Evidence for evolution - FOSSILS

Human biology unit 4

What is evolution?

The change in characteristics of a species over time

What is a fossil?

Any preserved trace left by a previously living organism

Examples of fossils are;

Bones, teeth, shells, footprints,, faeces, burrows, plant/animal impressions

Why are fossils important?

Allow us to determine exactly what extinct species looked like, other material associated with/ bones help develop a picture of life in the past. Fossil records can help build a sequence of the evolution of the plant/animal

What is fossil record

Record of the occurrence and evolution of living organisms through geological time as inferred from fossils

How is fossil record evidence for evolution

Establishes evolutionary links between species (shows common ancestry). Provides evidence of which organisms lived on earth in the past. Provides examples of organisms which may now be extinct. Provides examples of transitional organisms between species

What are the chances of fossils forming?

Very small chance. Dead organisms decay via micro organisms & there is no trace of them. Fossilisation can occur if buried by drifting sand, mud deposited by rivers, volcanic ash or buried rapidly by others of it’s species slowing the decay process.

Why is dying in water ideal for fossilisation?

Remains are more likely to be buried by sediment and less likely to be destroyed by scavengers or erosion

Why is a low energy environment (lake/swamp) ideal for fossilisation?

Remains are less. likely to be destroyed by mechanical processes

Why is finer sediment (mud) ideal for fossilisation

Finer sediment reduces amount of oxygen coming in contact with corpse & slows bacterial decay, enabling soft tissues to be preserved.

Why is ice ideal for fossilisation?

Being trapped in ice = low temperatures which will stop decay and whole bodies with soft parts can be preserved

Why is alkaline soil ideal for fossilisation?

Alkaline soil environment favours the preservation of bone as new minerals are deposited into the pores of bones (petrified)

Why is an acidic environment ideal for fossilisation?

An acidic environment favours the preservation of soft tissues and bone, provided it doesn’t contain any oxygen and is at a low temp, complete preservation can occur