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10 Cards in this Set
- Front
- Back
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What are fossils |
Fossils are the preserved remains or traces of dead organisms. They are found in rocks.
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Steps of fossilisation 1. |
Organism dies and falls into a soft silt at the bottom of the lake or sea. |
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2. |
The remains become covered by silt. |
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3. |
Silt gradually turns to rock, encasing the dead organism. |
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4. |
Over millions of years the hard parts of the organism are replaced by minerals. |
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5. |
Tectonic activity makes the rock rise, and erosion at the surface may expose the fossil. |
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4 types of fossils |
- parts that won't decay ( human fossils) -parts replaced by minerals (part of an animal) -parts preserved(whole animals) -evidence is preserved( footprints) |
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Factors that may cause a species to become extinct. |
-New diseases -New predators -New, more successful competitors -Changes to the environment over geological time - such as a change in climate -A single catastrophic event - such as a massive volcanic eruption |
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Speciation |
Formation of new and distinct species in the course of evolution |
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Isolation |
New species can arise as a result of isolation. This is where two populations of a species become geographically separated. For example, Charles Darwin described speciation of finches this way.
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