The document provides a history of evolutionary thought. It discusses key figures and ideas that contributed to the development of the theory of evolution by natural selection, including: 1) Before 1850, most people believed that species were unchanging and each was created for its environment. Charles Darwin began to doubt this after observing variation between organisms on his voyage. 2) Darwin was influenced by James Hutton and Charles Lyell's findings that the earth changes slowly over time, and by Georges Cuvier's discovery that species can go extinct. 3) Alfred Russell Wallace independently conceived of natural selection. Darwin published On the Origin of Species in 1859 introducing his theory of evolution by natural selection.

2. History of EvolutionaryHistory of Evolutionary
ThoughtThought
• SpeciesSpecies- a group of organisms that can- a group of organisms that can
iinterbreednterbreed and produceand 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.

3. Charles DarwinCharles Darwin
• 02/12/1809 – 4/19/188202/12/1809 – 4/19/1882
• At age of 22, sailed onAt age of 22, sailed on
“HMS Beagle” to“HMS Beagle” to
Galapagos islandsGalapagos islands
• Believed God createdBelieved God created
each species to match itseach species to match its
habitat and a specieshabitat and a species
never changed.never changed.

4. Charles Darwin cont.Charles Darwin cont.
• Five year journey, heFive year journey, he
made observationsmade observations
and recorded them inand recorded them in
a journal.a journal.
• Darwin began toDarwin began to
doubt that speciesdoubt that species
remained “constant.”remained “constant.”

5. James Hutton and CharlesJames Hutton and Charles
LyellLyell
• Founders modernFounders modern
geology.geology.
• The crust of the earthThe crust of the earth
has been slowly changinghas been slowly changing
over time.over time.
• Some of earth’sSome of earth’s
formations have takenformations have taken
millions of years to form.millions of years to form.
• The earth is older thanThe earth is older than
what people thought.what people thought.

6. George CuvierGeorge Cuvier
• Species can go extinct.Species can go extinct.
• Proved this studyingProved this studying
fossils.fossils.
• Ex.) Mammoth fossilsEx.) Mammoth fossils
• The earths crust isThe earths crust is
“layered” with fossils.“layered” with fossils.
• Deeper crust = olderDeeper crust = older
fossilsfossils

7. Jean Baptiste LamarckJean Baptiste Lamarck
• Species change overSpecies 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 beThese traits can be
passed to offspring.passed to offspring.
• Right idea, wrongRight idea, wrong
explanation.explanation.

8. Alfred Russell WallaceAlfred Russell Wallace
• Studied differentStudied different
species around thespecies around the
world.world.
• There is a constantThere is a constant
struggle for food.struggle for food.
• Weaker individualsWeaker individuals
will die out.will die out.
• Survival of the fittest.Survival of the fittest.

9. Thomas MalthusThomas Malthus
• Applied Wallace’sApplied Wallace’s
concept to humans livingconcept to humans living
in London.in London.
• Population growth wasPopulation growth was
very high.very high.
• People were dying due toPeople were dying due to
starvation and disease.starvation and disease.
• The environment cannotThe environment cannot
support everyone.support everyone.
• This applies to allThis applies to all
species.species.

10. 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… Darwin
felt ideas applied even
more directly to plants
and animals
Sent copy of his essay
to Darwin  Darwin
realized these were
same ideas he had

11. Charles DarwinCharles Darwin
• In 1859, Darwin publishedIn 1859, Darwin published
“The Origin of Species.”“The Origin of Species.”

12. Major points of Darwin’s book:Major points of Darwin’s book:
• Organisms have traits that help themOrganisms have traits that help them
survive.survive.
• Species do change over time.Species do change over time.
• These gradual changes may causeThese gradual changes may cause
one species to change into newone species to change into new
species.species.
• African apes are close geneticAfrican apes are close genetic
relatives of modern humans.relatives of modern humans.

13. Darwin’s Theory –Darwin’s Theory –
Evolution by Natural SelectionEvolution by Natural Selection

14. What causes evolution?What causes evolution?
• EvolutionEvolution is the GENETIC change in membersis the GENETIC change in members
of a species over time.of a species over time.
• Darwin’s most important insight was thatDarwin’s most important insight was that
members of a species vary.members of a species vary.
• Ex) LivestockEx) Livestock
• Farmers use variation inFarmers use variation in artificial selectionartificial selection
or “selective breeding”or “selective breeding”
• Nature provides the variation, humans selectNature provides the variation, humans select
and breed useful variations to improve crops,and breed useful variations to improve crops,
etc.etc.
• Later, Darwin stated reason for why species inLater, Darwin stated reason for why species in
nature change…nature change…
• Called “Called “natural selectionnatural selection ” …” …

15. Natural SelectionNatural Selection
• Natural Selection is the “process” thatNatural Selection is the “process” that
drives evolution.drives evolution.
• Process by which individuals that areProcess by which individuals that are
better suited to their environmentbetter suited to their environment
survive and reproduce mostsurvive and reproduce most
successfully.successfully.

16. Natural SelectionNatural Selection
1.) Every species contains1.) Every species contains varietyvariety.. Causes?Causes?
2.) Living things face a2.) Living things face a constant struggleconstant struggle forfor
existence.existence. Why?Why?
3.) Only individuals that survive can reproduce.3.) Only individuals that survive can reproduce.
““Survival of the fittest”?Survival of the fittest”?
AdaptationAdaptation??
4.) Results in changes in the4.) 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 foris now better suited for
survival.survival. HOW? If not?HOW? If not?

17. Darwin’s Theory –Darwin’s Theory –
Evolution by Natural SelectionEvolution by Natural Selection

18. 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 forcompetition for
leaves in treesleaves in trees
• Members with bestMembers with best adaptationadaptation will survive andwill survive and
reproduce –reproduce – long necklong neck
• Results inResults in genetic changegenetic change== frequency long neckfrequency long neck
allele increasing and short neck allele decreasingallele increasing and short neck allele decreasing
• Results in next generation of the species beingResults in next generation of the species being
“genetically better” than the previous generation-“genetically better” than the previous generation-
number of giraffes with long neck more prevalentnumber of giraffes with long neck more prevalent
in populationin population

19. Evolution and NaturalEvolution and Natural
SelectionSelection
“Misconceptions”“Misconceptions”
• Q: Why is variation important?Q: Why is variation important?
• A: Variation is key because the environment anA: Variation is key because the environment an
organism lives in is constantly changingorganism 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

20. Evolution and NaturalEvolution and Natural
SelectionSelection
“Misconceptions”“Misconceptions”
• Q: What is an adaptation?Q: What is an adaptation?
-adaptation is-adaptation is NOTNOT a process by which organisma process by which organism
“changes” to survive“changes” to survive
-It is-It is incorrectincorrect to say… “When the environmentto say… “When the environment
changed the dark moths were the best at adapting andchanged the dark moths were the best at adapting and
remained hidden from the birds.”remained hidden from the birds.”
-It is also-It is also incorrectincorrect to say… “The moth populationto say… “The moth population
adapted to the environment after the pollution increasedadapted to the environment after the pollution increased
and thus lived.”and thus lived.”

21. Evolution and NaturalEvolution and Natural
SelectionSelection
“Misconceptions”“Misconceptions”
• A:A: AnAn adaptation is a trait an organism is bornadaptation is a trait an organism is born
with thatwith that becausebecause of what the environment isof what the environment is
like it increases the organism’s chances oflike it increases the organism’s chances of
survivingsurviving
-peppered moths could not consciously change-peppered moths could not consciously change
their color from peppered to darktheir color from peppered to dark
-this is what you are implying if you write “the-this is what you are implying if you write “the
dark moths were the best at adapting to …”dark moths were the best at adapting to …”
-NO organism can change its genetic traits-NO organism can change its genetic traits
(DNA)(DNA)

22. Evolution and Natural SelectionEvolution and Natural Selection
“Misconceptions”“Misconceptions”
• Q: Definition ofQ: Definition of evolutionevolution is- genetic change inis- genetic change in
a species over time… What does genetica species over time… What does genetic
change refer to?change refer to?
-It is understood that an organism can NOT change its-It is understood that an organism can NOT change its
DNA …so how does genetic change apply…DNA …so how does genetic change apply…
• A: Genetic change means changes in allele frequency inA: Genetic change means changes in allele frequency in
thethe gene poolgene pool, which lead to changes in genotypic, which lead to changes in genotypic
frequency, and then changes in phenotypic frequency asfrequency, and then changes in phenotypic frequency as
wellwell

23. Evolution and NaturalEvolution and Natural
SelectionSelection
“Misconceptions”“Misconceptions”
• Q: Entire species is better suited …Q: Entire species is better suited …
means…means…
• A: “TheA: “The entire populationentire population of the species is nowof the species is now
better suited for survival.”better suited for survival.”
• Q: How would this apply to the pepperedQ: How would this apply to the peppered
moths?moths?
• A: The species of moths is now better suited forA: The species of moths is now better suited for
survival because the population consists of mostlysurvival because the population consists of mostly
dark moths.dark moths.

24. Evolution and NaturalEvolution and Natural
SelectionSelection
• The definition of evolution isThe definition of evolution is ……
-genetic change amongst members of a species-genetic change amongst members of a species
-this is happening in the population in terms of-this is happening in the population in terms of
the alleles causing changes in both genotypicthe alleles causing changes in both genotypic
and phenotypic frequencies…and phenotypic frequencies…

25. Evolution and NaturalEvolution and Natural
SelectionSelection
• We can describe the genetic change amongst theWe can describe the genetic change amongst the
population two ways…population two ways…
• Directional selection vs. balancingDirectional selection vs. balancing
selectionselection
• Both terms describe how the allele frequencies areBoth terms describe how the allele frequencies are
changing as a result of natural selection…changing as a result of natural selection…

26. Evolution of Peppered Moths…
Genetic Change Amongst the Peppered Moth Population
0
0.2
0.4
0.6
0.8
1
1.2
Year 1 Year 3 Year 5 Year 7 Year 9
Year
AlleleFrequencies
p
q

27. Evolution of PepperedEvolution of Peppered
Moths…Moths…
• Frequency of the dominant allele (p orFrequency of the dominant allele (p or
peppered)peppered) decreaseddecreased
• Frequency of the recessive allele (q orFrequency of the recessive allele (q or
dark)dark) increasedincreased
• This isThis is directional selectiondirectional selection

28. Directional SelectionDirectional Selection
• Frequency of an allele isFrequency of an allele is
pushed in one directionpushed in one direction
without oppositionwithout opposition

29. Sickle Cell Anemia: TheSickle Cell Anemia: The
PuzzlePuzzle
• Recessive diseaseRecessive disease
originated in Africaoriginated in Africa
• AfricaAfrica 1/100 aa1/100 aa
• United StatesUnited States 1/500 aa1/500 aa
• Why has naturalWhy has natural
selection not actedselection not acted
against the sickle cellagainst the sickle cell
allele (a) in Africa toallele (a) in Africa to
reduce its frequency?reduce its frequency?

30. Genetic Change Amongst the African
Population
0
0.2
0.4
0.6
0.8
1
1.2
1 2 3 4 5
Year
AlleleFrequeny
p
q

31. Balancing SelectionBalancing Selection
• Two opposite forces affect the allele in aTwo opposite forces affect the allele in a
populationpopulation
• Allele frequency may vary year to year, butAllele 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 sickleex) sickle cell allele (aa) – lethal - death by sickle
cell =cell = decreasedecrease
ex) sickle cell allele (a) – favorable - (Aa) resistant toex) sickle cell allele (a) – favorable - (Aa) resistant to
malaria =malaria = increaseincrease
ex) no sickle cell allele (AA) – lethal - death byex) no sickle cell allele (AA) – lethal - death by
malaria =malaria = decreasedecrease

32. How Species Form?How Species Form?
• Natural selection favors variationsNatural selection favors variations
that increases a species survival.that increases a species survival.
• If environment changes, naturalIf environment changes, natural
selection will occur.selection will occur.
• Can members of a species changeCan 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

33. How Species Form?How Species Form?
• Ecological Races (subspecies)Ecological Races (subspecies)
– Populations of the same species thatPopulations of the same species that
differ genetically because they havediffer genetically because they have
adapted to different living conditions.adapted to different living conditions.
– Still members of same species.Still members of same species.

34. Why might members ofWhy might members of
same species be separated?same species be separated?
• Different groups of subspecies mayDifferent groups of subspecies may
become isolated from each other.become isolated from each other.
• Isolation makes it difficult for membersIsolation makes it difficult for members
of the same species to mate.of the same species to mate.
• Geographic IsolationGeographic Isolation
• Populations separated into differentPopulations separated into different
environments due to geographicalenvironments due to geographical
features (mountains, canyons, bodiesfeatures (mountains, canyons, bodies
of water, etc.)of water, etc.)

36. Speciation cont.Speciation cont.
• When geographical isolation preventsWhen geographical isolation prevents
interbreeding for long periods of time,interbreeding for long periods of time,
populations in different places becomepopulations in different places become
increasingly different due to differentincreasingly different due to different
environments.environments.
• Eventually if the groups can no longerEventually if the groups can no longer
mate and create fertile offspring, theymate and create fertile offspring, they
will be considered separate species.will be considered separate species.

37. MacroevolutionMacroevolution
• Evolutionary relationships on a “large scale”Evolutionary relationships on a “large scale”
• Scientists attempt to explainScientists attempt to explain diversification of lifediversification of life
• Scientists attempt at determining how livingScientists 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 ancestor”Humans and apes shared a common ancestor”
““Modern day whales had a distant ancestor thatModern day whales had a distant ancestor that
lived on land and walked on four limbs”lived on land and walked on four limbs”

38. Evidence of EvolutionEvidence of Evolution
• Fossil EvidenceFossil Evidence
• Structural EvidenceStructural Evidence
• Developmental EvidenceDevelopmental Evidence
• DNA EvidenceDNA Evidence

39. What is a fossil?What is a fossil?
• Any traces of dead organisms.Any traces of dead organisms.
• Organism must be buried byOrganism must be buried by
sediment. Usually happens insediment. Usually happens in
swamps, mud, tar pits, or the oceanswamps, mud, tar pits, or the ocean
bottom.bottom.
• ““Hard stuff” fossilizes.Hard stuff” fossilizes.

40. What can fossils tell us?What can fossils tell us?
• A glimpse into the history of an organismsA glimpse into the history of an organisms
past.past.
• Transitional species = “intermediateTransitional species = “intermediate
forms”forms”
• Ex.) Whale evolutionEx.) Whale evolution

41. Structural EvidenceStructural Evidence
• Comparing the way two organisms are putComparing the way two organisms are put
together to determine if related or sharetogether to determine if related or share
common ancestor.common ancestor.
• Homologous StructuresHomologous Structures : structures that are: structures that are
similar in structure differ in function.similar in structure differ in function.

42. Structural Evidence cont.Structural Evidence cont.
• Vestigial structuresVestigial structures : Structures reduced in: Structures reduced in
size and have no present function; “remants ofsize and have no present function; “remants of
organism’s past”organism’s past”

43. Developmental EvidenceDevelopmental Evidence
• Compares embryosCompares embryos of different species to determineof different species to determine
how closely organisms are related and whether or nothow closely organisms are related and whether or not
might share a common ancestor.might share a common ancestor.
• Longer early stages of development are similar betweenLonger early stages of development are similar between
organisms= more closely relatedorganisms= more closely related

44. Fish
Salamander
Fish
Tortoise Chicken Rabbit HumanRabbit

45. DNA EvidenceDNA Evidence
• DNA evidence supports the other three.DNA evidence supports the other three.
• If species change over time, their DNA willIf species change over time, their DNA will
also change.also change.
• Similar organisms=similar DNASimilar organisms=similar DNA
sequencessequences
• More similar DNA = more closely related.More similar DNA = more closely related.