Classification & EvolutionClassification & Evolution

Evolution - MicroevolutionEvolution - MicroevolutionA change within the gene pool of A change within the gene pool of a population over time (changes a population over time (changes

in the percentages of alleles)in the percentages of alleles)

Lamarck vs. DarwinLamarck vs. Darwin

The Theory of EvolutionThe Theory of EvolutionDarwin Darwin

Descent with Modification: Descent with Modification: DarwinDarwin - Organisms can have offspring that are - Organisms can have offspring that are

modified forms of themselves.modified forms of themselves. Modern InterpretationModern Interpretation – DNA mutations and – DNA mutations and

genetic recombination through meiosis and genetic recombination through meiosis and fertilization cause variations within populationsfertilization cause variations within populations

Natural SelectionNatural Selection Organisms have more babies than can be Organisms have more babies than can be

supported by the environmentsupported by the environment The most successful at surviving and The most successful at surviving and

reproducing pass those genes on and become reproducing pass those genes on and become more numerous in the populationmore numerous in the population

Therefore, evolution is due to Therefore, evolution is due to multiple forms within multiple forms within

populations – if an uncommon populations – if an uncommon form works better – it will form works better – it will

become more common over become more common over time time (populations change over (populations change over time to what works the best)time to what works the best)

These smaller changes become These smaller changes become bigger over time. The bigger over time. The commonalities among commonalities among

organisms are evidence of organisms are evidence of common ancestry.common ancestry.

Selection Factors Selection Factors (Pressures)(Pressures)

Predator/Prey – ability to get prey or Predator/Prey – ability to get prey or evade predatorsevade predators

Competition – better competitor for Competition – better competitor for food, homes, matesfood, homes, mates

Abiotic Factors (amt. of ppt., wind, Abiotic Factors (amt. of ppt., wind, type of soil, amt. of sunlight, type of soil, amt. of sunlight, temperature)temperature)

Sex SelectionSex Selection

The five mechanisms of The five mechanisms of evolution – evolution – It’s not just Natural It’s not just Natural

SelectionSelection

Small population (Genetic Drift)Small population (Genetic Drift) – next – next generation doesn’t match probability so generation doesn’t match probability so get a change in the allelic frequencies due get a change in the allelic frequencies due to chanceto chance

Non-random matingNon-random mating – type of selection – type of selection MutationMutation Gene FlowGene Flow – things moving in or out of a – things moving in or out of a

population changing the allelic frequenciespopulation changing the allelic frequencies Natural SelectionNatural Selection – most important and – most important and

only one that makes improvements!only one that makes improvements!

5 Fingers of Evolution - TedEd

Examples of the 5 Examples of the 5 mechanisms of Evolutionmechanisms of Evolution

Natural Selection is the only Natural Selection is the only mechanism of evolution that creates mechanism of evolution that creates

Adaptations!!Adaptations!!Adaptations:

Genetic traits that allow organisms to survive better in their environment

Even though natural selection Even though natural selection causes things to generally causes things to generally improve and become more improve and become more

adapted to their environment, adapted to their environment, evolution doesn’t always create evolution doesn’t always create

the “perfect” best adapted the “perfect” best adapted forms if the “perfect” random forms if the “perfect” random

mutation doesn’t happenmutation doesn’t happen

Why biodiversity remainsWhy biodiversity remains Even though natural selection tends to Even though natural selection tends to

eliminate diversity for the best suited eliminate diversity for the best suited forms – diversity is maintained by:forms – diversity is maintained by: Meiosis and genetic recombinationMeiosis and genetic recombination HeterozygosityHeterozygosity Continued mutationsContinued mutations Neutral mutationsNeutral mutations Multiple Selection FactorsMultiple Selection Factors Continuously changing environmentsContinuously changing environments

This is important because if environment This is important because if environment changes – there will be a part of the changes – there will be a part of the population or species that can survivepopulation or species that can survive

Evidence of EvolutionEvidence of Evolution

1. Direct evidence:1. Direct evidence: FinchesFinches FishFish peppered mothspeppered moths InsectsInsects bacteriabacteria

Evidence of Evolution Evidence of Evolution ContinuedContinued

2. Artificial Selection2. Artificial Selection PigeonsPigeons Mustard PlantMustard Plant

3.3. Fossils – Fossils – see new things and see many see new things and see many things disappearthings disappear

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

See fossils of things that no longer exist and things See fossils of things that no longer exist and things that weren’t in the older fossils – appears to be newthat weren’t in the older fossils – appears to be new

Evidence of Evolution Evidence of Evolution ContinuedContinued

4.4. Taxonomy (The Study of Taxonomy (The Study of Classification)Classification)

Shows unity and diversity – everything Shows unity and diversity – everything seems to be related and modified seems to be related and modified

versions of each otherversions of each other

Taxonomy – Taxonomy – the study of the study of classificationclassification

Why do we classify things?Why do we classify things?Helps us understand how things are related Helps us understand how things are related which helps us understand things in generalwhich helps us understand things in general

Linnaeus came up with a classification Linnaeus came up with a classification system to better understand living thingssystem to better understand living things

The system ended up being a hierarchyThe system ended up being a hierarchy

What is a hierarchy?What is a hierarchy?

Classify shoes with a partnerClassify shoes with a partner Is this a hierarchy?Is this a hierarchy? What does it help us understand What does it help us understand

about shoes?about shoes? What is the classification scheme for What is the classification scheme for

living things like?living things like?

The classification systemThe classification system Domain, Kingdom, Phylum, Class, Domain, Kingdom, Phylum, Class,

Order, Family, Genus, SpeciesOrder, Family, Genus, Species (Kings play cards on fine green sheets)(Kings play cards on fine green sheets) The hierarchy shows a unity that all The hierarchy shows a unity that all

living things are related and share a living things are related and share a common ancestor (seem to be common ancestor (seem to be modified versions of each other)modified versions of each other)

It also shows diversity – that they have It also shows diversity – that they have changed a great deal over timechanged a great deal over time

Biological TaxaBiological Taxa

Example of ClassificationExample of Classification Goes from general to Goes from general to

specificspecific Continually branchesContinually branches The longer things stay The longer things stay

together before together before branching, the more branching, the more they have in commonthey have in common

If two things are in the If two things are in the same category – they same category – they share everything more share everything more general in commongeneral in common

TaxonomyTaxonomyAll living things have some things in common

Some have more things in common and more closely related

The further down the scheme they stay together (from general to specific), the more traits they share in common and the more related they are

How do we Classify to show How do we Classify to show

evolutionary relationshipsevolutionary relationships?? Comparative AnatomyComparative Anatomy

Homologous Structures – structurally similar Homologous Structures – structurally similar even though have different functions (shows even though have different functions (shows relatedness vs. individual engineering)relatedness vs. individual engineering)

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

Comparative Embryology Comparative Embryology – – the longer in the longer in development things look the same the more development things look the same the more related – ex. all vertebrates go through the same related – ex. all vertebrates go through the same stages early on – changes in genes and reading of stages early on – changes in genes and reading of genes causes different formsgenes causes different forms

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

Comparative AnatomyComparative Anatomy

Analogous structures – similar due to like Analogous structures – similar due to like environments, built from different structures (ex. environments, built from different structures (ex. Wings or birds and insects) Wings or birds and insects) DO NOT SHOW DO NOT SHOW RELATEDNESS – NOT USED FOR CLASSIFICATIONRELATEDNESS – NOT USED FOR CLASSIFICATION

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 dog)Wing of bat, whale fin, arm of human, paw of dog)

Use ONLY homologous structures for classificationUse ONLY homologous structures for classification Problem with comparative anatomy – like Problem with comparative anatomy – like

structures not necessarily from common ancestor structures not necessarily from common ancestor – may be shaped by same environmental factors– may be shaped by same environmental factors

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 EmbryologyLiving things share some common embryological development Living things share some common embryological development

– the longer the same, the more related– the longer the same, the more related

Comparative BiochemistryComparative BiochemistryAll things show some DNA and protein relatedness – the more All things show some DNA and protein relatedness – the more

DNA and proteins they have in common – the more closer DNA and proteins they have in common – the more closer related.related.

If they have the same protein, more amino acids in common in If they have the same protein, more amino acids in common in the protein – the more relatedthe protein – the more related

Comparative BiochemComparative BiochemIf have same proteins, closer their DNA sequences – the more If have same proteins, closer their DNA sequences – the more

alikealike

Dolphins are closer related to bats than sharks – can tell through proteins and DNA that they are more

related

Evolution – a step furtherEvolution – a step further MicroevolutionMicroevolution – change in the gene – change in the gene

pool within a population (change in pool within a population (change in allelic frequencies)allelic frequencies)

SpeciationSpeciation – creation of new species – creation of new species MacroevolutionMacroevolution – creating all of the – creating all of the

various taxa from a common various taxa from a common ancesterancester

Species ConceptSpecies Concept

Species – organisms that Species – organisms that interbreed and produce fertile interbreed and produce fertile

offspring under natural offspring under natural conditionsconditions

Speciation – the formation of Speciation – the formation of new speciesnew species

Species concept - Why species remain Species concept - Why species remain distinct:distinct:

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 impossible Mechanical Isolation – physically impossible to mateto mate

Gametic Isolation – gametes can’t match upGametic Isolation – gametes can’t match up Infertility of HybridsInfertility of Hybrids

Speciation – Speciation – see the appearance of new see the appearance of new species in fossils – where did they come from?species in fossils – where did they come from?

Production of new species due to Production of new species due to separationseparation 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

Separated groups undergo different Separated groups undergo different mutations mutations

Each separated part of the species is Each separated part of the species is acted upon by different “selectors” and acted upon by different “selectors” and eventually become so different that they eventually become so different that they can’t or do not any longer interbreedcan’t or do not any longer interbreed

Examples of SpeciationExamples of Speciation

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

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

anywayanyway Small group leaving may not be Small group leaving may not be

representative of wholerepresentative of whole More change due to chance in small groupsMore change due to chance in small groups 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 mutationsDifferent mutations Different selective pressuresDifferent selective pressures

Therefore: Microevolution over time slowly Therefore: Microevolution over time slowly changes each population until they are changes each population until they are

different speciesdifferent species

MacroevolutionMacroevolution substantial change in organismssubstantial change in organisms 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 The appearance of mammals seems to be all at once?????to 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

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 suddently to a new structure leads suddently to a new function)function) Example – lattice-like bones of birds – Example – lattice-like bones of birds –

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

Changes in developmental genesChanges in developmental genes Mass ExtinctionMass Extinction – due to huge – due to huge

geographical changes (climate, geographical changes (climate, destruction of habitats) – leaves it destruction of habitats) – leaves it open for species to fill new placesopen for species to fill new places

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

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

radationsradations

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? What is missing from the fossil What is missing from the fossil

record?record? Do different mechanisms work at Do different mechanisms work at

different levels?different levels?