Flashcards in 6.1 and 6.2 The Origins Of Life on Earth/Exploring the Fossil Evidence Deck (16)
When did life approx begin on earth?
3500million years ago
How old is the earth predicted to be?
4500million years old
What is the debate for where life on Earth came from?
Life developed due to the conditions on earth or simple life forms arrived from a different planet
What is meant by dating rocks?
As fossils are found in rocks, we can date when the different organisms existed
Why are scientists not clear about when life on Earth existed?
There is no repeatable or reproducible evidence
Name 4 ways fossils can be formed.
•from the hard parts of animals that can't decay, eg. Bones, teeth, shells and claws
•from organisms that haven't decayed due to the lack of conditions for decay when they died, eg. Preserved in ice
•when the parts of the organism are replace by other materials such as minerals when they decay
•as preserved traces of organisms, eg. Footprints, burrows and rootlet traces
Why did most organisms that does not leave a fossil?
The exact conditions for fossil formations were not present
What are fossils?
The remains of organisms that lived many years ago which are found in rock
Why did most early life forms not leave a fossil?
They had soft bodies so few traces were left behind
Why are traces that were left behinds likely to have been destroyed?
Geological activity such as earthquakes would have destroyed them
Name 3 reasons the fossil record is incomplete
•soft bodied organisms didn't leave fossils
•many organisms died without the exact conditions for fossil formation
•some fossils have been destroyed over time
What can we learn from fossils?
How different organisms have changed as life developed on earth
Why can prehistoric remains stay in good shape in either glaciers, bogs or tree sap?
There is no oxygen reaching them there so they can't decay
Name 3 places where fossils can't decay due to lack of oxygen
•ancient tree sap
Name 7 reasons for extinction in organisms
•single catastrophic events