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The Fossil Record
- 1. The Fossil RecordDef: the traces or remains of animals or plants from a previous geologic time.
- 2. Paleontologist Study fossilsto learn about past geologic events, climates, and evolution.
- 3. Most fossils arefound in sedimentary rockā¦ Cover a dead object without damaging it. Keep other animals from destroying āpotentialā fossils. keichosaurus
- 4. No fossils inigneous or metamorphic rocks !? Living things covered with hot, molten lava tend to burn upā¦ ā¦ and fossils in metamorphised rocks become pressured/heated beyond recognition.
- 5. Usually, only theHARD parts of an organism are preservedā¦bones, shells, teeth. Sometimes, only a replica of the organism remains.
- 6. Normallyā¦ Dead plants& animals are usually eaten by other animals or decomposed by bacteria before they can become fossils. Only dead orgs that get buried quickly by sediment stand a chance of getting preserved as fossils.
- 7.
- 8. Mummification Organisms becomedried out. Usually found in desert caves or buried in desert sand. Org doesnāt rot : bacteria need moisture to āwork.ā
- 9. Amber Hardened treesap. Delicate structures preserved (legs, antennae) DNA has been extracted from these fossilsā¦
- 10. Tar Beds Poolsof āblack goldā at the Earthās surface usually covered by water. Animals come to drink, get stuck in the tar, and get sucked inā¦ La Brea Tar Pits in L.A.
- 11. Freezing Low tempsof frozen soil & ice protect & preserve organisms. Org doesnāt rot: bacteria canāt survive freezing temps. Rhinos, mastodons, mammoths found in Alaska & Siberia.
- 12. Petrification Mineral-rich groundwaterremoves & replaces the original mineral with a harder mineral (such as silica, calcite, pyrite). Petrified wood!
- 13. Traces of OrganismsTRACE FOSSILS such as tracks, footprints, borings, and burrows can provide information about organisms.
- 14. Imprints Leaves, stems,shelled creatures, flowers, fishā¦ become stuck in soft clay and leave an imprint which shows the surface features of the organism.
- 15. Molds An organismgets buried in soft sedimentā¦ ā¦ its remains decay, leaving an empty spaceā¦a ābubbleā of nothing in the shape of the organism A mold retains the shape & exterior markings of the org, but tells us zero about the āinsides.ā
- 16. Casts When sandor mud gets inside a mold & hardens, a cast is formed. A cast is a replica of the outer surface of the original org. Montana Rhinos
- 17. Index Fossils Certainfossils are found only in the rock layers of a particular geologic age. These are known as INDEX FOSSILS. Paradoxides :Cambrian Era
- 18. To Qualify asan Index Fossil: Must be āworld-wide.ā Must be distinctive. Must have a āshortā life span. Must be numerous! Echioceras: Jurassic Period