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

ENDOSYMB T I HO ET O I RC Y

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

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!

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

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

Charles Darwin (1809-1882) Charles Darwin (1809-1882) Sailed around the world 1831-1836Sailed around the world 1831-1836

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!!

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

Galapagos Galapagos TortoisesTortoises

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

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.

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.

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

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

What color genes are in the beetle gene pool?

What’s happening to the color genes in thebeetle gene pool?Why is this happening?

Explain why we say green beetles have been selected against while brown beetles have been selected for?

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.

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

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

Primate FossilsPrimate Fossils

Australopithecus Homo erectus Homo sapien

Remember PANGEA?

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

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

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.

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!

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

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!

Homologous Body Structures…………Homologous Body Structures…………

…………are the result of divergent evolution

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.

Embryological developmentEmbryological development

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”!

Vestigial Structures in snakes

Vestigial Structures in whales

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?

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?

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

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

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

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

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

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

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

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)

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)

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

Single-Gene vs. Polygenic Single-Gene vs. Polygenic TraitsTraitsSingle-GeneSingle-Gene::

2 Distinct Phenotypes2 Distinct Phenotypes

PolygenicPolygenic::

Many PhenotypesMany Phenotypes

(EG: tongue rolling)

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

Are you more closely related to a turtle or a frog?

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