Topic 6c- Fossils

Question 1

What are fossils?

Answer 1

Fossils are the remains of organisms from many years ago which are found in rocks.

Question 2

How can fossils be formed?

Answer 2

• From gradual replacement by minerals- things such as teeth and bones that don’t decay easily and are replaced overtime by minerals as they decay, forming a rock-like substance shaped like the original hard part. The surrounding sediments also turn into rock.
• From casts and impressions- when an organism is buried in a soft material e.g. clay. The material hardens around it and the organism decays leaving a cast of itself. (things such as burrows or footprints could be preserved in this way)
• From preservation in places where no decay happens- this would be due to there being an abscence of oxygen, not enough water, incorrect PH for bacteria to function

Question 3

Why would no decay occur? What substances could allow for this?

Answer 3

• In amber (fossilised tree sap) → no oxygen or moisture so no decay microbes can survive
• In glaciers where it’s too cold for the decay microobes to work
• Peat bogs → too acidic for decay microobed to function

Question 4

Why is there a lack of evidence within the fossil record?

Answer 4

• scientists believe that many early organisms were soft bodied and therfore tended to decay away wothout forming fossils
• fossils that did form millions of years ago may have been destroyed by geological activity

Question 5

How can fossils be used today?

Answer 5

By comparing fossils with species alive today, we dan see how many of today’s species have developed from simple organisms over millions of years