Early Plants and Animals
The first plants on Earth were blue-green algae. These appeared about 3.5 billion years ago.
The first spiders appeared 400 million years ago. The first ferns grew 300 million years ago. The first dinosaurs appeared 230 million years ago.
Most species change over time.
When the Tyrannosaurus first appeared about 98 million years ago, they were the size of Labrador dogs. But it grew bigger and bigger. Some 30 million years later, the T-rex was 12 metres long and had teeth between 15 and 30 centimetres long.
Not all species change. Ginkgo trees, Coelacanth fish, and crocodiles are almost the same as they were millions of years ago. Because of this they are nicknamed 'living fossils'.
Can you think why living fossils are just like their ancestors?
