2. ““Nothing inNothing in
biology makesbiology makes
sense EXCEPTsense EXCEPT
in the light ofin the light of
evolution.”evolution.”
TheodosiusTheodosius
DobzhanskyDobzhansky
Evolution
Charles Darwin in later yearsCharles Darwin in later years
3. IntroductionIntroduction
• Change is routine in biology.Change is routine in biology.
• All life is united.All life is united.
• Modern biology is defined by life’s unityModern biology is defined by life’s unity
and diversity.and diversity.
4. • The history of life is aThe history of life is a
saga of a restlesssaga of a restless
Earth billions of yearsEarth billions of years
oldold
– Fossils documentFossils document
this historythis history
Figure 1.10
5. – Evolution is one of biology’s bestEvolution is one of biology’s best
demonstrated, most comprehensive, anddemonstrated, most comprehensive, and
longest lasting theorieslongest lasting theories
– Evolution is the unifying theme of biologyEvolution is the unifying theme of biology
6. Charles DarwinCharles Darwin
• On November 24, 1859, Charles DarwinOn November 24, 1859, Charles Darwin
publishedpublished On the Origin of Species byOn the Origin of Species by
Means of Natural SelectionMeans of Natural Selection..
• It has two main points:It has two main points:
1.1. Evidence that modern species descendedEvidence that modern species descended
from ancestral species.from ancestral species.
2.2. Natural selection is the mechanism fromNatural selection is the mechanism from
descent with modification.descent with modification.
7. Evidence of EvolutionEvidence of Evolution
• Earth was formed about 4.6 billionEarth was formed about 4.6 billion
years ago.years ago.
• 3.9 billion years ago, fossil evidence3.9 billion years ago, fossil evidence
leads scientists to believe that thereleads scientists to believe that there
was a major change in weatherwas a major change in weather
patterns, causing massive rainstormspatterns, causing massive rainstorms
and flooding.and flooding.
– This is due to carbon dating.This is due to carbon dating.
– It is thought that the Earth was too hot toIt is thought that the Earth was too hot to
support life until this point. No evidence ofsupport life until this point. No evidence of
any living organism found in fossils.any living organism found in fossils.
8. What are Fossils?What are Fossils?
• Preserved remnants or impressions left byPreserved remnants or impressions left by
organism that lived in the past.organism that lived in the past.
• Fossils give some idea of the Earth’sFossils give some idea of the Earth’s
history.history.
• Most fossils are found in sedimentaryMost fossils are found in sedimentary
rock.rock.
9. Fossils (con’t)Fossils (con’t)
• Rock is divided into rock layers, and eachRock is divided into rock layers, and each
layers has a unique set of fossilslayers has a unique set of fossils
representing it.representing it.
• Younger rock is layered on top of olderYounger rock is layered on top of older
rock.rock.
• The fossil record refers to the ordered wayThe fossil record refers to the ordered way
in which fossils appear in the rock layers,in which fossils appear in the rock layers,
representing the passing of geologicalrepresenting the passing of geological
time.time.
10. Fossils (con’t)Fossils (con’t)
• The oldest fossils date back to 3.5 billionThe oldest fossils date back to 3.5 billion
years ago.years ago.
• They are prokaryotic bacteria.They are prokaryotic bacteria.
11. Fossils (con’t)Fossils (con’t)
• Fossils have been found in the followingFossils have been found in the following
layers, giving scientists an idea of thelayers, giving scientists an idea of the
appearance of various animals:appearance of various animals:
(oldest(oldest youngest)youngest)
– Fishlike fossilsFishlike fossils
– AmphibiansAmphibians
– ReptilesReptiles
– MammalsMammals
– BirdsBirds
18. • Life evolvesLife evolves
– Each species is one twig of a branching tree ofEach species is one twig of a branching tree of
life extending back in timelife extending back in time
Figure 1.11
Giant
panda
Spectacled
bear
Sloth
bear
Sun
bear
American
black bear
Asiatic
black bear
Polar
bear
Brown bear
Ancestral bear
19. Evolution:Evolution: genetic adaptation of agenetic adaptation of a
population of organisms to theirpopulation of organisms to their
environment over timeenvironment over time
MicroevolutionMicroevolution: Small-scale changes in: Small-scale changes in
gene frequencies within a population.gene frequencies within a population.
MacroevolutionMacroevolution: Large-scale: Large-scale
evolutionary change resulting in newevolutionary change resulting in new
species and higher taxa (genera,species and higher taxa (genera,
families, etc.) and the extinction offamilies, etc.) and the extinction of
species.species.
21. Early Ideas On Earth’sEarly Ideas On Earth’s
OrganismsOrganisms
• AristotleAristotle
believed speciesbelieved species
werewere fixedfixed
creationscreations
arranged byarranged by
theirtheir complexitycomplexity
• IdeaIdea lasted 2000lasted 2000
yearsyears
22. Early Ideas On Earth’sEarly Ideas On Earth’s
OrganismsOrganisms
• LinnaeusLinnaeus – 1– 1stst
toto
group similargroup similar
organisms andorganisms and
assign themassign them LatinLatin
namesnames
• Two word nameTwo word name
(Genus species)(Genus species)
• Known asKnown as BinomialBinomial
nomenclaturenomenclature
23. :
Contributor’s to Darwin’sContributor’s to Darwin’s
thinking included:thinking included:
• Charles Lyell –Charles Lyell –
uniformatarianismuniformatarianism
• Georges Cuvier –Georges Cuvier – speciesspecies
extinction (Catastrophism)extinction (Catastrophism)
• Thomas Malthus –Thomas Malthus – strugglestruggle
for existence (resources)for existence (resources)
24. :
Contributor’s to Darwin’sContributor’s to Darwin’s
thinking included:thinking included:
• James Hutton -James Hutton - GradualismGradualism
• John Baptiste Lamarck –John Baptiste Lamarck –
Inheritance of acquiredInheritance of acquired
CharacteristicsCharacteristics andand Law of UseLaw of Use
and Disuseand Disuse
• Alfred Russel Wallace –Alfred Russel Wallace –
organisms evolved fromorganisms evolved from
common ancestorscommon ancestors
26. CatastrophismCatastrophism
• Idea proposed byIdea proposed by GeorgeGeorge
CuvierCuvier
• Studied fossil inStudied fossil in sedimentarysedimentary
rock stratarock strata of Parisof Paris
• FoundFound some speciessome species
completely disappearedcompletely disappeared inin
more recent layersmore recent layers
27. CatastrophismCatastrophism
• Stated thatStated that
speciesspecies
disappear due todisappear due to
aa catastrophiccatastrophic
event of theevent of the
earth’s crustearth’s crust
(volcano,(volcano,
earthquake…)earthquake…)
28. Hutton’s Theory ofHutton’s Theory of
Geological ChangeGeological Change
•James HuttonJames Hutton, 1795, Scottish, 1795, Scottish
geologistgeologist
•StudiedStudied invertebrate fossils ininvertebrate fossils in
Paris MuseumParis Museum
•Described TheDescribed The GeologicalGeological
ForcesForces That Have ChangedThat Have Changed LifeLife
on Earthon Earth Over Millions of YearsOver Millions of Years
(erosion, earthquakes,(erosion, earthquakes,
volcanoes…)volcanoes…)
29. Hutton’s Theory ofHutton’s Theory of
Geological ChangeGeological Change
• Changes inChanges in
Earth’s crust dueEarth’s crust due
toto slowslow
continuouscontinuous
processesprocesses
• Idea Known asIdea Known as
GradualismGradualism
30. Charles LyellCharles Lyell
• Proposed theory ofProposed theory of
UniformitarianismUniformitarianism
• GeologicalGeological
processes atprocesses at
uniform ratesuniform rates
building & wearingbuilding & wearing
down Earth’s crustdown Earth’s crust
• Proposed that theProposed that the
Earth was millionsEarth was millions
of years instead ofof years instead of
a few thousanda few thousand
years oldyears old
31. Principles of GeologyPrinciples of Geology
• Published byPublished by LyellLyell Just Before TheJust Before The
BeagleBeagle Set Sail & read by DarwinSet Sail & read by Darwin
• ExplainedExplained Geological ProcessesGeological Processes
That Shaped The EarthThat Shaped The Earth
• Helped Darwin UnderstandHelped Darwin Understand SeaSea
Shells In The Andes Mountains AtShells In The Andes Mountains At
12,000+ Feet12,000+ Feet
– Expanded Earth’s AgeExpanded Earth’s Age
32. Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Jean-Baptiste LamarckJean-Baptiste Lamarck ,,
18091809
• One Of First ScientistsOne Of First Scientists
To Understand ThatTo Understand That
Change Occurs OverChange Occurs Over
TimeTime
• Stated that ChangesStated that Changes
Are Adaptations ToAre Adaptations To
EnvironmentEnvironment acquiredacquired
in an organism’sin an organism’s
lifetimelifetime
• Said acquired changesSaid acquired changes
33. Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Idea calledIdea called LawLaw
of Use andof Use and
DisuseDisuse
• If a body partIf a body part
were used, itwere used, it
got strongergot stronger
• If body partIf body part
NOT used, itNOT used, it
deteriorateddeteriorated
34. Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Inheritance of AcquiredInheritance of Acquired
CharacteristicsCharacteristics
• Proposed That By Selective Use OrProposed That By Selective Use Or
Disuse Of Organs, OrganismsDisuse Of Organs, Organisms
Acquired Or Lost Certain TraitsAcquired Or Lost Certain Traits
During Their LifetimeDuring Their Lifetime
• TheseThese Traits Could Then Be PassedTraits Could Then Be Passed
On To Their OffspringOn To Their Offspring
• Over Time This Led ToOver Time This Led To NewNew
SpeciesSpecies
35. Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Use & Disuse -Use & Disuse -
Organisms CouldOrganisms Could
Change The Size OrChange The Size Or
Shape Of Organs ByShape Of Organs By
Using Them Or NotUsing Them Or Not
Using ThemUsing Them
• Blacksmiths & TheirBlacksmiths & Their
SonsSons (muscular arms)(muscular arms)
• Giraffe’s Necks LongerGiraffe’s Necks Longer
from stretching)from stretching)
36.
37. Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Inheritance Of Acquired TraitsInheritance Of Acquired Traits
– Traits Acquired During Ones LifetimeTraits Acquired During Ones Lifetime
Would Be Passed To OffspringWould Be Passed To Offspring
Clipped ears of dogs could be passed to offspring!
38. Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Tendency Toward PerfectionTendency Toward Perfection
• Organisms Are ContinuallyOrganisms Are Continually
Changing and Acquiring FeaturesChanging and Acquiring Features
That Help Them Live MoreThat Help Them Live More
Successfully In Their EnvironmentSuccessfully In Their Environment
• Example:Example: Bird Ancestors DesiredBird Ancestors Desired
To Fly So They Tried Until WingsTo Fly So They Tried Until Wings
DevelopedDeveloped
39. Lamarck’s MistakesLamarck’s Mistakes
• Lamarck Did NOT Know howLamarck Did NOT Know how
traits weretraits were inherited (Traits areinherited (Traits are
passed through genes)passed through genes)
• Genes Are NOT Changed ByGenes Are NOT Changed By
Activities In LifeActivities In Life
• Change ThroughChange Through MutationMutation
Occurs Before An Organism IsOccurs Before An Organism Is
BornBorn
41. Voyage of the BeagleVoyage of the Beagle
Charles DarwinCharles Darwin
• Born Feb. 12, 1809Born Feb. 12, 1809
• Joined Crew of HMSJoined Crew of HMS
Beagle, 1831Beagle, 1831
• NaturalistNaturalist
• 5 Year Voyage5 Year Voyage
around worldaround world
• Avid Collector ofAvid Collector of
Flora & FaunaFlora & Fauna
• Astounded By VarietyAstounded By Variety
of Lifeof Life
42. A reconstruction of the HMS Beagle sailing off Patagonia.A reconstruction of the HMS Beagle sailing off Patagonia.
Darwin’s Voyage of DiscoveryDarwin’s Voyage of Discovery
43. Darwin Left England in 1831Darwin Left England in 1831
Darwin returned 5 years later in 1836Darwin returned 5 years later in 1836
45. The Galapagos IslandsThe Galapagos Islands
• Small Group of Islands 1000 kmSmall Group of Islands 1000 km
West of South AmericaWest of South America
• Very Different ClimatesVery Different Climates
• Animals On Islands UniqueAnimals On Islands Unique
• TortoisesTortoises
• IguanasIguanas
• FinchesFinches
47. The Galapagos IslandsThe Galapagos Islands
• Volcanic islandsVolcanic islands
off the coast ofoff the coast of
South AmericaSouth America
• Island speciesIsland species
varied fromvaried from
mainland speciesmainland species
& from island-to-& from island-to-
island speciesisland species
• Each island hadEach island had
long or short necklong or short neck
tortoisestortoises
54. The Galapagos IslandsThe Galapagos Islands
• Finches on the islandsFinches on the islands resembled aresembled a
mainland finchmainland finch
• More types of finches appeared on theMore types of finches appeared on the
islandsislands where the available food waswhere the available food was
different (seeds, nuts, berries, insects…)different (seeds, nuts, berries, insects…)
• Finches hadFinches had different types of beaksdifferent types of beaks
adapted to theiradapted to their type of food gatheringtype of food gathering
55.
56.
57. Darwin’s Finches
• FourteenFourteen
species ofspecies of
GalápagosGalápagos
finches havefinches have
beak shapesbeak shapes
adapted toadapted to
suit theirsuit their
environmentenvironment
58.
59. The beaks of the new species
are adapted to exploit a
different food source.
The tools to open nuts, catch
insects, probe for grubs, etc.
are all different.
60. • The evolutionaryThe evolutionary
view of life cameview of life came
into focus in 1859into focus in 1859
when Charleswhen Charles
Darwin publishedDarwin published
The Origin ofThe Origin of
SpeciesSpecies
• No mention ofNo mention of
human evolutionhuman evolution
• Little mention ofLittle mention of
origin of life,origin of life,
focused onfocused on
“descent with“descent with
modification”modification”
The Darwinian View of LifeThe Darwinian View of Life
Figure 1.12
61. • Darwin was struck by the diversity of animals onDarwin was struck by the diversity of animals on
the Galápagos Islandsthe Galápagos Islands
Natural SelectionNatural Selection
• He thought of adaptation to the environmentHe thought of adaptation to the environment
and the origin of new species as closelyand the origin of new species as closely
related processesrelated processes
– As populations separated by a geographicAs populations separated by a geographic
barrier adapted to local environments, theybarrier adapted to local environments, they
became separate speciesbecame separate species
62. Survival of the FittestSurvival of the Fittest
Organisms that “fit” their environment the best are
favored and go on to produce viable offspring.
63. Natural SelectionNatural Selection
• The basic idea of natural selection is:The basic idea of natural selection is:
1.1. That a population of organisms can changeThat a population of organisms can change
over generations.over generations.
2.2. However, this only happens whenHowever, this only happens when
individuals having certain heritable traitsindividuals having certain heritable traits
leave more offspring than other individuals.leave more offspring than other individuals.
64. Essentials of Natural SelectionEssentials of Natural Selection
1.1. Organisms produce far more offspringOrganisms produce far more offspring
than can survivethan can survive
2.2. Competition for resourcesCompetition for resources
3.3. Individuals vary within a speciesIndividuals vary within a species
4.4. Those variants with better adapted traitsThose variants with better adapted traits
survive and reproduce, passing on thosesurvive and reproduce, passing on those
traits to the next generation.traits to the next generation.
65. Evolutionary AdaptationsEvolutionary Adaptations
A population increases in theA population increases in the
frequency of traits that are suitedfrequency of traits that are suited
to the environment.to the environment.
Result of natural selection.Result of natural selection.
66. Natural Selection BasicsNatural Selection Basics
• All species tend to produce excessiveAll species tend to produce excessive
numbers offspring.numbers offspring.
– The chances of the parents genetics survivingThe chances of the parents genetics surviving
increases.increases.
– However, the production of more individualsHowever, the production of more individuals
can lead to a struggle for resources and life incan lead to a struggle for resources and life in
a population; therefore, only a smalla population; therefore, only a small
percentage will survive.percentage will survive.
67. • Individual variation is evident in almostIndividual variation is evident in almost
all species and most is inherited.all species and most is inherited.
– All offspring of a particular species will notAll offspring of a particular species will not
be identical.be identical.
68. Darwin’s Conclusions aboutDarwin’s Conclusions about
Natural SectionNatural Section
• Individual’s whose inherited traits are bestIndividual’s whose inherited traits are best
suited to the local environment are likely tosuited to the local environment are likely to
survive and reproduce.survive and reproduce.
• Eventually, the best traits will accumulateEventually, the best traits will accumulate
in the population over time andin the population over time and
generations.generations.
70. Darwin and GeneticsDarwin and Genetics
• Modern Synthesis – the joining of genetics withModern Synthesis – the joining of genetics with
evolutionary biologyevolutionary biology
• Darwin couldn’t explain the heredity process ofDarwin couldn’t explain the heredity process of
evolution.evolution.
• At the same time he was completing his studies,At the same time he was completing his studies,
Mendel was working on inheritance.Mendel was working on inheritance.
• Mendel’s work explains the process needed forMendel’s work explains the process needed for
natural selection to work.natural selection to work.
71. Population EvolutionPopulation Evolution
• Populations – group of individuals of thePopulations – group of individuals of the
same species living in the same area atsame species living in the same area at
the same time.the same time.
• Populations is the smallest biological unitPopulations is the smallest biological unit
that can evolve.that can evolve.
• Evolution can only be tracked by how aEvolution can only be tracked by how a
population changes over time.population changes over time.
72. Immigration leads to newImmigration leads to new
variationvariation
• Immigration providesImmigration provides
new genetic materialnew genetic material
for selection to actfor selection to act
uponupon
73. Population GeneticsPopulation Genetics
Field of study that emphasizes theField of study that emphasizes the
extensive genetic variation withinextensive genetic variation within
populations and tracks the geneticpopulations and tracks the genetic
makeup of populations over time.makeup of populations over time.
74. MicroevolutionMicroevolution
Microevolution – the generation-to-Microevolution – the generation-to-
generation change in a population’sgeneration change in a population’s
frequencies of alleles.frequencies of alleles.
75. 3 Causes of Microevolution are:3 Causes of Microevolution are:
1.1. Genetic DriftGenetic Drift
-- Change in the gene pool of a small population dueChange in the gene pool of a small population due
to chanceto chance
1.1. Bottleneck EffectBottleneck Effect
- Genetic drift due to a drastic reduction in populationGenetic drift due to a drastic reduction in population
sizesize
1.1. Founder EffectFounder Effect
- Cause of genetic drift when a few individualsCause of genetic drift when a few individuals
colonize an island, lake, or other isolate habitatcolonize an island, lake, or other isolate habitat
76. Other factors in evolutionOther factors in evolution
• If there is no relation between fitness andIf there is no relation between fitness and
the character in question, then naturalthe character in question, then natural
selection is not acting on itselection is not acting on it
• Chance events can still make these traitsChance events can still make these traits
show change over time = RANDOMshow change over time = RANDOM
DRIFTDRIFT
78. Not all populations areNot all populations are
evolving.evolving.
Populations that do not evolve arePopulations that do not evolve are
said to be in Hardy-Weinbergsaid to be in Hardy-Weinberg
equilibrium.equilibrium.
79. Darwinian FitnessDarwinian Fitness
• Darwinian Fitness – the contribution anDarwinian Fitness – the contribution an
individual makes to the gene pool of theindividual makes to the gene pool of the
next generation relative to the contributionnext generation relative to the contribution
of other individuals.of other individuals.
– Who has the best features and passed on theWho has the best features and passed on the
most is the most “fit.”most is the most “fit.”
80. Natural Selection OutcomesNatural Selection Outcomes
1.1. Directional selection – causes a changeDirectional selection – causes a change
in appearance of a populationin appearance of a population
2.2. Diversifying selection – leads to aDiversifying selection – leads to a
balance between two of more varieties inbalance between two of more varieties in
a populationa population
3.3. Stabilizing selection – allows someStabilizing selection – allows some
variation for a a trait, but only within avariation for a a trait, but only within a
narrow range (most prevalent)narrow range (most prevalent)
81. SummarySummary
• Natural Selection acts on whatever variation isNatural Selection acts on whatever variation is
present at the time. This variation is generatedpresent at the time. This variation is generated
randomly with respect to selection pressuresrandomly with respect to selection pressures
• Selection can be directional, stabilizing orSelection can be directional, stabilizing or
disruptivedisruptive
• Random factors can also play a part in evolutionRandom factors can also play a part in evolution
Editor's Notes
A galapagos tortoise. This one is from Santa Cruz Island. They are the largest species of tortoise in the world and they live to be about 200 years old.
