Flashcards in Bio Quiz 2 Deck (45)
What is a fossil?
Any evidence of a once-living organism.
Give some examples of things that are considered fossils.
casts, molds, footprints, track ways and feeding traces.
Ordinarily, which parts of the organisms are preserved?
The hard parts (shells, bones, teeth)
What is one of the keys of preservation?
The absence of oxygen and the presence of water.
Can you date dirt?
Can you date volcanic ash?
Yes, using potassium/argon
Can you date fossils?
What is unaltered remain?
RARE fossils with little or no change in structure and composition.
Why are unaltered remains rare?
Because the conditions to form seldom occur.
What are the 3 types of unaltered remains?
Encrustations, amber entombment, refrigeration
What are the 2 versions of body fossils?
What are encrustations?
When dissolved minerals in water form a thin crust on whatever it lies on.
What do you get when you dissolve away the encrustation?
Original material (usually bones/shells)
What can encrustations tell us?
How organisms grew when alive.
What is amber entombment?
When insects are trapped in resin, which hardens into amber.
What do you get from amber entombment?
Original cellular material, at least partial DNA.
When would you be able to get blood or DNA from a dinosaur in an amber entombment?
If the insect had bitten a dinosaur.
What is refrigeration?
When animals are trapped in ice from the ice age.
What can we retrieve from refrigeration?
Lots of cellular materials, at least partial DNA samples.
What are altered remains?
Sediments compressed by overlying sediments and undergo lithification.
What is lithification?
The process of turning to stone
What are the 4 types of altered remains?
permineralization, replacement, recrystallization, carbonization
What is permineralization?
When the pores in bones/shells/plantstems are filled with mineral deposits.
What can you see from permineralization?
The general structure (especially bones and hand tissue), no original material, no DNA, bad detail.
What is replacement?
When acidic groundwater dissolves a hard structure in an organism that is trapped in sediments. A mineral is deposited in its place.
What can we find from replacement?
Lots of detail (even their last meal, feathers).
What is recrystallization?
The conversion of the fossil to new mineral (coarser crystals of the original material).
What can we get from recrystallization?
No DNA, bad detail.
Where do the crystals often form?
Inside shells and hollow bones.