vertebrate history in rocks (what are fossils (usually found in…
vertebrate history in rocks
what are fossils
a hardened remain of evidence of a living organism from long ago.
imprints on rocks, old bones, shells skeletons, other parts of the organism.
how does it become a fossil
a chemical process when tissue is replaced by hard material.
because tissue decays quick only some organisms are preserved as fossils
usually found in sedimentary rock
sedimentary rock- hardened layers of sediments
contain particles of sand clay mud and slit
over long periods of time layers press together and become rock. trapping whatever was between inside.
interpretation of fossils
a fossils age
fossils in higher layers of rocks are younger that fossils in lower layers of rocks.
this is not always the best method though because of earthquakes and other things that could shake the fossil around.
scientist usually use the fact that in fossils there are different elements and usually the elements will decay or change into other chemicals. the more decay, the older the fossil.
the first vertebrate to ever live was a fish.
appeared on earth around 530 million years ago.
amphibians descended fro,m fish
appeared around 380 million years ago.
reptiles evolved from amphibians.
appeared around 320 million years ago.
mammals came from reptiles
appeared 220 million years ago.
birds came last
appeared 150 million years ago.
scientists that study extincted organisms are called paleontologists.
they also examine bone structures.
can infer how animals will evolve.