B2.8 Fossilisation

Fossilisation

• Creature is alive.
• Creature dies.
• Soft parts rot away.
• Hard parts are covered by sediment.
• Hard parts replaced by minerals, turns into rock.
• Layers of sediment compressed over time forming sedimentary rock.
• rocks are move and lifted by geological processes.
• Rock is worn away.
• Fossil is discovered
• In some special occasions soft tissue may be preserved in amber, peat bogs, ice and tar. This is because these conditions stop decomposers and detritivores from working.

Incomplete fossil record

• Earliest life forms had no hard parts.
• Most organisms don't become fossils.
• Rocks containing fossils are destroyed by a range of geological processes.
• Not every fossil will be found.

Extinctions

• �Climate
• change over geological time (e.g. ice ages)
• Major
• catastrophic events (e.g. massive volcanic eruptions, meteor impacts etc.
• �New
• predators (e.g. humans entering new habitats)
• �New
• diseases (e.g. Dutch elm disease)
• �New
• competitors (e.g. grey squirrels)

Species

• A group of organisms which can breed to produce fertile offspring �
• �Most organisms of different species are unable to breed at all �
• �Closely related species may be able to breed to create infertile offspring
• Endemic species are found no where else