Biology 12.1 The Fossil Record

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Permineralization
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minerals carried by water are deposited around a hard structure ; may also replace the hard structure itself
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Natural casts
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when flowing water removes all of the original bone or tissue, leaving just an impression in sediment ; minerals fill in the mold, recreating the original shape of the organism
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Trace fossils
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record the activity of an organism ; include nests, burrows, imprints of leaves, and footprints
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Amber-preserved fossils
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organisms that become trapped in tree resin that hardens into amber after the tree gets buried underground
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Preserved remains
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when an entire organism becomes encased in material such as ice or volcanic ash or immersed in bogs
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Relative dating
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estimates the time during which an organism lived by comparing the placement of fossils of that organism with the placement of fossils in other layers of rock
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Radiometric dating (estimating actual age)
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technique that uses the natural decay rate of unstable isotopes found in materials in order to calculate the age of that material
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isotope
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atoms of an element that have the same number of protons but a different number of neutrons
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half-life
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amount of time it takes for half of the isotope in a sample to decay into a different element, or its product isotope

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