Early Theories of Early Theories of EvolutionEvolution

Theory of Use and DisuseTheory of Use and Disuse

► Jean Baptiste Jean Baptiste LAMARCKLAMARCK (1744-1829)(1744-1829)

► Theory was based on Theory was based on NEEDNEED Organs neededOrgans needed if if

environmental stresses its environmental stresses its function, while those function, while those organs not neededorgans not needed gradually gradually disappeared disappeared because of disuse.because of disuse.

IF YOU DON’T USE IT, YOU IF YOU DON’T USE IT, YOU LOSE IT!LOSE IT!

Theory of Use and DisuseTheory of Use and Disuse►Lamarck believed in the inheritance of Lamarck believed in the inheritance of

ACQUIRED CHARACTERISTICSACQUIRED CHARACTERISTICS Body changes due to an organism’s Body changes due to an organism’s

behavior or experience that occur within behavior or experience that occur within an organism’s life an organism’s life could then be passed could then be passed on to offspringon to offspring

EXAMPLES: EXAMPLES: ►Webbed footWebbed foot of water birds – the repeated of water birds – the repeated

stretching of membrane between the toes was stretching of membrane between the toes was passed on to offspringpassed on to offspring

►Organisms not using Organisms not using tailtail would produce would produce offspring with smaller tailsoffspring with smaller tails

Acquired CharacteristicsAcquired Characteristics

►Giraffe Example:Giraffe Example: Giraffes must Giraffes must stretch their stretch their

necksnecks to reach leaves on to reach leaves on the tops of treesthe tops of trees

This This longer neck then got longer neck then got passed to offspringpassed to offspring

Disproving LamarckDisproving Lamarck

►Experiments were conducted to try to Experiments were conducted to try to prove Lamarck’s ideas, but prove Lamarck’s ideas, but none of none of them were successfulthem were successful Petals on flowersPetals on flowers Female waist (corsets)Female waist (corsets) Tails of miceTails of mice

Darwin’s TheoriesDarwin’s Theories► Charles Charles Darwin Darwin

(1809-1882)(1809-1882) 1831 – traveled 1831 – traveled

aboard aboard HMS BeagleHMS Beagle as a as a recorder/naturalistrecorder/naturalist

Collected Collected many many specimensspecimens and and documented many of documented many of his his observations observations - - noted much variety!noted much variety!

Darwin’s TheoriesDarwin’s Theories Spent time in the Spent time in the Galapagos Galapagos

IslandsIslands►Tortoises on different Tortoises on different

islands displayed islands displayed different characteristicsdifferent characteristics

Harriett was 5 when Harriett was 5 when Darwin captured her. Lived Darwin captured her. Lived to be 176 years old (Died to be 176 years old (Died June 2006)June 2006)

►Finch beaks (Finch beaks (1313 varieties) varieties) varied in size & shapevaried in size & shape from island to islandfrom island to island

Took 20 years to organize Took 20 years to organize data and develop his theory data and develop his theory of evolution!of evolution!

Darwin’s TheoriesDarwin’s Theories► Alfred WALLACEAlfred WALLACE, independent of Darwin, , independent of Darwin,

also developed ideas that were very also developed ideas that were very similar to Darwin’s – they presented their similar to Darwin’s – they presented their ideas jointly to the public in 1858 ideas jointly to the public in 1858 (Linnaean Society in London)(Linnaean Society in London)

►Darwin wrote Darwin wrote On The Origin of On The Origin of

SpeciesSpecies presenting his theory presenting his theory

of evolution based on natural of evolution based on natural

selection. selection.

What is The Theory of Natural What is The Theory of Natural Selection?Selection?

►NATURAL SELECTION – individuals NATURAL SELECTION – individuals within a population with the within a population with the most most favorable traitsfavorable traits for an environment for an environment survive and pass on those traitssurvive and pass on those traits

►Based on 4 statementsBased on 4 statements 1) Organisms produce 1) Organisms produce many offspringmany offspring and and

have potential to grow uncheckedhave potential to grow unchecked 2) 2) Variations Variations exist within a species (at exist within a species (at

that time DID NOT know that it was a that time DID NOT know that it was a result of result of mutations & genetic mutations & genetic recombinationrecombination))

What is The Theory of Natural What is The Theory of Natural Selection?Selection?

3) 3) Competition for limited resourcesCompetition for limited resources (struggle for (struggle for existence – food, disease, predators)existence – food, disease, predators)

4) 4) Environment selectsEnvironment selects organisms with favorable organisms with favorable traitstraits►““Survival of the fittestSurvival of the fittest””►ADAPTATION – a variation that ADAPTATION – a variation that improves an improves an

organism’s chance of survivalorganism’s chance of survival

►A population adapts to their environment as their A population adapts to their environment as their proportion of genes for a favorable trait increasesproportion of genes for a favorable trait increases

► DARWIN’S THEORY IS DARWIN’S THEORY IS STILL RELIED UPON TODAYSTILL RELIED UPON TODAY AND AND IS SUPPORTED THROUGH EXPERIMENTATION. IS SUPPORTED THROUGH EXPERIMENTATION.

Natural Selection ExampleNatural Selection Example► The peppered moth The peppered moth

Before the industrial revolution in Britain, Before the industrial revolution in Britain, most most peppered moths were of the pale varietypeppered moths were of the pale variety & were & were well well camouflaged against the pale birch treescamouflaged against the pale birch trees that they like to sit on. that they like to sit on.

Moths with the Moths with the mutant black coloringmutant black coloring were easily were easily spotted and spotted and eaten by birdseaten by birds - giving the white - giving the white peppered variety an advantage peppered variety an advantage

Natural Selection ExampleNatural Selection Example► Then the industrial revolution came Then the industrial revolution came

along in the 19th century. along in the 19th century. ► Airborne Airborne pollutionpollution in industrial areas in industrial areas

mottled the birch tree bark with mottled the birch tree bark with sootsoot, , and now the and now the mutant black-peppered mutant black-peppered moths blended better against the moths blended better against the darkened barkdarkened bark, while the white , while the white variety became much more variety became much more vulnerablevulnerable to predators to predators

► Over time the mutated Over time the mutated black black peppered moths were peppered moths were naturally naturally selected to surviveselected to survive and became far and became far more numerous in urban areas than more numerous in urban areas than the pale variety. the pale variety.

► Peppered Moth Simulation