Fossils

Question 1

What are fossils?

Answer 1

-Fossils are the remains of organisms from many thousands of years ago, found in rocks
-they help us understand the evolution of organisms over time.

Question 2

What are the three ways fossils can form?

Answer 2

-through gradual replacement by mineral
-from casts and impressions
-from preservation in environments where decay doesn’t occur

Question 3

Describe the process of gradual replacement by minerals.

Answer 3

-things like teeth, shells, bones etc., which don’t decay easily, can last a long time when buried.
-They’re eventually replaced by minerals as they decay, 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 and eventually someone digs it up.
-this is the way most fossils form

Question 4

Explain how casts and impressions are formed.

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 a cast of itself
-Things like footprints can also be pressed into these materials when soft, leaving an impression when it hardens.

Question 5

How do fossils form in places where decay doesn’t occur?

Answer 5


1)In amber (a clear yellow ‘stone’ made from fossilised resin) and far pits there’s no oxygen or moisture so decay microbes can’t survive.
2) In glaciers it’s too cold for the decay microbes to work.
3)Peat bops are too acidic for decay microbes.

Question 6

What are some hypotheses about how life first originated?

Answer 6

Hypotheses include the possibility of life originating in a primordial swamp or under the sea on Earth, or simple organic molecules being brought to Earth on comets and evolving into life forms.

Question 7

Why is it difficult to provide evidence supporting or disproving hypotheses about the beginning of life?

Answer 7

-There is a lack of good valid evidence
-Early forms of life were often soft-bodied, and soft tissue tends to decay completely, leading to an incomplete fossil record.
-geological activity such as tectonic plate movement may have destroyed fossils formed millions of years ago.