The History Of life-Fossils and Evolution Flashcards
what are fossils?
a fossil is any preserved evidence of an organism
why cant most organisms become fossilized?
because they decompose before they get the chance
this type of fossil is any indirect evidence left by an organism (footprints, burrows, and fossilized feces
trace fossil
an impression of an organism
molds and casts
the original matierial of an organisms is substituted for mineral crystasls that can leave detailed replicas of hard or soft parts
replacement
empty pore spaces are filled by minerals
petrified or permineralized
preserved tree saps traps an entire organism, the sap hardens into this type of fossil and preserves the trapped organism
amber
mummification or freezing preserve
original material
nearly all fossil are formed in what type of rock?
sedimentary rock
how are the fossils formed in sedimentary rock?
the sediments build up until they cover the organism remains, meinerals replace organisc matter or fill the empty pore spaced of the organism
what are the types of techniques used to date fossils?
radiosmetric dating, relative dating or a substances half life
radiometric dating
uses the decay of radioactive isotopes to measure the age of a rock
where can radioactive isotopes be found?
radioactive isotopes that are used for radiometric dating are only found in metamorphic or igneous rocks
relative dating
is used to determing the age of rocks by comparing with other layers
half life of substance
a substances half life is the amount of time it takes for the original isotope to decay
