Evolution and the Origin of Evolution and the Origin of LifeLife

Origin of LifeOrigin of Life

Need to make the monomers of the Need to make the monomers of the macromoleculesmacromolecules

Need to make polymers of the Need to make polymers of the monomersmonomers

Need to form cellsNeed to form cells Need to be able to pass information Need to be able to pass information

from cell to cellfrom cell to cell

1. Making the first organic 1. Making the first organic moleculesmolecules

Oparin and Haldane – believed organic molecules Oparin and Haldane – believed organic molecules could be synthesized from inorganic molecules in could be synthesized from inorganic molecules in the early atmospherethe early atmosphere

Early atmosphere had no oxygen which usually Early atmosphere had no oxygen which usually scavenges electrons so different reactions can scavenges electrons so different reactions can happenhappen

Also need a lot of energy to form bonds like Also need a lot of energy to form bonds like lightening and radiation from the sun with no ozonelightening and radiation from the sun with no ozone

Miller and Urey – took H2O, H2, CH4, NH3 although Miller and Urey – took H2O, H2, CH4, NH3 although the atmosphere was probably more like CO, CO2, the atmosphere was probably more like CO, CO2, N2 (due to volcanic action) and hit it with electricity N2 (due to volcanic action) and hit it with electricity and were able to make some a.a., sugars, lipids, and were able to make some a.a., sugars, lipids, and nitrogen basesand nitrogen bases

Some believe that all organic cmpds were originally Some believe that all organic cmpds were originally formed from inorganic molecules emitted from formed from inorganic molecules emitted from hyrdothermal vents in the ocean floorhyrdothermal vents in the ocean floor

Some believe they came from spaceSome believe they came from space

2. Must form polymers2. Must form polymers

In living things today, need enzymes to In living things today, need enzymes to form polymersform polymers

If dilute monomers in water – no reactionsIf dilute monomers in water – no reactions If drop onto hot sand or rocks – can make If drop onto hot sand or rocks – can make

proteinsproteins Inorganic catalysts like Zn++ may have Inorganic catalysts like Zn++ may have

helped combine polymershelped combine polymers May have stuck to clay which is charged May have stuck to clay which is charged

and brought monomers close togetherand brought monomers close together

3. Must form cells3. Must form cells Formation of Protobionts – molecules Formation of Protobionts – molecules

aggregating forming a separate internal aggregating forming a separate internal environment - Chemical reactions can take environment - Chemical reactions can take place within it and communicate with place within it and communicate with outsideoutside

Proteinoids – throw some proteins together Proteinoids – throw some proteins together and form microspheres that are selectively and form microspheres that are selectively permeable, can discharge voltage by ion permeable, can discharge voltage by ion flow like nerves,and can divide as add extra flow like nerves,and can divide as add extra proteinprotein

Liposomes – mix lipids together to form a Liposomes – mix lipids together to form a lipid bilayer, able to engulf smaller lipid bilayer, able to engulf smaller liposomes and splitliposomes and split

Coacervates – mix proteins, nucleic acids, Coacervates – mix proteins, nucleic acids, sugars and cell assemble – if add enzymes – sugars and cell assemble – if add enzymes – get taken into coacervate – they can then get taken into coacervate – they can then take in molecules and chemical react using take in molecules and chemical react using the enzymes and put products outthe enzymes and put products out

4. Must be able to pass 4. Must be able to pass instructions to make molecules or instructions to make molecules or

can never improvecan never improve

If want to pass info. on must be able If want to pass info. on must be able to copy itto copy it

Can get RNA to copy itself in a tt/ can Can get RNA to copy itself in a tt/ can act as enyzmesact as enyzmes

RNA can fold into many shapes thru RNA can fold into many shapes thru b.p.b.p.

Some RNA may become more stable, Some RNA may become more stable, copy faster – may be acted on by copy faster – may be acted on by natural selectionnatural selection

Evolution – Chapter 22Evolution – Chapter 22

Taxonomy – grouped things to better Taxonomy – grouped things to better understand them and saw a pattern of understand them and saw a pattern of relatedness relatedness

Kingdom – Phylum – Class – Order – Family – Kingdom – Phylum – Class – Order – Family – Genus - SpeciesGenus - Species

Darwin saw descent with modification – all Darwin saw descent with modification – all living things are descendents of a common living things are descendents of a common ancestor and acquired modifications or ancestor and acquired modifications or adaptations that allowed them to survive in adaptations that allowed them to survive in their environmenttheir environment

Darwin’s FinchesDarwin’s Finches

Darwin – Evolution – Explanation Darwin – Evolution – Explanation for Unity and Diversityfor Unity and Diversity

Observation:Observation: Organisms have more babies than Organisms have more babies than survive and resources can only support so muchsurvive and resources can only support so much

ConclusionConclusion – strongest survive – only those that – strongest survive – only those that can get resourcescan get resources

Observation:Observation: There are variations in There are variations in populations (due to mutation and genetic populations (due to mutation and genetic recombination)recombination)

Observation:Observation: Characteristics best suited to Characteristics best suited to survive reproduce more and pass on those char.survive reproduce more and pass on those char.

Conclusion:Conclusion: Get a gradual change in population Get a gradual change in population over time to those best suitedover time to those best suited

Darwin’s EvolutionDarwin’s Evolution

1.1. Organisms are modified over time Organisms are modified over time (Descent with modification)(Descent with modification)

2.2. Mechanism – Natural Selection Mechanism – Natural SelectionVariation must already be presentVariation must already be presentMust be able to survive to Must be able to survive to reproduce to pass on traits to reproduce to pass on traits to offspringoffspring

Environment acts on inherited Environment acts on inherited variations – Populations evolve not variations – Populations evolve not individualsindividuals

Evidence of EvolutionEvidence of Evolution Artificial Selection – by selecting certain Artificial Selection – by selecting certain

natural variations – we’ve created whole new natural variations – we’ve created whole new organismsorganisms Ex. Pigeons Ex. Pigeons

http://home.iprimus.com.au/spud1/pigeon_pictures.htmhttp://home.iprimus.com.au/spud1/pigeon_pictures.htm Ex. Mustard Plant – forms kale, broccoli, Ex. Mustard Plant – forms kale, broccoli,

cauliflower, cabbage, & brussel sproutscauliflower, cabbage, & brussel sprouts Insecticide treatment of bugsInsecticide treatment of bugs Anti-biotic resistant bacteriaAnti-biotic resistant bacteria Finches – beak size goes up and down due to Finches – beak size goes up and down due to

wet vs. dry yearswet vs. dry years Peppered Moths Peppered Moths

Peppered Moth Video Darwin's finches

Examples of Natural Examples of Natural SelectionSelection

insect mimicry

Evidence of EvolutionEvidence of Evolution Taxonomy – shows living things are all Taxonomy – shows living things are all

related – more similar in structure related – more similar in structure probably the more relatedprobably the more related

Biogeography (where species are Biogeography (where species are distributed) – Organisms living near one distributed) – Organisms living near one another are more like each other than another are more like each other than organisms living in similar environments organisms living in similar environments so came from a common ancestor and so came from a common ancestor and then adapted to the environmentthen adapted to the environment

Fossil Record – fossils show descendancy – Fossil Record – fossils show descendancy – relatedness matches age of fossilsrelatedness matches age of fossils

Don’t find different vertebrate classes in the same Don’t find different vertebrate classes in the same age rock – appears to happen chronologicallyage rock – appears to happen chronologically

Can find transitional fossils linking ancient and Can find transitional fossils linking ancient and modern speciesmodern species

Evidence of Evolution Cont.Evidence of Evolution Cont. Comparative AnatomyComparative Anatomy

Homologous Structures – shows Homologous Structures – shows relatedness vs. individual engineeringrelatedness vs. individual engineering

Vestigial Organs – “left-overs” – no funtion Vestigial Organs – “left-overs” – no funtion in current timesin current times

Comparative Embryology – all Comparative Embryology – all vertebrates go through the same vertebrates go through the same stages early onstages early on

Biochemistry/Molecular Biology – same Biochemistry/Molecular Biology – same DNA in all organisms – looks like DNA in all organisms – looks like modified copies of each other modified copies of each other (mutations to make different proteins)(mutations to make different proteins)

Homologous StructuresHomologous Structures

Homologous Structures show evolutionary Homologous Structures show evolutionary relationships and should be used for classificationrelationships and should be used for classification

Analogous structures do not show evolutionary Analogous structures do not show evolutionary relationship and are not used for classificationrelationship and are not used for classification

Comparative EmbryologyComparative Embryology

Molecular Biology Molecular Biology ComparisonsComparisons

Hierarchy of Living ThingsHierarchy of Living Things

Evolution of Populations Evolution of Populations Chapter 23Chapter 23

PopulationPopulation – groups of same species all – groups of same species all living together – may be geographically living together – may be geographically isolated but may mix some for isolated but may mix some for reproduction but not as often as with ownreproduction but not as often as with own

Gene PoolGene Pool – all the genes available in a – all the genes available in a populationpopulation

Genetic StructureGenetic Structure – frequencies of alleles – frequencies of alleles and genotypesand genotypes

Hardy-WeinbergHardy-Weinberg – the genetic structure of – the genetic structure of a population will stay the same unless a population will stay the same unless acted upon by outside factors (normal acted upon by outside factors (normal genetic recombination won’t change the genetic recombination won’t change the overall frequencies of alleles or genotypes)overall frequencies of alleles or genotypes) This describes a population that is in This describes a population that is in

equilibrium – non-evolving and stableequilibrium – non-evolving and stable

Hardy-Weinberg EquationsHardy-Weinberg Equations If there are 2 alleles at a locus: p+q=1If there are 2 alleles at a locus: p+q=1 p=frequency of 1 allele (usu. dominant)p=frequency of 1 allele (usu. dominant) q=frequency of other allele (recessive)q=frequency of other allele (recessive) Example with genes A and a: A+a=1Example with genes A and a: A+a=1 Chance of getting the AA genotype = chance Chance of getting the AA genotype = chance

of getting A x chance of getting a 2of getting A x chance of getting a 2ndnd A or p A or p22

Chance of getting the genotype aa = chance Chance of getting the genotype aa = chance of getting a x chance of getting an a or qof getting a x chance of getting an a or q22

Chance of getting Aa (2 ways) (Chance of Chance of getting Aa (2 ways) (Chance of getting A x chance of getting a) x 2 or 2pqgetting A x chance of getting a) x 2 or 2pq

Hardy WeinbergHardy Weinberg

All genotypes must = 100%All genotypes must = 100%

Therefore:Therefore: PP22 + 2pq + q + 2pq + q22 = 1 = 1

PP2 = homozygous dominant2 = homozygous dominant

qq2 = homozygous recessive2 = homozygous recessive

2pq2pq = heterozygous = heterozygous

Hardy-WeinbergHardy-Weinberg= A

= a

Allelic frequencies:

A = 19/30 = 0.63 (63%)

a = 11/30 = .37 (37%)

p + q = 1

.63 + .37 = 1

AA (.63) (.63) = .40 (40%)

aa (.37) (.37) = .14 (14%)

Aa (.37) (.63) 2 = .47 (47%)

aA

.40 + .47 + .14 = 1

P2 + 2pq + q2 = 1P2 + 2pq + q2 = 1

Uses of Hardy-WeinbergUses of Hardy-Weinberg Calculate the genotypic frequencies if Calculate the genotypic frequencies if

know alleles or calculate allelic freq. if know alleles or calculate allelic freq. if know genotypesknow genotypes

Example #1:Example #1:20/500 plants are white (aa)

320/500 are red (AA)

160/500 are pink (Aa)

a: 40 alleles + 160 = 200/1000 = 20% or .2

A: 640 alleles + 160 = 800/1000 = 80% or .8

A + a = 1

Example # Example # 2:2:13% of population is homozygous recessive

q2 = .13 q = .36

p + q = 1

P = .64

2pq = Aa Or

p2 + 2pq + q2 = 1p2 + 2pq + q2 = 1

.41 + x + .13 = 1.41 + x + .13 = 1

X = .46 (46% of X = .46 (46% of population is carries the population is carries the genegene

Uses of Hardy-WeinbergUses of Hardy-Weinberg Use equation to calculate what Use equation to calculate what

frequencies expected in next generation frequencies expected in next generation to see if population is changingto see if population is changing

If genetic structure is changing then the If genetic structure is changing then the population is evolvingpopulation is evolving

MicroevolutionMicroevolution – change in genetic – change in genetic structure from one generation to the structure from one generation to the next.next. May have microevolution of some loci and May have microevolution of some loci and

not othersnot others

Hardy/Weinberg PracticeHardy/Weinberg PracticeTesting for H/W EquilibriumTesting for H/W Equilibrium

If a population is in H/W equilibrium, the If a population is in H/W equilibrium, the genotypes will match H/W predictions given the genotypes will match H/W predictions given the allelic frequenciesallelic frequencies

4% of a population has sickle cell anemia 4% of a population has sickle cell anemia (recessive trait)(recessive trait)

Calculate the frequencies for all 3 genotypesCalculate the frequencies for all 3 genotypes In this particular process 60% of the people are In this particular process 60% of the people are

heterozygous and 36% do not have an allele for heterozygous and 36% do not have an allele for sickle cell.sickle cell.

Draw a conclusion based on the expected and Draw a conclusion based on the expected and actual data – make a hypothesis why they are actual data – make a hypothesis why they are different.different.

The interlocking finger The interlocking finger conundrumconundrum

In a small isolated village of 2000 people, In a small isolated village of 2000 people, 1400 people’s left thumb ends up on top 1400 people’s left thumb ends up on top when they interlock their fingers.when they interlock their fingers.

Calculate p and q for this population.Calculate p and q for this population. A few centuries later, this population has A few centuries later, this population has

grown to 5000 people, and there are now grown to 5000 people, and there are now 2000 left thumb on top people. Calculate 2000 left thumb on top people. Calculate p and q.p and q.

It is doubtful that there is any selection It is doubtful that there is any selection going on here. Propose other mechanisms going on here. Propose other mechanisms for the allelic change.for the allelic change.

MicroevolutionMicroevolution Deviation in the Hardy-Weinberg Equation Deviation in the Hardy-Weinberg Equation (i.e. changes in an allelic frequency over (i.e. changes in an allelic frequency over

generations)generations) There are 4 things that can change the There are 4 things that can change the

genetic structure of a population over time genetic structure of a population over time beside mutationbeside mutation

What are these mechanisms? Read about What are these mechanisms? Read about each one on pages 475-479. Each group each one on pages 475-479. Each group member will read about one (non-random member will read about one (non-random mating, genetic drift (founder and mating, genetic drift (founder and bottleneck), gene flow. You can also read bottleneck), gene flow. You can also read about natural selection if you think it is about natural selection if you think it is necessary. Take turns explaining each one.necessary. Take turns explaining each one.

Microevolution ContinuedMicroevolution Continued

You will illustrate each of these You will illustrate each of these mechanisms of allelic change based on a mechanisms of allelic change based on a story about a community of angry birds.story about a community of angry birds.

Mutations are the underlying factor of Mutations are the underlying factor of the other 4 mechanisms of allelic change the other 4 mechanisms of allelic change so we won’t illustrate mutation by itself.so we won’t illustrate mutation by itself.

Now lets go to our story

It’s Now 2075It’s Now 2075

Pick one gene:Pick one gene:

Eyebrow geneEyebrow geneallele 1: V-shapedallele 1: V-shaped

allele 2: sunglass likeallele 2: sunglass like

Head FeatherHead Feather allele 1: roundedallele 1: rounded

gene gene allele 2: pointedallele 2: pointed

Eye geneEye gene allele 1: regularallele 1: regular

allele 2: glowingallele 2: glowing

What is the Red Angry Bird What is the Red Angry Bird Population Like Now?Population Like Now?

For the gene you chose and the mechanism you are assigned, make up a plausible and creative story to explain the mechanism incorporating environmental

factors and correct terminology

What Causes Deviation From Hardy –What Causes Deviation From Hardy –Weinberg?Weinberg?

Genetic driftGenetic drift – changes due to chance – – changes due to chance – only improvement would be luckonly improvement would be luck Larger populations more closely reflects Larger populations more closely reflects

frequency of past generations – smaller frequency of past generations – smaller populations will tend to change by chancepopulations will tend to change by chance

Factors that increase genetic drift:Factors that increase genetic drift: Bottleneck – disasters kill off a bunch – Bottleneck – disasters kill off a bunch –

remaining small population isn’t remaining small population isn’t representative of original population – representative of original population – drift moredrift more

Founder – a small group colonizes an Founder – a small group colonizes an island – small group will tend to not be island – small group will tend to not be representative of whole grouprepresentative of whole group

Deviations from Hardy-Deviations from Hardy-WeinbergWeinberg

Gene FlowGene Flow – genetic exchange – – genetic exchange – interaction of one pop. with anotherinteraction of one pop. with another May be due to migration, wind, etc.May be due to migration, wind, etc. Ex. Other pop. has more aa due to local Ex. Other pop. has more aa due to local

environment so increases freq. in other environment so increases freq. in other populationpopulation

MutationsMutations– change in one allele to – change in one allele to another – must be in gameteanother – must be in gamete Infrequent and usually causes small Infrequent and usually causes small

variation so by itself – doesn’t change variation so by itself – doesn’t change pop. muchpop. much

Provides variation for selectionProvides variation for selection (Don’t forget genetic recombination)(Don’t forget genetic recombination)

Deviations from Hardy-Deviations from Hardy-WeinbergWeinberg

Non-random MatingNon-random Mating – in-breeding, – in-breeding, self-fertilization, only mating in close self-fertilization, only mating in close proximity, mating based on selective proximity, mating based on selective characteristicscharacteristics All usually increase homozygosityAll usually increase homozygosity

******Natural SelectionNatural Selection – Hardy- – Hardy-Weinberg assumes that all genotypes Weinberg assumes that all genotypes have the same ability to survive and have the same ability to survive and reproduce which isn’t true – this is reproduce which isn’t true – this is probably the major factor controlling probably the major factor controlling evolutionevolution

Evolution – Deviation from Evolution – Deviation from Hardy-WeinbergHardy-Weinberg

Anyone of the previous things can cause Anyone of the previous things can cause evolution but natural selection acts on evolution but natural selection acts on all changes to determine what allele has all changes to determine what allele has the highest concentration over time so the highest concentration over time so with natural selection a disproportionate with natural selection a disproportionate # of alleles are passed to the next # of alleles are passed to the next generationgeneration

Natural Selection is the only adaptive Natural Selection is the only adaptive mechanismmechanism

Evolution: Needs variationEvolution: Needs variation Variation must be present though for Variation must be present though for

anything to change therefore mutation anything to change therefore mutation and recombination must be at the rootand recombination must be at the root

Variations must be heritable or can’t effect Variations must be heritable or can’t effect evolutionevolution

However, many mutations wont’ make a However, many mutations wont’ make a difference due to:difference due to: Reduncancy of the genetic codeReduncancy of the genetic code Mutation in non-coding regionsMutation in non-coding regions Mutations in genes not expressedMutations in genes not expressed Mutations not in germ cells Mutations not in germ cells Changes that aren’t adaptiveChanges that aren’t adaptive

Measuring Genetic VariationMeasuring Genetic VariationPolymorphismsPolymorphisms

How many loci aren’t fixedHow many loci aren’t fixed Average # of loci that are heterozygousAverage # of loci that are heterozygous Nucleotide diversity - # of nucleotides Nucleotide diversity - # of nucleotides

different – compare DNA between 2 different – compare DNA between 2 individuals and pool data from many individuals and pool data from many comparisionscomparisions

Our genetic diversity among humans is 14% Our genetic diversity among humans is 14% by gene or loci, but our nucleotide diversity by gene or loci, but our nucleotide diversity is 0.1% so with 6 x 10is 0.1% so with 6 x 1099 b.p – about 6 x 10 b.p – about 6 x 1066

are different or out of every 1000 b.p. – 999 are different or out of every 1000 b.p. – 999 are the sameare the same

Once have variation – Once have variation – Evolution need selective Evolution need selective

pressurepressure Selective Pressure between Selective Pressure between

populations is due to geographic populations is due to geographic variation (different local conditions) – variation (different local conditions) – acts upon previous mutations to acts upon previous mutations to change genetic structure and may change genetic structure and may create subpopulations or clinescreate subpopulations or clines

Selective Pressure within populations Selective Pressure within populations is due to competition for food, is due to competition for food, homes, & mates, environmental homes, & mates, environmental conditions (weather), conditions (weather),

Types of Natural SelectionTypes of Natural Selection StabilizingStabilizing – select against the extremes – select against the extremes

(human birth weight)(human birth weight) DirectionalDirectional – during environmental – during environmental

changes or migration, shifts to a new changes or migration, shifts to a new phenotype (bird beaks, scale sucking fish)phenotype (bird beaks, scale sucking fish)

DiversifyingDiversifying – selects for both extremes – selects for both extremes (finches in Africa – selects against medium (finches in Africa – selects against medium beak that isn’t good at cracking either beak that isn’t good at cracking either food sourced)food sourced)

Separate Selection based on sexSeparate Selection based on sex – leads to – leads to sexual dimorphism (selected bysexual dimorphism (selected by

pressure to mate)pressure to mate)

Natural Selection Should Lead Natural Selection Should Lead Away from Diversity so…Away from Diversity so…

Why do populations remain Why do populations remain diverse?diverse? DiploidyDiploidy – hides variation from selection – – hides variation from selection –

heterozygous conditions keeps alleles in heterozygous conditions keeps alleles in population since recessive alleles can’t be acted population since recessive alleles can’t be acted on by selection when coupled with a dominant on by selection when coupled with a dominant one (protects alleles not suited to environment)one (protects alleles not suited to environment)

Balanced PolymorphismsBalanced Polymorphisms 2 variations may work the best2 variations may work the best Heterozygous advantage – Aa works bestHeterozygous advantage – Aa works best Alternating selective pressure, diversitying Alternating selective pressure, diversitying

selective pressuresselective pressures Neutral EffectsNeutral Effects – variations make no difference – variations make no difference

(not adaptive) but may become adaptive later(not adaptive) but may become adaptive later Not alter reproductive fitness (Huntingdon’s)Not alter reproductive fitness (Huntingdon’s)

Why Populations Remain Why Populations Remain DiverseDiverse

Continued MutationContinued Mutation – the same mutation – the same mutation may keep arising like in neurofibromatosismay keep arising like in neurofibromatosis 1/4000 spontaneous gamete mutations1/4000 spontaneous gamete mutations

Gene FlowGene Flow – gene may not be deleterious in – gene may not be deleterious in a nearby population (ex. Sickle cell allele)a nearby population (ex. Sickle cell allele)

Natural Selection may not have had time to Natural Selection may not have had time to remove the allele yetremove the allele yet – may have not been – may have not been deleterious previously and is now being deleterious previously and is now being selected against but not yet gone (ex. selected against but not yet gone (ex. Cystic fibrosis in Caucasians – allele gives Cystic fibrosis in Caucasians – allele gives resistance to cholera)resistance to cholera)

SpeciationSpeciation

New species appear in rock – where did New species appear in rock – where did they come from? How did new species they come from? How did new species form?form?

SpeciesSpecies – can interbreed and produce – can interbreed and produce fertile offspring under natural conditions – fertile offspring under natural conditions – physically and biochemically distinct – not physically and biochemically distinct – not just mixturesjust mixtures

AnagenesisAnagenesis – one species transforms into – one species transforms into anotheranother

CladogenesisCladogenesis – an ancestor produces one – an ancestor produces one or more different variations and all exist or more different variations and all exist simaltaneously (increases the # of simaltaneously (increases the # of species)species)

Why species remain distinctWhy species remain distinct

Pre-zygotic BarriersPre-zygotic Barriers Habitat Isolation – live in different areasHabitat Isolation – live in different areas Behavioral Isolation – mating rituals, firefly Behavioral Isolation – mating rituals, firefly

lighting patternslighting patterns Temporal Isolation – different mating times Temporal Isolation – different mating times

(seasonal), different times of flowering, (seasonal), different times of flowering, nocturnal vs. daynocturnal vs. day

Mechanical Isolation – physically Mechanical Isolation – physically impossible to mateimpossible to mate

Gametic Isolation – gametes can’t match Gametic Isolation – gametes can’t match upup

Why Species remain distinctWhy Species remain distinct

Post-zygotic BarriersPost-zygotic Barriers Poor Hybrid viability – embryos diePoor Hybrid viability – embryos die Poor Hybrid fertility – offspring can’t Poor Hybrid fertility – offspring can’t

reproducereproduce Hybrid Breakdown – make a weak or Hybrid Breakdown – make a weak or

sterile second generationsterile second generation

Origin of New Species – Origin of New Species – members must become separated so members must become separated so

acted on differently by natural acted on differently by natural selectionselection

Allopatric SpeciationAllopatric Speciation – a population – a population becomes separated by a physical becomes separated by a physical barrier – have different selective barrier – have different selective pressures after separation pressures after separation

Examples Examples migration to different islandsmigration to different islands New mountain separates themNew mountain separates them Lake dries up to multiple little pondsLake dries up to multiple little ponds

Origin of New Species Cont.Origin of New Species Cont. Sympatric Speciation – a population Sympatric Speciation – a population

becomes reproductively isolated but still becomes reproductively isolated but still lives with the parent populationlives with the parent population

ExamplesExamples Plant that becomes polyploid can only Plant that becomes polyploid can only

reproduce with other polyploid plants and not reproduce with other polyploid plants and not others of its kind (25-50% of plants – oats, others of its kind (25-50% of plants – oats, cotton, potatoes, tobacco)cotton, potatoes, tobacco)

Animals – genetic change causes a difference Animals – genetic change causes a difference that keeps them from mating – may eat a that keeps them from mating – may eat a different food source and don’t mate with different food source and don’t mate with others eating a different food source. May others eating a different food source. May become adapted to live on a certain plant and become adapted to live on a certain plant and never meet the group living on a different plantnever meet the group living on a different plant

Sex Selection may play a role (females only Sex Selection may play a role (females only mate with males with a certain trait)mate with males with a certain trait)

Why evolution takes places Why evolution takes places once a population becomes once a population becomes

separatedseparated Organisms on the edge are usually Organisms on the edge are usually

different anywaydifferent anyway Founder effect (small group leaving may Founder effect (small group leaving may

not be representative of whole)not be representative of whole) Genetic DriftGenetic Drift Neutral mutations may become fixed Neutral mutations may become fixed

without selective pressures due to small without selective pressures due to small population sizepopulation size

Different selective pressuresDifferent selective pressures

Therefore: Microevolution over time slowly Therefore: Microevolution over time slowly changes each populationchanges each population

This is called adaptive divergence – This is called adaptive divergence – adapt to environment which causes a adapt to environment which causes a 2ndary reproductive isolation2ndary reproductive isolation

Sometimes there are adaptive “peaks” Sometimes there are adaptive “peaks” – may have several forms that are – may have several forms that are optimized for success (more than 1 optimized for success (more than 1 selective pressure) and chance may selective pressure) and chance may cause to a change in form or cause to a change in form or environment may slowly change environment may slowly change causing a shift from 1 peak to another causing a shift from 1 peak to another

What happens if separated What happens if separated species come back together?species come back together?

May interbreed and become a mix May interbreed and become a mix May stay separate due to May stay separate due to

reproductive barriersreproductive barriers Hybrid Zone – only interbreed where Hybrid Zone – only interbreed where

overlap and other parts of population overlap and other parts of population remain separateremain separate

If there aren’t true reproductive If there aren’t true reproductive barriers – still a separate species?barriers – still a separate species?

MacroevolutionMacroevolution substantial change in organismssubstantial change in organisms Origin of taxonmic groups higher than Origin of taxonmic groups higher than

speciesspecies Origin of new phyla, classes, orders, Origin of new phyla, classes, orders,

familiesfamilies Is it due to the cumulative product of Is it due to the cumulative product of

microevolution or some big event microevolution or some big event or…????or…????

The appearance of flowering plants The appearance of flowering plants seems to be all at once?????seems to be all at once?????

The appearance of mammals seems to The appearance of mammals seems to be all at once?????be all at once?????

Punctuated EquilibriumPunctuated Equilibrium

Big changes (episodes of speciation) Big changes (episodes of speciation) followed by slow gradual change (if followed by slow gradual change (if optimized for environment – shouldn’t be a optimized for environment – shouldn’t be a lot of change due to selection unless large lot of change due to selection unless large change in selection pressures)change in selection pressures)

Due to quick geographic separation and Due to quick geographic separation and genetic driftgenetic drift

Due to sudden genome changesDue to sudden genome changes Changes may not be shown in fossilsChanges may not be shown in fossils

FossilsFossils Organic parts of dead organisms decay – rest of Organic parts of dead organisms decay – rest of

inorganic material like shells etc. remain in inorganic material like shells etc. remain in sedimentary rocksedimentary rock

Minerals may replace organic part of dead Minerals may replace organic part of dead organisms and harden it which preserves it organisms and harden it which preserves it (petrification)(petrification)

May leave a mold (imprint) in rock that is later May leave a mold (imprint) in rock that is later hardened by minerals (makes a cast) May be hardened by minerals (makes a cast) May be footprints, burrows, things that leave hints of footprints, burrows, things that leave hints of behaviorbehavior

Whole organism may be preserved in the absence Whole organism may be preserved in the absence of decomposers like in amber, ice, acid bogs, dry of decomposers like in amber, ice, acid bogs, dry areasareas

Dead organism pressed between rocks – may Dead organism pressed between rocks – may preserve even organic parts like cells – sometimes preserve even organic parts like cells – sometimes pollen is preserved because it is in a hard casepollen is preserved because it is in a hard case

Fossils continuedFossils continued

Most fossils would be organisms that Most fossils would be organisms that lasted a long time, were abundant, lasted a long time, were abundant, had shells or hard skeletonshad shells or hard skeletons

Any fossils found are by luckAny fossils found are by luck Had to wash with sedimentsHad to wash with sediments Rock had to last untouchedRock had to last untouched Had to be exposedHad to be exposed Had to be foundHad to be found

Dating FossilsDating Fossils Sedimentation isn’t uniform – rocks are Sedimentation isn’t uniform – rocks are

found in layers or strata – the further down found in layers or strata – the further down “the stack”, the older it is (only relative “the stack”, the older it is (only relative age)age)

Correlate age of strata from 1 place to Correlate age of strata from 1 place to another by similar strata with same fossilsanother by similar strata with same fossils

Based on times of great change between Based on times of great change between strata, mass extinction followed by an strata, mass extinction followed by an explosion in adaptive radiation divides explosion in adaptive radiation divides Earth’s history into 4 eras: Precambrian, Earth’s history into 4 eras: Precambrian, Paleozoic, Mesozoic, CenozoicPaleozoic, Mesozoic, Cenozoic

Radiometric DatingRadiometric Dating Use ½ life of radioactive elements Use ½ life of radioactive elements Time it takes for 50% to decayTime it takes for 50% to decay Know ratio of C-14/C-12 in living Know ratio of C-14/C-12 in living

thingsthings Measure how much relative C-14/C12 Measure how much relative C-14/C12

now and can tell how many ½ livesnow and can tell how many ½ lives Example: Fossil has ¼ C-14/C-12 as Example: Fossil has ¼ C-14/C-12 as

living organism = 2 ½ lives – to get living organism = 2 ½ lives – to get age – take ½ life of C-14 x 2.age – take ½ life of C-14 x 2.

Dating QuestionsDating Questions

How do we know that ½ life is a steady How do we know that ½ life is a steady decaydecay

How do we know it isn’t altered by climateHow do we know it isn’t altered by climate How do we know fossil had same ratio as How do we know fossil had same ratio as

living organisms todayliving organisms today How accurate is the measure of C-14/C-12How accurate is the measure of C-14/C-12 Error is 10% - how do you measure error?Error is 10% - how do you measure error?

Mechanisms of Mechanisms of MacroevolutionMacroevolution

Pre-adaptationPre-adaptation – structure is adapted – structure is adapted for 1 thing and later used for another for 1 thing and later used for another function (gradual change in existing function (gradual change in existing structure leads to a new function)structure leads to a new function) Example – lattice-like bones of birds – Example – lattice-like bones of birds –

some dinosaurs had it but must have some dinosaurs had it but must have had another functionhad another function

Changes in developmental genesChanges in developmental genes Heterchrony – changes in Heterchrony – changes in

developmental timing or ratedevelopmental timing or rate Homeosis – alteration in placement of Homeosis – alteration in placement of

body partsbody parts

Developmental Gene Developmental Gene ChangesChanges

Examples:Examples: Allometric growth – differences in Allometric growth – differences in

relative rate of growth of a certain part relative rate of growth of a certain part during development like skull bones and during development like skull bones and brainsbrains

Padeomorphosis – change in Padeomorphosis – change in developmental timing – adult keeps developmental timing – adult keeps characteristics of juvenile form of characteristics of juvenile form of ancestorancestor

Changes in genes that control Changes in genes that control rate of growth or rate of growth or

developmental timing can developmental timing can make big changesmake big changes

Mechanisms of Macroevol. Mechanisms of Macroevol. Cont.Cont.

Species SelectionSpecies Selection – things evolve into – things evolve into other species or may branch into other other species or may branch into other species and only strongest species species and only strongest species survivessurvives

Mass ExtinctionMass Extinction – due to huge – due to huge geographical changes (climate, geographical changes (climate, destruction of habitats) – leaves it open destruction of habitats) – leaves it open for species to fill new places “adaptive for species to fill new places “adaptive radiation”radiation”

Examples: Continental DriftExamples: Continental Drift End of PaleozoicEnd of Paleozoic – Pangaea formed – Pangaea formed

Permian extinction – species now in Permian extinction – species now in competition with things never saw competition with things never saw beforebefore

Less shore-line, extreme volcanism with Less shore-line, extreme volcanism with great temperature effectsgreat temperature effects

Mass extinction (90% species gone) – Mass extinction (90% species gone) – chance for new specieschance for new species

Early MesozoicEarly Mesozoic – Pangaea breaks up – Pangaea breaks up – geographical isolation– geographical isolation Formation of mountains, new islands, Formation of mountains, new islands,

earthquakesearthquakes

Mass Extinction causing Mass Extinction causing Macroevolution Cont.Macroevolution Cont.

Cretaceous ExtinctionCretaceous Extinction – possible asteroid – possible asteroid hit – large layer of rock made of sediments hit – large layer of rock made of sediments found in asteroids but not on earth (large found in asteroids but not on earth (large craters present)craters present)

loss of more than 50% of marine speciesloss of more than 50% of marine species Cooler tempatures, shallow seas recededCooler tempatures, shallow seas receded

With any of these times of mass extinction With any of these times of mass extinction – surviving species are a stock for new – surviving species are a stock for new

radiations, fossils do show periods of mass radiations, fossils do show periods of mass extinction and adaptive radiations, extinction and adaptive radiations,

organisms filling the void left by othersorganisms filling the void left by others

Mechanisms of Macroevolution Mechanisms of Macroevolution Cont.Cont.

Accumulation of MicroevolutionAccumulation of Microevolution not not preserved in fossil record or preserved in fossil record or intermediates not found due to small intermediates not found due to small numbersnumbers

CladogramsCladogramsDiagrams that show probable relationships between the taxa, Diagrams that show probable relationships between the taxa, sequence of origin, common ancestors, shared characteristicssequence of origin, common ancestors, shared characteristics

Systematics – study of biodiversity Systematics – study of biodiversity in an evolutionary contextin an evolutionary context

Want to decide an organisms taxa based on Want to decide an organisms taxa based on evolutionary relationshipsevolutionary relationships

How do scientists decide?How do scientists decide? Comparative AnatomyComparative Anatomy

Analogous structures – similar due to like Analogous structures – similar due to like environments, built from different structures environments, built from different structures (ex. Wings or birds and insects)(ex. Wings or birds and insects)

Homologous structures – similar due to common Homologous structures – similar due to common structure and therefore common ancestry (ex. structure and therefore common ancestry (ex. Wing of bat, whale fin, arm of human, paw of Wing of bat, whale fin, arm of human, paw of dog)dog)

Should only use homologous structures for Should only use homologous structures for classificaitonclassificaiton

Problem with comparative anatomy – like Problem with comparative anatomy – like structures not necessarily from common structures not necessarily from common ancestor – may be due to convergent evolution – ancestor – may be due to convergent evolution – shaped by same environmental factorsshaped by same environmental factors

Systematics – classifying Systematics – classifying cont.cont.

ProteinsProteins – closer the aa sequence – probably – closer the aa sequence – probably from a closer common ancestorfrom a closer common ancestor

DNADNA – closer nucleotides sequences – more – closer nucleotides sequences – more related (dolphins are closer to bats than related (dolphins are closer to bats than sharks) sharks) Can extract DNA from fossilsCan extract DNA from fossils DNA-DNA Hybridization – see overall similarity of DNA-DNA Hybridization – see overall similarity of

genomes by checking amountof H-bonding genomes by checking amountof H-bonding between 2 ss DNA’s from 2 different organismsbetween 2 ss DNA’s from 2 different organisms

Restriction MappingRestriction Mapping DNA sequencing – compare rRNA’s to look for DNA sequencing – compare rRNA’s to look for

branching since seems to have changed the branching since seems to have changed the slowestslowest

Molecular clocks – if rate of DNA change is constant Molecular clocks – if rate of DNA change is constant and can calculate when diverged using fossils and can calculate when diverged using fossils dating – can calculate the rate of DNA change/timedating – can calculate the rate of DNA change/time

Summary of MacroevolutionSummary of Macroevolution

May be due to rapid changes:May be due to rapid changes: Mass separationsMass separations Rapidly changing environmentsRapidly changing environments Chromosomal or developing genes Chromosomal or developing genes

mutatingmutating Mutations acted upon by huge Mutations acted upon by huge

genetic drift and selectiongenetic drift and selection Mass extinctions causing adaptive Mass extinctions causing adaptive

radiationsradiations

Remaining Questions about Remaining Questions about MacroevolutionMacroevolution

Could it really be compounded Could it really be compounded microevolution?microevolution?

What is gradual vs. quick?What is gradual vs. quick? Is the fossil record complete?Is the fossil record complete? Do different mechanisms work at Do different mechanisms work at

different levels?different levels?