B6: Fossils

Question 1

What are fossils?

Answer 1

The remains of organisms from thousands of years ago, which are found in rocks.

Question 2

How are fossils formed from gradual replacement by minerals?

Answer 2

1) teeth, shells, bones etc. that don’t decay last a long time when buried
2) eventually replaced by minerals as they decays, forming a rock like substance shaped like the original hard part
3) the surrounding sediments also turn to rock, but the fossils stays distinct inside the rock

Question 3

How are fossils formed from casts and impressions?

Answer 3

1) When an organism is buried in a soft material like clay which hardens around it, the organism decays leaving a cast of itself. An animal’s burrow or plant’s roots can be preserved as casts
2) footprints can also be pr seed into gear materials when soft, leaving an impression when it hardens

Question 4

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

Answer 4

1) in amber and tar pits there’s no oxygen or moisture so decay microbes can’t survive
2) in glaciers it’s too cold for decay microbes to work
3) peat bogs are too acidic for decay microbes

Question 5

Can fossils tell us how life began?

Answer 5

They show how much or little organisms have evolved, but not how they came to be.