Fossil Flashcards
What are fossils?
Remains of organisms from many years ago which are found in rocks.
They provide the evidence that organisms lived ages ago.
Name the 3 ways fossils form in rocks?
From gradual replacement by minerals.
From casts and impressions.
From preservation in places where no decay happens.
How do fossils form from gradual replacement by minerals?
Things like teeth, bones, shells which don’t decay easy can last a long time when buried.
Eventually replaced by minerals as they decay forming a rock like substance shaped like the orginial hard part.
Surrounding sediment also turns rock but fossil stays distinct inside the rock and evetually someone digs it up.
How do fossils from from casts and impressions?
Sometimes fossils are formed when an organism is buried in a soft material like clay.
Clay later hardens around it and organism decays leaving a cast of itself.
An animal burrows or plants roots can be preserved by casts.
Footprints can be pressed into soft materials leaving n impression when it hardens.
How do fossils form from preservation in places where no decay happens?
In amber and tar pits there’s no oxygen or moisture so decay microbes can’t survive.
In glaciers its too cold for decay microbes to work.
Peat bogs are too acidic for decay microbes.
What do fossils show us?
How many of todays species have eveolved over millions of years.
Why cant hypotheses about how the earth formed can supported?
Theres a lack of valid and reliable evidence.
What do scientists believe?
Many early organisms were soft-bodied and soft tissue tends to decay away completely.
So fossil record is incomplete.
What could have happened to fossils that formed millions of years ago?
They could have been destroyed by geological activity.
