Fossils: Our Keys to the Past and Evidence of Evolution

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Fossils Our Keys to the Past and Evidence of
Evolution
By Shannon Reardon Adam Bouchardand
Kristan Brodie
http//www.kpbsd.k12.ak.us/chapman/demers/images/c
ollage2.JPG
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What is a fossil?

• A fossil is remains of ancient life
• Fossil is derived from the Latin term fossilis -
  meaning any object extracted from the ground
  including minerals and archeological artifacts
• In the 18th century paleontology (the study of
  ancient life) was created

paleo
ology
old or ancient
study of
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Why are fossils important?

• It enabled scientists to see occurrence of
  extinction in different species
• It gave Darwin evidence that earth is older than
  previously believed and that very slow changes
  over a long period of time can add up to
  substantial changes in organisms
• Can be used to correlate and match up rock units
  from different places giving relative ages
• It shows evidence of continental drift the
  theory that continents were once one large
  landmass

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Plummer et al 2003
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Fossilization
ization
TO MAKE

• Hard parts of organisms are more likely to be
  preserved than soft parts.
• Soft parts are likely to decay or be consumed by
  other organisms
• Because of this soft bodied creatures such as
  jellyfish may not be fossilized either
• Buried organisms are more likely to be fossilized
  because it minimizes the decay, consumption, and
  destruction of the remains

BURIED IN SEDIMENT OR SOIL
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Types of Fossils

• Unaltered remains original material of the
  organism has not been changed to another
  substance
• Altered remains original material has undergone
  permineralization, recrystalization, replacement,
  carbonization
• Impressions organisms leave an imprint in
  sediment, can form casts and molds
• Traces other evidence that an organism existed,
  ex. tracks, trails, footprints

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Unaltered Parts
Altered remains Carbonization of a leaf
http//www.studyworksonline.com/cda/image/preview/
0,1127,1309,00.jpg
http//www.fp.sfasu.edu/geology/GeologyTutorial/Fo
ssils/CARBONization01.JPG
Impression - Cast and Mold
http//gpc.edu/pgore/myphotos/fossils/castmold.j
pg
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Permineralization petrified wood
Trace fossil
http//www.dinosaursrock.com/SteveDiloposaurusFoot
Print.jpg
http//www.clas.ufl.edu/users/pciesiel/gly3603c/wo
od1.jpg
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Radioactive Dating and Geologic Time Scale

• By Adam Bouchard

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Age on Earth

• EVIDENCE suggests age of the Earth is about 4.6
  to 4.7 billion years old
• Evidence is gathered from radioactive dating of
  rocks from the earth, moon and meteorites
• Relative age places rock units or geologic
  events in sequential order
• Absolute age numerical or chronological age of
  a rock or geologic event

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Radioactive Dating Definitions

• Radioactive isotope - an atomic form of a
  chemical element that is unstable
• Radioactive decay - the spontaneous nuclear
  disintegration of certain isotopes
• Radioactive dating a way of determining the age
  of rocks and fossils on a scale of absolute time.
  It is based on the half-life of radioactive
  isotopes
• Half-life the time it takes for ½ the atoms of
  the radioactive parent to decay to atoms of the
  daughter element

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