History of Evolutionary History of Evolutionary ThoughtThought

• SpeciesSpecies- a group of organisms that can - a group of organisms that can iinterbreednterbreed and produce and produce fertile offspringfertile offspring..

• Before 1850Before 1850, , most people believedmost people believed……– The earth was formed by supernatural eventsThe earth was formed by supernatural events– Earth never changes.Earth never changes.– The earth was only a few thousand years old.The earth was only a few thousand years old.– Each species was made by a divine creator.Each species was made by a divine creator.– Each species was made to fit its environment.Each species was made to fit its environment.– Species never changed and did not go extinct.Species never changed and did not go extinct.

Charles DarwinCharles Darwin

• 02/12/1809 – 4/19/188202/12/1809 – 4/19/1882

• At age of 22, sailed on At age of 22, sailed on “HMS Beagle” to “HMS Beagle” to Galapagos islandsGalapagos islands

• Believed God created Believed God created each species to match each species to match its habitat and a its habitat and a species never changed.species never changed.

Charles Darwin cont.Charles Darwin cont.

• Five year journey, Five year journey, he made he made observations and observations and recorded them in a recorded them in a journal.journal.

• Darwin began to Darwin began to doubt that species doubt that species remained remained “constant.”“constant.”

James Hutton and Charles James Hutton and Charles LyellLyell

• Founders modern Founders modern geology.geology.

• The crust of the earth The crust of the earth has been slowly has been slowly changing over time.changing over time.

• Some of earth’s Some of earth’s formations have taken formations have taken millions of years to millions of years to form.form.

• The earth is older than The earth is older than what people thought.what people thought.

George CuvierGeorge Cuvier

• Species can go extinct.Species can go extinct.

• Proved this studying Proved this studying fossils.fossils.

• Ex.) Mammoth fossilsEx.) Mammoth fossils

• The earths crust is The earths crust is “layered” with fossils. “layered” with fossils.

• Deeper crust = older Deeper crust = older fossilsfossils

Jean Baptiste LamarckJean Baptiste Lamarck

• Species change over Species change over time.time.

• Species can “acquire” Species can “acquire” traits in their lifetime.traits in their lifetime.

• Ex.) Big muscles.Ex.) Big muscles.

• These traits can be These traits can be passed to offspring.passed to offspring.

• Right idea, wrong Right idea, wrong explanation.explanation.

Alfred Russell WallaceAlfred Russell Wallace• Studied different Studied different

species around the species around the world.world.

• There is a constant There is a constant struggle for food.struggle for food.

• Weaker individuals Weaker individuals will die out. will die out.

• Survival of the Survival of the fittest.fittest.

Thomas MalthusThomas Malthus• Applied Wallace’s Applied Wallace’s

concept to humans concept to humans living in London.living in London.

• Population growth was Population growth was very high. very high.

• People were dying due People were dying due to starvation and to starvation and disease.disease.

• The environment The environment cannot support cannot support everyone.everyone.

• This applies to all This applies to all species.species.

Lamark

Species do change

Malthus

Wallace

Lyell

Earth old enough for change to occur, causing Darwin to question if life could change as well?

Population ideas apply to all species… Darwinfelt ideas applied even more directly to plantsand animals

Sent copy of his essayto Darwin Darwin realized these were same ideas he had

Charles Darwin Charles Darwin

• In 1859, Darwin In 1859, Darwin published “The Origin of published “The Origin of Species.”Species.”

Major points of Darwin’s book:Major points of Darwin’s book:

• Organisms have traits that help Organisms have traits that help them survive.them survive.

• Species do change over time.Species do change over time.

• These gradual changes may cause These gradual changes may cause one species to change into new one species to change into new species.species.

• African apes are close genetic African apes are close genetic relatives of modern humans.relatives of modern humans.

Darwin’s Theory – Darwin’s Theory – Evolution by Natural Evolution by Natural

SelectionSelection

What causes evolution?What causes evolution?• EvolutionEvolution is the GENETIC change in is the GENETIC change in

members of a species over time.members of a species over time.• Darwin’s most important insight was that Darwin’s most important insight was that

members of a species vary.members of a species vary.• Ex) LivestockEx) Livestock• Farmers use variation in Farmers use variation in artificial artificial

selection or “selective breeding”selection or “selective breeding”• Nature provides the variation, humans Nature provides the variation, humans

select and breed useful variations to select and breed useful variations to improve crops, etc.improve crops, etc.

• Later, Darwin stated reason for why Later, Darwin stated reason for why species in nature change…species in nature change…

• Called “Called “natural selectionnatural selection” …” …

Natural SelectionNatural Selection• Natural Selection is the “process” that Natural Selection is the “process” that

drives evolution.drives evolution.• Process by which individuals that are Process by which individuals that are

better suited to their environment better suited to their environment survive and reproduce most successfully.survive and reproduce most successfully.

Natural SelectionNatural Selection1.) Every species contains 1.) Every species contains varietyvariety. . Causes?Causes?

2.) Living things face a 2.) Living things face a constant struggleconstant struggle for for

existence. existence. Why?Why?

3.) Only individuals that survive can 3.) Only individuals that survive can reproduce. reproduce.

“ “Survival of the fittest”? Survival of the fittest”?

AdaptationAdaptation??

4.) Results in changes in the 4.) Results in changes in the gene poolgene pool. .

How is genetic change measured?How is genetic change measured?

5.) 5.) Entire speciesEntire species is now better suited for is now better suited for

survival. survival. HOW? If not?HOW? If not?

Darwin’s Theory – Darwin’s Theory – Evolution by Natural Evolution by Natural

SelectionSelection

Natural Selection (Review)Natural Selection (Review)• VariationVariation (caused by genetics)= (caused by genetics)= neck lengthneck length

• More individuals than can survive= More individuals than can survive= competition for leaves in treescompetition for leaves in trees

• Members with best Members with best adaptationadaptation will survive will survive and reproduce – and reproduce – long necklong neck

• Results in Results in genetic changegenetic change= = frequency long frequency long neck allele increasing and short neck allele neck allele increasing and short neck allele decreasingdecreasing

• Results in next generation of the species Results in next generation of the species being “genetically better” than the previous being “genetically better” than the previous generation- number of giraffes with long generation- number of giraffes with long neck more prevalent in populationneck more prevalent in population

Evolution and Natural Evolution and Natural Selection Selection

“Misconceptions”“Misconceptions”• Q: Why is variation important?Q: Why is variation important?

• A: Variation is key because the environment A: Variation is key because the environment an organism lives in is constantly changingan organism lives in is constantly changing

-ex) England- factories/pollution-ex) England- factories/pollution-What if amongst the moths there was no -What if amongst the moths there was no variation… only peppered no dark…variation… only peppered no dark…-Result might have been… -Result might have been… EXTINCTIONEXTINCTION

Evolution and Natural Evolution and Natural Selection Selection

“Misconceptions”“Misconceptions”• Q: What is an adaptation?Q: What is an adaptation?

-adaptation is -adaptation is NOTNOT a process by which organism a process by which organism “changes” to survive“changes” to survive

-It is -It is incorrectincorrect to say… “When the environment to say… “When the environment changed the dark moths were the best at changed the dark moths were the best at adapting and remained hidden from the birds.”adapting and remained hidden from the birds.”-It is also -It is also incorrectincorrect to say… “The moth to say… “The moth population adapted to the environment after the population adapted to the environment after the pollution increased and thus lived.”pollution increased and thus lived.”

Evolution and Natural Evolution and Natural Selection Selection

“Misconceptions”“Misconceptions”• A: A: AnAn adaptation is a trait an organism is adaptation is a trait an organism is

born with that born with that becausebecause of what the of what the environment is like it increases the environment is like it increases the organism’s chances of survivingorganism’s chances of surviving

-peppered moths could not consciously -peppered moths could not consciously change their color from peppered to dark change their color from peppered to dark -this is what you are implying if you write -this is what you are implying if you write “the dark moths were the best at adapting “the dark moths were the best at adapting to …”to …”-NO organism can change its genetic traits-NO organism can change its genetic traits (DNA)(DNA)

Evolution and Natural Evolution and Natural Selection Selection

“Misconceptions”“Misconceptions”• Q: Definition of Q: Definition of evolutionevolution is- genetic change is- genetic change

in a species over time… What does genetic in a species over time… What does genetic change refer to?change refer to?

-It is understood that an organism can NOT change -It is understood that an organism can NOT change its DNA …so how does genetic change apply…its DNA …so how does genetic change apply…

• A: Genetic change means changes in allele A: Genetic change means changes in allele frequency in the frequency in the gene poolgene pool, which lead to , which lead to changes in genotypic frequency, and then changes changes in genotypic frequency, and then changes in phenotypic frequency as wellin phenotypic frequency as well

Evolution and Natural Evolution and Natural Selection Selection

“Misconceptions”“Misconceptions”• Q: Entire species is better suited … Q: Entire species is better suited …

means…means…• A: “The A: “The entire populationentire population of the species is of the species is

now better suited for survival.”now better suited for survival.”

• Q: How would this apply to the Q: How would this apply to the peppered moths?peppered moths?

• A: The species of moths is now better suited A: The species of moths is now better suited for survival because the population consists for survival because the population consists of mostly dark moths. of mostly dark moths.

Evolution and Natural Evolution and Natural Selection Selection

• The definition of evolution isThe definition of evolution is … …

-genetic change amongst members of a -genetic change amongst members of a species species

-this is happening in the population in -this is happening in the population in terms of the alleles causing changes in terms of the alleles causing changes in both genotypic and phenotypic both genotypic and phenotypic frequencies…frequencies…

Evolution and Natural Evolution and Natural Selection Selection

• We can describe the genetic change amongst the We can describe the genetic change amongst the population two ways…population two ways…

• Directional selection vs. balancing selectionDirectional selection vs. balancing selection

• Both terms describe how the allele frequencies Both terms describe how the allele frequencies are changing as a result of natural selection…are changing as a result of natural selection…

Evolution of Peppered Moths…Genetic Change Amongst the Peppered Moth Population

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Evolution of Peppered Evolution of Peppered Moths…Moths…

• Frequency of the dominant allele (p Frequency of the dominant allele (p or peppered) or peppered) decreaseddecreased

• Frequency of the recessive allele (q Frequency of the recessive allele (q or dark) or dark) increasedincreased

• This is This is directional selectiondirectional selection

Directional SelectionDirectional Selection

•Frequency of an allele is Frequency of an allele is pushed in one direction pushed in one direction without oppositionwithout opposition

Sickle Cell Anemia: The Sickle Cell Anemia: The PuzzlePuzzle

• Recessive disease Recessive disease originated in Africaoriginated in Africa

• AfricaAfrica 1/100 aa1/100 aa• United StatesUnited States 1/500 1/500

aaaa

• Why has natural Why has natural selection not acted selection not acted against the sickle cell against the sickle cell allele (a) in Africa to allele (a) in Africa to reduce its frequency?reduce its frequency?

Genetic Change Amongst the African

Population

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Balancing SelectionBalancing Selection• Two opposite forces affect the allele in a Two opposite forces affect the allele in a

populationpopulation

• Allele frequency may vary year to year, but Allele frequency may vary year to year, but over time usually remains same (value)over time usually remains same (value)

ex) sickle cell allele (aa) – lethal - death by sickle ex) sickle cell allele (aa) – lethal - death by sickle cell = cell = decreasedecrease

ex) sickle cell allele (a) – favorable - (Aa) resistant ex) sickle cell allele (a) – favorable - (Aa) resistant to malaria = to malaria = increaseincrease

ex) no sickle cell allele (AA) – lethal - death by ex) no sickle cell allele (AA) – lethal - death by malaria = malaria = decreasedecrease

How Species Form?How Species Form?

• Natural selection favors variations Natural selection favors variations that increases a species survival.that increases a species survival.

• If environment changes, natural If environment changes, natural selection will occur.selection will occur.

• Can members of a species change Can members of a species change enough to form a new species?enough to form a new species?

• SpeciationSpeciation- generation of a new - generation of a new speciesspecies

How Species Form?How Species Form?

• Ecological Races (subspecies)Ecological Races (subspecies)– Populations of the same species Populations of the same species

that differ genetically because they that differ genetically because they have adapted to different living have adapted to different living conditions.conditions.

– Still members of same species.Still members of same species.

Why might members of Why might members of same species be same species be separated?separated?• Different groups of subspecies may Different groups of subspecies may

become isolated from each other.become isolated from each other.• Isolation makes it difficult for Isolation makes it difficult for

members of the same species to members of the same species to mate.mate.

• Geographic IsolationGeographic Isolation• Populations separated into different Populations separated into different

environments due to geographical environments due to geographical features (mountains, canyons, features (mountains, canyons, bodies of water, etc.)bodies of water, etc.)

Speciation cont.Speciation cont.

• When geographical isolation prevents When geographical isolation prevents interbreeding for long periods of time, interbreeding for long periods of time, populations in different places populations in different places become increasingly different due to become increasingly different due to different environments.different environments.

• Eventually if the groups can no longer Eventually if the groups can no longer mate and create fertile offspring, they mate and create fertile offspring, they will be considered separate species.will be considered separate species.

MacroevolutionMacroevolution• Evolutionary relationships on a “large scale”Evolutionary relationships on a “large scale”• Scientists attempt to explainScientists attempt to explain diversification of diversification of

lifelife• Scientists attempt at determining how living Scientists attempt at determining how living

organisms on Earth are related to each otherorganisms on Earth are related to each other• ““Common Ancestor”Common Ancestor”

• Ex) Charles Darwin said…Ex) Charles Darwin said…

““Humans and apes shared a common Humans and apes shared a common ancestor”ancestor”““Modern day whales had a distant ancestor Modern day whales had a distant ancestor that lived on land and walked on four limbs”that lived on land and walked on four limbs”

Evidence of EvolutionEvidence of Evolution

• Fossil EvidenceFossil Evidence

• Structural EvidenceStructural Evidence

• Developmental EvidenceDevelopmental Evidence

• DNA EvidenceDNA Evidence

What is a fossil?What is a fossil?

• Any traces of dead organisms.Any traces of dead organisms.

• Organism must be buried by Organism must be buried by sediment. Usually happens in sediment. Usually happens in swamps, mud, tar pits, or the swamps, mud, tar pits, or the ocean bottom.ocean bottom.

• ““Hard stuff” fossilizes.Hard stuff” fossilizes.

What can fossils tell us?What can fossils tell us?• A glimpse into the history of an A glimpse into the history of an

organisms past.organisms past.

• Transitional species = “intermediate Transitional species = “intermediate forms”forms”

• Ex.) Whale evolutionEx.) Whale evolution

Structural EvidenceStructural Evidence• Comparing the way two organisms are put Comparing the way two organisms are put

together to determine if related or share together to determine if related or share common ancestor.common ancestor.

• Homologous StructuresHomologous Structures: structures that : structures that are similar in structure differ in function.are similar in structure differ in function.

Structural Evidence cont.Structural Evidence cont.• Vestigial structuresVestigial structures: Structures reduced : Structures reduced

in size and have no present function; in size and have no present function; “remants of organism’s past” “remants of organism’s past”

Developmental EvidenceDevelopmental Evidence• Compares embryosCompares embryos of different species to of different species to

determine how closely organisms are related and determine how closely organisms are related and whether or not might share a common ancestor.whether or not might share a common ancestor.

• Longer early stages of development are similar Longer early stages of development are similar between organisms= more closely relatedbetween organisms= more closely related

FishSalamander

Fish

Tortoise Chicken Rabbit HumanRabbit

DNA EvidenceDNA Evidence

• DNA evidence supports the other three.DNA evidence supports the other three.

• If species change over time, their DNA If species change over time, their DNA will also change.will also change.

• Similar organisms=similar DNA Similar organisms=similar DNA sequences sequences

• More similar DNA = more closely related.More similar DNA = more closely related.