Fossils are the remains or traces of ancient plants and animals preserved in rock. They provide evidence of lifeforms that existed millions of years ago. Fossils form when the hard parts of organisms, such as bones, shells, or bark, become buried and slowly replace with minerals from groundwater. Over millions of years, the remains take on the properties of the surrounding rock. Fossils give insights into early life on Earth and how organisms have evolved over long periods of geological time.

1. Fossils

2. What are Fossils?
• Fossils are the remains or marks of plants
and animals that lived a very long time
ago. They are usually found in rock and
stone.
• Fossils are important because they tell us
a story about things that lived on the earth
before us.

3. What Things Become Fossils?
• Animals and plants become fossils.
• So do nests, eggs, footprints and even
animal droppings!

4. How are Fossils Made?
• Fossils are made from the hard parts of
plants and animals, such as:
- bark, seed cases, bones and teeth.
• These parts do not easily rot away after
plants and animals die.
• Fossils take millions of
years to form.

5. Turning to Stone
• For example:
- A starfish dies.
- The soft parts of its body rot away quickly.
- The harder parts slowly get covered by mud.
- After millions of years, the starfish is deep in the ground.
- The mud around it is crushed by the land on top and
turned to stone.
- So are the remains of the starfish.
- Millions of years later, the stone gets worn away and the
fossil can be seen.

6. How Fossils are Formed

7. From the Sea
• The first creatures on the earth lived in the
sea.
• Some sea creatures made good fossils
because they had hard shells and hard
bones.
Trilobite Fossil
Horseshoe Crab Fossil
Fish Fossil

8. Plants
• At first, there were only Pine Cone Fossil
living things in the sea.
• Slowly, over millions of
years, plants began to grow
on the land.
• Some of these plants have
left fossils in the rock.

9. Animals
• Animal fossils are often bones that have been turned to rock. Sometimes
part of the flesh is preserved, but most of the time only skeletons remain.
• Because of this, it is more difficult to find fossils of invertebrates.
(Invertebrates are animals that don’t have bones.)
• We have discovered several types of animal fossils: bones, skin, teeth,
claws, eggs, nests, muscles, and organs.
• We have also found lots of fossils of footprints, which tell us how much
animals and dinosaurs weighed and how they might have walked.

10. When Did They Live?
• First Fish  570 million years ago.
• First plants on land  440 million
years ago.
• First insects and amphibians  400
million years ago.
• First reptiles  360 million years ago.
• First dinosaurs  245 million years
ago.
• First birds  210 million years ago.