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Flashcards in Fossils Deck (11)
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1
Q

What are fossils?

A

Remains of organisms from many years ago found in rocks

2
Q

What are the three ways in which fossils are formed?

A

From gradual replacement by minerals
From casts and impressions
From preservation in places where no decay happens

3
Q

Describe gradual replacement by minerals?

A

Things like teeth shells and bones don’t decay very easily
They are eventually replaced by minerals as they decay forming a rock like substance in its origami shape
The surrounding sediment also turns to rock but the fossils stays distinct inside the rock and eventually someone digs it up

4
Q

What is the most common formation of fossils?

A

Gradual replacement by minerals

5
Q

Describe fossil formation from casts and impressions?

A

When an organism is buried in a soft material like clay the clay hardens around it and the organism decays leaving a cast of itself

An animals burrow or a plants roots can be preserved as cast

Things like footprints can be or see into these material when it’s soft leaving an impression when it hardens

6
Q

Describe the formation of fossils from preservation?

A

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 decayed microbes to work

Peat bogs are too acidic

The animals remains are preserved

7
Q

What do fossils show?

A

How living things have evolved

Evidence of extinct organisms

8
Q

What are two theories about where life came from?

A

Primordial swamp

On comets

9
Q

Why are these two theories not believed?

A

Can’t be supported or disproved because there is a lack of valid and reliable evidence

10
Q

Why do many scientists believe?

A

Many early organisms were soft bodies and soft tissue tends to decay completely making the fossil record incomplete

11
Q

What is the other problem with fossil reliability?

A

Fossils that formed millions of years ago may have been destroyed by geological activity