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Flashcards in Fossils Deck (24)
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What is a fossil

Any preserved trace left by an rganisms that lived in the past


What are types of fossil



How are fossils formed

Formed when hard body parts or organisms such as bone or teeth are buried by drifting sand, deposited by rivers, volcanic ash


Requirements for fossil formation

1. Quick burial
2. Presence of hard body parts
3. Absence of decay microorganisms
4. Long period of being left undisturbed


Where are fossils often found?

1. Near lakes and rivers due to build up of sediment when flooding occurs
2. In caves because limestone may be deposited around dead organisms or the roof of the cave may collapse
3. Or found by chance or excavation of a site


What are artefacts

Objects that have been deliberately made by humans


Examples of artefacts

Stone tools
Cave paintings


How does the fossil record provide evidence for evolution

It provides evidence of which organisms lived on earth in the past and establishes links between species to determine commmon acenstry


What are the two types of dating

Absolute dating
Relative Dating


What is absolute dating?

Finding the actual date of a specimen


What is relative dating?

Tells us if the sample is older or younger than the other


What is potassium argon dating

It is dating volcanic rock next to the fossil not the fossil itself


What is the P-A dating based on?

Based on the decay of radioactive potassium 40 to form calcium and argon


What is P-A dating half-life?

Potassium has a half-life of 1.25-1.3B years so, over a period of 1.25B years, half the original potassium -40 would have decayed


How can P-A age fossils?

The ratio of potassium 40 to argon 40 determines the age in a rock sample, the ratio of argon compared to potassium the older it is


What is the limitations of P-A

1. Not all rocks are suitable because not all rocks are volcanic
2. Can only date a rock sample, not the fossil itself
3. Only date samples past 200 000 years
4. Must be suitable rock of the same age as the fossil


What is radio carbon dating based on?

Based on the decay of radioactive isotope of carbon -14 to nitrogen


What is the half-life of R-C dating?

Half life is 5730 years, so over a period of 5730 years there will be half the original carbon 14 amount


How can R-C dating help to date fossils?

The ratio of carbon -14 to carbon 12 can help to determine the age of the fossil


What is the limitations of R-C dating?

1. Required 3 grams of organic material
2. After 70 000 years the quantity of carbon -14 is too small to be used, can only date back than 60,000 years


What is stratigraphy

The study of layers


What are the principles of stratigraphy

1. Principle of rock strata
2. Principle of correlation of rock strata


What is the principle fo rock strata

Assumes layers of the rock, the layers at the top are the younger than the below

Distortions in the earth's crust do occur and the sequence of rock layers can be different


What is the principle of correlation of rock strata

Have to match layers of rock from different areas to determine the youngest and oldest

This can be done by examining the rock and studying the fossils it contains

Particular fossils are widely distributed and were present on Earth for only a short time which can be used as index fossils