Fossils Flashcards
Give the rough dates of;
-Origin of prokaryotic life
-Formation of the Earth
-Big bang
Origin of prokaryotic life (3.5 billion)
Formation of the Earth (4.57 billion)
Big bang (13.7 billion)
What are fossils?
*Transformed body parts-shells, bones, teeth
*Activity (‘trace fossils’) -burrows, footprints
*Preserved remains (‘sub fossils’)- shells, remains in amber
*Organic chemicals any body part
How are fossils formed?
(By a series unlikely of events) what are they ?
- Body survives long enough after death to undergo fossilisation this could be difficult as;
-Soft parts are destroyed quickly
-Eaten, degraded by microbes
-Few fossils of soft bodied organisms e.g. worms and plants
-Even hard parts are likely to be destroyed e.g Crushed by rocks, wave action, scavengers - Remains must become buried in sediment at the bottom of a water column.
-Fossils are only found in sedimentary rocks (e.g limestone and sand stone) - The chance of fossilisation depends on proximity to sediment. Chance for fossilisation gets higher in water organisms closer or in the sediment
- Permineralization
Sediment covered by more layers
Compacts into rock – may deform or destroy the fossil
Hard minerals leach out of rocks and impregnate the remains
Original compounds replaced and leach out - Exposure – The final ‘unlikely event’ ‘Fossil’ means ‘something dug up’
Tectonic processes can move the fossil around and re-expose it in a terrestrial area which makes it easier to be lost for ever
Fossils are rare in comparison to the number of organisms that have existed in the 3.5 billion year history of life.
What does the quality of the fossil depend on?
State of body at the start of the process and geological factors – pressure, minerals present
What are alternative routes to fossilisation of buried remains
external or internal mould or marks
How do we date fossils?
*Radio-carbon dating
5730 years after death ½ the C14 → N14
Can work out date of death by examining the ratio
Only for fossils up to 40,000 years old
only if sediments has some sort of organic compound
(absolute dating)
Volcanic ash
Many sediments contain volcanic ash (‘tephra’)
Potassium and Argon
Decay more slowly than C14 – fossils older than
100,000 years
Paleomagnetic dating (older fossils)
Currents in Earth’s core change direction of magnetic field ‘Normal’ / ’Reversed’
Determines alignment of magnetic particles when rocks form
Age rocks by comparing the polarity of sediments to cores of rock from sea bed
(relative dating)
What is relative dating?
Compare fossils to fossils of known age from other strata that look similar
Why are fossils important?
e.g Fossil butterflies, 65 Myr BP nb
Molecular evidence reveals increasing amounts of information about evolution
Shows how closely extant species are related and how quickly they may have diverged – e.g. ‘molecular clocks’
Only fossils tell us what extinct species were like and how they lived.
‘Functional morphology’ ADAPTATIONS
Describe the fossil record
What is fossil study called?
when did serious analysis of fossils begin?
Study of fossils is called ‘Paleontology’
Fossils provide a record of the history of life
Deeper ‘strata’ (layers) equate to greater age of the rocks and any fossils they contain.
Serious analysis began in the 1960
Evermore detailed analysis; 2020, 11k species at 0.1my resolution (Fan et al. 2020)
When was the first human around?
When did mammals diversify?
First humans 195-160000 yr bp
Mammals diversify – 65 Myr bp
How is the geological time scale divided ?
‘Eras’, ‘Periods’ and ‘Epochs’
Based on rock strata and refined with new dating techniques
Each stretch of time has a characteristic fossil fauna
Boundaries reflect sudden changes in fauna
When was the extinction of most dinosaurs
Cretaceous, 65 – 144 Myr BP
Sinosauropteryx
How do we know perhaps some dinosaurs had feathers?
Melanosomes – contain the pigment in hair and feathers
What are extant saurischian dinosaurs
lizard-hipped dinosaurs
birds evolved from lizard hipped dinosaurs not bird-hipped dinosaurs
Jurassic, 144 – 206 Myr BP
‘Quarry dinosaurs’
Very large herbivores
4 species
Up to 26m
Est. weight 50 – 113 tonnes
