Why doesn’t every plant and animal turn into a fossil?

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There are multiple reasons as to why not every plant and animal turns into a fossil. The first thing that must be considered is the type of organism. Some organisms have only soft body parts that have a lower chance of being preserved because they simply decay too quickly, while others have hard body parts such as shells, bones or teeth that have a greater chance of being preserved.

In general, for an organism to become fossilized, it needs to be buried rapidly in order to be protected from the elements and predators. This can happen by being covered in sediment in areas of high sedimentation such as the bottom of a lake. It could happen by being trapped in amber or volcanic ash as well. Because of this, fossilization often depends on the environment. Organisms that die in areas where they will be exposed for a long period of time have a much less likely chance of being fossilized. 

Because it is fairly rare for an organism to become a fossil, our fossil record is not a complete record of life on earth. It is biased toward organisms that have hard body parts and those that lived in areas more favorable for fossilization. 

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Fossils are the preserved remains of or impressions of an organism. Many plants and animals do not become fossils because they decompose or are eaten before they can be fossilized.

Organisms decompose quicker when exposed to oxygen. Dead organisms are also more likely to be eaten by scavengers when exposed to the open environment.

Thus, many fossils are formed when organisms are covered by sediments. Sediments are particles that fall from and settle to the bottom of a lake, river, pond, or other water source. These sediments cover and thicken around the organism. Mold fossils occur when a covered organism dissolves and forms an impression of itself in the sediments. A cast fossil forms when the covered organism becomes mineralized with the sediments and forms a three-dimensional replica of itself.

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