0
EvolutionEvolution
Biology’s Unifying ThemeBiology’s Unifying Theme
““Nothing inNothing in
biology makesbiology makes
sense EXCEPTsense EXCEPT
in the light ofin the light of
evolution.”evolu...
IntroductionIntroduction
• Change is routine in biology.Change is routine in biology.
• All life is united.All life is uni...
• The history of life is aThe history of life is a
saga of a restlesssaga of a restless
Earth billions of yearsEarth billi...
– Evolution is one of biology’s bestEvolution is one of biology’s best
demonstrated, most comprehensive, anddemonstrated, ...
Charles DarwinCharles Darwin
• On November 24, 1859, Charles DarwinOn November 24, 1859, Charles Darwin
publishedpublished...
Evidence of EvolutionEvidence of Evolution
• Earth was formed about 4.6 billionEarth was formed about 4.6 billion
years ag...
What are Fossils?What are Fossils?
• Preserved remnants or impressions left byPreserved remnants or impressions left by
or...
Fossils (con’t)Fossils (con’t)
• Rock is divided into rock layers, and eachRock is divided into rock layers, and each
laye...
Fossils (con’t)Fossils (con’t)
• The oldest fossils date back to 3.5 billionThe oldest fossils date back to 3.5 billion
ye...
Fossils (con’t)Fossils (con’t)
• Fossils have been found in the followingFossils have been found in the following
layers, ...
Types of FossilsTypes of Fossils
CastsCasts
• Replica of anReplica of an
organismorganism
AmberAmber
• Preserved and frozenPreserved and frozen
fossilsfossils
TraceTrace
• Evidence of activityEvidence of activity
PetrifiedPetrified
• Stone copyStone copy
MoldsMolds
• Empty space in rockEmpty space in rock
• Life evolvesLife evolves
– Each species is one twig of a branching tree ofEach species is one twig of a branching tree o...
Evolution:Evolution: genetic adaptation of agenetic adaptation of a
population of organisms to theirpopulation of organism...
History ofHistory of
EvolutionaryEvolutionary
ThoughtThought
Early Ideas On Earth’sEarly Ideas On Earth’s
OrganismsOrganisms
• AristotleAristotle
believed speciesbelieved species
were...
Early Ideas On Earth’sEarly Ideas On Earth’s
OrganismsOrganisms
• LinnaeusLinnaeus – 1– 1stst
toto
group similargroup simi...
:
Contributor’s to Darwin’sContributor’s to Darwin’s
thinking included:thinking included:
• Charles Lyell –Charles Lyell –...
:
Contributor’s to Darwin’sContributor’s to Darwin’s
thinking included:thinking included:
• James Hutton -James Hutton - G...
Evolutionary TimelineEvolutionary Timeline
CatastrophismCatastrophism
• Idea proposed byIdea proposed by GeorgeGeorge
CuvierCuvier
• Studied fossil inStudied fossil ...
CatastrophismCatastrophism
• Stated thatStated that
speciesspecies
disappear due todisappear due to
aa catastrophiccatastr...
Hutton’s Theory ofHutton’s Theory of
Geological ChangeGeological Change
•James HuttonJames Hutton, 1795, Scottish, 1795, S...
Hutton’s Theory ofHutton’s Theory of
Geological ChangeGeological Change
• Changes inChanges in
Earth’s crust dueEarth’s cr...
Charles LyellCharles Lyell
• Proposed theory ofProposed theory of
UniformitarianismUniformitarianism
• GeologicalGeologica...
Principles of GeologyPrinciples of Geology
• Published byPublished by LyellLyell Just Before TheJust Before The
BeagleBeag...
Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Jean-Baptiste LamarckJean-Baptiste Lamarck ,,
18091809
• One O...
Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Idea calledIdea called LawLaw
of Use andof Use and
DisuseDisus...
Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Inheritance of AcquiredInheritance of Acquired
Characteristics...
Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Use & Disuse -Use & Disuse -
Organisms CouldOrganisms Could
Ch...
Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Inheritance Of Acquired TraitsInheritance Of Acquired Traits
–...
Lamarck’s Theory ofLamarck’s Theory of
EvolutionEvolution
• Tendency Toward PerfectionTendency Toward Perfection
• Organis...
Lamarck’s MistakesLamarck’s Mistakes
• Lamarck Did NOT Know howLamarck Did NOT Know how
traits weretraits were inherited (...
Charles DarwinCharles Darwin
the Naturalistthe Naturalist
Voyage of the BeagleVoyage of the Beagle
Charles DarwinCharles Darwin
• Born Feb. 12, 1809Born Feb. 12, 1809
• Joined Crew...
A reconstruction of the HMS Beagle sailing off Patagonia.A reconstruction of the HMS Beagle sailing off Patagonia.
Darwin’...
Darwin Left England in 1831Darwin Left England in 1831
Darwin returned 5 years later in 1836Darwin returned 5 years later ...
HMS Beagle’s VoyageHMS Beagle’s Voyage
The Galapagos IslandsThe Galapagos Islands
• Small Group of Islands 1000 kmSmall Group of Islands 1000 km
West of South Am...
The Galapagos Islands are 600 miles
off of Ecuador, on the equator.
The Galapagos IslandsThe Galapagos Islands
• Volcanic islandsVolcanic islands
off the coast ofoff the coast of
South Ameri...
Galapagos Tortoise
14 varieties
10 survive
Galapagos Tortoise from island with tree cacti
Galapagos marine iguana
evolved from land iguana.
Found only on the Galapagos
islands, different islands host
different ra...
Galapagos land iguanas
Galapagos
Penguin
Survives because of large
fish and crustacean
populations fed by the
nutrient-rich upwellings of
the col...
The Galapagos IslandsThe Galapagos Islands
• Finches on the islandsFinches on the islands resembled aresembled a
mainland ...
Darwin’s Finches
• FourteenFourteen
species ofspecies of
GalápagosGalápagos
finches havefinches have
beak shapesbeak shape...
The beaks of the new species
are adapted to exploit a
different food source.
The tools to open nuts, catch
insects, probe ...
• The evolutionaryThe evolutionary
view of life cameview of life came
into focus in 1859into focus in 1859
when Charleswhe...
• Darwin was struck by the diversity of animals onDarwin was struck by the diversity of animals on
the Galápagos Islandsth...
Survival of the FittestSurvival of the Fittest
Organisms that “fit” their environment the best are
favored and go on to pr...
Natural SelectionNatural Selection
• The basic idea of natural selection is:The basic idea of natural selection is:
1.1. T...
Essentials of Natural SelectionEssentials of Natural Selection
1.1. Organisms produce far more offspringOrganisms produce ...
Evolutionary AdaptationsEvolutionary Adaptations
A population increases in theA population increases in the
frequency of t...
Natural Selection BasicsNatural Selection Basics
• All species tend to produce excessiveAll species tend to produce excess...
• Individual variation is evident in almostIndividual variation is evident in almost
all species and most is inherited.all...
Darwin’s Conclusions aboutDarwin’s Conclusions about
Natural SectionNatural Section
• Individual’s whose inherited traits ...
Only the strong survive!!!Only the strong survive!!!
Darwin and GeneticsDarwin and Genetics
• Modern Synthesis – the joining of genetics withModern Synthesis – the joining of ...
Population EvolutionPopulation Evolution
• Populations – group of individuals of thePopulations – group of individuals of ...
Immigration leads to newImmigration leads to new
variationvariation
• Immigration providesImmigration provides
new genetic...
Population GeneticsPopulation Genetics
Field of study that emphasizes theField of study that emphasizes the
extensive gene...
MicroevolutionMicroevolution
Microevolution – the generation-to-Microevolution – the generation-to-
generation change in a...
3 Causes of Microevolution are:3 Causes of Microevolution are:
1.1. Genetic DriftGenetic Drift
-- Change in the gene pool ...
Other factors in evolutionOther factors in evolution
• If there is no relation between fitness andIf there is no relation ...
Chance events influenceChance events influence
evolutionevolution
Not all populations areNot all populations are
evolving.evolving.
Populations that do not evolve arePopulations that do no...
Darwinian FitnessDarwinian Fitness
• Darwinian Fitness – the contribution anDarwinian Fitness – the contribution an
indivi...
Natural Selection OutcomesNatural Selection Outcomes
1.1. Directional selection – causes a changeDirectional selection – c...
SummarySummary
• Natural Selection acts on whatever variation isNatural Selection acts on whatever variation is
present at...
New evolution
New evolution
New evolution
New evolution
New evolution
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  • 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.
  • Transcript of "New evolution"

    1. 1. EvolutionEvolution Biology’s Unifying ThemeBiology’s Unifying Theme
    2. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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
    12. 12. Types of FossilsTypes of Fossils
    13. 13. CastsCasts • Replica of anReplica of an organismorganism
    14. 14. AmberAmber • Preserved and frozenPreserved and frozen fossilsfossils
    15. 15. TraceTrace • Evidence of activityEvidence of activity
    16. 16. PetrifiedPetrified • Stone copyStone copy
    17. 17. MoldsMolds • Empty space in rockEmpty space in rock
    18. 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. 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.
    20. 20. History ofHistory of EvolutionaryEvolutionary ThoughtThought
    21. 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. 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. 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. 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
    25. 25. Evolutionary TimelineEvolutionary Timeline
    26. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 36. 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!
    37. 37. 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
    38. 38. 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
    39. 39. Charles DarwinCharles Darwin the Naturalistthe Naturalist
    40. 40. 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
    41. 41. 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
    42. 42. Darwin Left England in 1831Darwin Left England in 1831 Darwin returned 5 years later in 1836Darwin returned 5 years later in 1836
    43. 43. HMS Beagle’s VoyageHMS Beagle’s Voyage
    44. 44. 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
    45. 45. The Galapagos Islands are 600 miles off of Ecuador, on the equator.
    46. 46. 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
    47. 47. Galapagos Tortoise 14 varieties 10 survive
    48. 48. Galapagos Tortoise from island with tree cacti
    49. 49. Galapagos marine iguana evolved from land iguana. Found only on the Galapagos islands, different islands host different races.
    50. 50. Galapagos land iguanas
    51. 51. Galapagos Penguin Survives because of large fish and crustacean populations fed by the nutrient-rich upwellings of the cold Humbolt current
    52. 52. 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
    53. 53. Darwin’s Finches • FourteenFourteen species ofspecies of GalápagosGalápagos finches havefinches have beak shapesbeak shapes adapted toadapted to suit theirsuit their environmentenvironment
    54. 54. 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.
    55. 55. • 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
    56. 56. • 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
    57. 57. Survival of the FittestSurvival of the Fittest Organisms that “fit” their environment the best are favored and go on to produce viable offspring.
    58. 58. 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.
    59. 59. 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.
    60. 60. 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.
    61. 61. 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.
    62. 62. • 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.
    63. 63. 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.
    64. 64. Only the strong survive!!!Only the strong survive!!!
    65. 65. 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.
    66. 66. 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.
    67. 67. Immigration leads to newImmigration leads to new variationvariation • Immigration providesImmigration provides new genetic materialnew genetic material for selection to actfor selection to act uponupon
    68. 68. 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.
    69. 69. 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.
    70. 70. 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
    71. 71. 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
    72. 72. Chance events influenceChance events influence evolutionevolution
    73. 73. 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.
    74. 74. 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.”
    75. 75. 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)
    76. 76. 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
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