Fossils

Fossil Formation (organism→stone):

1) Organism dies near/in water.
2) The area is covered in sediment, such as sand, mud, or silt.
3) Soft parts are much less likely to decay if oxygen is lacking, as decomposers cannot respire as quickly.
4) From above, turn the sediment into rock.
5) Minerals replace body tissues (e.g., skeleton) to form rock, so the organism is now a fossil.

- Hard parts are more likely to fossilise, e.g., bones.
- Additionally, you can preserve organisms by trapping them in amber, burying them in volcanic ash, trapping them in ice, or trapping them in a peat bog.
- There are two types of fossils:
→ Main fossil: Actual organism in stone.
→ Trace fossil: Evidence an organism was there, e.g., a footprint.

The Fossil Record:

- Radiometric dating of rocks can give fossils an absolute age.

How Does It Show Evolution?

- You can see species appearing/disappearing.
- Some species evolve, and some go extinct.

Incomplete:

- Conditions must be ideal for the formation of a fossil.
- Most fossils are then destroyed over time.
- Some species, such as soft-bodied organisms, rarely fossilise.
- Fossils are hard to find for humans.
→ Certain species possess a superior fossil record due to the accidental discovery of their fossils.

- A creature in between 2 types of organisms evolved into one type of organism, proving Darwin's theory of evolution.

- Some organisms have rarely changed over billions of years, e.g., some forms of ancient bacteria.
- Some of these bacteria have left behind traces of unique chemicals, which scientists have now dated back to 3.5 billion years.