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Fossils & The Geologic Column 
Exploring Creation with GGeenneerraall SScciieennccee 
Science is Organized Knowledge
What do They Study? 
• AArrcchheeoollooggiissttss 
– study aarrttiiffaaccttss (evidence of human life on Earth) 
• PPaalle...
Fossils 
• Evidence of organisms that once lived on Earth 
• Most are found in sedimentary rock layers 
• Very small perce...
Fossilization 
• For a fossil to be discovered, a 
deceased organism must be: 
– covered quickly to prevent 
decay or phys...
Types of Fossils 
• Original Remains (True Form Fossils) 
– Preserved in amber, tar or ice 
• Petrified Fossils 
– Organic...
Original Remains (True Form Fossils) 
– Complete organisms preserved in amber (solidified resin), tar or ice 
• Organisms ...
Petrifaction (mineralization) 
• remains are exposed to water containing large amounts of 
minerals 
• Over time, organic ...
Carbon Films & Impressions 
• Impression: 
• Plant/animal is buried in sediment and liquids/gases are forced out 
• Carbon...
Trace Fossils 
• preserved evidence of the activities of deceased 
organisms (footprints, burrows, nests, etc.)
Mold & Cast Fossils 
•Organic remains become encased in sedimentary rock 
•Weathering disintegrates remains; hollow mold i...
Experiment 7.1 
Making a Fossil Cast
The Fossil 
Record 
• 95% of all discovered fossils 
are marine invertebrates, 
mostly shellfish 
• 4.75% are algae and pl...
Geologic Time 
• Assumes 
sedimentation occurs 
evenly and slowly 
over millions of years 
• Large gaps remain in 
the fos...
Fossil Sorting 
• Fossil sorting is thought 
to represent the history 
of life on earth. 
• Fossils in the lowest rock 
la...
• Cenozoic 
– "new life" 
• Mesozoic 
– "middle life" 
– dinosaurs 
• Paleozoic 
– "ancient life" 
Precambrian
Extinction 
• When a species cannot adapt to it’s environment (because of 
predation, loss of habitat or food supply, cata...
Out of Place Fossils 
• The Coelacanth was thought to 
have gone extinct with the 
dinosaurs 65 million years ago 
until i...
Living Fossils 
· Crocodiles - dates back 230 million years 
· Army Ants - dates back 100 million years 
· Cockroaches - d...
Trilobites 
• Large class of extinct, marine, 
bottom-dwelling arthropods 
– abundant in Cambrian era rock layers 
– now e...
Puzzling Fossil Facts 
• The fossils found in one layer of stratified rock can be considerably different 
than the fossils...
The "Cambrian Explosion" 
• Evidence in the fossil record shows that all major phylla were established in the 
transition ...
Transitional Fossils 
• Intermediate fossils are few and far 
between (and some say non-existent). 
– Archaeopteryx and Ti...
Fossil Dating Methods 
• Relative Age 
– Geologic time scale created with the belief that 
younger fossils are deposited o...
Relative Dating 
• Gives approximate age 
relative to where it is found 
• Performed by estimating fossil 
age compared wi...
Index Fossils 
• Geologists use 
these common 
fossils to “date” 
rock layers 
• Paleontologists 
use age of rock 
layers ...
Hydrologic Sorting
Experiment 6.2 
Separation of Sediments
Absolute dating 
• Offers a numeric age 
• Performed by radiometric 
dating or dendrochronology 
• Drawbacks 
– part of th...
The Guesswork of 
Radiometric Dating 
• Many things are assumed or 
"guessed at" when a rock or 
fossil is dated using 
ra...
Radiometric Dating Timeline 
dinosaurs 
humans 
first life 
© NASA 
origin of Earth 
first complex cells
ECGS Module 7
ECGS Module 7
ECGS Module 7
ECGS Module 7
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ECGS Module 7

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Fossil formation and the geologic column

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ECGS Module 7

  1. 1. Fossils & The Geologic Column Exploring Creation with GGeenneerraall SScciieennccee Science is Organized Knowledge
  2. 2. What do They Study? • AArrcchheeoollooggiissttss – study aarrttiiffaaccttss (evidence of human life on Earth) • PPaalleeoonnttoollooggiissttss – study ffoossssiillss (preserved remains of plants/animals) • GGeeoollooggiissttss – study rroocckkss (combined minerals that form Earth's crust)
  3. 3. Fossils • Evidence of organisms that once lived on Earth • Most are found in sedimentary rock layers • Very small percentage of living things become fossils
  4. 4. Fossilization • For a fossil to be discovered, a deceased organism must be: – covered quickly to prevent decay or physical destruction – fossilized (usually by mineralization; requires water) – preserved from further potential destruction • erosion, rock deformation, etc. – unburied by paleontologists
  5. 5. Types of Fossils • Original Remains (True Form Fossils) – Preserved in amber, tar or ice • Petrified Fossils – Organic materials of dead organism are replaced with minerals deposited out of water & turned to stone • Carbon Films & Impressions – Liquids/gasses from organisms leave a "picture" or indentation • Trace Fossils – preserved evidence of the activities of deceased organisms (footprints, burrows, nests, etc.) • Molds & Casts – Under water, as sedimentary rock forms around dead organism, a mold is made. Later, the space left from the decayed organism is filled with sediment, forming a cast.
  6. 6. Original Remains (True Form Fossils) – Complete organisms preserved in amber (solidified resin), tar or ice • Organisms must be preserved quickly to prevent: • decomposition • scavengers • crushing/deformation
  7. 7. Petrifaction (mineralization) • remains are exposed to water containing large amounts of minerals • Over time, organic materials are replaced by minerals • Most fossils are a jumbled mess of petrified bones which paleontologists piece together.
  8. 8. Carbon Films & Impressions • Impression: • Plant/animal is buried in sediment and liquids/gases are forced out • Carbon film: • Thin, filmy, carbon residue leaves a “picture” of the creature
  9. 9. Trace Fossils • preserved evidence of the activities of deceased organisms (footprints, burrows, nests, etc.)
  10. 10. Mold & Cast Fossils •Organic remains become encased in sedimentary rock •Weathering disintegrates remains; hollow mold is formed •Other sediments (or magma) seep into the rock and fill the space, forming a cast of the original organism
  11. 11. Experiment 7.1 Making a Fossil Cast
  12. 12. The Fossil Record • 95% of all discovered fossils are marine invertebrates, mostly shellfish • 4.75% are algae and plants • 0.2375% are non-marine invertebrates and insects • 0.0125% are vertebrates (fish, birds, mammals) • only 0.0025% of all unearthed vertebrate fossils consist of more than a single bone
  13. 13. Geologic Time • Assumes sedimentation occurs evenly and slowly over millions of years • Large gaps remain in the fossil record – they may be still hidden, have been destroyed, or never existed
  14. 14. Fossil Sorting • Fossil sorting is thought to represent the history of life on earth. • Fossils in the lowest rock layers are believed to have lived before those in upper layers. • The first appearance of a fossil could indicate when it first evolved. • The last appearance of a fossil is believed to be the time it went extinct.
  15. 15. • Cenozoic – "new life" • Mesozoic – "middle life" – dinosaurs • Paleozoic – "ancient life" Precambrian
  16. 16. Extinction • When a species cannot adapt to it’s environment (because of predation, loss of habitat or food supply, cataclysmic events, etc.) all of it’s kind may die. • The fossil record shows many examples of organisms we no longer see living on earth today • In evolutionary terms, extinction can help a more “fit” population flourish because it no longer competes for resources • Widespread extinction may indicate worldwide cataclysmic events such as a global flood or ice age
  17. 17. Out of Place Fossils • The Coelacanth was thought to have gone extinct with the dinosaurs 65 million years ago until it was discovered off the coast of Madagascar in 1938. • Many other “misplaced” fossils puzzle scientists since they don’t fit within the sorted geologic column (hoof prints with dinosaur bones, etc.) • Sometimes "older" fossils are found in rock layers above less primitive fossil forms. Coelacanth Living Fossil
  18. 18. Living Fossils · Crocodiles - dates back 230 million years · Army Ants - dates back 100 million years · Cockroaches - dates back 350 million years · Coelacanth - dates back 400 million years · Crinoid or Sea Lilly dates back 150 million years · Cycads dates back 240 million years · Dragonfly dates back 230 million years · Ginkgo dates back 270 million years · Horseshoe Crab - dates back 300 million years · Nautilus - dates back 500 million years · Neopilina molluscs - dates back 400 million years · Salamanders dates back 150 million years · Sturgeon dates back 250 million years · Tuatara dates back 200 million years. · Velvet Worm dates back 500 million years · Wollemi Pine - dates back 150 million years
  19. 19. Trilobites • Large class of extinct, marine, bottom-dwelling arthropods – abundant in Cambrian era rock layers – now extinct (or are they?) • Possessed extremely sophisticated compound eyes and vision
  20. 20. Puzzling Fossil Facts • The fossils found in one layer of stratified rock can be considerably different than the fossils found in another section of the same stratified rock. • It is disputed how long it takes fossils to form. Depending upon the conditions in which it formed, there is evidence that it could be millions of years or less than 50 years. – burial in hot, silica-rich volcanic ash can produced rapid fossilization
  21. 21. The "Cambrian Explosion" • Evidence in the fossil record shows that all major phylla were established in the transition from Late Precambiran to Early Cambrian time • In the creationist model, these animals represent descendants of original created kinds that became extinct during the Flood of Genesis. • Gradual evolution struggles to account for the sudden appearance of so many types of life at one time. – "Punctuated Equilibrium" is one proposed solution • It is puzzling why there are little to no "precursor" fossils to all these varieties of life.
  22. 22. Transitional Fossils • Intermediate fossils are few and far between (and some say non-existent). – Archaeopteryx and Tiktaalik are two impressive (and relatively recent) finds – All are "mosaics", lacking in-between features such as scaly feathers – Some modern-day mosaic species have similar characteristics • platypus and hoatzin chicks Archaeopteryx - feathered bird with teeth Tiktaalik - four-legged fish?
  23. 23. Fossil Dating Methods • Relative Age – Geologic time scale created with the belief that younger fossils are deposited on top of older fossils (referred to as "stratigraphy" and based on the "principle of superposition") • Absolute Age – Dendrochronology (using cross-dating of tree ring patterns of petrified wood buried along with other fossils to date the rock layer) – Radioisotope dating • Molecular Clocks – Genetic divergence used to "count backwards" • Known Age – There really is no way to “absolutely” know the exact age of a fossil • unless a written date is found on or near it or it is referred to in a historical document
  24. 24. Relative Dating • Gives approximate age relative to where it is found • Performed by estimating fossil age compared with that of surrounding fossils and rock layers • Drawbacks – provides no info about age in years – based on assumptions of worldwide, uniform sedimentation similar to rates we see now – large gaps in the geologic record leave room for much speculation
  25. 25. Index Fossils • Geologists use these common fossils to “date” rock layers • Paleontologists use age of rock layers to “date” these fossils • These are all marine fossils - found all over the world
  26. 26. Hydrologic Sorting
  27. 27. Experiment 6.2 Separation of Sediments
  28. 28. Absolute dating • Offers a numeric age • Performed by radiometric dating or dendrochronology • Drawbacks – part of the fossil is destroyed during the test – large margin of error – Assumptions of test question validity of dates
  29. 29. The Guesswork of Radiometric Dating • Many things are assumed or "guessed at" when a rock or fossil is dated using radioisotopes. • All these "guesses" add up to unreliable results. • Different elements are used for different time periods based on their rate of decay – circular verification
  30. 30. Radiometric Dating Timeline dinosaurs humans first life © NASA origin of Earth first complex cells

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