What is a fossil?
The image below shows animals whose species have died out. What name is given to animals that no longer exist?
The photograph shows stromatolite fossils found in rocks in Western Australia. These fossils are believed to be the oldest known fossils ever found.
They were formed by ancient blue-green algae and are estimated to be about 3.5 billion years old.
What do these fossils tell us about life on Earth?
Hint: Algae are aquatic plants (they live in water).