Fossils Flashcards

1
Q

what is the definition of fossil?

A

any preserved remains of a once living organism

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2
Q

why are fossils important to scientist ?

A

allows them to build a sequence of evolution of particular organsims

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3
Q

what is a petrified fossil

A

the turning of something into stone

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4
Q

how is a petrified fossil formed?

A

water full of minerals seeps into the layers of sediment to reach the dead organism when the water evaporates the minerals harden called perminralisation

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5
Q

how is a mold fossil formed?

A

when the hard parts of an organism are buried in sediment and then they dissolve leaving a hollow area

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6
Q

how is a cast fossil made?

A

water with dissolved minerals and sediment fills the molds it then evaporates only leaving the minerals

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7
Q

how are carbon films made?

A

when an organism dies eventually there will only be carbon left this shows the organisms delicate parts

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8
Q

what is a trace fossil ?

A

shows the activity of an organism eg footprint set in sediment

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9
Q

what is a preserved remain?

A

an organism that gets preserved in or close to there original state

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10
Q

what is a preserved remain in amber?

A

an organism gets trapped in sticky tree resin it then gets covered more

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11
Q

what are preserved remains in tar?

A

organsims get trapped in a tar pit dies and then the tar soaks into the bones resulting in bones to stop decaying

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12
Q

what are preserved remains in ice?

A

organism dies in a very cold region its body gets frozen in ice which preserves the organism

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13
Q

what is vital to the formation fossils ?

A

-organism becomes fossilised when buried
-buried rapidly or in wrong conditions decomposition occurs
-wet and acidic soil dissolves bone
-no oxygen

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14
Q

how are fossils discovered?

A
  • erosion = earth movement and excavation
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15
Q

what is the process of a fossils discovered?

A

-excavation sites
-sections are marked out
-small handed tools used to remove soil
-soil is sieved
-photographed at each stage
-each item is labelled and catalouged
-fossils clean

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16
Q

what is fossil dating and what are the two types?

A

determines the age of the fossils
absolute dating = actual age of specimen in years
relative dating = tell us wether a sample is older or younger then another

17
Q

what are the two types of absolute dating ?

A

potassium-argon
radiocarbon

18
Q

what is potassium-argon dating based on ?

A

the decay of radioactive potassium-40 into calcium-40 and argon-40

19
Q

what is the age range that potassium-argon dating can be used on?

A

rocks aged older then 100,000-200,000 year old

20
Q

what are the limitations to potassium-argon dating?

A

-it has to be older than 100,000 years old
-not all rocks have potassium in them

21
Q

what is radiocarbon dating based on ?

A

carbon-14 decaying into nitrogen

22
Q

what is the age range that radiocarbon dating can be used on?

A

60,000 year

23
Q

what is the limitations to radiocarbon dating ?

A

can only be used after 60,000 years

24
Q

give an overview of carbon-14 and how it used

A

-animals eat carbon 14 when they die the decay of carbon 14 remains consistant
- this is then compared to the carbon 12 to determine the age

25
what is dendrochronology ?
tree ring dating which can help verify radiocarbon dating
26
what is the age range that dendrochronology can be used on?
up to 9,000 years old
27
what is relative dating using ?
-the stratigraphy -the principle of superposition -correlation of rock strata -fluoride dating
28
what is fluoride dating ?
based on the number of fluoride ions that are replacing the other ions in the bones.
29
what is potassium -40 half life
1.25 billion years
30
what is carbon -14 half life?
5730 years