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8/14/2019 Evolution Internet

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EvolutionEvolution

The Study of How SpeciesThe Study of How Species

Change Over Time!Change Over Time!


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Evolutionary TheoryEvolutionary Theory

Jean Baptise de Lamark (1744-Jean Baptise de Lamark (1744-1829)1829)

1809, proposed an explanation of1809, proposed an explanation ofthe origin of species in his bookthe origin of species in his book

Zoological PhilosophyZoological Philosophy

1.1.The needs of an organism determinedThe needs of an organism determinedthe characteristics that evolved in thethe characteristics that evolved in the

organismorganism

2.2. Useful characteristics acquired in theirUseful characteristics acquired in their

lifetime can be transferred to its offspringlifetime can be transferred to its offspringThis is called Use and Dissuse


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Use and DisuseUse and Disuse

How did the giraffeHow did the giraffeget a long neck?get a long neck?

No silly, he didntNo silly, he didntstretch it out!stretch it out!


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Charles Darwin (1807-1882)Charles Darwin (1807-1882)

WroteWrote Origin of

Origin of

SpeciesS

pecies whichwhich

presentedpresentedobservations thatobservations that

demonstrated alldemonstrated all

living thingsliving things

evolved from otherevolved from otherliving thingsliving things

Based on VariationBased on Variationand Naturaland Natural

SelectionSelection


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Some of Darwin's ideas thatSome of Darwin's ideas that

support evolutionsupport evolution

OverproductionOverproduction Within a population,Within a population,

more offspring aremore offspring are

born then canborn then can

possibly survive.possibly survive.

Competition:Competition: Numbers ofNumbers of

individuals in aindividuals in a

population remainpopulation remain

the same fromthe same from

generation togeneration to

generation.generation.

A struggle forA struggle forsurvival issurvival is

suggestedsuggested

This is the basis forThis is the basis for

lifelife


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Survival of theSurvival of the

FittestFittest IndividualsIndividualswho survivewho survive

are the onesare the onesbest adaptedbest adaptedto exist in theirto exist in theirenvironmentenvironment

due to thedue to thepossession ofpossession ofvariations.variations.


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ReproductionReproduction IndividualsIndividuals

that survivethat survive

willwillreproducereproduceand transmitand transmitthesethese

variations tovariations totheirtheiroffspringoffspring..


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SpeciationSpeciation As time and generationsAs time and generations

continue, manycontinue, many

adaptations areadaptations areperpetuated in individualsperpetuated in individuals

until new species evolveuntil new species evolve

in forms different fromin forms different from

the common ancestorthe common ancestor


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Natural SelectionNatural Selection

Traits which are beneficial to the survival of anTraits which are beneficial to the survival of anorganism in a particular environment tend to beorganism in a particular environment tend to be

retained and passed on, increasing in frequencyretained and passed on, increasing in frequency

with in the populationwith in the population Trait which have low survival tend to decrease inTrait which have low survival tend to decrease in

FrequencyFrequency

When environmental conditions change, trait thatWhen environmental conditions change, trait that

were formally associated with low survival maywere formally associated with low survival mayhave greater survivalhave greater survival


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Problem with DarwinsProblem with Darwins

Theory:Theory:

He did not have any geneticHe did not have any genetic

backing for his theory!backing for his theory!


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Modern Evolutionary TheoryModern Evolutionary Theory

Supports DarwinsSupports Darwinstheory of evolutiontheory of evolution

through mechanismsthrough mechanisms

of genetic inheritanceof genetic inheritance

Genetic Variation isGenetic Variation isprovided by mutationsprovided by mutations

and sexualand sexual

reproductionreproduction

Mutations areMutations arespontaneousspontaneous . Some. Some

are harmful, someare harmful, some

dont do anything atdont do anything at

all, and a smallall, and a smallercenta e hel the


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MutationsMutations

Definition:Definition: A random changeA random change

in the chemicalin the chemical

nature of DNAnature of DNA

Mutations mustMutations mustoccur in the sexoccur in the sexcells in order to becells in order to be

passed on to thepassed on to the

next generation.next generation.

Mutations in bodyMutations in bodycells will only affectcells will only affect

the individual, notthe individual, not

their offspringtheir offspring


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Vestigial StructuresVestigial Structures Anatomical structures which are no longerAnatomical structures which are no longer

useful have evolved to become smalleruseful have evolved to become smaller


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Comparing Structures andComparing Structures and

FunctionsFunctions

ComparativeComparativeanatomyanatomy

Similarities inSimilarities inanatomical featuresanatomical features


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Comparison of EmbryonicComparison of Embryonic

DevelopmentDevelopment

EarlyEarlyvertebratevertebrate

embryosembryoscloselyclosely

resemble oneresemble one

anotheranother


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Comparative BiochemistryComparative Biochemistry

Their structure and function can beTheir structure and function can besimilar even though may not showsimilar even though may not show

structural similaritystructural similarityThe closer biochemical similarities,The closer biochemical similarities,

the closer the relationship amongthe closer the relationship among

organismsorganisms Ex: nucleic acids.Ex: nucleic acids.


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Mechanisms and Patterns ofMechanisms and Patterns of

Evolution: GeologicalEvolution: Geological

ObservationsObservations Fossils:Fossils:

Law of Super-Law of Super-posistionposistion

Carbon DatingCarbon Dating Radio active decayRadio active decay

Common AncestryCommon Ancestry

Divergence ofDivergence ofmodern forms ofmodern forms of

living things fromliving things frompre-existing lifepre-existing life

formsforms

This is the centralThis is the centralconcept in organicconcept in organic

(species) evolution(species) evolution


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Concepts of EvolutionConcepts of Evolution

GeographicGeographicIsolationIsolation

Favors speciationFavors speciationby segregating aby segregating a

small group fromsmall group from

the main populationthe main population

with a geographiwith a geographi

barrierbarrier Ex: Islands,Ex: Islands,

mountains, rivers .mountains, rivers .

In time, isolatedIn time, isolated

populations maypopulations mayevolve into


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Darwin's FinchesDarwin's Finches


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Adaptive radiationAdaptive radiation

Rapid speciation of a single or few speciesRapid speciation of a single or few speciesto fill many ecological niches.to fill many ecological niches.


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Geographic Isolation Cont.Geographic Isolation Cont.

FactorsFactors1.1. It may have possessed different initialIt may have possessed different initial

gene frequencies than the maingene frequencies than the mainpopulationpopulation

2.2. Different mutations occur with in mainDifferent mutations occur with in main

population and isolated populationpopulation and isolated population

3.3. Different environmental factorsDifferent environmental factors

DifferentDifferent selecting agentsselecting agents (factors that(factors thatdetermine who survives) on eachdetermine who survives) on each

populationpopulation


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Time Frame for EvolutionTime Frame for Evolution

Gradualism:Gradualism: EvolutionaryEvolutionary

change is slow andchange is slow and

continuouscontinuous

PunctuatedPunctuated

equilibrium:equilibrium: Long periods ofLong periods of

stability interruptedstability interrupted

by geologically briefby geologically brief

periods ofperiods ofsignificant changesignificant change

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