Fossils Flashcards
What are these
Fossils are the remains of organisms that have been preserved in rock
Why are they important
They provide valuable evidence for the emergence of life on earth
What is palaeontology
It is the study of ancient life through fossils
Explain the formation of fossils
When organisms , a die they become covered in sand
More sediment is deposited over forming a thick layer
The layer of sediment became compressed and hardens to form rock
In the rock organisms start to fossilise
Their Bones and teeth (the hard part ) is replaced with minerals such as calcium carbonate and silica from the rock
Mineralisation of skeletons causes them to harden and they can be preserved for millions of years
List the types of fossils
Petrifaction or mineralisation
Moulds and impressions
Trace fossils
Natural preservatives
Explain each types of fossil
Petrifaction or mineralisation -actual part, such as a bone or whole skeleton or tough plant tissue, is rapped under layers of sand. Minerals leach into the hard body tissues, which then become preserved.
Soft body parts decay and are not preserved.
What is Moulds and impressions
After the organism has been buried in layers of sediment, the sand hardens around the organism. The whole organism may disintegrate or be dissolved by weak acidic soil water. Only the shape or mould is left in the rock. Impressions are similar and the fossils are formed when semi-soft organs such as leaves become compressed between layers of sediment.
What are trace fossils
These provide evidence of the animal having been in the area, e.g. footprints in rock, trails, and nests of organisms. The Laetoli footprints in Tanzania are an important find that indicated an upright primate was in the area about 3, 7 mya. The footprints were made in soft volcanic ash that was covered in sediment which was rained on andthen hardened.
What are natural preservatives
Animals become trappedinnatural substances of bodies. that preserve wholeorparts
What are the two main ways we date fossils
Relative dating
Radiometric dating
What is relative dating
It refers to looking at the relative depths of fossils in rock layers where the fossils are found
Relative dating gives the order events, but not the actual age of the fossils.
What is radiometric dating
Radiometric dating uses the radioactive material in rocks to determine when the rocks were formed in the rock layer
The radioactive elementsinrock change slowly over time. They may change their structure or “decay”. The process is termed - radioactive decay.
Eg Potassium is an element that is present in all rocks and it changes slowly to Argon. Scientists know how long it takes for Potassium to decay. By comparing how much Potassium has changed into Argon, scientists can get an idea of how many millions of years old a rock and its fossils are.
What other elements do scientist look at in radiometric dating
Fluorine analysis
Carbon -14
Uranium -lead decay
