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Fossils
Fossils and other types of fossilization
| Question | Answer |
|---|---|
| What are fossils? | Preserved remains or traces of animals, plants, and other organism from the remote past Found in sedimentary rock layers Can be as small as bacteria or as giant as a dinosaur Paleontology is the study of fossils. |
| Condition for forming fossils? | Quick burial of organism Layers of sediments build up over the organism Left for a long period of time Most fossil remains are from hard structures such as bones and teeth. Erosion and uplifting exposes them to the Earth’s surface. |
| Sedimentary Rocks | Formed in layers by the deposition of rocks Sediments are pressed and cemented together. Fossils are found here because sedimentary rocks form at low temperatures pressure. Fossils and the rock layer that they are found are approximately the same age. |
| Law of Superposition | Geologists assume the newest rock layers are on top of the older ones unless some type of disturbance occurs This law helps scientists determine the age of fossils we can say one fossil is older than another because of the strata in which it was found. |
| Fossil Record | History of life as documented by fossils Tells us when organisms lived and how they changed over millions of years (evolved) Can also give us a clue as to the environment at that time Recorded on the Geologic Time Scale |
| Types of Fossilization | Petrification Replacement Permineralization Molds and Casts Carbonization Fossil Resin (amber) Tar and Ice Trace Fossils |
| Petrification | Two types – Replacement and Permineralization Both result in organic material converting into stone or a similar substance Petrified wood is the most well know example of this process. |
| Replacement | Happens when water dissolves the original solid material and replaces them with mineral matter such as calcite, silica, pyrite and hematite Happens slowly Bones, shells, and wood are often fossilized in this manner. |
| Permineralization | Groundwater carries dissolved minerals into the pores and cavities of bone, wood, or shells. The original material is preserved rather than replaced. Bones, teeth, and shells can be preserved this way. |
| molds and casts | Mold – organism dies and there is no filling of the cavity with minerals Cast – organism dies and the cavity fills with minerals, maybe sand or clay Many times shells are fossilized through these processes. |
| carbonization | The process by which all substances of plants and animals decay, except carbon. This leaves a carbon film on the sedimentary rock. This process particularly occurs in plants and fish. |
| fossil resin | Resin comes from certain plants, it is thought to protect them from insects and seals off injuries. The sticky resin captures insects and invertebrates. It hardens and they are preserved in the resin including their DNA. Fossil resin is aka amber. |
| tar and ice | An animal can become trapped in tar and the whole body can be preserved. An example is the La Brea Tart Pits L.A. Freezing can also trap whole animals. Mammoth’s bodies have been found with skin, hair and even organs. |
| trace fossils | Provides indirect evidence of life in the past rather than the body of the animal itself. Examples of trace fossils Footprints Tracks Burrows Feces Borings |
Created by:
ssennott
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