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vertebrate history in rocks (what are fossils (EX: imprint in rock like a…
vertebrate history in rocks
what are fossils
EX: imprint in rock like a foot print
a fossil can also be remains of bone shells skeletons or other body parts
a fossil is a hardened remains or other evidence of a living thing that lived a long time ago
fossils are made by a chemical process that happens over time, where an animals tissue is replaced by minerals
because animals decompose fast only a few are preserved as fossils
fossils are found most frequently in
sedimentary rock
made of clay mud or silt
sediment can build up in many ways EX: wind can blow a thick layer of sand onto dunes
it can also form when muddy water stands still for a long time so the dirrty settles at he bottom
over time the sediment can compact and animals can be trapped in the sediment
interpretation of fosils
a fossils age
but earthquakes can shift or even turn the fossil upside down so it's not always accurate
the fossils that are lower down are normally older becuse the sediment settled there first then other fossils where created later
the more decayed form of the element the older the fossil
some contain radioactive elements that decay at or change over a known period of time
using fossils
fossils show the first vertebrates to live on earth where fishes
they use fossils to determine the likely course of evolution the vertebrates have taken
fish appeared on earth 530 million years ago
birds where the latest to appear only 150 million years ago
mammals first lived on this earth 220 million years ago
birds and mammals are descendants from reptiles
320 million years ago amphibians gave rise to reptiles
by studying fossils paleontologists can see how animals evolved over the years
age
paleontologist studies extinct organisms