AP Biology
2006-2007
Darwin andEvolutionbyNatural Selection-
Evidence
Raven Chapters 1 & 22
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Science clearly favors critical inquiry
TINTORETTO The Creation of the Animals 1550TINTORETTO The Creation of the Animals 1550
What wasthe doctrineof the time?
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Evolution as Change Over Time
Evolution!
Evolution!
Evolution!
Early ideas ofevolution!Early ideas ofevolution!
Evolution!
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LaMarck (1744-1829)
Organisms adapted totheir environments byacquiring traits
change in their life timechange in their life time
Disuseorganisms lost parts because they did not use them— like the missing eyes & digestive system of thetapewormDisuseorganisms lost parts because they did not use them— like the missing eyes & digestive system of thetapeworm
Perfection with Use & Needthe constant use of an organ leads that organ toincrease in size — like the muscles of a blacksmithor the large ears of a night-flying batPerfection with Use & Needthe constant use of an organ leads that organ toincrease in size — like the muscles of a blacksmithor the large ears of a night-flying bat
transmit acquired characteristics to nextgeneration
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Malthus (1766-1834)
Lyell (1797-1875)
Geologist
Wrote- Principles of Geology
Outlined the story of ancient world ofplants and animals in flux
Uniformitarianism
Economist
Wrote- Essay on the Principle ofPopulation
Studies of human population limited byresources (Struggle for existance)
Malthusian catastrophe
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Then along comes Darwin…
Charles Darwin
1809-1882
British naturalist
Proposed the idea ofevolution by naturalselection
Collected clearevidence to supporthis ideas
1831-1836
22 years old!
Galapagos
Islands
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In historical context
Other people’s ideas paved thepath for Darwin’s thinking
competition:
struggle for survivalpopulation growth exceeds food supply
land masses change overimmeasurable time
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Unique species
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Finch?
Sparrow?
Woodpecker?
Warbler?
Darwin found… birds
Finch?
Sparrow?
Woodpecker?
Warbler?
Collected manydifferent birds on theGalapagos Islands.Collected manydifferent birds on theGalapagos Islands.
Thought he foundvery different kinds…Thought he foundvery different kinds…
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Darwin was amazed tofind out:
All 14 species of birdswere finches…
Finch?
Sparrow?
Woodpecker?
Warbler?
But Darwin found… a lot of finches
Large GroundFinch
Small GroundFinch
Warbler Finch
Veg. Tree Finch
But there is only onespecies of finch on themainland!
How didone speciesof finches becomeso many differentspecies now?
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Correlation of species to food source
SeedeatersSeedeaters
FlowereatersFlowereaters
InsecteatersInsecteaters
Rapid speciation:new species filling new niches,because they inheritedsuccessful adaptations.
Adaptive radiation
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(a) Cactus eater. The long,sharp beak of the cactusground finch (Geospizascandens) helps it tearand eat cactus flowersand pulp.
(c) Seed eater. The large groundfinch (Geospiza magnirostris)has a large beak adapted forcracking seeds that fall fromplants to the ground.
(b) Insect eater. The green warblerfinch (Certhidea olivacea) uses itsnarrow, pointed beak to grasp insects.
Beak variation in Galapagos finches
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Differences inbeaks allowedsome finches to…
successfullycompete
successfully feed
successfullyreproduce
pass successfultraits onto theiroffspring
Darwin’s finches
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Correlation of speciesto food source
Whoa,Turtles, too!
More observations…
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Many islands also showdistinct local variations intortoise morphology…
…perhaps these arethe first steps in thesplitting of one speciesinto several?
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![Armadillo[1].png](data/images/img48.png)
Glyptodont fossilsGlyptodont fossils
Modern armadillosModern armadillos
Modern slothModern sloth
Sloth fossilsSloth fossils
Why should extinctspecies & living speciesbe found on thesame continent?
More observations…
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This is not just aprocess of thepast…
It is allaroundus today
Artificial selection
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Selectivebreeding
the raw geneticmaterial (variation)is hidden there
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Selective breeding
Hidden variationcan be exposedthrough selection!
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A Reluctant Revolutionary
Returned to England in 1836
wrote papers describing his collections& observations
long treatise on barnacles
draft of his theory ofspecies formation in 1844
instructed his wife topublish this essay uponhis death
reluctant to publish butdidn’t want ideas to diewith him
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And then came the letter….
Alfred Russel Wallacea young naturalist workingin the East Indies, hadwritten a short paper with anew idea. He asked Darwinto evaluate his ideas andpass it along for publication.
Alfred Russel Wallacea young naturalist workingin the East Indies, hadwritten a short paper with anew idea. He asked Darwinto evaluate his ideas andpass it along for publication.
Then, in 1858, Darwin received a letterthat changed everything…Then, in 1858, Darwin received a letterthat changed everything…
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The time was ripe for the idea!
Your wordshave come truewith a vengeance…I never saw a more strikingcoincidence…so all my originality,whatever it may amount to,will be smashed.
To Lyell—
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Voyage: 1831-1836
November 24, 1859, Darwin published
“On the Origin of Species by Means of Natural Selection”
Darwin: Reluctant Rebel
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Essence of Darwin’s ideas
Evolution by Means of Natural Selection
variation exists in populations
over-production of offspring
more offspring than the environment can support
competition
for food, mates, nesting sites, escape predators
differential survival
successful traits = adaptations
differential reproduction
adaptations become morecommon in populationadaptations become morecommon in population
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LaMarckian vs. Darwinian view
LaMarck
in reaching highervegetation giraffesstretch their necks &transmits the acquiredlonger neck to offspring
Darwin
giraffes born with longernecks survive better &leave more offspring whoinherit their long necks
