Fossils Pt2

Question 1

Define fossil and it’s uses

Answer 1

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

Question 2

Describe the process of fossil formation

Answer 2

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

Question 3

How do the different natures of soil effect bone fossilisation

Answer 3

-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

Question 4

Where are fossil predominantly found? why?

Answer 4

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

Question 5

How are some means of discovering/exposing fossils/artefacts

Answer 5

-erosion
-earth movements
-excavation

Question 6

Define an artefact

Answer 6

objects deliberately made/modified by humans

Question 7

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

Answer 7

• 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

Question 8

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

Answer 8

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

Question 9

What is the difference between relative and absolute dating

Answer 9

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

absolute: actual age of specimen in years found

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

What is the half life of K-40

Answer 13

1.25 billion years

Question 14

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

Answer 14

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)

Question 15

How does carbon-14 dating occur

Answer 15

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

Question 16

What is the half-life of C-14

Answer 16

5730 years

Question 17

What is dendrochronology? Half-life?

Answer 17

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

Question 18

Define stratigraphy? What is it useful for

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is the correlation of rock strata?

Answer 20

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

Question 21

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

Answer 21

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

Question 22

Define the problems with fossil record

Answer 22

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

Question 23

What are the required conditions for fossil formation

Answer 23

-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

Question 24

How to tell of rock is older

Answer 24

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