Understanding Evolution Conceptual Framework

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Understanding Evolution conceptual framework

This list of conceptual understandings regarding evolution are aligned across grade levels to help instructors identify

age-appropriate learning goals for their students and understand how concepts taught at one grade level lay thegroundwork for more sophisticated concepts later on. Access a printable pdfversion of this document.

The Framework is divided into five strands:History of life | Evidence of evolution | Mechanisms of evolution | Nature of science | Studying

evolution

History of life

Guide to Evo 101

Conceptual framework

Teaching resourcedatabase

Image library

Dealing withobjections to evolution

Correctingmisconceptions

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Life has been on Earth along time.

Life has been on Earthfor billions of years.

Biological evolutionaccounts for diversityover long periods of time.



Life forms have changedover time.

Life forms have changedover time.

Through billions o f yearsof evolution, life formshave continued todiversify in a branchingpattern, from single-celledancestors to the diversityof life on Earth today.

Through billions of yearsof evolution, life formshave continued todiversify in a branchingpattern, from single-celledancestors to the diversityof life on Earth today.

Through billions of yearsof evolution, life formshave continued todiversify in a branchingpattern, from single-celledancestors to the diversityof life on Earth today.

Many forms of life in thepast were different fromliving things today.

Many forms of life in thepast were similar topresent-day living things.

Life forms of the pastwere in some ways verydifferent from living formsof today, but in otherways very similar.



Evolution is still continuingtoday.

Humans directly impactbiodiversity, which maythen impact futureevolutionary potential.

Present-day life formsare related to past life

forms.

Present-day life formsare descended from past

life forms; all life isrelated.

Present-day speciesevolved from earlier

species; the relatednessof organisms is the result

Present-day speciesevolved from earlier

species; the relatednessof organisms is the result

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of common ancestry.

Life on Earth 3.8 billionyears ago consisted ofone-celled organismssimilar to present-daybacteria.

There is evidence ofeukaryotes in the fossilrecord from about one

billion years ago; somewere the precursors ofmulticellular organisms.

The early evolutionaryprocess of eukaryotesincluded the merging ofprokaryote cells.

of common ancestry.

Life on Earth 3.8 billionyears ago consisted ofone-celled organismssimilar to present-daybacteria.

There is evidence ofeukaryotes in the fossilrecord from about one

billion years ago; somewere the precursors ofmulticellular organisms.

The early evolutionaryprocess of eukaryotesincluded the merging ofprokaryote cells.

Geological change andbiological evolution arelinked.

Tectonic plate movementhas affected thedistribution and evo lution

of living things.

Living things have had amajor influence on thecomposition o f theatmosphere and on thesurface of the planet.


Tectonic plate movementhas affected the evolutionand distribution of living

things.

Living things have had amajor influence on thecomposition o f theatmosphere and on thesurface of the planet.


Tectonic plate movementhas affected the evolutionand distribution of living

things.

Living things have had amajor influence on thecomposition of theatmosphere and on thesurface of the planet.

Many life forms havegone extinct.

Most species that oncelived on Earth have goneextinct.

Most species that oncelived on Earth have goneextinct.

During the course ofevolution, only a smallpercentage of specieshave survived untiltoday.

During the course ofevolution, only a smallpercentage of specieshave survived untiltoday.

Background extinctionsare a normal occurrence.


Rates of extinction vary.


Rates of extinction vary.

Mass extinctions occur.

Extinction can result fromenvironmental change.





Human influence may becausing a modern massextinction.

Extinction can stimulateevolution by opening upresources.

Extinctions may createopportunities for furtherevolution in other lineagesto occur.

Extinctions may createopportunities for furtherevolution in other lineagesto occur.

Rates of evolution vary. Rates of evolution vary.


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Evidence of evolution

Rates of speciation vary.

Evolutionary change cansometimes happenrapidly.

Some lineages remainrelatively unchanged forlong periods of time.

Rates of speciation vary.

Evolutionary change cansometimes happenrapidly.

Some lineages remainrelatively unchanged forlong periods of time.

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Today there are manydiverse forms of life.

Life is very diverse. The patterns of life'sdiversity through timeprovide evidence ofevolution.

The patterns of life'sdiversity through timeprovide evidence ofevolution.

The patterns of life'sdiversity through timeprovide evidence ofevolution.

Evolution can sometimesbe directly observed.

Plants and animals havefeatures that allow them

to live in variousenvironments.

There is a fit betweenorganisms and their

environments, thoughnot always a perfect fit.

An organism's featuresreflect its evolutionary

history.


history.


history.

Form is linked to function. Form is linked to function. There is a fit betweenorganisms and theirenvironments, though notalways a perfect fit.

There is a fit between theform of a trait and itsfunction, though notalways a perfect fit.

Some traits of organismsare not adaptive.

There is a fit betweenorganisms and theirenvironments, though notalways a perfect fit.


Some traits of organismsare not adaptive.Featuressometimes acquire new

functions through naturalselection.

There is a fit betweenorganisms and theirenvironments, though notalways a perfect fit.


Some traits of organismsare not adaptive.Featuressometimes acquire new

functions through naturalselection.

Fossils provide evidenceof past life.



The fossil record providesevidence for evolution.

The fossil record providesevidence for evolution.

The fossil recorddocuments thebiodiversity of the past.

The fossil recorddocuments thebiodiversity of the past.

The fossil record containsorganisms withtransitional features.


The fossil recorddocuments patterns o f

extinction and theappearance of new


The fossil recorddocuments patterns o f

extinction and theappearance of new


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forms. forms.

The sequence of forms inthe fossil record isreflected in the sequenceof the rock layers in whichthey are found andindicates the order inwhich they evolved.


Radiometric dating can

often be used todetermine the age offossils.


Radiometric dating can

often be used todetermine the age offossils.

Living things are alike insome ways and differentin other ways.

There are similarities anddifferences among fossilsand living organisms.




All life forms sharefundamental similarities.

Similarities amongexisting organismsprovide evidence forevolution.

Similarities amongexisting organisms(including morphological,developmental, andmolecular similarities)reflect common ancestryand provide evidence forevolution.

Anatomical similarities o fliving things reflectcommon ancestry.

There are similarities inthe cell function of allorganisms.

All life forms use thesame basic DNA buildingblocks.

Anatomical similarities o fliving things reflectcommon ancestry.

There are similarities inthe cell function of allorganisms.

All life forms use thesame basic DNA buildingblocks.

Developmental similaritiesof living things oftenreflect their relatedness.

Not all similar traits arehomologous; some arethe result of convergentevolution.



The geographicdistribution of speciesoften reflects howgeologic change hasinfluenced lineagesplitting.

Selective breeding canproduce offspring with

new traits.

Artificial selectionprovides a model for

natural selection.


natural selection.


natural selection.


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Mechanisms o f evolution

People selectively breeddomesticated plants andanimals to produceoffspring with preferredcharacteristics.



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Evolution is often definedas a change in allelefrequencies within apopulation.

The Hardy-Weinbergequation describesexpectations about thegene pool of a populationthat is not evolving onethat is very large, matesrandomly, and does notexperience mutation,natural selection, or gene

flow.

Evolution results fromnatural selection actingupon variation within apopulation.

Evolution occurs throughmultiple mechanisms.

Evolution results fromselection acting upongenetic variation within apopulation.

Evolution occurs throughmultiple mechanisms.

Evolution results fromnatural selection actingupon genetic variationwithin a population.

Evolution results fromgenetic drift acting upongenetic variation within apopulation.

Evolution results fromgenetic drift acting upongenetic variation within apopulation.

Evolution results from

mutations.

Evolution results fromgene flow.

Evolution results fromhybridization.

There is variation withina population.



Variation is the result ofgenetic recombination ormutation.

The variation that occurs

within a population israndom.


Natural selection acts onthe variation that exists ina population.

Natural selection andgenetic drift act on thevariation that exists in apopulation.


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Natural selection acts onphenotype as anexpression of genotype.

The amount of geneticvariation within apopulation may affect thelikelihood of survival ofthe population; the lessthe available diversity, theless likely the population

will be able to surviveenvironmental change.

Natural selection acts onphenotype as anexpression of genotype.

Phenotype is a product ofboth genotype and theorganism's interactionswith the environment.

Variation of a characterwithin a population may

be discrete or continuous.

Continuous charactersare generally influencedby many different genes.

Living things haveoffspring.

Offspring inherit manytraits from their parents,but are not exactlyidentical to their parents.

Offspring inherit manytraits from their parents,but are not identical totheir parents.

New heritable traits canresult fromrecombinations ofexisting genes or fromgenetic mutations inreproductive cells.

New heritable traits canresult from mutations.

Mutations are random. Mutation is a randomprocess.

Offspring inherit manytraits from their parents,but are not exactly thesame as their parents.

Siblings are similar to, butnot identical to, oneanother.

Organisms cannotintentionally produceadaptive mutations inresponse toenvironmental influences.

Complex structures maybe produced incrementallyby the accumulation ofsmaller useful mutations.

Organisms cannotintentionally produceadaptive mutations inresponse toenvironmental influences.

Complex structures maybe produced incrementallyby the accumulation ofsmaller advantageousmutations.

Advantageous featureshelp living things survive.

Traits that areadvantageous oftenpersist in a population.

Inherited characteristicsaffect the likelihood of anorganism's survival andreproduction.

Inherited characteristicsaffect the likelihood of anorganism's survival andreproduction.

Depending upon theenvironment, some livingthings will survive betterthan others.

Individual organisms withadvantageous traits aremore likely to survive andhave offspring.

Over time, the proportionof individuals withadvantageouscharacteristics mayincrease (and theproportion withdisadvantageouscharacteristics maydecrease) due to theirlikelihood o f surviving andreproducing.

Populations, notindividuals, evolve.

Over time, the proportionof individuals withadvantageouscharacteristics mayincrease (and theproportion withdisadvantageouscharacteristics maydecrease) due to theirlikelihood o f surviving andreproducing.

Traits that confer an Traits that confer an


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advantage may persist inthe population and arecalled adaptations.

advantage may persist inthe population and arecalled adaptations.

Complex traits can arisethrough the cooption ofanother trait.

The number of offspringthat survive to reproducesuccessfully is limited by

environmental factors.

Organisms with similarrequirements maycompete with oneanother for limitedresources.



Depending onenvironmental conditions,inherited characteristicsmay be advantageous,neutral, or detrimental.



Depending onenvironmental conditions,inherited characteristicsmay be advantageous,neutral, or detrimental.

Environmental changesmay affect an organism'sability to survive.

Environmental changesaffect opportunities andcan influence naturalselection.

Environmental changesmay provide opportunitiesthat can influence naturalselection.

Natural selection can acton the variation in apopulation in different

ways.

Natural selection mayfavor individuals with oneextreme value for a trait,shifting the average valueof that trait in onedirection over the courseof many generations.

Selection favoring anextreme trait valuereduces genetic variationin a population.

Natural selection may

favor individuals withtraits at each extreme o fthe range for that trait.

Selection favoringindividuals with traits ateach extreme of a rangemaintains geneticvariation in a population.

Natural selection mayfavor individuals with anintermediate value for atrait.

Selection favoring an

intermediate value for atrait reduces genetic


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variation in a population.

Natural selectionsometimes favorsheterozygotes overhomozygotes at a locus.

Heterozygote advantagepreserves geneticvariation at that locus(i.e., within the

population, it maintainsmultiple alleles at thatlocus).

Natural selectionsometimes favors raretraits and acts againstthose that become toocommon in a population.

Frequency-dependentselection preservesgenetic variation in apopulation.

Sexual selection occurs

when selection acts oncharacteristics that affectthe ability of individualsto obtain mates.

Sexual selection can leadto physical and behavioraldifferences between thesexes.

Fitness is reproductivesuccess the number ofviable offspring producedby an individual incomparison to otherindividuals in a

population/species.

An individual's fitness (orrelative fitness) is thecontribution thatindividual makes to thegene pool of the nextgeneration relative to

other individuals in thepopulation.

An organism's fitnessdepends on both itssurvival and itsreproduction.

Fitness is often measuredusing proxies like mass,number of matings, andsurvival because it isdifficult to measurereproductive successdirectly.

Fitness is often measuredusing proxies like mass,number of matings, andsurvival because it isdifficult to measurereproductive success.

Natural selection is


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capable of acting atmultiple hierarchicallevels: on genes, on cells,on individuals, onpopulations, on species,and on larger clades.

Random factors canaffect the survival ofindividuals and ofpopulations.

Random factors canaffect the survival ofindividuals and ofpopulations.

Smaller populations aremore strongly affected bygenetic drift than arelarger populations.

Genetic drift can causeloss of genetic variation ina population.

Founder effects occurwhen a population isfounded from a smallnumber of individuals.

Founder effects can affect

the genetic makeup of anewly started population(and reduce its geneticvariation) throughsampling error.

Bottlenecks occur when apopulation's size is greatlyreduced.

Bottlenecks can affect thegenetic makeup of apopulation (and reduce itsgenetic variation) throughsampling error.

A species is often definedas a group of individualsthat actually orpotentially interbreed innature.

There are manydefinitions of species.

Speciation is the splittingof one ancestral lineageinto two or moredescendant lineages.

Speciation is often theresult of geographic

isolation.

Speciation is the splittingof one ancestral lineageinto two or moredescendant lineages.

Speciation is often theresult of geographic

isolation.


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Nature of science

Speciation can also occurwithout geographicisolation.

Speciation requiresreproductive isolation.

Speciation requiresreproductive isolation.

Reproductive isolation canoccur throughmechanisms that preventfertilization fromoccurring.

Reproductive isolation canalso occur throughmechanisms that actafter fertilization, when afertilized egg (or theindividual resulting fromthat egg) has low fitness.

Occupying newenvironments can providenew selection pressuresand new opportunities,leading to speciation.

Occupying newenvironments can providenew selection pressuresand new opportunities,leading to speciation.

Occasionally offspring,known as hybrids, resultfrom matings betweendistinct species orbetween distinct parentalforms.

Some hybrids haveincreased fitness relativeto their parents.

Some hybrids havedecreased fitness relativeto their parents.

Evolution does not

consist of progress in anyparticular direction.

Evolution does not

consist of progress in anyparticular direction.

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Science deals with thenatural world and naturalexplanations.

Science focuses onnatural phenomena andprocesses.



Scientific ideas maychange based on what

we observe andexperience.

Scientific ideas maychange with new

evidence.

Scientific knowledge isopen to question and

revision as we come upwith new ideas and






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discover new evidence. discover new evidence. discover new evidence.

We learn about thenatural world using oursenses and extensions ofour senses.

Scientists base theirideas on evidence fromthe natural world.

A hallmark of science isexposing ideas to testing.



Scientists test their ideasusing multiple lines o fevidence.

Scientists use multipleresearch methods(experiments,observations,comparisons, andmodeling) to collectevidence.

Scientists test their ideasusing multiple lines o fevidence.

Scientists use multipleresearch methods(experiments,observational research,comparative research,and modeling) to collectdata.

Scientists test their ideasusing multiple lines ofevidence.

Scientists use multipleresearch methods(experiments,observational research,comparative research,and modeling) to collectdata.

Scientists can test ideasabout events andprocesses long past, verydistant, and not directlyobservable.



Scientists may exploremany different

hypotheses to explaintheir observations.

Scientists may exploremany different

hypotheses to explaintheir observations.

The real process ofscience is complex,iterative, and can takemany different paths.




Scientific findings andevidence inspire newquestions and shape thedirections of futurescientific research.

Accepted scientific

theories are not tenuous;they must surviverigorous testing and besupported by multiplelines of evidence to beaccepted.

Accepted scientific


Accepted scientific


Science is a humanendeavor.





Authentic scientificcontroversy and debatewithin the communitycontribute to scientificprogress.

Authentic scientificcontroversy and debatewithin the communitycontribute to scientificprogress.


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Studying evolution

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Our knowledge of theevolution of living thingsis always being refined aswe gather moreevidence.



Scientists study livingthings.

Scientists study livingthings and how they arerelated.

Scientists use multiplelines of evidence to studylife over time.

Our understanding of lifethrough time is basedupon multiple lines ofevidence.

Our understanding of lifethrough time is basedupon multiple lines ofevidence.

Scientists use thesimilarity of DNAnucleotide sequences toinfer the relatedness oftaxa.

Scientists use multiplelines of evidence(including mo rphological,developmental, andmolecular evidence) toinfer the relatedness oftaxa.

Scientists use anatomicalfeatures to infer therelatedness of taxa.

Scientists use anatomicalevidence to infer therelatedness of taxa.

Scientists usedevelopmental evidenceto infer the relatedness oftaxa.

Scientists study fossils. Scientists study fossilsand how and when theywere formed.

Scientists use fossils tolearn about past life.

Scientists use fossils(including sequences o ffossils showing gradualchange over time) tolearn about past life.

Scientists use fossils(including sequences o ffossils showing gradualchange over time) tolearn about past life.

Scientists study rocks. Scientists study rocks andhow and when they wereformed.

Scientists use geologicalevidence to establish theage of fossils.

Scientists use physical,chemical, and geologicalevidence to establish theage of fossils.

Scientists use physical,chemical, and geologicalevidence and comparativeanatomy to establish the

age of fossils.

Scientists use thegeographic distribution offossils and living things tolearn about the history oflife.

Scientists useexperimental evidence tostudy evolutionaryprocesses.

Scientists use thegeographic distribution offossils and living things tolearn about the history oflife.

Scientists useexperimental evidence tostudy evolutionaryprocesses.

Scientists use artificialselection as a model tolearn about natural

selection.


selection.


selection.


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Read how others have recognized the Understanding Evolution website.

Classification is based onevolutionaryrelationships.

Evolutionary relationshipsmay be represented bybranching trees (i.e.phylogenies orcladograms).


Evolutionary trees (e.g.,phylogenies orcladograms) portrayhypotheses aboutevolutionary relationships.

Evolutionary trees (e.g.,

phylogenies orcladograms) are builtfrom multiple lines ofevidence.


Evolutionary trees (i.e.,phylogenies orcladograms) portrayhypotheses aboutevolutionary relationships.

Evolutionary trees (i.e.,

phylogenies orcladograms) are builtfrom multiple lines ofevidence.

The principle of parsimonysuggests that thephylogenetic hypothesismost likely to be true isthe one requiring thefewest evolutionarychanges.

Evolutionary trees can beused to make inferencesand predictions.

As with other scientificdisciplines, evolutionarybiology has applicationsthat factor into everydaylife.

As with other scientificdisciplines, evolutionarybiology has applicationsthat factor into everydaylife, for example inagriculture, biodiversityand conservation biology,and medicine and health.

Because of commonancestry, modelorganisms can be used toprovide insight into thebiology of otherorganisms.


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Understanding Evolution Conceptual Framework