1 evolution unit chapters 10 and 11. 2 history of evolutionary thought copyright cmassengale

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Evolution Evolution UnitUnit

Chapters 10 and 11Chapters 10 and 11

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History of History of Evolutionary Evolutionary

ThoughtThought

copyright cmassengale

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Evolutionary TimelineEvolutionary Timeline


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Early Ideas On Earth’s Early Ideas On Earth’s OrganismsOrganisms

Linnaeus Linnaeus – 1– 1stst to to group similar group similar organisms and organisms and assign them assign them LatinLatin names names

Two word name Two word name (Genus species)(Genus species)

Known as Known as Binomial Binomial nomenclature nomenclature


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:

Contributor’s to Darwin’s Contributor’s to Darwin’s thinking included:thinking included:

Leclerc de Buffon – Leclerc de Buffon – proposed proposed that species shared ancestors that species shared ancestors instead of arising separately instead of arising separately

Erasmus Darwin – Erasmus Darwin – organisms organisms could evolve from a common could evolve from a common ancestorancestor


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:

Contributor’s to Darwin’s Contributor’s to Darwin’s thinking included:thinking included:

Cuvier – Cuvier – CatastrophismCatastrophism– Stated that species disappear due to a Stated that species disappear due to a

catastrophic event catastrophic event of the earth’s crust of the earth’s crust (volcano, earthquake…)(volcano, earthquake…)

Hutton – Hutton – GradualismGradualism– Changes on Earth formed as product of Changes on Earth formed as product of slow slow

but continuousbut continuous and cumulative processes and cumulative processes


Contributor’s to Contributor’s to Darwin’s thinking Darwin’s thinking

included:included: Charles Lyell –Charles Lyell –UniformitarianismUniformitarianism

– Geologic processes that shape the Geologic processes that shape the Earth are uniform through time Earth are uniform through time

Alfred Wallace Alfred Wallace – organisms evolved from common organisms evolved from common

ancestorsancestors

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Lamarck’s Theory of Lamarck’s Theory of EvolutionEvolution

Was first scientist to Was first scientist to recognize that organisms recognize that organisms have changed over timehave changed over time

Stated that changes are Stated that changes are adaptations to adaptations to environment environment acquired in acquired in an organism’s lifetimean organism’s lifetime

Said acquired changes Said acquired changes were passed to offspringwere passed to offspring


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Law of Use and Disuse– Organisms Could Organisms Could

Change The Size Or Change The Size Or Shape Of Organs By Shape Of Organs By Using Them Or Not Using Them Or Not Using ThemUsing Them

– If a body part were If a body part were used, it got strongerused, it got stronger

– If body part NOT If body part NOT used, it deterioratedused, it deterioratedcopyright cmassengale

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Inheritance of Acquired Inheritance of Acquired CharacteristicsCharacteristics– idea that an organism can pass on

characteristics that it acquired during its lifetime to its offspring

– Over Time This Led To New Species


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Lamarck’s MistakesLamarck’s Mistakes

Lamarck’s theories were INCORRECT!

Lamarck Did NOT Know how traits were inherited (Traits are passed through genes)– Genes Are NOT Changed By Activities In Life

– Change Occurs Through Mutations Before An Organism Is Born


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Charles Darwin Charles Darwin the Naturalistthe Naturalist


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Voyage of the BeagleVoyage of the Beagle

Charles DarwinCharles Darwin Joined Crew of HMS Beagle, Joined Crew of HMS Beagle,

18311831 NaturalistNaturalist 5 Year Voyage around world5 Year Voyage around world Become known as the Become known as the

“Father of Evolution”“Father of Evolution” Astounded By Variety of Astounded By Variety of

LifeLife Wrote “The Origin of Wrote “The Origin of

Species”Species”


15A reconstruction of the HMS Beagle sailing off Patagonia.A reconstruction of the HMS Beagle sailing off Patagonia.

Darwin’s Voyage of Darwin’s Voyage of DiscoveryDiscovery


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Darwin Left England in Darwin Left England in 18311831

Darwin returned 5 years later in 1836Darwin returned 5 years later in 1836copyright cmassengale

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HMS Beagle’s VoyageHMS Beagle’s Voyage


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The Galapagos The Galapagos IslandsIslands

Small Group of Islands West of Small Group of Islands West of South AmericaSouth America

Very Different ClimatesVery Different Climates Animals On Islands UniqueAnimals On Islands Unique

»TortoisesTortoises»IguanasIguanas»FinchesFinches


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Volcanic islands off Volcanic islands off the coast of South the coast of South AmericaAmerica

Island species Island species varied from varied from mainland species & mainland species & from island-to-from island-to-island speciesisland species

Each island had Each island had long or short neck long or short neck tortoisestortoises


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Finches on the islands Finches on the islands resembledresembled a mainland fincha mainland finch

More types of finches appeared More types of finches appeared on the islands where the on the islands where the available food was different available food was different (seeds, nuts, berries, insects…)(seeds, nuts, berries, insects…)

Finches had Finches had different types of different types of beaksbeaks adapted to their adapted to their type of type of food gatheringfood gathering


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Darwin’s Darwin’s Observations & Observations &

ConclusionsConclusions


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Voyage of the BeagleVoyage of the Beagle

– During His Travels, Darwin During His Travels, Darwin Made Numerous Made Numerous Observations And Observations And Collected Evidence That Collected Evidence That Led Him To Propose A Led Him To Propose A RevolutionaryRevolutionary Hypothesis Hypothesis About The Way Life About The Way Life Changes Over TimeChanges Over Time


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Darwin’s ObservationsDarwin’s Observations Patterns of Patterns of

Diversity were Diversity were shownshown

Unique Unique Adaptations in Adaptations in organismsorganisms

Species Not Evenly Species Not Evenly DistributedDistributed

» Australia, Australia, Kangaroos, but Kangaroos, but No RabbitsNo Rabbits

» S. America, S. America, LlamasLlamas


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DefinitioDefinitionn

• Evolution is the gradual change in a population of organisms over time


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Darwin’s ObservationsDarwin’s Observations

Left unchecked, the number of organisms of each species will increase exponentially, generation to generation

In nature, populations tend to remain stable in size

Environmental resources are limited.


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Darwin’s ConclusionDarwin’s Conclusion• Production of more

individuals than can be supported by the environment leads to a struggle for existence among individuals

• Only a fraction of offspring survive each generation

• Survival of the Fittest


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Darwin’s ObservationsDarwin’s Observations• Individuals of a

population vary extensively in their characteristics with no two individuals being exactly alike.

• Much of this variation between individuals is inheritable. copyright cmassengale

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Darwin’s ConclusionDarwin’s Conclusion Individuals who inherit characteristics Individuals who inherit characteristics

most fit for their environmentmost fit for their environment are likely are likely to reproduce more offspring than less fit to reproduce more offspring than less fit individuals.individuals.

The The unequal ability of individuals to unequal ability of individuals to survive and reproduce survive and reproduce leads to a gradual leads to a gradual change in a population, with favorable change in a population, with favorable characteristics accumulating over characteristics accumulating over generations.generations.

This is called This is called Natural SelectionNatural Selectioncopyright cmassengale

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Darwin’s Theory of Darwin’s Theory of EvolutionEvolution

Organisms Change Over Organisms Change Over TimeTime


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Natural Selection Driving force Driving force for for

evolutionevolution During the struggle for During the struggle for

resources, the strongest resources, the strongest survive & reproducesurvive & reproduce

Idea that at least some Idea that at least some of the differences of the differences between individuals, between individuals, which impact their which impact their survival and fertility, survival and fertility, are are inheritable inheritable

Therefore, natural Therefore, natural selection acts upon selection acts upon mutationsmutations..


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Origin of SpeciesOrigin of Species

Darwin Presents His Darwin Presents His CaseCase


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Publication of “On The Publication of “On The Origin of Species”Origin of Species”

Upon His Return To England, Upon His Return To England, Darwin Developed His Darwin Developed His Observations Into The Theory of Observations Into The Theory of EvolutionEvolution

But He But He Did Not Publish For Did Not Publish For 25 Years25 Years – –

Why?Why?copyright cmassengale

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Publication of “The Origin of Publication of “The Origin of Species”Species”

Darwin Knew That His Theory Darwin Knew That His Theory Would Be Would Be Extremely Extremely Controversial Controversial And Would Be And Would Be AttackedAttacked

His Theory His Theory Challenged Challenged Established Religious & Established Religious & Scientific BeliefsScientific Beliefs


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Publication of “On The Publication of “On The Origin of Species”Origin of Species”

He Refused To Publish He Refused To Publish Until He Received An Essay Until He Received An Essay From From Alfred WallaceAlfred Wallace– Fellow NaturalistFellow Naturalist– Independently Developed Independently Developed

The Same TheoryThe Same Theory– After 25 Years, Someone After 25 Years, Someone

Else Had Come To The Else Had Come To The Same Conclusions From Same Conclusions From Their Observations Of Their Observations Of NatureNature


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Wallace’s Wallace’s ContributionContribution

• Alfred Wallace:Alfred Wallace:• Independently came Independently came

to same Conclusion to same Conclusion as Darwin that as Darwin that species changed over species changed over time because of their time because of their struggle for existencestruggle for existence

• When Darwin read When Darwin read Wallace’s essay, he Wallace’s essay, he knew he had to publish knew he had to publish his findingshis findings


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Natural Variation and Natural Variation and Artificial SelectionArtificial Selection

Abandoned The Idea That Abandoned The Idea That Species Were Perfect & Species Were Perfect & UnchangingUnchanging

Observed Significant Variation Observed Significant Variation in All Species Observedin All Species Observed

Observed Farmers Use Variation Observed Farmers Use Variation To Improve Crops & Livestock To Improve Crops & Livestock – Called Called Selective BreedingSelective Breeding


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Natural VariationNatural Variation– Differences Among Differences Among

Individuals Of A SpeciesIndividuals Of A Species Artificial SelectionArtificial Selection

– Selective Breeding To Selective Breeding To Enhance Desired Traits Enhance Desired Traits Among Stock or CropsAmong Stock or Crops


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Key Concept:Key Concept:

In In Artificial SelectionArtificial Selection,, Nature Provided The Nature Provided The Variation Among Different Variation Among Different Organisms, And Humans Organisms, And Humans Selected Those Variations Selected Those Variations That They Found That They Found UsefulUseful


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Evolution by Evolution by Natural Selection Natural Selection

ConceptsConcepts


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Four Main Principles of Four Main Principles of Natural SelectionNatural Selection

Genetic VariationGenetic Variation OverpopulationOverpopulation AdaptationAdaptation Descent with ModificationDescent with Modification

Genetic VariationGenetic Variation

Genetic VariationGenetic Variation– Variations come from mutations Variations come from mutations

and gene shuffling that result and gene shuffling that result from sexual reproduction.from sexual reproduction.

– In genetics terms, evolution is In genetics terms, evolution is any change in allele frequency in any change in allele frequency in a population.a population.

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OverpopulationOverpopulation

OverproductionOverproduction:: Organisms Organisms reproduce more than its reproduce more than its environment can handle.environment can handle. – Overproduction leads to Overproduction leads to competitioncompetition– CompetitionCompetition: the struggle for : the struggle for

existenceexistence» Organisms compete for food, living Organisms compete for food, living

space, and reproduction. space, and reproduction.

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AdaptationAdaptation AdaptationAdaptation

– Inherited Characteristic That Inherited Characteristic That Increases an Organisms Chance for Increases an Organisms Chance for SurvivalSurvival

Examples of AdaptationsExamples of Adaptations– MimicryMimicry: one species mimics (imitates) the : one species mimics (imitates) the

color, pattern, or behavior of another in color, pattern, or behavior of another in order to gain protectionorder to gain protection

– CamouflageCamouflage: a species’ ability to conceal : a species’ ability to conceal itself from its predators by blending into its itself from its predators by blending into its environment.environment.

MimicryMimicry

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• Another example of mimicry involves the monarch butterfly, which is toxic and very nasty when eaten. Its bright orange coloration is a warning to birds to leave it alone. The non-toxic viceroy butterfly has developed colors and wing patterns that are very similar to those of the monarch and so most birds won’t take a chance by taste-testing it!

Which is the poisonous snake??

CamouflageCamouflage

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Descent with ModificationDescent with Modification Darwin proposed that Darwin proposed that

organisms descended organisms descended from from common common ancestorsancestors

Idea that organisms Idea that organisms change with time, change with time, diverging from a diverging from a common formcommon form

Caused Caused evolution of evolution of new species new species with with better adaptations better adaptations

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Survival of the FittestSurvival of the Fittest FitnessFitness

– Ability of an Individual To Survive Ability of an Individual To Survive & Reproduce& Reproduce

– Fitness is central to the process of Fitness is central to the process of evolutionevolution

Individuals With Low FitnessIndividuals With Low Fitness– Either Die or Produce Few Either Die or Produce Few

OffspringOffspring

Survival of the FittestSurvival of the Fittest

AKA AKA Natural SelectionNatural Selection

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Survival of the FittestSurvival of the Fittest

Key ConceptOver Time, Natural Over Time, Natural Selection Results In Selection Results In Changes In The Inherited Changes In The Inherited Characteristics Of A Characteristics Of A Population. These Changes Population. These Changes Increase A Species Fitness Increase A Species Fitness In Its EnvironmentIn Its Environment

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Theory of Evolution Theory of Evolution TodayToday

Supporting Supporting EvidenceEvidence


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Evidence of EvolutionEvidence of Evolution Darwin Argued That Living Things Darwin Argued That Living Things

Have Been Evolving On Earth For Have Been Evolving On Earth For Millions of YearsMillions of Years. Evidence For . Evidence For

This Process Could Be Found In:This Process Could Be Found In:– The The Fossil RecordFossil Record– The The Geographical DistributionGeographical Distribution of of

Living SpeciesLiving Species– Anatomical StructuresAnatomical Structures of Living of Living

OrganismsOrganisms– Similarities In Similarities In Early DevelopmentEarly Development


Fossil RecordFossil Record

Fossils In Different Layers of Fossils In Different Layers of Sedimentary Rock Sedimentary Rock showed evidence of showed evidence of gradual change over timegradual change over time

FossilFossil: preserved remains of ancient : preserved remains of ancient organismsorganisms

Fossil RecordFossil Record: provides evidence : provides evidence about the history of life on Earthabout the history of life on Earth– Most fossils form in sedimentary Most fossils form in sedimentary

rockrock

____________________________________________ Fossils that are found in a lower layer are Fossils that are found in a lower layer are

older than fossils that are found in a higher older than fossils that are found in a higher stratastrata

FossilsFossils

Radioactive (Radiometric) datingRadioactive (Radiometric) dating– Technique used to calculate age of fossils Technique used to calculate age of fossils

based on the amount of remaining based on the amount of remaining radioactive isotopes it containsradioactive isotopes it contains»Age of fossil is based on half-livesAge of fossil is based on half-lives

Half lifeHalf life: length of time required for : length of time required for half of the radioactive atoms in a half of the radioactive atoms in a sample to decaysample to decay

Half-life Practice Half-life Practice ProblemsProblems What percentage of a radioactive

element will be left after:– a. 1 half-life b. 2 half-lives c. 3 half-lives

If a rock sample originally contained 12 g of Uranium-235, how much will be left after:– a. 1 half-life b. 2 half-lives c. 3 half-lives

Gold-198 has a half-life of 2.7 days. How much of a 96 g sample of gold-198 will be left after 8.1 days?

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Comparative AnatomyComparative Anatomy


Homologous Structures: Same structure with a different function

Comparative AnatomyComparative Anatomy

Analogous Structures: Different structures that have the same function


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Comparative AnatomyComparative Anatomy Vestigial Organs: Remnants of

structures that were functional in ancestral species– Organs or structures that have lost Organs or structures that have lost

their function in the organism and their function in the organism and have become reduced in size have become reduced in size

– Modern animals may have structures that serve little or no function»Example: Appendix In Man

Eyes on a cave fish (blind)

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Comparative Embryology Comparative embryologyComparative embryology:: comparing comparing

the formation and development of the formation and development of embryos embryos – EmbryoEmbryo – early stages of vertebrate – early stages of vertebrate

developmentdevelopment Early stages of development in many Early stages of development in many

vertebrates are very similarvertebrates are very similar– Same development orderSame development order– Similar tissues and organ structure such as Similar tissues and organ structure such as

gills and a tailgills and a tail– Similar features in young embryos suggest

evolution from a distant common ancestor

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A B C D E F G H

BiochemistryBiochemistry All living things are biochemically All living things are biochemically

similar.similar. Similarities in Similarities in amino acid amino acid

sequences sequences can determine can determine relatedness.relatedness.

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Geographic Distribution Geographic Distribution of Living Speciesof Living Species

Biogeography:Biogeography:– Different Animals Different Animals

On Different On Different Continents But Continents But Similar Similar Adaptations To Adaptations To Shared Shared EnvironmentsEnvironments


3 Ways Natural Selection 3 Ways Natural Selection Affects Phenotype Affects Phenotype

DistributionDistribution

1.1. Directional SelectionDirectional Selection

2.2. Stabilizing SelectionStabilizing Selection

3.3. Disruptive SelectionDisruptive Selection

Directional SelectionDirectional Selection Individuals at one end of a distribution Individuals at one end of a distribution

curve have a higher fitness than curve have a higher fitness than individuals in the middle or at the other individuals in the middle or at the other endend– In diagram, birds w/ big beaks have In diagram, birds w/ big beaks have

higher fitnesshigher fitnessDirectional Selection

Directional SelectionFood becomes scarce.

Low mortality, high fitness

High mortality, low fitness

Directional Selection

Food becomes scarce.

Key



Stabilizing SelectionStabilizing Selection Individuals near Individuals near

the center of the the center of the curve have curve have higher fitness higher fitness than individuals than individuals at either endat either end– In this diagram, In this diagram,

birds w/ median birds w/ median birth weight have birth weight have higher fitness higher fitness than heavy or than heavy or light weight birdslight weight birds

Stabilizing SelectionKey

Per

cen

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f P

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Birth Weight

Selection against both

extremes keep curve narrow and in same

place.



Stabilizing Selection

Per

cen

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f P

op

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Birth Weight

Selection against both

extremes keep curve narrow and in same

place.



Stabilizing SelectionKey

Disruptive SelectionDisruptive Selection Individuals at the upper and lower Individuals at the upper and lower

ends of the curve have higher ends of the curve have higher fitness than individuals near the fitness than individuals near the middlemiddle– In diagram, birds with small and large In diagram, birds with small and large

beak sizes have higher fitness than birds beak sizes have higher fitness than birds with a medium beak sizewith a medium beak size

Disruptive SelectionLargest and smallest seeds become more common.

Nu

mb

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f B

ird

sin

Po

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Beak Size

Population splits into two subgroups specializing in different seeds.

Beak SizeN

um

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Bir

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Disruptive SelectionLargest and smallest seeds become more common.

Nu

mb

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of

Bir

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Beak Size

Population splits into two subgroups specializing in different seeds.

Beak SizeN

um

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f B

ird

sin

Po

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KeyLow mortality, high fitnessHigh mortality, low fitness

Patterns of EvolutionPatterns of Evolution

Three patterns of evolution:Three patterns of evolution:– Convergent EvolutionConvergent Evolution– Divergent EvolutionDivergent Evolution– CoevolutionCoevolution


Convergent EvolutionConvergent Evolution Convergent EvolutionConvergent Evolution

– Evolution toward similar characteristics in Evolution toward similar characteristics in unrelated speciesunrelated species

– Analogous structures are examples of Analogous structures are examples of convergent evolution. convergent evolution.

Divergent EvolutionDivergent Evolution

Divergent EvolutionDivergent Evolution– When closely related species When closely related species

evolve in different directionsevolve in different directions– Also called Also called

adaptive adaptive

radiationradiation

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CoevolutionCoevolution Sometimes organisms that are closely Sometimes organisms that are closely

connected connected to one another by ecological to one another by ecological interactions interactions evolve evolve together.together.

Example: Flowering plants and Example: Flowering plants and

a specific pollinatora specific pollinator

CoevolutionCoevolution: :

Two species evolve in Two species evolve in

response response to changes to changes

in each other. in each other.

1 evolution unit chapters 10 and 11. 2 history of evolutionary thought copyright cmassengale

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