EVOLUTION. Best hypothesis:Best hypothesis: Chemical EvolutionChemical Evolution –1 billion years...

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EVOLUTIONEVOLUTION


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• Best hypothesis:Best hypothesis: • Chemical EvolutionChemical Evolution

– 1 billion years1 billion years

• Biological EvolutionBiological Evolution– 3.7 billion years3.7 billion years– prokaryotes--prokaryotes--

>eukaryotes-->eukaryotes-->diversification>diversification

How Did Life Evolve??How Did Life Evolve??


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Characteristics of KingdomsCharacteristics of Kingdoms

• ArchaebacteriaArchaebacteria• EubacteriaEubacteria

– ProkaryotesProkaryotes– single-celledsingle-celled– decomposersdecomposers– help in digestionhelp in digestion– can cause can cause

diseasesdiseases


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• ProtistaProtista

– EukaryoticEukaryotic

–one-celledone-celled

– some algaesome algae

– ponds and seaponds and sea

– some cause some cause diseasedisease



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• FungiFungi

– EukaryoticEukaryotic

– mostly mostly multicellularmulticellular

– chitin cell wallchitin cell wall

– decomposersdecomposers

– mutualismsmutualisms



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• PlantsPlants– EukaryoticEukaryotic– multicellularmulticellular– photosyntheticphotosynthetic– cellulose cell cellulose cell

wallwall– annuals and annuals and

perennialsperennials



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• AnimalsAnimals– EukaryoticEukaryotic– multicellularmulticellular– heterotrophicheterotrophic– no cell wallno cell wall– invertebrates invertebrates

and and vertebratesvertebrates



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• 5 years5 years• ObservedObserved

– FossilsFossils– BehaviorBehavior– GeologyGeology– Anat/PhysAnat/Phys– PhylogenyPhylogeny– HomologyHomology– EmbryologyEmbryology

Darwin’s VoyageDarwin’s Voyage


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• Noted subtle differences in Noted subtle differences in finches & tortoises, by island finches & tortoises, by island & compared to mainland& compared to mainland

Galapagos IslandsGalapagos Islands


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Darwinian TheoryDarwinian Theory

First event:First event: Chance VariationChance Variation (mutation)(mutation)

Second event:Second event: Natural SelectionNatural Selection

Can you think of Can you think of some examples?some examples?


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Evolution Via Natural SelectionEvolution Via Natural Selection

• Describes how Describes how populationspopulations change change over time.over time.

• Four assumption must be made:Four assumption must be made: Over-productionOver-production

VariationVariation

Limits on population growthLimits on population growth

Survival of the fittestSurvival of the fittest


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1.1. Overproduction Overproduction• More organisms are produced More organisms are produced

each generation than can surviveeach generation than can survive


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2.2. Genetic VariationGenetic Variation

• Chance Chance mutationmutation within the within the chromosomeschromosomes


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Genetic Mutations Lead to Genetic Mutations Lead to Visible Changes in PhenotypeVisible Changes in Phenotype


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3.3. Limits on Population Limits on Population GrowthGrowth

•Limiting factors such as foodLimiting factors such as food


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4. 4. Survival of Survival of the Fittestthe Fittest


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Individuals that are Individuals that are best-best-suitedsuited to the environment to the environment produce produce more offspringmore offspring


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Individuals that are Individuals that are poorly-poorly-suitedsuited to the environment to the environment

produce produce less offspringless offspring


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A A PopulationPopulation Changes Over TimeChanges Over Time


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• Lyell (Geologist)Lyell (Geologist)– Earth was ancient & Earth was ancient &

ever- ever- changingchanging

Influences on Darwin’s TheoryInfluences on Darwin’s Theory


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• Smith (fossil strata)Smith (fossil strata)



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• Malthus Malthus (Economist)(Economist)

–““Survival of the Survival of the Fittest”Fittest”

• Political & Political & Philosophical Philosophical RenaissanceRenaissance



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MicroevolutionMicroevolution• SmallSmall genetic changes in a genetic changes in a

populationpopulation• Change in frequency of a Change in frequency of a single single

alleleallele due to due to selectionselection


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MacroevolutionMacroevolution• Large-scale changes in Large-scale changes in

organismsorganisms• Involves Involves new new generagenera


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• Considered separate species Considered separate species if they if they cannot interbreedcannot interbreed (or (or are reproductively isolated)are reproductively isolated)

What is a Species?What is a Species?


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How Many Species How Many Species AreAre There?There?

• 1.751.75 million currently million currently describeddescribed

• Probably Probably 13-14 million13-14 million species species

– most of those undiscovered most of those undiscovered are insects, fungi and bacteriaare insects, fungi and bacteria

• 70% of 70% of knownknown species are species are invertebrates (probably invertebrates (probably 95%95% of of all species)all species)


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Species VariabilitySpecies Variability

• Natural selection Natural selection tends to tends to PRESERVE PRESERVE variabilityvariability to make to make sure that there are sure that there are enough alleles enough alleles around to be ready around to be ready for environmental for environmental changes in the changes in the future.future.


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Latent VariabilityLatent Variability

• May show up in May show up in artificial breedingartificial breeding (breeding for a (breeding for a larger size of larger size of cattle, corn, etc.)cattle, corn, etc.)


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How are New Species How are New Species Maintained?Maintained?


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• GeographicGeographic– Substrate, islands: they never meetSubstrate, islands: they never meet

• TemporalTemporal– Breed in different seasons, time of dayBreed in different seasons, time of day

• BehavioralBehavioral– Courtship differs: not attractiveCourtship differs: not attractive

• AnatomicalAnatomical– Parts don’t match any moreParts don’t match any more

• GameticGametic–Zygotes die or infertile offspringZygotes die or infertile offspring

Isolating MechanismsIsolating Mechanisms


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Speciation by IsolationSpeciation by Isolation


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Specia-Specia-tion tion without without IsolationIsolation


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Adaptive RadiationAdaptive Radiation


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Problem With “Species” Problem With “Species” Definition:Definition:

If they never have the If they never have the opportunity to interbreed, opportunity to interbreed, how do you know if they how do you know if they can?can?


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Development of a Development of a Reproductive Isolating Reproductive Isolating

MechanismMechanism


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What if they breed, but don’t What if they breed, but don’t produce viable offspring? produce viable offspring? (mules)(mules)


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What About What About AsexuallyAsexually Reproducing Species?Reproducing Species?


SAVANNASSAVANNAS• DirectionalDirectional

• StabilizingStabilizing

• DiversifyingDiversifying

Types of Natural SelectionTypes of Natural Selection


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• CenterCenter are the only are the only ones to reproduceones to reproduce

• Individuals Individuals look more look more similarsimilar over time over time

• Mean does not Mean does not changechange

• Range Range narrowsnarrows

Stabilizing SelectionStabilizing Selection


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• EndsEnds are the only ones are the only ones to reproduceto reproduce

• Produces 2 separate Produces 2 separate phenotypesphenotypes

• Mean does not change Mean does not change (but few individuals at (but few individuals at mean)mean)

• Range Range increasesincreases

Disruptive SelectionDisruptive Selection


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• Just one sideJust one side reproducereproduce

• Population looks Population looks different over timedifferent over time

• Mean Mean changeschanges

• Range Range does not does not changechange

Directional SelectionDirectional Selection


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Co-EvolutionCo-Evolution

• Evolved from more negative Evolved from more negative associationsassociations

• Organism impacted Organism impacted had two options:had two options:–escapeescape relationship relationship–or adapt to it: or adapt to it: make make

it self- advantageousit self- advantageous


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• Ant and Aphid

• Ant protects aphids eggs, feeds larva, tends them, keeps them safe

• Aphid supplies the ant with food

• “honeydew” it secretes from it’s body

Example of Co-EvolutionExample of Co-Evolution


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• Gene poolGene pool has always had 2 color has always had 2 color variationsvariations– Common Common gray mothsgray moths and very rare and very rare dark dark

mothsmoths..

Peppered Moth Peppered Moth Case StudyCase Study


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• Soot from industrialization fell on Soot from industrialization fell on trees, trees, killing gray lichenskilling gray lichens on tree on tree barkbark

• Over the years, populations of Over the years, populations of dark dark mothsmoths increased in cities, while the increased in cities, while the gray mothsgray moths predominated predominated in the country in the country

• WHY???WHY???

Peppered Moth Peppered Moth Case StudyCase Study


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Anne F. MabenAnne F. Maben

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EVOLUTION. Best hypothesis:Best hypothesis: Chemical EvolutionChemical Evolution –1 billion years...

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