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How did life begin?How did life begin?
Miller and Urey’s Miller and Urey’s Experiment Experiment
Passed sparks Passed sparks through a mixture of through a mixture of hydrogen methane hydrogen methane ammonia and waterammonia and water
This produced This produced amino acids – the amino acids – the building blocks of lifebuilding blocks of life
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ENDOSYMB T I HO ET O I RC Y
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Theory of Life cont.Theory of Life cont.Endosymbiotic theoryEndosymbiotic theory
eukaryotic cells eukaryotic cells arose from living arose from living communities formed communities formed by prokaryotic by prokaryotic organismsorganisms
Ancient prokaryotes Ancient prokaryotes entered primitive entered primitive eukaryotic cells and eukaryotic cells and remained there as remained there as organellesorganelles
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LamarkLamarkTheory of acquired Theory of acquired characteristicscharacteristics
Lamark said Lamark said organisms acquired organisms acquired traits by using their traits by using their bodies in new waysbodies in new ways
These new These new characteristics were characteristics were passed to offspringpassed to offspring
Lamark was totally Lamark was totally wrong!wrong!
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Geologists: Geologists: Hutton and LyellHutton and Lyell
Fundamentalists said that the Fundamentalists said that the earth was around 6000 years oldearth was around 6000 years old
Hutton and Lyell argued that the Hutton and Lyell argued that the earth is many millions of years earth is many millions of years old b/cold b/c
layers of rock take time to formlayers of rock take time to form processes such as volcanoes processes such as volcanoes
and earthquakes shaped the and earthquakes shaped the earth and still occur todayearth and still occur today
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MalthusMalthus
Reasoned that if the Reasoned that if the human population human population continued to grow continued to grow unchecked, sooner or unchecked, sooner or later there would be later there would be insufficient living space insufficient living space and food for everyone and food for everyone
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Charles Darwin (1809-1882) Charles Darwin (1809-1882) Sailed around the world 1831-1836Sailed around the world 1831-1836
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2. What did 2. What did Darwin’s Darwin’s Travels revealTravels reveal
The diversity of living The diversity of living species was far greater species was far greater than anyone had than anyone had previously known!!previously known!!
These observations led These observations led him to develop the him to develop the theory of evolution!!theory of evolution!!
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3.How did tortoises and 3.How did tortoises and birds differ among the birds differ among the islands of the Galapagos?islands of the Galapagos?
Warbler finch
Woodpecker finch
Small insectivoroustree finch
Largeinsectivorous
tree finch
Vegetariantree finch
Cactus finch
Sharp-beaked finch
Small groundfinch
Mediumground finch
Large groundfinch
Insect eaters
Bud eater
Seed eaters
Cactuseater
Warbler
finch
Tree
finc
hes G
round finches
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Galapagos Galapagos TortoisesTortoises
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Evolution is when organisms change Evolution is when organisms change over time. So, modern organisms over time. So, modern organisms descended from ancient onesdescended from ancient ones
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Evolution is a Theory – Evolution is a Theory – Just like Gravity!Just like Gravity!
• Evolution is a well Evolution is a well supported explanation supported explanation of phenomena that of phenomena that have occurred in the have occurred in the natural worldnatural world
• A theory in science A theory in science must be supported by must be supported by facts, it can’t be facts, it can’t be based on supposition.based on supposition.
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Darwin Darwin finally finally published his published his ideas in 1859ideas in 1859
Only when other Only when other naturalists were naturalists were developing the developing the same theory that same theory that he had did Darwin he had did Darwin finally publish his finally publish his findings. findings.
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Artificial Selection Artificial Selection nature provides variation, humans select nature provides variation, humans select
variations that are useful. variations that are useful. Example - a farmer breeds only his best Example - a farmer breeds only his best
livestocklivestock
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Natural Natural SelectionSelection The traits that The traits that
help an organism help an organism survive in a survive in a particular particular environment are environment are “selected” in “selected” in natural selectionnatural selection
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What color genes are in the beetle gene pool?
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What’s happening to the color genes in thebeetle gene pool?Why is this happening?
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Explain why we say green beetles have been selected against while brown beetles have been selected for?
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Natural Selection and Natural Selection and Species FitnessSpecies Fitness Overtime, natural selection results in changes Overtime, natural selection results in changes
in the inherited characteristics of a population. in the inherited characteristics of a population. These changes increase a species fitness These changes increase a species fitness
(survival rate)(survival rate)
Bottom line:Bottom line:
Those that are best adapted to their Those that are best adapted to their environment survive to reproduce. environment survive to reproduce.
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Evidence of EvolutionEvidence of Evolution
1.1. Fossil RecordFossil Record
2.2. Geographic Distribution of Living Geographic Distribution of Living SpeciesSpecies
3.3. Homologous Body structuresHomologous Body structures
4.4. Similarities in EmbryologySimilarities in Embryology
5.5. Vestigial organsVestigial organs
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Evidence of Evidence of EvolutionEvolution
Fossil Record provides evidence Fossil Record provides evidence that living things have evolvedthat living things have evolved
Fossils show the history of life on Fossils show the history of life on earth and how different earth and how different groups of organisms have groups of organisms have changed over timechanged over time
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Primate FossilsPrimate Fossils
Australopithecus Homo erectus Homo sapien
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Remember PANGEA?
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Evidence of Evidence of EvolutionEvolution
2.2. Geographic Geographic Distribution of Living Distribution of Living SpeciesSpecies
Similar animals in Similar animals in different locations different locations were the product of were the product of different lines of different lines of descentdescent
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Evidence of EvolutionEvidence of EvolutionGeographic Distribution of Geographic Distribution of
Living SpeciesLiving Species
Analogous StructuresAnalogous Structures are the result ofare the result of convergent evolution convergent evolution
- Similar animals in Similar animals in
different locations exhibit different locations exhibit analogous structuresanalogous structures due due to similar environmental to similar environmental pressures.pressures.
Eg. North American flying Eg. North American flying squirrel and the squirrel and the Australian sugar gliderAustralian sugar glider
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w in g s o f b ird s w in g s o f d a m se lfl ie s
w in g s = a d a p ta tio n s fo r fl ig h t ( s im ila r b y fu n c tio n n o t d e sc e n t)
u n re la te d o rg a n ism s a d a p t in d e p e n d e n tly to a c o m m o n e n v iro n m e n t.
w h a t a b o u t w i n g s o f b u t t e r f l i e s ?
M o re e v id e n c e fo r a d a p ta tio n s
C o n v e rg e n t e v o lu tio n – n a tu ra l se le c tio n p re ssu re h a s se le c te d fo r b e st a d a p ta tio n .u n re la te d sp e c ie s to a c o m m o n e n v iro n m e n ta l c h a lle n g e .
This means they are analogous structures.
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Convergent evolutionConvergent evolution Fish: aquatic vertebrates Dolphins: aquatic mammals
similar adaptations to life in the sea
not closely related
Those fins & tails & sleek bodies areanalogous structures!
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Evidence of Evidence of EvolutionEvolution
Adaptive radiation leads to Adaptive radiation leads to Homologous Body Homologous Body
Structures thru Structures thru divergent evolutiondivergent evolution
Structures that have Structures that have different mature forms different mature forms but develop from the but develop from the same embryonic same embryonic tissuestissues
e.g. Wing of bat, leg of e.g. Wing of bat, leg of turtle & human arm, turtle & human arm, are similar by de- are similar by de- scent not function.scent not function.
Turtle
Alligator
Bird
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Convergent evolutionConvergent evolution Fish: aquatic vertebrates Dolphins: aquatic mammals
similar adaptations to life in the sea
not closely related
Those fins & tails & sleek bodies areanalogous structures!
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Homologous Body Structures…………Homologous Body Structures…………
…………are the result of divergent evolution
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13. Evidence of 13. Evidence of EvolutionEvolution
Similarities in Similarities in EmbryologyEmbryology
In their early In their early stages of stages of development, development, chickens, turtles chickens, turtles and rats look and rats look similar, providing similar, providing evidence that evidence that they shared a they shared a common common ancestry.ancestry.
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Embryological developmentEmbryological development
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Vestigial organsVestigial organs Modern animals may have structures Modern animals may have structures
that serve little or no functionthat serve little or no function remnants of structures that were functional remnants of structures that were functional
in ancestral speciesin ancestral species evidence of change over timeevidence of change over time
some snakes & whales show remains of some snakes & whales show remains of the pelvis & leg bones of walking the pelvis & leg bones of walking ancestorsancestors
eyes on blind eyes on blind cave fishcave fish
human tail bonehuman tail bone
This is not LaMarck’s loss from “disuse”!
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Vestigial Structures in snakes
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Vestigial Structures in whales
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Molecular recordMolecular record
0 25 50 75 100 1250
25
50
75
100
Millions of years ago
Horse/donkey
Sheep/goat
Goat/cow
Llama/cow
Pig/cow
Rabbit/rodent
Horse/cow
Human/rodent
Dog/cow
Human/cow
Human/kangaroo
Nu
cleo
tid
e su
bst
itu
tio
ns
Comparing DNA & protein structureComparing DNA & protein structure universaluniversal genetic code! genetic code!
DNA & RNADNA & RNA compare common genescompare common genes
cytochrome C (respiration)cytochrome C (respiration) hemoglobin (gas exchange)hemoglobin (gas exchange)
Closely related species have sequences that are more similar than distantly related speciesDNA & proteins are a molecular
record of evolutionary relationships
Closely related species have sequences that are more similar than distantly related speciesDNA & proteins are a molecular
record of evolutionary relationships
Why comparethese genes?
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Comparative hemoglobin structure
Number of amino acid differences betweenhemoglobin (146 aa) of vertebrate species and that of humansNumber of amino acid differences betweenhemoglobin (146 aa) of vertebrate species and that of humans
100 20 30 40 50 60 70 80 90 100 110 120
LampreyFrogBirdDogMacaqueHuman
328 45 67 125
Why does comparingamino acid sequencemeasure evolutionaryrelationships?
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Descent with Descent with Modification Modification Each living Each living
species has species has descended descended with changes with changes from other from other species over species over timetime
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Summary of Darwin’s TheorySummary of Darwin’s Theory
1. Organisms differ; variation is inherited1. Organisms differ; variation is inherited
2. Organisms produce more offspring than 2. Organisms produce more offspring than survivesurvive
3. Organisms compete for resources3. Organisms compete for resources
4. Organisms with advantages survive to pass 4. Organisms with advantages survive to pass those advantages to their childrenthose advantages to their children
5. Species alive today are descended with 5. Species alive today are descended with modifications from common ancestorsmodifications from common ancestors
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Variation in Variation in PopulationsPopulations
2 processes can 2 processes can
lead to this:lead to this:
MutationsMutations - -
change in DNA change in DNA
sequencesequence
Gene ShufflingGene Shuffling – –
from sexual from sexual
reproductionreproduction
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Gene Gene PoolPoolCombined genetic Combined genetic
info. of all info. of all membersmembers
Allele frequency is # Allele frequency is # of times alleles of times alleles occuroccur
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Genetic Drift changes populations…Genetic Drift changes populations…
RandomRandom change in allele frequency change in allele frequency causes an allele to become commoncauses an allele to become common
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Founder Effect:Founder Effect: a cause of a cause of genetic drift genetic drift attributable to attributable to colonization by a colonization by a limited number of limited number of individuals from a individuals from a parent populationparent population
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Evolution of PopulationsEvolution of Populations
Occurs when there is a Occurs when there is a change in relative change in relative frequency of frequency of alleles……….alleles……….
in other words – a in other words – a change in the contents change in the contents of the gene poolof the gene pool
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Gene FlowGene Flow: : genetic exchange genetic exchange due to the due to the migration of fertile migration of fertile individuals or individuals or gametes between gametes between populations populations (reduces (reduces differences differences between between populations)populations)
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Nonrandom mating aka artificial selectionNonrandom mating aka artificial selection: : inbreeding and assortive mating (both shift inbreeding and assortive mating (both shift frequencies of different genotypes)frequencies of different genotypes)
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Natural SelectionNatural Selection: : differential success differential success in reproduction; in reproduction; only form of only form of microevolution that microevolution that adapts a adapts a population to its population to its environmentenvironment
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Single-Gene vs. Polygenic Single-Gene vs. Polygenic TraitsTraitsSingle-GeneSingle-Gene::
2 Distinct Phenotypes2 Distinct Phenotypes
PolygenicPolygenic::
Many PhenotypesMany Phenotypes
(EG: tongue rolling)
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Natural Selection on Polygenic Natural Selection on Polygenic TraitsTraits
Shifts to Shifts to
middle rangemiddle range
Shifts to Shifts to
2 extremes2 extremes
Shifts to Shifts to
1 extreme1 extreme
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Are you more closely related to a turtle or a frog?
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Natural selection in Natural selection in action action
Insecticide & Insecticide & drug resistancedrug resistance insecticide didn’t insecticide didn’t
kill all individualskill all individuals resistant survivors resistant survivors
reproducereproduce resistance is inheritedresistance is inherited insecticide becomes less insecticide becomes less
& less effective& less effective