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'''Fossils''' (from Latin fossus, [[literally]] "having been dug up") are the [[preserved]] remains or traces of [[animals]], plants, and other [[organisms]] from the remote [[past]]. The [[totality]] of fossils, both [[discovered]] and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers ([http://en.wikipedia.org/wiki/Stratum strata]) is known as the fossil record. The [[study]] of fossils across [[geological time]], how they were [[formed]], and the [[evolutionary]] [[relationships]] between [http://en.wikipedia.org/wiki/Taxon taxa] ([http://en.wikipedia.org/wiki/Phylogenetics phylogeny]) are some of the most important [[functions]] of the [[science]] of [http://en.wikipedia.org/wiki/Paleontology paleontology]. Such a preserved specimen is called a "fossil" if it is older than some minimum age, most often the [[arbitrary]] date of 10,000 years ago. Hence, fossils range in age from the youngest at the start of the [http://en.wikipedia.org/wiki/Holocene Holocene Epoch] to the oldest from the [http://en.wikipedia.org/wiki/Archaean Archaean Eon] several billion years old. The [[observations]] that certain fossils were [[associated]] with certain rock strata led early [[geologists]] to [[recognize]] a [[geological timescale]] in the 19th century. The [[development]] of [http://en.wikipedia.org/wiki/Radiometric_dating radiometric dating] [[techniques]] in the early 20th century allowed geologists to determine the numerical or "absolute" age of the various strata and thereby the included fossils.
'''Fossils''' (from Latin fossus, [[literally]] "having been dug up") are the [[preserved]] remains or traces of [[animals]], plants, and other [[organisms]] from the remote [[past]]. The [[totality]] of fossils, both [[discovered]] and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers ([http://en.wikipedia.org/wiki/Stratum strata]) is known as the fossil record. The [[study]] of fossils across [[geological time]], how they were [[formed]], and the [[evolutionary]] [[relationships]] between [http://en.wikipedia.org/wiki/Taxon taxa] ([http://en.wikipedia.org/wiki/Phylogenetics phylogeny]) are some of the most important [[functions]] of the [[science]] of [http://en.wikipedia.org/wiki/Paleontology paleontology]. Such a preserved specimen is called a "fossil" if it is older than some minimum age, most often the [[arbitrary]] date of 10,000 years ago. Hence, fossils range in age from the youngest at the start of the [http://en.wikipedia.org/wiki/Holocene Holocene Epoch] to the oldest from the [http://en.wikipedia.org/wiki/Archaean Archaean Eon] several billion years old. The [[observations]] that certain fossils were [[associated]] with certain rock strata led early [[geologists]] to [[recognize]] a [[geological timescale]] in the 19th century. The [[development]] of [http://en.wikipedia.org/wiki/Radiometric_dating radiometric dating] [[techniques]] in the early 20th century allowed geologists to determine the numerical or "absolute" age of the various strata and thereby the included fossils.
Like extant [[organisms]], fossils vary in size from microscopic, such as single bacterial [[cells]] only one micrometer in diameter, to gigantic, such as [http://en.wikipedia.org/wiki/Dinosaur dinosaurs] and trees many meters long and weighing many tons. A fossil [[normally]] preserves only a portion of the deceased [[organism]], usually that portion that was partially mineralized during life, such as the bones and teeth of [http://en.wikipedia.org/wiki/Vertebrate vertebrates], or the chitinous [http://en.wikipedia.org/wiki/Exoskeleton exoskeletons] of [http://en.wikipedia.org/wiki/Invertebrate invertebrates]. Preservation of soft tissues is rare in the fossil record. Fossils may also consist of the marks left behind by the organism while it was alive, such as the footprint or feces (coprolites) of a [http://en.wikipedia.org/wiki/Reptile reptile]. These types of fossil are called [http://en.wikipedia.org/wiki/Trace_fossil trace fossils] (or ichnofossils), as opposed to body fossils. Finally, [[past]] life leaves some markers that cannot be seen but can be detected in the [[form]] of [http://en.wikipedia.org/wiki/Biochemistry biochemical signals]; these are known as chemofossils or biomarkers.
Like extant [[organisms]], fossils vary in size from microscopic, such as single bacterial [[cells]] only one micrometer in diameter, to gigantic, such as [http://en.wikipedia.org/wiki/Dinosaur dinosaurs] and trees many meters long and weighing many tons. A fossil [[normally]] preserves only a portion of the deceased [[organism]], usually that portion that was partially mineralized during life, such as the bones and teeth of [http://en.wikipedia.org/wiki/Vertebrate vertebrates], or the chitinous [http://en.wikipedia.org/wiki/Exoskeleton exoskeletons] of [http://en.wikipedia.org/wiki/Invertebrate invertebrates]. Preservation of soft tissues is rare in the fossil record. Fossils may also consist of the marks left behind by the organism while it was alive, such as the footprint or feces (coprolites) of a [http://en.wikipedia.org/wiki/Reptile reptile]. These types of fossil are called [http://en.wikipedia.org/wiki/Trace_fossil trace fossils] (or ichnofossils), as opposed to body fossils. Finally, [[past]] life leaves some markers that cannot be seen but can be detected in the [[form]] of [http://en.wikipedia.org/wiki/Biochemistry biochemical signals]; these are known as chemofossils or biomarkers.[http://en.wikipedia.org/wiki/Fossil]
==See also==
==See also==
*[http://en.wikipedia.org/wiki/Petrification Petrification]
*[http://en.wikipedia.org/wiki/Petrification Petrification]
[[Category: Earth Science]]
[[Category: Earth Science]]