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Evolution,Evolution,
Biodiversity, andBiodiversity, and
CommunityCommunity
ProcessesProcesses
La CaLa Cañada High Schoolñada High School
Dr. EDr. E
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What types of LifeWhat types of Life
exist on the Earth?exist on the Earth?
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Types of OrganismsTypes of Organisms
•• Prokaryotic KingdomProkaryotic Kingdom: : single-single-celled organisms containing nocelled organisms containing nointernal structures surrounded byinternal structures surrounded bymembranes (therefore there is nomembranes (therefore there is nonucleus)nucleus)
–– MoneraMonera –– bacteria and bacteria andcyanobacteriacyanobacteria
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Aerobic
bacteriaAncient Prokaryotes
Ancient Anaerobic
Prokaryote
Primitive Aerobic
Eukaryote
Primitive Photosynthetic
Eukaryote
Chloroplas
t
Photosynthetic
bacteriaNuclear
envelope
evolving Mitochondrion
Plants and
plantlike
protists
Animals, fungi, and
non-plantlike protists
Endosymbiotic TheoryEndosymbiotic Theory
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Types of OrganismsTypes of Organisms•• Eukaryotic KingdomsEukaryotic Kingdoms: : all organisms consisting ofall organisms consisting of
cells which contain membrane-bound nucleicells which contain membrane-bound nuclei
–– ProtistaProtista - mostly - mostly one-celled organisms one-celled organisms –– have have
characteristics of all three other Eukaryote Kingdomscharacteristics of all three other Eukaryote Kingdoms
–– FungiFungi - - organisms which decompose stufforganisms which decompose stuff
–– PlantaePlantae - - organisms which use photosynthesis to makeorganisms which use photosynthesis to make
their own foodtheir own food
•• AnnualsAnnuals complete complete life cycle in one seasonlife cycle in one season
•• PerennialsPerennials live for more than one seasonlive for more than one season
–– AnimaliaAnimalia - - organisms which must get organic compoundsorganisms which must get organic compounds
from food they eat - most are able to movefrom food they eat - most are able to move
•• InvertebratesInvertebrates –– no backboneno backbone
•• VertebratesVertebrates –– Fish, Amphibians, Reptiles, Birds andFish, Amphibians, Reptiles, Birds and
MammalsMammals
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NamingNaming
SpeciesSpecies
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Naming of SpeciesNaming of Species
The system of naming species was first developed byThe system of naming species was first developed bySwedish botanist and physician, Carolus Linnaeus in theSwedish botanist and physician, Carolus Linnaeus in themid- 1700smid- 1700s
••Taxonomy, which seeks to describe, name and classify organismsTaxonomy, which seeks to describe, name and classify organisms
••begins with assigning all species a two-part Latin name called abegins with assigning all species a two-part Latin name called abinomialbinomial
••first word of the binomial is the genus name of the species,first word of the binomial is the genus name of the species,
•• second word is the specific epithet for the species. second word is the specific epithet for the species.
–– scientific name for the blue crabscientific name for the blue crab is is Callinectes sapidusCallinectes sapidus
–– CallinectesCallinectes, the genus name, is the collective term which, the genus name, is the collective term whichincludes many species of crabs closely related to the blueincludes many species of crabs closely related to the bluecrabcrab
–– sapidussapidus, describes exactly which of the , describes exactly which of the CallinectesCallinectes species is species isbeing identifiedbeing identified
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Definition of SpeciesDefinition of Species
•• Morphological Species Concept (MSC)Morphological Species Concept (MSC)
–– traced back to the philosophies of Plato andtraced back to the philosophies of Plato andAristotle, and which Aristotle, and which continued to be usedcontinued to be useduntil the first half of the twentieth centuryuntil the first half of the twentieth century
–– defines species purely by their phenotypicdefines species purely by their phenotypictraits rather than their genetic complementtraits rather than their genetic complementor potential interbreedingor potential interbreeding
–– number of species classified was largenumber of species classified was largebecause each group of individuals thatbecause each group of individuals thatexhibited a slight phenotypic difference wereexhibited a slight phenotypic difference wereconsidered a different speciesconsidered a different species
http://www.falcons.co.uk/mefrg/Falco/13/Species.htmhttp://www.falcons.co.uk/mefrg/Falco/13/Species.htm
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Definition of SpeciesDefinition of Species
•• Biological Species Concept (BSC)Biological Species Concept (BSC)–– ‘‘a species is a group of interbreeding populations thata species is a group of interbreeding populations that
are genetically isolated from other groups byare genetically isolated from other groups byreproductive isolating mechanisms such as hybridreproductive isolating mechanisms such as hybridsterility or mate acceptabilitysterility or mate acceptability’’
•• Phylogenetic Species Concept (PSCPhylogenetic Species Concept (PSC–– Each population of sexually reproducing organismsEach population of sexually reproducing organisms
that possesses at least one diagnostic characterthat possesses at least one diagnostic characterpresent in all population members but absent from allpresent in all population members but absent from allclosest relatives is considered a speciesclosest relatives is considered a species
–– each geographically distinct form is classified as a each geographically distinct form is classified as aspeciesspecies
http://www.falcons.co.uk/mefrg/Falco/13/Species.htmhttp://www.falcons.co.uk/mefrg/Falco/13/Species.htm
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How did LifeHow did Life
Originate?Originate?
OrOr
Chemical EvolutionChemical Evolution
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EVOLUTIONEVOLUTION
isis
Gradual ChangeGradual Change
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Origin of LifeOrigin of Life•• 600 BC 600 BC AnaximanderAnaximander
–– life began in waterlife began in water..
–– early forms wereearly forms were simple. simple.
–– simple simple forms begatforms begat more more complex forms overcomplex forms over time time
•• AristotleAristotle (350 BC) (350 BC)
–– decayingdecaying material could be transformed by the material could be transformed by the‘‘Spontaneous Action of Nature' into living animalsSpontaneous Action of Nature' into living animals
•• ArchBishop UsherArchBishop Usher ( (earlyearly 1600 1600’’s)s) and his scholars and his scholars
–– provided exact dates for all the various occurrences in theprovided exact dates for all the various occurrences in thenew Bible being translated for King Jamesnew Bible being translated for King James
–– ‘‘provedproved’’ to the King that the world was created on to the King that the world was created onTuesday, October 8, 4004 BC at 9:30 in the morningTuesday, October 8, 4004 BC at 9:30 in the morning
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Chemical EvolutionChemical EvolutionOparin Hypothesis (early 1930s)Oparin Hypothesis (early 1930s)
1) 1) Formation of the planetFormation of the planet with gases in the with gases in theatmosphere that could serve as the rawatmosphere that could serve as the rawmaterials for life.materials for life.
–– most widely accepted astronomical theory formost widely accepted astronomical theory forthe origin of the earth and the rest of the solarthe origin of the earth and the rest of the solarsystem is that the solar system formed aboutsystem is that the solar system formed about4.7 billion years ago from a diffuse dust cloud4.7 billion years ago from a diffuse dust cloud
–– central portion probably condensed to formcentral portion probably condensed to formthe sun and areas in the outer parts of thethe sun and areas in the outer parts of thecloud condensed to form the planetscloud condensed to form the planets
–– beginning of the universe according to the "Bigbeginning of the universe according to the "BigBang" theory occurred about 15 billion yearsBang" theory occurred about 15 billion yearsagoago
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Chemical EvolutionChemical EvolutionOparin HypothesisOparin Hypothesis
2) 2) Random synthesis of simple organic moleculesRandom synthesis of simple organic molecules
(such as amino acids that make up proteins)(such as amino acids that make up proteins)
from the gases in the surrounding atmosphere.from the gases in the surrounding atmosphere.
3) 3) Formation of larger, more complex moleculesFormation of larger, more complex molecules
(Macromolecules) from the simple organic(Macromolecules) from the simple organic
molecules, e.g., the formation of simple proteins.molecules, e.g., the formation of simple proteins.
4) 4) Formation of coacervatesFormation of coacervates - unique droplets - unique droplets
containing the macromolecules , i.e., acontaining the macromolecules , i.e., a
coacervates consists of chemicals suspendedcoacervates consists of chemicals suspended
within a liquid surrounded by a membrane, e.g.within a liquid surrounded by a membrane, e.g.
a droplet consisting of chemicals in watera droplet consisting of chemicals in water
surrounded by an oil layer membrane.surrounded by an oil layer membrane.
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Chemical EvolutionChemical EvolutionOparin HypothesisOparin Hypothesis
5) 5) Development of some type of chemical organizersDevelopment of some type of chemical organizersthat function to give these droplets the ability tothat function to give these droplets the ability totake in molecules, discharge other molecules, andtake in molecules, discharge other molecules, andcontrol and maintain a characteristic chemicalcontrol and maintain a characteristic chemicalpattern. These chemical organizers wouldpattern. These chemical organizers wouldprobably be similar to nucleic acids (that make upprobably be similar to nucleic acids (that make upchromosomes).chromosomes).
6) 6) Development of controlled reproductionDevelopment of controlled reproduction to insure to insurethat resultant daughter cells have the samethat resultant daughter cells have the samechemical capabilities. The droplets could now bechemical capabilities. The droplets could now beconsidered to be primitive cells.considered to be primitive cells.
7) 7) Beginnings of evolutionary developmentsBeginnings of evolutionary developments so that a so that agroup of cells could adapt to changes in thegroup of cells could adapt to changes in theenvironment over time.environment over time.
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Miller-Urey ExperimentMiller-Urey Experiment•• conductedconducted in 1953 by Stanley Miller with Harold in 1953 by Stanley Miller with Harold
UreyUrey
•• the first experiment to about the evolution ofthe first experiment to about the evolution ofprebiotic chemicals and the origin of life onprebiotic chemicals and the origin of life onEarthEarth
–– mixture of methane, ammonia,mixture of methane, ammonia,hydrogen, and water vaporhydrogen, and water vaporintroduced into a 5-liter flaskintroduced into a 5-liter flask(simulate the Earth's primitive,(simulate the Earth's primitive,reducing atmosphere)reducing atmosphere)
–– energized by an electrical dischargeenergized by an electrical dischargeapparatus to represent ultravioletapparatus to represent ultravioletradiation from the Sunradiation from the Sun
–– products were allowed to condenseproducts were allowed to condenseand collect in a lower flask whichand collect in a lower flask which
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Miller-Urey ExperimentMiller-Urey Experiment–– heat supplied to this flask recycledheat supplied to this flask recycled
the water vapor just as waterthe water vapor just as waterevaporates from lakes and seas,evaporates from lakes and seas,before moving into the atmospherebefore moving into the atmosphereand condensing again as rainand condensing again as rain
–– after a day of continuous operationafter a day of continuous operation
•• a thin layer of hydrocarbons on thea thin layer of hydrocarbons on thesurface of the watersurface of the water
–– after about a week of operationafter about a week of operation
•• a dark brown scum had collected ina dark brown scum had collected inthe lower flask and was found tothe lower flask and was found tocontain several types of aminocontain several types of aminoacids, including glycine andacids, including glycine andalanine, together with sugars, tars,alanine, together with sugars, tars,and various other unidentifiedand various other unidentifiedorganic chemicalsorganic chemicals
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The Just-Right PlanetThe Just-Right PlanetRead CONNECTIONS on page 139.Read CONNECTIONS on page 139.
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Evolution of First LifeEvolution of First Life•• Formation of the earliest precursors of lifeFormation of the earliest precursors of life
––must have self-organizedmust have self-organized
––acquired the capabilities needed to survive and reproduceacquired the capabilities needed to survive and reproduce
•• BiomoleculesBiomolecules of life became enclosed within a lipid of life became enclosed within a lipid
membranemembrane
––forming rudimentary assemblages that resembled cells orforming rudimentary assemblages that resembled cells or
protocellsprotocells
•• Essential Essential protocellularprotocellular functions functions
––acquisition of energy from the environmentacquisition of energy from the environment
––use of energy to synthesize molecules use of energy to synthesize molecules –– metabolismmetabolism
––information transfer to succeeding generations information transfer to succeeding generations –– geneticsgenetics
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EvidenceEvidence
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FossilsFossils
•• Oldest fossils are theOldest fossils are theapproximately 3.465approximately 3.465billion-year-oldbillion-year-oldmicrofossils from themicrofossils from theApexApex Chert Chert, Australia, Australia
–– colonies ofcolonies ofcyanobacteriacyanobacteria(formerly called blue-(formerly called blue-green algae) whichgreen algae) which
built real reefs built real reefs
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FossilsFossils1600's - Danish scientist Nicholas Steno studied1600's - Danish scientist Nicholas Steno studied
the relative positions of sedimentary rocksthe relative positions of sedimentary rocks
–– LayeringLayering is the most obvious feature of sedimentary is the most obvious feature of sedimentary
rocksrocks
•• formed particle by particle and bed by bed, and the layersformed particle by particle and bed by bed, and the layers
are piled one on top of the otherare piled one on top of the other
•• any sequence of layered rocks, a given bed must be olderany sequence of layered rocks, a given bed must be older
than any bed on top of itthan any bed on top of it
–– Law of SuperpositionLaw of Superposition is fundamental to the is fundamental to the
interpretation of Earth history, because at any oneinterpretation of Earth history, because at any one
location it indicates the relative ages of rock layerslocation it indicates the relative ages of rock layers
and the fossils in them.and the fossils in them.
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Half-life for a given radioisotope is the time for half theHalf-life for a given radioisotope is the time for half theradioactive nuclei in any sample to undergoradioactive nuclei in any sample to undergo
radioactive decayradioactive decay
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Half-life for a given radioisotope is the time for half theHalf-life for a given radioisotope is the time for half theradioactive nuclei in any sample to undergoradioactive nuclei in any sample to undergo
radioactive decayradioactive decay
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BiologicalBiological
EvolutionEvolution
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(ORGANIC) EVOLUTION:(ORGANIC) EVOLUTION:
change in change in gene frequenciesgene frequencies
within populations fromwithin populations from
generation to generation.generation to generation.
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(ORGANIC) EVOLUTION:(ORGANIC) EVOLUTION:
gene frequencies over timegene frequencies over time
……no concepts ofno concepts of ““planningplanning”” or or
““progressprogress”” apply. No goals! apply. No goals!
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Early EvolutionistsEarly Evolutionists’’
Anthropocentric view:Anthropocentric view:
Scala Natura Scala Natura (ladder of life).(ladder of life).
A linear riseA linear rise
fromfrom
‘‘primitiveprimitive’’ to to
‘‘advancedadvanced’’..
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Early EvolutionistsEarly Evolutionists’’
Anthropocentric view:Anthropocentric view:
Scala Natura Scala Natura (ladder of life).(ladder of life).
Needless to say, weNeedless to say, we
are the are the mostmost
‘‘advancedadvanced’’ in this in this
schemescheme……after all, itafter all, it’’ss
our ladderour ladder!!!!
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Evolutionary BushEvolutionary Bush
One life-form splits into twoOne life-form splits into two
and those branches splitand those branches split
(independently) to make(independently) to make
more.more.
Tim
e T
ime
PhenotypicPhenotypic
‘‘distancedistance’’
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Evolutionary Bush --Evolutionary Bush --
thousands of earlier andthousands of earlier and
later branches.later branches.
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At any given moment (e.g. theAt any given moment (e.g. the
‘‘presentpresent’’), all we see is ), all we see is currentcurrent
diversitydiversity……
all all extinctextinct forms are gone (99.9%) forms are gone (99.9%)
Tim
e
Tim
e
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Four causes of evolutionaryFour causes of evolutionary
change:change:
1.1. MutationMutation:: fundamental origin of fundamental origin of allall genetic genetic
(DNA) change.(DNA) change.
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Four causes of evolutionaryFour causes of evolutionary
change:change:
1.1. MutationMutation:: fundamental origin of fundamental origin of allall genetic genetic
(DNA) change.(DNA) change.
Point mutationPoint mutation
……some at base-pair levelsome at base-pair level
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Four causes of evolutionaryFour causes of evolutionary
change:change:
1.1. MutationMutation:: fundamental origin of fundamental origin of allall
genetic (DNA) change.genetic (DNA) change.
Crossing-overCrossing-over
……others at grosserothers at grosser
chromosome levelchromosome level
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Four causes of evolutionaryFour causes of evolutionary
change:change:
1.1. MutationMutation: fundamental genetic shifts.: fundamental genetic shifts.
2.2. Genetic DriftGenetic Drift:: isolated populations accumulate isolated populations accumulate
different mutations over time.different mutations over time.
In a continuousIn a continuous
population, geneticpopulation, genetic
novelty can spreadnovelty can spread
locally.locally.
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Four causes of evolutionaryFour causes of evolutionary
change:change:
1.1. MutationMutation: fundamental genetic shifts.: fundamental genetic shifts.
2.2. Genetic DriftGenetic Drift:: isolated populations isolated populations
accumulate different mutations over time.accumulate different mutations over time.
Local spreading of allelesLocal spreading of alleles
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Four causes of evolutionaryFour causes of evolutionary
change:change:
1.1. MutationMutation: fundamental genetic shifts.: fundamental genetic shifts.
2.2. Genetic DriftGenetic Drift:: isolated populations isolated populations
accumulate different mutations over time.accumulate different mutations over time.
Local spreading of allelesLocal spreading of alleles
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Four causes of evolutionaryFour causes of evolutionary
change:change:
1.1. MutationMutation: fundamental genetic shifts.: fundamental genetic shifts.
2.2. Genetic DriftGenetic Drift:: isolated populations accumulate isolated populations accumulate
different mutations over time.different mutations over time.
Spreading processSpreading process
known as known as ‘‘genegene
flowflow’’..
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Four causes of evolutionaryFour causes of evolutionary
change:change:
But inBut in
discontinuousdiscontinuous
populations, populations, genegene
flowflow is blocked. is blocked.
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Four causes of evolutionaryFour causes of evolutionary
change:change:
VariationsVariations
accumulate withoutaccumulate without
inter-demicinter-demic exchange exchange
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Four causes of evolutionaryFour causes of evolutionary
change:change:
Of course, thisOf course, this
works at manyworks at many
lociloci
simultaneouslysimultaneously
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Four causes of evolutionary changeFour causes of evolutionary change
1.1. MutationMutation: fundamental genetic shifts.: fundamental genetic shifts.
2.2. Genetic DriftGenetic Drift: isolation : isolation accumulateaccumulate
mutationsmutations
3.3. Founder EffectFounder Effect:: sampling biassampling bias during during
immigration. When a new population isimmigration. When a new population is
formed, its genetic composition dependsformed, its genetic composition depends
largely on the gene frequencies within thelargely on the gene frequencies within the
group of first settlers.group of first settlers.
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Founder Effect.--Founder Effect.--
Human example: your tribe had toHuman example: your tribe had to
live near the Bering land bridgelive near the Bering land bridge……
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Founder Effect.--Founder Effect.--
……to invade & settle the to invade & settle the ‘‘New WorldNew World’’!!
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Audeskirk & Audeskirk, 1993
Galapagos FinchesGalapagos Finches
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Four causes of evolutionary change:Four causes of evolutionary change:
1.1. MutationMutation: fundamental genetic shifts.: fundamental genetic shifts.
2.2. Genetic DriftGenetic Drift: isolation : isolation accumulation ofaccumulation of
mutationsmutations
3.3. Founder EffectFounder Effect: immigrant sampling bias.: immigrant sampling bias.
4.4. Natural SelectionNatural Selection: differential: differential
reproduction of individuals in the samereproduction of individuals in the same
population based on genetic differencespopulation based on genetic differences
among them.among them.
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Four causes of evolutionaryFour causes of evolutionary
change:change:1.1. MutationMutation: fundamental genetic shifts.: fundamental genetic shifts.
2.2. Genetic DriftGenetic Drift: isolation : isolation accumulation ofaccumulation of
mutationsmutations
3.3. Founder EffectFounder Effect: immigrant sampling bias.: immigrant sampling bias.
4.4. Natural SelectionNatural Selection: reproductive race: reproductive race
These 4 interact synergisticallyThese 4 interact synergistically
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Evidence ofEvidence of
EvolutionEvolution
1. Biogeography:1. Biogeography:
Geographical distribution of speciesGeographical distribution of species
2. Fossil Record:2. Fossil Record:
Fossils and the order inFossils and the order in
which they appear in layers ofwhich they appear in layers of
sedimentary rock (sedimentary rock (strongeststrongest
evidenceevidence))
3. Taxonomy:3. Taxonomy:
Classification of life forms.Classification of life forms.
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4. Homologous Structures:4. Homologous Structures:
Structures thatStructures that
are similarare similar
because ofbecause of
commoncommon
ancestryancestry
(comparative(comparative
anatomy)anatomy)
Turtle Alligator Bird Mammals
Typical primitive
fish
5. Comparative Embryology: 5. Comparative Embryology:
Study ofStudy of
structuresstructures
that appearthat appear
duringduring
embryonicembryonic
developmentdevelopment
6. Molecular Biology:6. Molecular Biology:
DNA and proteins (amino acids)DNA and proteins (amino acids)
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History ofHistory of
Theories ofTheories of
EvolutionEvolution
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Old Theories of EvolutionOld Theories of EvolutionJean Baptiste Lamarck (early 1800Jean Baptiste Lamarck (early 1800’’s)s)
proposed:proposed:
““The inheritance of acquiredThe inheritance of acquiredcharacteristicscharacteristics””
He proposed that by using or not usingHe proposed that by using or not usingits body parts, an individual tends toits body parts, an individual tends to
develop certain characteristics, which itdevelop certain characteristics, which itpasses on to its offspring.passes on to its offspring.
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““The Inheritance of AcquiredThe Inheritance of Acquired
CharacteristicsCharacteristics””
•• Example:Example:
A giraffe acquired its long neckA giraffe acquired its long neck
because its ancestor stretched higherbecause its ancestor stretched higher
and higher into the trees to reachand higher into the trees to reach
leaves, and that the animalleaves, and that the animal’’ss
increasingly lengthened neck wasincreasingly lengthened neck was
passed on to its offspring.passed on to its offspring.
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Charles DarwinCharles Darwin•• Darwin set sail on the H.M.S. BeagleDarwin set sail on the H.M.S. Beagle
(1831-1836) to survey the south seas(1831-1836) to survey the south seas(mainly South America and the(mainly South America and theGalapagos Islands) to collect plants andGalapagos Islands) to collect plants andanimals.animals.
•• On the Galapagos Islands, DarwinOn the Galapagos Islands, Darwinobserved species that lived no where elseobserved species that lived no where elsein the world.in the world.
•• These observations led Darwin to writeThese observations led Darwin to writea booka book
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Pinta IslandIntermediate
shell
Pinta
Isabela IslandDome-shaped shell
Hood IslandSaddle-backed
shellHoodFloreana
Santa Fe
Santa
Cruz
James
Marchena
Fernandina
Isabela
Tower
Giant Tortoises of the Giant Tortoises of the GalápagosGalápagosIslandsIslands
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http://www.galapagosislands.com
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Charles DarwinCharles Darwin
Wrote in 1859:Wrote in 1859:
““On the Origin of Species by Means ofOn the Origin of Species by Means ofNatural SelectionNatural Selection””
Two main conclusions:Two main conclusions:
1.1. Species were not created in theirSpecies were not created in theirpresent form, but evolved frompresent form, but evolved fromancestral species.ancestral species.
2.2. Proposed a mechanism for evolution:Proposed a mechanism for evolution:NATURAL SELECTIONNATURAL SELECTION
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DarwinDarwin’’s Observationss Observations
1.1. Most species produce more offspringMost species produce more offspringthan can be supported by thethan can be supported by the
environmentenvironment
2.2. Environmental resources are limitedEnvironmental resources are limited
3.3. Most populations are stable in sizeMost populations are stable in size
4.4. Individuals vary greatly in theirIndividuals vary greatly in theircharacteristics (phenotypes)characteristics (phenotypes)
5.5. Variation is heritable (genotypes)Variation is heritable (genotypes)
Natural SelectionNatural Selection
•• Individuals with favorable traits areIndividuals with favorable traits are
more likely to leave more offspringmore likely to leave more offspring
better suited for their environmentbetter suited for their environment
•• Also known as Also known as ““DifferentialDifferential
ReproductionReproduction””
Example:Example:
English pEnglish peeppppeerreedd
moth moth (Biston betularia)
Modes of ActionModes of Action
•• Natural selection has three modes of action:Natural selection has three modes of action:
1.1. Stabilizing selectionStabilizing selection
2.2. Directional selectionDirectional selection
3.3. Diversifying selectionDiversifying selection
Number
of
Individuals
Size of individuals
Small Large
1.1. Stabilizing SelectionStabilizing Selection
Acts upon extremes and favorsActs upon extremes and favors
the intermediatethe intermediate
Number
of
Individuals
Size of individuals
Small Large
2.2. Directional SelectionDirectional Selection
Favors variants of one extremeFavors variants of one extreme
Number
of
Individuals
Size of individuals
Small Large
3.3. Diversifying SelectionDiversifying Selection
Favors variants of oppositeFavors variants of opposite
extremesextremes
Number
of
Individuals
Size of individuals
Small Large
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SpeciationSpeciation
Evolution of new speciesEvolution of new species
Reproductive BarriersReproductive Barriers
Any mechanism that impedes twoAny mechanism that impedes twospecies from producing fertilespecies from producing fertileand/or viable hybrid offspring.and/or viable hybrid offspring.
Two barriers:Two barriers:
1.1. Pre-zygotic barriersPre-zygotic barriers
2.2. Post-zygotic barriersPost-zygotic barriers
1.1. Pre-zygotic BarriersPre-zygotic Barriers
a. Temporal isolation:a. Temporal isolation:
Breeding occurs at different times forBreeding occurs at different times fordifferent speciesdifferent species
b. Habitat isolation:b. Habitat isolation:
Species breed in different habitatsSpecies breed in different habitats
c. Behavioral isolation:c. Behavioral isolation:
Little or no sexual attraction betweenLittle or no sexual attraction betweenspeciesspecies
1.1. Pre-zygotic BarriersPre-zygotic Barriers
d. Mechanical isolation:d. Mechanical isolation:
Structural differences prevent gameteStructural differences prevent gamete
exchangeexchange
e. Gametic isolation:e. Gametic isolation:
Gametes die before uniting with gametesGametes die before uniting with gametes
of other species, or gametes fail to uniteof other species, or gametes fail to unite
2.2. Post-zygotic BarriersPost-zygotic Barriersa. Hybrid inviability:a. Hybrid inviability:
Hybrid zygotes fail to develop or fail toHybrid zygotes fail to develop or fail to
reach sexual maturityreach sexual maturity
b. Hybrid sterility:b. Hybrid sterility:
Hybrid fails to produce functional gametesHybrid fails to produce functional gametes
c. Hybrid breakdown:c. Hybrid breakdown:
Offspring of hybrids are weak or infertileOffspring of hybrids are weak or infertile
86
Evidence forEvidence for
NaturalNatural
SelectionSelection
Artificial SelectionArtificial Selection
The selective breeding ofThe selective breeding of
domesticated plants and animalsdomesticated plants and animals
by manby man
Question: WhatQuestion: What’’s the ancestor ofs the ancestor of
the domesticated dog?the domesticated dog?
Population GeneticsPopulation Genetics
The science of genetic change inThe science of genetic change in
population population –– Hardy-Weinberg Hardy-Weinberg
PopulationPopulation
A localized group of individualsA localized group of individuals
belonging to the same speciesbelonging to the same species
SpeciesSpecies
A group of populations whoseA group of populations whoseindividuals have the potential toindividuals have the potential tointerbreed and produce viableinterbreed and produce viable
offspringoffspring
Gene PoolGene PoolThe total collection of genes in aThe total collection of genes in a
population at any one timepopulation at any one time
90
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20. http://biology.usgs.gov/s+t/SNT/noframe/pi179.htm
21. http://www.npca.org/magazine/2001/march_april/nonnative_species.asp
22. http://www.bagheera.com/inthewild/spot_spkey.htm
23. Biology, 2003, Prentice Hall
24. http://www.nearctica.com/ecology/habitats/island.htm
25. http://www.valdosta.edu/~grissino/geog4900/lect_1.htm