B2 - Fossils

  • Gradual replacement
  • Casts and impressions
  • Areas with no decay
  • Start of life
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Where are fossils found?
In rocks.
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How does gradual replacement preserve fossils?
Thins like teeth, shells and bones don't decay easily. Eventually they are replaced by minerals as they decay forming a rock-like substance shaped like the original part.
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Hosw do casts and impressions preserve fossils?
Orgamisms can be buried in a soft material like clay. The clay later hardens as the organism decays, leaving a cast of the organism in the hard clay.
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How do areas where no decay happens preserve fossils?
In amber and tar pits there's no oxygen or moisture so decay microobes can't survive. In glaciers it's too cold and peat bogs are too acidic. The result is a perfectly preserved oragnism.
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What are the two theories for how life began?
Premodial swamp - amino acids were mixed by lightening. Comet - life arrived on earth in a comet.
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Why is there very little evidence for these theories?
The very eariest life forms were probably organic so they weren't preserved.
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Other cards in this set

Card 2

Front

How does gradual replacement preserve fossils?

Back

Thins like teeth, shells and bones don't decay easily. Eventually they are replaced by minerals as they decay forming a rock-like substance shaped like the original part.

Card 3

Front

Hosw do casts and impressions preserve fossils?

Back

Preview of the front of card 3

Card 4

Front

How do areas where no decay happens preserve fossils?

Back

Preview of the front of card 4

Card 5

Front

What are the two theories for how life began?

Back

Preview of the front of card 5
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