8.1 Scientific Contribution to a Theory of Evolution

1. 8.1 Scientific Contribution to a Theory of Evolution SBI3U Ms. De Sousa

2. Georges- Louis Leclerc (1707-1788) • Challenged the ideathat life formswereunchanging • Noticedsimilaritiesbetweenhumans and apes suggestingtheyhad a commonancestor • Based on hisassumptionsheassumedthatearthwasmucholderthan 6000 years.

3. Georges Cuvier • Analysed Mary Anning’sstudies of fossils in England. • Developped the science of paleontology; a studyof fossilsas a way to examine ancientlife.

4. Fossil records Strata are sedimentary rock that have compactedintolayers over manygenerations. Eachstrata layer tells a story. A variety of fossilscanbefoundwithineach layer. Consideringthateach layer wascompactedat a different point in time, the fossilswithinthem are presumed to have been fromthatera.

5. Georges Cuvier • When Cuvier lookedthrough the fossils, itshowedevidencethatorganismswereappearing and disappearingform the layers. • Thus, the stratashowedevidence of extinction.

6. Cuvier and Catastrophism • Cuvier speculatedthatearthhadundergonemanynaturaldisasterskillingvariousspecies. • Floods, diseases, droughts and volcaniceruptionswere all differentforms of catastrophicevents (revolutions) thatcontributed to extinction. • Cuvier usedcatastrophism as a theory to explainhisobservations in the stratalayers.

7. Charles Lyell (1797- 1875) • Believed in Uniformitarianism. • He believedthat the earthwas more than 6000 yearsold and that the differencesseen in specieswere due to slow subtle changes.

8. Jean-Baptist Lamarck (1744-1829) • Lamarck compared the fossils to today’sspecies and came to the conclusion thatspecieschanged over time. • He concludedthattherewas a line of decentbetween ancestral species and today’sspecies • Lamarck believedthatspeciesbecameincreasinlgy more complexovertimeuntiltheyreachedperfectionand werebetteradapted to theirenvironment.

9. Lamarck’sTheory • Created the law of Inheritance of acquiredcharacteristics: • He believedthatovertimeorganismsbecameincreasingly more adapted to theirenvironment. • The body parts thatwereused more oftenwouldbecome more prominent and bettersuited for the environment. • He believedthatthese changes wouldthenbepassedon fromgeneration to generation.

10. Charles Darwin (1809-1882) • Through the theoriesprior to him and his observations, Darwin was able to devleop the Theory of Evolution by Natural Selection.

11. The Voyage of the Beagle • Charles Darwin took a trip to the GalapagosIslandsto futherunderstand the variation of species. • The shiphetravelledwasknown as the Beagle .

12. The Voyage of the Beagle

13. The voyage of the beagle • The voyage began on the South American coastline. • Darwin collectedmanysamples of plants and animalsand lookedattheiradaptations in differentenvironments.

14. Observation 1: • The organisms (flora and fauna) in the South American shorlinewereverydifferentthan the organisms in the EuropeanCoatline. • Charles Darwin’s theory was that species change over time, or evolve, in response to their environment.

15. Observation 2: • After an earthquake has occured, Darwin was able to lookedat the strata of the earththatwaslifted. • Darwin foundfossilswithineachstrata layer and observed how differenttheywerefrom one another.

16. Observation 3: • Darwin observedthat the finches on the Galapagosislandscloselyresembled the finches on the westcoast line of South America. • This couldpossiblyindicatethattherewas a naturaldisasterthatseparated the birdsintoseparate niches.

17. Observation 4: • When Darwin visited the GalapagosIslands, heobserved a variety of finchesspecies. • The finchesvariedslightlyfromisland to island. • It seemedthateachfinchhadadapted to eatingdifferentfood. Theirbeaksdiffered in response to thisenvironmental change.

18. Darwin’sFinches

19. Darwin’sFinches Based on his observations, Darwin believed the following about the finches. • Storm may have blown the flockfrom South America • No birdsoccupiedthe different niches available on the Galapagos. Thus, the fincheswere able to move intonew ways of feedingwithoutcompetition and survive.

20. Darwin’sFinches 3) Over manygenerations, the birdswithadaptedbeaksthatweresuccessfulin gettingfoodsurvived and successfullyraisedtheiroffspring. • The variation inherent in the population isselected for and results in differential reproduction.

21. Darwin’sFinches 4) Islandsseparated by oceans (30km) preventedinterbreedingand barrierlead to separategene pools on eachisland.

22. Darwin’sFinches 5) Overtime, enoughmutationsmay have accumulated in the gene pool sothattheywouldbeunable to interbreedwithbirds of other populations.

23. Darwin’sAnalysis • Populations change over time. According to Malthus, this change happens due to the starvations or diseaseof the otherspeciesthatdid not have a selectiveadvantage.

24. Darwin’sAnalysis 2) Survival of the Fittest: • Individualswith a selectiveadvantagesurvive in their local environmentsallowingthem to pass on theseadvantageous traits to the offspring.

25. Darwin’sAnalysis 3) All life decendedfromsomeunknownorganism. • Because the descendants spreadintodifferentregions, organismsdevelopped adaptations thatenabledthem to survive in local environment.