Fossils Pt2 Flashcards

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1
Q

Define fossil and it’s uses

A

Any preserved remains of a once living organism
-allows scientists to build a sequence of evolution for particular organisms
-other materials within bone can determine climate, diet, presence of other organisms in the time period

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2
Q

Describe the process of fossil formation

A

parts become fossilised when buried by sand/mud/volcanic ash or other members of species
-if buried rapidly or conditions not ideal for decay, decomp. is slowed

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3
Q

How do the different natures of soil effect bone fossilisation

A

-wet/acidic: dissolves minerals in bone=no fossil formed
-no oxygen (like peat): complete preservation of soft tissue and bone=fossil
-alkaline soils: best for preserving bone
-new minerals: deposit in pores of bone

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4
Q

Where are fossil predominantly found? why?

A

At edge of ancient lakes/river systems, in caves, or, in volcanically active areas.
- organisms can be buried rapidly
-prevents decomposition
-built up sediment from lakes/rivers slow flow/flooding
-etc

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5
Q

How are some means of discovering/exposing fossils/artefacts

A

-erosion
-earth movements
-excavation

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6
Q

Define an artefact

A

objects deliberately made/modified by humans

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7
Q

What are the fundamentals of excavation sites and explain why they are in place

A
  • section marked out
    -small hand tools used to remove soil (minimise damage to material)
    -soil is sieved (small fragments not overlooked)
    -photograph each stage (positions of uncovered material may be carried out later)
  • each item labelled+categorised for later study
  • fossils/artefacts cleaned, pieced together and molds are made
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8
Q

What is fossil dating and why is it important? What can dating provide

A

Determining the age of fossils/artefacts
-helps find out sequence of changes in a species

Provides:
-absolute data: actual age of specimen
-relative data: comparison whether one sample is younger/older than other

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9
Q

What is the difference between relative and absolute dating

A

relative: comparison whether one sample is younger/older than other, no actual age determined

absolute: actual age of specimen in years found

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10
Q

Define potassium argon dating. What is it’s use? What is it’s limit?

A

Based on decay of radioactive potassium to form calcium and argon
- used to date rocks older than 100000-200000 years
- not all rock types suitable for method of dating, must be older than 100000-200000

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11
Q

What is an isotope? Explain it’s correlation to potassium in absolute dating

A

Atoms of the same element with different number of neutrons
-Potassium is a mixture of 3 isotopes
-39,40,41

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12
Q

Describe the use of potassium-40 in absolute dating/potassium-argon dating

A

radioactive isotope that decays into argon-40 and calcium-40 at an extremely slow but constant rate
-slow rate allows for determination of K and argon in sample which is used to calculate age of rock
-as rock ages K proportion decreases as argon sample increases

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13
Q

What is the half life of K-40

A

1.25 billion years

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14
Q

Define carbon-14/radiocarbon dating. What is it’s use? What is it’s limit?

A

Based on decay of radioactive isotope of carbon, carbon-14, into nitrogen
-carbon-14 is produced in upper atmosphere by action of cosmic radiation on nitrogen
-up to 60000 years determination and must contain organic material (such as bone)

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15
Q

How does carbon-14 dating occur

A
  1. 1 atom of every (10^2) of carbon atoms in plants is C-14 atom for photosynthesis
  2. Animal/person eats plant, then, C-14 becomes part of organism
  3. Organism dies, C-14 intake stops but the rate of C-14 decay continues
  4. Ratio of C-14 to C-12 used to determine age of sample
    The ratio does vary so radiocarbon dating is verified using dendrochronology
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16
Q

What is the half-life of C-14

A

5730 years

17
Q

What is dendrochronology? Half-life?

A

Tree ring dating, uses rings on surface of cut tree
- half-life: till about 9000years

18
Q

Define stratigraphy? What is it useful for

A

Study of strata/layers
-principle of superposition
-correlation of rock strata

19
Q

What is the principle of superposition? What is it’s downside?

A

Assumes that layers of sedimentary rock on surface are younger than at bottom
-sequence of rock may be turned upside down
-animals/people could have buried fossils/artefacts after soil deposition

20
Q

What is the correlation of rock strata?

A

Matches layers of rock form different areas
-matching can be done by studying rock and fossil contained within

21
Q

Define index fossils. Why are they useful? Provide an example

A

Those which are widely distributed and or easily found and were present for a short length of time
-make correlation of strata more precise
e.g. fossilised pollen are useful as index and can also construct a picture of vegetation existing at time as well as type of climate

22
Q

Define the problems with fossil record

A

Incomplete
-small number of fossils discovered
-buried too deep
-destroyed by human activity

Found fossils can be problematic
-C dating must contain carbon and the material can only be dated back 60 000 years
-K argon dating relies on volcanic lava being present

Unusual to find fossil of an entire organism

23
Q

What are the required conditions for fossil formation

A

-quick burial of material
-little to no oxygen
-alkaline soils
-presence of hard body parts
-an absence of decay organisms
-long period of stability-organism must be left undisturbed

24
Q

How to tell of rock is older

A

Locations with fossils closer to the surface will contain older rock strata. When fossils are further below layers, a location contains younger strata.