fossils are the preserved remains of living organisms.
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what are the two different types of fossils?
body and trace.
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What is an organism?
An individual life form e.g. animals, plants, fungus or bacteria.
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What is a body fossil?
The hard part to an organism, such as the skeleton or shell.
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Describe the process of 'replacement'?
atom by atom substitution of one mineral for another.
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Describe the process of 'dissolution'?
the process whereby minerals that make up the fossils are dissolved away and removed in solution by groundwater.
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what is a mould?
the impression of the outside or inside of a fossil.
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what is a cast?
an in-filled fossil void, usually with another mineral.
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what are the most important factors that affect fossilisation?
-original composition -energy levels -transport distance -speed of burial -amount of oxygen -size of sediment -diagenesis -compaction
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explain original composition?
many fossils made of calcite/aragonite. can be easily altered. hard parts made of silica may be unaltered.
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explain energy levels?
high energy = lots of fragments due to lots of movement and breakage. Low energy = more complete fossils due to lack of movement and collisions.
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explain how transport distance affects fossilisation?
fossils fragmented during transport, due to abrasion/ collisions causing breakage.
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explain rapidity of burial?
faster burial means more chance of whole body fossil being preserved.
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how does amount of oxygen affect fossilisation?
presence of oxygen speeds up breakdown of organisms due to bacterial decay.
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how does sediment affect preservation?
fine sediment = preserves organisms better than course grained. Only poorly preserved fossils can be found in course grained.
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explain diagenesis?
changes within the sediments after burial. Composition & acidity of percolating groundwater is important as it may dissolve/replace fossil with another material.
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