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Fossils: Our Keys to the Past and Evidence of Evolution

Chapter 7.2http://www.kpbsd.k12.ak.us/chapman/demers/images/collage2.JPG

1Evidence of EvolutionSimilar body structuresPatterns of early developmentMolecular structureFossils!!

What is a fossil?Fossil: remains of ancient lifeComes from the Latin term fossilis - meaning any object extracted from the ground including minerals and archeological artifactsIn the 18th century paleontology (the study of ancient life) was created Paleo- = old or ancient ; -ology = study of

Why are fossils important?Let scientists see extinction in different speciesGave Darwin evidence that earth is older than previously believedvery slow changes over a long period of time can add up to substantial changes in organisms

Giant Sloth vs. Living Sloth

Size Comparison (same bone next to a quarter)Why are fossils important?Give relative ages of rockscorrelate and match up rock units from different places Evidence of continental drift the theory that continents were once one large landmass

Plummer et al 2003*Distribution of plant and animal fossils give evidence of supercontinents

Plummer et al 2003*Pangaea breakup and continental driftFossilizationHard parts of organisms are more likely to be preserved than soft parts. Soft parts are likely to decay or be consumed by other organismsBecause of this soft bodied creatures such as jellyfish may not be fossilized eitherBuried organisms are more likely to be fossilized because it minimizes the decay, consumption, and destruction of the remains-ization = to makeBURIED IN SEDIMENT OR SOILTypes of FossilsUnaltered remains original material of the organism has not been changed to another substanceAltered remains original material has undergone permineralization, recrystalization, replacement, carbonization

Types of FossilsImpressions casts and moldsorganisms leave an imprint in sedimentTraces other evidence that an organism existedex. tracks, trails, footprints

Unaltered PartsAltered remains Carbonization of a leafImpression - Cast and Moldhttp://www.studyworksonline.com/cda/image/preview/0,1127,1309,00.jpghttp://gpc.edu/~pgore/myphotos/fossils/cast&mold.jpghttp://www.fp.sfasu.edu/geology/GeologyTutorial/Fossils/CARBONization01.JPG

Trace fossilhttp://www.dinosaursrock.com/SteveDiloposaurusFootPrint.jpg

Permineralization petrified woodhttp://www.clas.ufl.edu/users/pciesiel/gly3603c/wood1.jpgRadioactive Dating and Geologic Time ScaleAge on Earth4.6 to 4.7 billion years oldFrom *evidence*Evidence is gathered from radioactive dating of rocks from the earth, moon and meteorites

Age on EarthRelative age: places rock units or geologic events in sequential orderEx: My phone is older than his.Absolute age : numerical or chronological age of a rock or geologic eventEx: My phone is 2 years old and his is a week old.

Newest layer

Oldest layer

Radioactive Dating DefinitionsRadioactive dating a way of determining the age of rocks and fossils on a scale of absolute timebased on the half-life of radioactive isotopesRadioactive isotope - an atomic form of a chemical element that is unstableRadioactive Dating DefinitionsRadioactive decay - the spontaneous nuclear disintegration of certain isotopesHalf-life the time it takes for the atoms of the radioactive parent to decay to atoms of the daughter element