Fossils

Question 1

What are fossils?

Answer 1

Fossils are the remains of dead animals from many years ago, found in rocks.

Question 2

What do fossils provide evidence for?

Answer 2

Evolution

Question 3

How are fossils formed from Gradual Replacement by Minerals?

Answer 3

Teeth, shells and bones (things which don’t decay easily) can last a long time when buried. They’re eventually replaced by minerals, forming a rock-like substance shaped like the original hard part.
The surrounding sediments also turn to rock, but the fossil stays distinct inside the rock until someone digs it up.

Question 4

How are fossils formed from Casts and Impressions?

Answer 4

Sometimes, fossils are formed when an organism is buried in a soft material like clay. The clay later hardens around it and the organism decays, leaving the cast of itself.
Animal burrows and plant roots can be preserved as casts.
Footprints can be pressed into clay when it’s soft, leaving an impression.

Question 5

How are fossils formed from preservation in places where no decay happens?

Answer 5

In amber and tar pits, there’s no oxygen or moisture so decay microbes can’t survive.
In glaciers, it’s too cold for the decay microbes to work.
Peat bogs are too acidic for decay microbes.
These things preserve organisms.