Fossil- Evidence for Evolution

Question 1

What are fossils?

Answer 1

Fossils are any preserved trace left by an organism that lived long ago.

Question 2

Give examples of fossils.

Answer 2

Footprints
Burrows
Faeces
Bones
Shells
Teeth

Question 3

What are artefacts?

Answer 3

Artefacts are objects that have been deliberately made by humans.

Often found in association with human fossils

Question 4

How do fossils provide evidence for evolution?

Answer 4

Fossils show that living things have changed (evolved) over time, e.g. horse

Shows that many life forms no longer exist but many resemble modern species. Present complex organisms have evolved from simpler organisms in the past.

Question 5

What can fossils be used for?

Answer 5

Evidence of evolution

Inform us about what the environment was like in the past

Help correlate rock layers to date organisms

Question 6

How are fossils formed?

Answer 6

1.Organism is buried by sediment (e.g. volcanic ash/silt) shortly after it dies. Soft parts often decay.

2. Over a long period of time, more sediment builds up and compresses to form rock
3. Minerals in groundwater replace the bone, forming a fossil
4. Movement of tectonic plates lifts up sediments and pushes fossil closer to the surface.
5. Erosion wears away the rock layers, so eventually, the fossil is either naturally exposed or excavated

Question 7

Why is the chance of fossilisation small?

Answer 7

The chance of fossilisation in small due to decay by micro-organisms.

Question 8

What are the conditions needed for fossil formation?

Answer 8

A quick burial

The presence of hard body parts

Absence of decay organisms

Long period of stability- organism needs to be left undisturbed (but also must be unearthed for some time)

Other factors that support fossil formation include:
- Very cold temperatures
- Dry conditions
- High salt content (stops bacterial decay)

Question 9

Describe how soil is important for fossilisation.

Answer 9

Wet/acidic soil- minerals in bone dissolve. No fossilisation.

Wet/acidic soil with no oxygen- preservation of soft tissue as well as bone can occur.

Alkaline soil- produces best fossils. Minerals in bone don’t dissolve. New minerals (line/iron oxide) fill bone and petrify it (turn it to rock)

Question 10

Where are fossils found?

Answer 10

Edges of ancient lakes/rivers
Caves
Volcanic areas (ash)