number of founding species that evolved number of founding species that evolved through natural processesthrough natural processes

Idea was not acceptedIdea was not accepted• Did not provide a mechanism for evolutionDid not provide a mechanism for evolution• Earth was not old enough to allow time for Earth was not old enough to allow time for

the process of evolutionthe process of evolution1769-1832 G. Cuvier; theory of 1769-1832 G. Cuvier; theory of catastrophism (creationist w/extinction)catastrophism (creationist w/extinction)

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Evolution of Evolutionary Thought IIIEvolution of Evolutionary Thought III

1726-1797 James Hutton developed 1726-1797 James Hutton developed uniformitarianism – gradual changeuniformitarianism – gradual change

1797-1875 Charles Lyell’s “Old Earth 1797-1875 Charles Lyell’s “Old Earth Hypothesis” supported Hutton, gave time Hypothesis” supported Hutton, gave time for gradual change for gradual change (Archbishop James Ussher calculated the date of the creation (Archbishop James Ussher calculated the date of the creation of the Earth…Oct 23, 4004BC…using biblical lineages.)of the Earth…Oct 23, 4004BC…using biblical lineages.)

1744-1829 Jean Baptiste de Lamarck - 1744-1829 Jean Baptiste de Lamarck - inheritance of acquired characteristics inheritance of acquired characteristics (‘cuz (‘cuz if you are gonna be wrong…do it spectacularly!’)if you are gonna be wrong…do it spectacularly!’)

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Evolution of Evolutionary Thought IVEvolution of Evolutionary Thought IV

1809-1882 Charles Darwin1809-1882 Charles Darwin• Developed the theory of evolutionDeveloped the theory of evolution

– Species evolved through natural selection;Species evolved through natural selection;– Adaptation to their ever-changing environment.Adaptation to their ever-changing environment.

1823-1913 Alfred Wallace; supported 1823-1913 Alfred Wallace; supported Darwin's theory (worked separately, came Darwin's theory (worked separately, came up with same conclusion, came in “2up with same conclusion, came in “2nd”nd”))

Present theory of evolution by natural Present theory of evolution by natural selectionselection

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Darwin’s FinchesDarwin’s Finches

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EVOLUTION:The genetic makeup of the

population changes over time, driven by natural selection

NATURAL SELECTIONOn average, the fittest

organisms leavethe most offspring

Competition for survival and reproduction

A Flowchart ofA Flowchart ofEvolutionary ReasoningEvolutionary Reasoning

Potential forrapid reproduction

Relatively constantresources and

population over time

Variability instructures and

behaviors

Some variability is inherited

(observations)

(conclusions)

Chapter 14 8 Evolution by Natural SelectionEvolution by Natural Selection

Postulate 1:Postulate 1: Individual members of a Individual members of a population differ from one another in population differ from one another in many respects many respects • Variations arise purely by chance Variations arise purely by chance

resulting from random mutations in DNA resulting from random mutations in DNA • Differences are obvious in many Differences are obvious in many

physical characteristics and extend to physical characteristics and extend to molecular levelmolecular level

Chapter 14 9


Postulate 2: Postulate 2: At least some of the At least some of the differences among members of a differences among members of a population are due to characteristics population are due to characteristics that may be passed from parent to that may be passed from parent to offspringoffspring• However, the mechanism of inheritance However, the mechanism of inheritance

was not understood at this point in time was not understood at this point in time (Mendel was working at about the same (Mendel was working at about the same time…and was ignored until someone time…and was ignored until someone saw that Mendel and Darwin/Wallace saw that Mendel and Darwin/Wallace supported each other.)supported each other.)

Chapter 14 11

Evolution by Natural SelectionEvolution by Natural Selection

Postulate 3:Postulate 3: In each generation, some In each generation, some individuals in a population survive and individuals in a population survive and reproduce successfully but others do reproduce successfully but others do notnot• Darwin observed that many more Darwin observed that many more

individuals are born than surviveindividuals are born than survive• Some individuals have more offspring Some individuals have more offspring

than others than others


Postulate 4:Postulate 4: Individuals with Individuals with advantageous traits survive longest advantageous traits survive longest and leave the most offspring, a and leave the most offspring, a process known as process known as natural selectionnatural selection


Gregor Mendel’s theories of inheritance Gregor Mendel’s theories of inheritance (1865) confirmed Darwin’s (1865) confirmed Darwin’s assumption that certain traits are assumption that certain traits are heritableheritable

New variations arise by chance as a New variations arise by chance as a result of random mutations in DNAresult of random mutations in DNA

New variations may be good, bad, or New variations may be good, bad, or neutralneutral

Chapter 14 14 Populations EvolvePopulations Evolve

Natural selection acts on individuals Natural selection acts on individuals within a population; however, it is the within a population; however, it is the population that changes over timepopulation that changes over time

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Evidence of Evolution:Evidence of Evolution:FossilsFossils

Transitional forms are evidence of evolutionary Transitional forms are evidence of evolutionary changechange

Fossils of ancient species tend to be simpler in Fossils of ancient species tend to be simpler in form than modern speciesform than modern species

Several series of fossils have been found that Several series of fossils have been found that exhibit the evolution of body structures over exhibit the evolution of body structures over timetime

Interpretation of fossil data controversialInterpretation of fossil data controversial

• Dating of fossilsDating of fossils

• Do fossils really show transitional forms?Do fossils really show transitional forms?

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Information from Fossils?Information from Fossils?

Chapter 14 17

Fossils of Extinct OrganismsFossils of Extinct Organisms

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Evidence of Evolution:Evidence of Evolution:Comparative…Comparative…

……AnatomyAnatomy• Homologous structuresHomologous structures

– structures that have the same evolutionary origin structures that have the same evolutionary origin despite their current appearance or functiondespite their current appearance or function

• Analogous structuresAnalogous structures– structures that are outwardly similar in structures that are outwardly similar in

appearance, but differ in their evolutionary originappearance, but differ in their evolutionary origin• Vestigial structuresVestigial structures

– remnants of structures that are inherited from remnants of structures that are inherited from ancestorsancestors

– Had important functions in ancestorsHad important functions in ancestors– Serve no obvious purpose in present day Serve no obvious purpose in present day

organismorganism

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Analogous StructuresAnalogous Structures

NotNot homologous; homologous;notnot analogous analogous

Homologous;Homologous;notnot analogous analogous

NotNot homologous; homologous;analogousanalogous

Homologous;Homologous;analogousanalogous

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Homologous StructuresHomologous Structures

FlyingFlying SwimmingSwimming RunningRunning GraspingGrasping

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Vestigial StructuresVestigial Structures

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……EmbryologyEmbryology• Early vertebrate embryos similarEarly vertebrate embryos similar• Tail and gill archesTail and gill arches

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Comparative EmbryologyComparative Embryology

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……Biochemistry & molecular biologyBiochemistry & molecular biology• All have DNA, RNA, ribosomes, ATP, etc.All have DNA, RNA, ribosomes, ATP, etc.• DNA similaritiesDNA similarities

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How Organisms How Organisms EvolveEvolve

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Population Genetics andPopulation Genetics andEvolution IEvolution I

Gene pools and allele frequenciesGene pools and allele frequencies

Evolution: Change in gene frequenciesEvolution: Change in gene frequencies

• Due to differential reproduction among Due to differential reproduction among organisms bearing different allelesorganisms bearing different alleles

• Fitness of the selected allele leads to viable Fitness of the selected allele leads to viable offspringoffspring

• Evolutionary changes are not "good" or Evolutionary changes are not "good" or "progressive" in any absolute sense"progressive" in any absolute sense

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Population Genetics andPopulation Genetics andEvolution IIEvolution II

Natural selection causes changes in gene Natural selection causes changes in gene frequencies of a populationfrequencies of a population• Does not genetically change individuals!Does not genetically change individuals!• Affects individuals, but Affects individuals, but evolution occurs in evolution occurs in

populationspopulationsMutations: Source of new alleles Mutations: Source of new alleles Sexual reproduction produces new Sexual reproduction produces new combinations of allelescombinations of alleles• Crossing over in meiosisCrossing over in meiosis• Random fertilization of gametesRandom fertilization of gametes

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Mechanisms of Evolution IMechanisms of Evolution IThe hypothetical equilibrium populationThe hypothetical equilibrium population• Hardy-Weinberg equilibrium Hardy-Weinberg equilibrium For a population to be at equilibrium, 5 For a population to be at equilibrium, 5

conditions MUST be true…conditions MUST be true…1.1. No MutationsNo Mutations2.2. No Migration/Emigration (gene flow)No Migration/Emigration (gene flow)3.3. Large population size Large population size 4.4. Random MatingRandom Mating5.5. No Natural SelectionNo Natural Selection……this would mean there is NO Evolution!this would mean there is NO Evolution!

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Genetic DriftGenetic Drift

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Genetic BottlenecksGenetic BottlenecksReduce VariabilityReduce Variability

TimeTimeTimeTime

Chance loss of blueChance loss of blue

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Mechanisms of Evolution IIMechanisms of Evolution II

Nonrandom mating and sexual selectionNonrandom mating and sexual selection

Natural selectionNatural selection

• Types of natural selectionTypes of natural selection

– Directional selectionDirectional selection

– Stabilizing selectionStabilizing selection

– Disruptive selectionDisruptive selection

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Types of Natural SelectionTypes of Natural SelectionLarge SizeLarge SizeFavoredFavored

Large SizeLarge SizeFavoredFavored

DirectionalDirectionalSelectionSelection

DirectionalDirectionalSelectionSelection

Average SizeAverage SizeFavoredFavored

Average SizeAverage SizeFavoredFavored

StabilizingStabilizingSelectionSelectionStabilizingStabilizingSelectionSelection

Extreme SizeExtreme SizeFavoredFavored

Extreme SizeExtreme SizeFavoredFavored

DisruptiveDisruptiveSelectionSelectionDisruptiveDisruptiveSelectionSelection

VariationVariationreducedreduced

over timeover time

VariationVariationreducedreduced

over timeover time

MeanMeanchangedchangedover timeover time

MeanMeanchangedchangedover timeover time

VariationVariationbecomesbecomespolarizedpolarized

VariationVariationbecomesbecomespolarizedpolarized

BeforeBeforeSelectionSelection

AfterAfterSelectionSelection

Tim

e

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Forces of Natural SelectionForces of Natural Selection

Abiotic factors (environmental changes!)Abiotic factors (environmental changes!)

Biotic factorsBiotic factors• Coevolution - constant mutual feedback Coevolution - constant mutual feedback

between two speciesbetween two species– Competition for limited resourcesCompetition for limited resources– PredationPredation– Symbiosis Symbiosis – Parasitism, commensalism, and mutualismParasitism, commensalism, and mutualism

Altruism - self-sacrificeAltruism - self-sacrifice

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Causes of ExtinctionCauses of ExtinctionLocalized distribution (i.e. all in one place)Localized distribution (i.e. all in one place)

Overspecialization (i.e. can only eat one thing)Overspecialization (i.e. can only eat one thing)

Environmental changesEnvironmental changes• Competition for limited resourcesCompetition for limited resources• Predators and parasites cause diseasesPredators and parasites cause diseases• Habitat destructionHabitat destruction

– DeforestationDeforestation– MeteoritesMeteorites– FiresFires– Volcanic eruptionsVolcanic eruptions

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Stabilizing Selection &Stabilizing Selection &Balance PolymorphismBalance Polymorphism

HH

HH

Hh

Hh

Hh

hh

hh

hh

Dies of malariaDies of malaria

HH

Lives and Lives and reproducesreproduces

Dies ofDies ofsickle-cell anemiasickle-cell anemia

Dies of malariaDies of malaria Lives and Lives and reproducesreproduces

Dies ofDies ofsickle-cell anemiasickle-cell anemia

HomozygousHomozygousNormalNormal

HomozygousHomozygousDefectiveDefectiveHeterozygousHeterozygous


The endThe end

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Principles Evolution APBioCh13-14