pal chap 6 extinction
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EXTINCTIONEXTINCTION
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Accepting the Fact of Extinction Accepting the Fact of Extinction
zz Historical reasons for not acceptingHistorical reasons for not accepting
zz Divine providenceDivine providence – – all life was created atall life was created at
once and God would protect itonce and God would protect it
zz Fossils represented yet undiscovered speciesFossils represented yet undiscovered species
zz The floodThe flood – – all things were savedall things were saved
zz Creationists now accept extinction but notCreationists now accept extinction but not
new formsnew forms
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Accepting the Fact of Extinction Accepting the Fact of Extinction
zz “ “Extinction is the rule, not the exception.Extinction is the rule, not the exception.” ”
J. LucasJ. Lucas--Clark Clark
zz “ “ All species that have ever lived are, to a All species that have ever lived are, to afirst approximation, deadfirst approximation, dead” ” D.D. RaupRaup
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Accepting the Fact of Extinction Accepting the Fact of Extinction
zz Modern reluctance to accept extinctionModern reluctance to accept extinction
zz Conscious that all species eventually becomeConscious that all species eventually become
extinct, yet we hate to see it happen.extinct, yet we hate to see it happen.
zz Humans are the only animal that activelyHumans are the only animal that actively
tries to prevent the extinction of othertries to prevent the extinction of other
speciesspecies
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The Cali fornia Condor
(Gymnogyps californianus ) is a North American species of birdin the New World vulture
family Cathartidae andthe largest North American land bird. Although other fossilmembers are known,
it is the only surviving
member of the genusGymnogyps .
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a conservation plan was put in place by theUnited States government that led to the captureof all the remaining wild condors in 1987. These
22 birds were bred at the San Diego Wild AnimalPark and the Los Angeles Zoo. Numbers rosethrough captive breeding and, beginning in 1991,condors have been reintroduced into the wild.
The project is the most expensive speciesconservation project ever undertaken in theUnited States. (Wikipedia)
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Accepting the Fact of Extinction Accepting the Fact of Extinction
zz Reasons for resisting extinction of otherReasons for resisting extinction of other
speciesspecieszz Useful to humans in some way?Useful to humans in some way?
zz
Fear of change?Fear of change?
zz Sentimentality?Sentimentality?
zz Others???Others???
zz Why are we worried about our impactWhy are we worried about our impact visvisaa visvis extinctions?extinctions?
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Accepting the Fact of Extinction Accepting the Fact of Extinction
zz Have other species ever had a similarHave other species ever had a similar
impact on life?impact on life?zz Fish?Fish?
zz
N. American placental mammals?N. American placental mammals?
zz Would the world be better off withoutWould the world be better off without
humans?humans?
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CatastrophismCatastrophism
zz Georges LouisGeorges Louis LeClercLeClerc
“ “BuffonBuffon” ” 17781778zz Earth was old and hadEarth was old and had
changing conditionschanging conditions
zz CatastrophesCatastrophesexplainedexplainedunconformities andunconformities andextinctionsextinctions
zz Creationist still believeCreationist still believethisthis
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CatastrophismCatastrophism
zz CuvierCuvier 17961796
zz “ “a world before oursa world before ours” ”
zz Earth history = a seriesEarth history = a series
of catastrophesof catastrophes
zz Believed in extinctionBelieved in extinction
zz Described manyDescribed many
fossil/extinct forms of lifefossil/extinct forms of life
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Great Chain of BeingGreat Chain of Being
zz Various lives continually evolving to more Various lives continually evolving to more
advanced forms. Canadvanced forms. Can’ ’ t break the chain ort break the chain ormore advanced forms will not appear.more advanced forms will not appear.
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18401840’ ’ ss
zz UniformitarianismUniformitarianism
zz Dinosaur fossilsDinosaur fossils
zz William SmithWilliam Smith – – Faunal successionFaunal succession
zz CharlesCharles LyellLyell – – down a side track down a side track
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DarwinDarwin
zz Each new fauna outEach new fauna out--competed previouscompeted previous
faunafauna
zz Survival of the fittest meant generallySurvival of the fittest meant generally
improving forms of lifeimproving forms of life -- “ “chain of lifechain of life” ” zz If an old fauna lived today, it would beIf an old fauna lived today, it would be
outout--competed by modern life?competed by modern life? – – example,example,
South American marsupials and N.South American marsupials and N. American American placentalsplacentals
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DARWINDARWIN
zz Jurassic Park Jurassic Park – – would a past animalwould a past animal
triumph today? Starve to death?triumph today? Starve to death?
zz Put Pleistocene Mammoths in Eocene panPut Pleistocene Mammoths in Eocene pan--tropical conditions.tropical conditions.
zz If world is constantly changing, isIf world is constantly changing, is “ “fitnessfitness” ”
also changing?also changing?
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Longevity or ExtinctionLongevity or Extinction
zz There are some longThere are some long--lived things.lived things.
zz Tautologies and Circular Reasoning.Tautologies and Circular Reasoning.
zz Lack of evidence in fossil record as to causeLack of evidence in fossil record as to causezz Inadequacy of modern analoguesInadequacy of modern analogues
zz Darwinian failures to adapt orDarwinian failures to adapt or “ “Bad GenesBad Genes” ”
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Condors and VulturesCondors and Vultures
Failure to adapt?Replacement by more Adapted species?
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NeocatastrophismNeocatastrophism
zz Bad Luck?Bad Luck?
zz Asteroids? Asteroids?
zz Small changes in environment?Small changes in environment?
zz Human interference?Human interference?
zz Extinction resistanceExtinction resistance
zz Widespread distribution?Widespread distribution?
zz LongevityLongevity – – a handicap or advantage?a handicap or advantage?
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The Survivorship CurveThe Survivorship Curve
zz Leigh VanLeigh Van Valen Valen
zz MostMost TaxaTaxa have short liveshave short lives
zz FewFew taxataxa have longer liveshave longer lives
zz Chance of survival sameChance of survival same
zz Red Queen HypothesisRed Queen Hypothesis
zz Constant need to improveConstant need to improve
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Can Species Improve?Can Species Improve?
zz Punctuated Equilibrium suggests that theyPunctuated Equilibrium suggests that they
can only be replaced by other, improvedcan only be replaced by other, improvedspecies.species.
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Mass ExtinctionsMass Extinctions
zz Mid 1800Mid 1800’ ’ s Time Scale Designations of thes Time Scale Designations of the
larger units based on mass extinctionslarger units based on mass extinctionszz 19801980’ ’ s asteroid impact hypothesiss asteroid impact hypothesis
renewed interest in mass extinctionrenewed interest in mass extinction
zz Newer theories and new evidence toNewer theories and new evidence to
explain mass extinctionsexplain mass extinctions
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The Big FiveThe Big Fivezz Late OrdovicianLate Ordovician
zz Late DevonianLate Devonianzz Permian/TriassicPermian/Triassic – – End of PaleozoicEnd of Paleozoic
zz Late TriassicLate Triassic
zz Cretaceous/TertiaryCretaceous/Tertiary – – End of MesozoicEnd of Mesozoic
zz SmallerSmaller
zz
Eocene/OligoceneEocene/Oligocenezz PleistocenePleistocene MegafaunaMegafauna
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A Common Cause A Common Cause