Pal Chap 6 Extinction

7/30/2019 Pal Chap 6 Extinction

http://slidepdf.com/reader/full/pal-chap-6-extinction 1/22

EXTINCTIONEXTINCTION



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




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




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



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 .



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)




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?




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?



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



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



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.



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



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



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?



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” ”



Condors and VulturesCondors and Vultures

Failure to adapt?Replacement by more Adapted species?



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?



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



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.



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



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



A Common Cause A Common Cause

Documents

Pal Chap 6 Extinction